salinomycin and Breast-Neoplasms

Breast cancer continues to be a serious health problem particularly in developed countries. Of particular concern is triple negative breast cancer (TNBC) which does not respond well to standard hormone therapy and is associated with poor overall patient prognosis. Recent studies indicate that Wnt/β-catenin signaling is particularly activated in TNBC, such that the Wnt receptor frizzled-7 (FZD7) and the Wnt co-receptor LRP6 were found to be up regulated in TNBC. In addition, it has been demonstrated that transcriptional knockdown of LRP6 or FZD7 in TNBC cells suppressed tumor growth in vivo. Furthermore, salinomycin, a selective breast cancer stem cell killer, was recently demonstrated to be an inhibitor of Wnt/β-catenin signaling by inducing LRP6 degradation. Therefore, the Wnt/β-catenin signaling pathway and particularly the Wnt receptors on the cell surface may serve as novel therapeutic targets for the treatment of TNBC.

Topics: Breast Neoplasms; Cell Proliferation; Female; Frizzled Receptors; Humans; Low Density Lipoprotein Receptor-Related Protein-6; Pyrans; Receptor, ErbB-2; Receptors, Estrogen; Receptors, Progesterone; Wnt Signaling Pathway

Recent studies have identified a small population of highly tumorigenic cells with stem cell properties in human breast and other solid tumors that are considered to be the source of tumor initiation and maintenance; these cells are referred to as cancer stem cells (CSCs). Preclinical data suggest that current breast cancer treatment strategies lead to CSC enrichment, contributing to chemotherapy and radiotherapy resistance, although a strong correlation with clinical parameters and prognosis is yet to be established. Importantly, overcoming treatment failure by effective targeting of CSCs may be an appealing approach, potentially leading to improved clinical outcomes for patients with breast cancer. Several preclinical studies provide promising results that support this hypothesis. The purpose of this review is to summarize the role of CSCs in breast cancer recurrence and resistance and to discuss current attempts of CSC targeting.

Topics: Aldehyde Dehydrogenase 1 Family; Breast Neoplasms; CD24 Antigen; Cell Differentiation; Cell Transformation, Neoplastic; Disease Progression; Drug Resistance, Neoplasm; Female; Humans; Hyaluronan Receptors; Isoenzymes; Metformin; Neoplasm Invasiveness; Neoplastic Stem Cells; Pyrans; Retinal Dehydrogenase; Treatment Outcome

Macrophages are sentinels of the immune system, which are often hijacked by tumor cells to assist tumor growth and metastasis. Herein our results showed that low dose salinomycin (SAL) in the range of 10-50 nM could efficiently induce M1 macrophage polarization in a dose- and time- dependent manner in vitro, with 30 nM SAL being optimal to generate M1-type macrophages from RAW246.7 cells. In animal study, intratumorally injected SAL (50 µg/kg) increased proportion of CD86 cells (by 28.9%), and decreased CD206 cells (by 14.2%) in transplant 4T1 tumors, in comparison with PBS group. Thus it resulted in significant regression in tumor growth (20% tumor inhibition) and pulmonary metastasis (reduced the number of metastatic nodes by 58%) in SAL group, whereas lipopolysaccharide (LPS) and paclitaxel (PTX) groups showed comparable number of metastatic lesions and volume of tumor. LPS treatment could as well lead to inflammatory reactions in tumor with SAL group, but resulted in systemic inflammation (elevated levels of IL-1α, IL-1β and TNF-α in serum), and PTX (10 μg/kg) treatment increased both types of macrophages. For the first time, we employed salinomycin below the dose of direct antitumor activity could effectively prime M1 type macrophage stimulation and regress tumor growth and metastasis.

Topics: Animals; Breast Neoplasms; Female; Humans; Macrophages; Phenotype; Pyrans

Paclitaxel is widely used in the treatment of breast, ovarian, lung, and other cancers. Its primary mechanism is to prevent microtubule depolymerization causing loss of dynamic instability crucial for normal microtubule function leading to mitotic arrest. Prolonged mitotic arrest results in cell death as a secondary response. The effects of paclitaxel are typically studied in cell lines which precludes assessment of the possible influence of tumor-associated cells. We therefore examined paclitaxel action ex vivo in fresh explant cultures of human breast tumors. Surprisingly, we found that paclitaxel failed to induce tumor cell death in explant culture, in contrast to several other cytotoxic agents including salinomycin and vincristine. The lack of effect was not due to defective drug uptake, and furthermore, analysis of H&E stained tumor slices indicated that paclitaxel treatment caused defective (granular) mitosis and chromosomal condensation in 5-10% of tumor cells after 72 h. These results suggest that while paclitaxel was able to penetrate into the tumor slice and disrupt mitosis in cycling tumor cells, any ensuing cell death likely occurred beyond the useful lifetime of the tumor slices. We conclude that explant culture systems may be inappropriate for the study of cytotoxic drugs where a delay exists between the drug's primary and secondary modes of action.

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Death; Female; Humans; MCF-7 Cells; Mitosis; Paclitaxel; Pyrans; Time Factors; Tissue Culture Techniques; Vincristine

The polyether ionophore salinomycin (SAL) has been found to selectively target breast cancer cells, including those with stem-like phenotype. On the other hand, SAL amides and esters obtained through derivatisation of the C1 carboxyl of the ionophore were found to exhibit anticancer properties, whilst reducing potential toxicity issues which often occur during standard chemotherapy. However, the studies on the activity and especially on the mechanisms of action of this class of semi-synthetic products against breast cancer cells are very limited. Therefore, in this work, we confirmed the anti-breast cancer activity of SAL, and further investigated the potential of its selected C1 amide and ester analogs to destroy breast cancer cells, including the highly aggressive triple-negative MDA-MB-231 cells. Importantly, SAL esters were found to be more potent than the native structure and their amide counterparts. Our data revealed that SAL ester derivatives, particularly compounds 5 and 7 (2,2,2-trifluoroethyl and benzotriazole ester of SAL, respectively), increase the level of p-eIF2α (Ser51) and IRE1α proteins. Additionally, an increased level of DNA damage indicators such as γH2AX protein and modified guanine (8-oxoG) was observed. These findings suggest that the apoptosis of MCF-7 and MDA-MB-231 cells induced by the most promising esters derived from SAL may result from the interaction between ER stress and DNA damage response mechanisms.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Proliferation; Endoplasmic Reticulum Stress; Endoribonucleases; Esters; Eukaryotic Initiation Factor-2; Female; Humans; MCF-7 Cells; Molecular Structure; Phosphorylation; Protein Serine-Threonine Kinases; Pyrans; Reactive Oxygen Species; Signal Transduction; Structure-Activity Relationship

Cancer stem cells (CSCs) comprise a diminutive population of the tumor but pose major obstacles in cancer treatment, often their presence being correlated with poor prognosis, therapeutic resistance and relapse. Nanocarriers of combined drugs regimes demonstrate improved pharmacokinetics and decreased systemic toxicity by targeting the bulk tumor cells along with CSCs, holding the key to future successful chemotherapy. Herein, we developed lipid nanocapsules (LNCs) with co-encapsulated paclitaxel (PTX) and salinomycin (SAL) to eliminate breast cancer cells (MCF-7; non-bCSCs) and cancer stem cells (bCSCs) respectively. LNCs loaded with either PTX or SAL alone or in combination were fabricated by the phase inversion temperature (PIT) method. Physicochemical properties such as nano-size (90 ± 5 nm) and spherical morphology of LNCs were confirmed by dynamic light scattering (DLS) and scanning electron microscopy (SEM) respectively. More than 98 % encapsulation efficiency of drug, alone or in combination, and their controlled drug release was obtained. Drug loaded LNCs were efficiently internalized and exhibited cytotoxicity in non-bCSCs and bCSCs, with dual drug loaded LNCs offering superior cytotoxicity and anti-bCSCs property. Drug loaded nanocapsules induced apoptosis in bCSCs, potentiated with the co-delivery of paclitaxel and salinomycin. Synergistic cytotoxic effect on both cells, non-bCSCs and bCSCs and effective reduction of the tumor mammospheres growth by co-encapsulated paclitaxel and salinomycin suggest LNCs to be promising for treatment of breast cancer.

Topics: Breast Neoplasms; Cell Line, Tumor; Female; Humans; Lipids; Nanocapsules; Neoplastic Stem Cells; Paclitaxel; Pyrans

The nonadherent mammosphere assay has been commonly used to investigate cancer stem cell activities in breast cancers that have the ability to form tumorspheres and maintain tumor growth. The sphere formation step is critical, in that it enables the construction of the mammosphere models for downstream assays. The mammosphere assay has also been used to assess the effects of drug treatment on the tumorspheres formed from primary cancer cells or cell lines. Traditionally, the mammosphere formation has been evaluated by standard microscopy systems that required external software for additional analyses. However, this method can be time-consuming and low-throughput, thus impractical for high-throughput characterization of mammosphere models and screening for potential therapeutic cancer drugs. To overcome these challenges, we developed a plate-based high-throughput method to rapidly analyze mammospheres in whole wells using the Celigo Image Cytometer. The method is employed to characterize mammosphere formation and morphology for adherent and nonadherent propagation of four breast cancer cell lines (MCF7, MDA-MB-436, MDA-MB-231, and SKBR3). Next, the dose-dependent effects of four small molecule drugs (doxorubicin, paclitaxel, 8-quinolinol, and salinomycin) are characterized based on sphere formation and viability stained with calcein AM and propidium iodide. We observed growth and morphometric differences between adherent and nonadherent propagation of the four cell lines. Furthermore, drug treatments induced various effects on mammosphere formation, morphology, and viability. The proposed image cytometry method provides a useful tool suitable for high-throughput characterization and analysis of mammospheres, which can improve assay efficiency when investigating the formation capabilities and drug-induced cytotoxicity effects.

Topics: Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Doxorubicin; Female; High-Throughput Screening Assays; Humans; Image Cytometry; MCF-7 Cells; Neoplastic Stem Cells; Oxyquinoline; Paclitaxel; Pyrans; Spheroids, Cellular

Tumors are heterogeneous in nature, composed of different cell populations with various mutations and/or phenotypes. Using a single drug to encounter cancer progression is generally ineffective. To improve the treatment outcome, multiple drugs of distinctive mechanisms but complementary anticancer activities (combination therapy) are often used to enhance antitumor efficacy and minimize the risk of acquiring drug resistance. We report here the synergistic effects of salinomycin (a polyether antibiotic) and dasatinib (a Src kinase inhibitor).. Functionally, both drugs induce cell cycle arrest, intracellular reactive oxygen species (iROS) production, and apoptosis. We rationalized that an overlapping of the drug activities should offer an enhanced anticancer effect, either through vertical inhibition of the Src-STAT3 axis or horizontal suppression of multiple pathways. We determined the toxicity induced by the drug combination and studied the kinetics of iROS production by fluorescence imaging and flow cytometry. Using genomic and proteomic techniques, including RNA-sequencing (RNA-seq), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western Blot, we subsequently identified the responsible pathways that contributed to the synergistic effects of the drug combination.. Compared to either drug alone, the drug combination showed enhanced potency against MDA-MB-468, MDA-MB-231, and MCF-7 human breast cancer (BC) cell lines and tumor spheroids. The drug combination induces both iROS generation and apoptosis in a time-dependent manner, following a 2-step kinetic profile. RNA-seq data revealed that the drug combination exhibited synergism through horizontal suppression of multiple pathways, possibly through a promotion of cell cycle arrest at the G1/S phase via the estrogen-mediated S-phase entry pathway, and partially via the BRCA1 and DNA damage response pathway.. Transcriptomic analyses revealed for the first time, that the estrogen-mediated S-phase entry pathway partially contributed to the synergistic effect of the drug combination. More importantly, our studies led to the discoveries of new potential therapeutic targets, such as E2F2, as well as a novel drug-induced targeting of estrogen receptor β (ESR2) approach for triple-negative breast cancer treatment, currently lacking of targeted therapies.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Breast Neoplasms; Dasatinib; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Drug Synergism; E2F2 Transcription Factor; Estrogen Receptor beta; Female; G1 Phase Cell Cycle Checkpoints; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Humans; MCF-7 Cells; Pyrans; Reactive Oxygen Species; Transcriptome

Topics: Animals; Anti-Bacterial Agents; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Female; Gene Expression Regulation, Neoplastic; Humans; Immunosuppression Therapy; Indoleamine-Pyrrole 2,3,-Dioxygenase; Mice; Mice, Inbred C57BL; Models, Molecular; Neoplasms, Experimental; Protein Conformation; Pyrans; T-Lymphocytes

Conventional chemotherapy is hampered by the presence of breast cancer stem cells (BCSCs). It is crucial to eradicating both the bulky breast cancer cells and BCSCs, using a combination of conventional chemotherapy and anti-CSCs drugs. However, the synergistic ratio of drug combinations cannot be easily maintained in vivo. In our previous studies, we demonstrated that the simultaneous delivery of two drugs via nanoliposomes could maintain the synergistic drug ratio for 12 h in vivo. However, nanoliposomes have the disadvantage of quick drug release, which makes it difficult to maintain the synergistic drug ratio for a long time. Herein, we developed a co-delivery system for docetaxel (DTX)-a first-line chemotherapy drug for breast cancer-and salinomycin (SAL)-an anti-BCSCs drug-in rigid nanoparticles constituted of polylactide-co-glycolide/D-alpha-tocopherol polyethylene glycol 1000 succinate (PLGA/TPGS).. Nanoparticles loaded with SAL and DTX at the optimized ratio (NSD) were prepared by the nanoprecipitation method. The characterization, cellular uptake, and cytotoxicity of nanoparticles were investigated in vitro, and the pharmacokinetics, tissue distribution, antitumor and anti-CSCs activity of nanoparticles were evaluated in vivo.. We demonstrated that a SAL/DTX molar ratio of 1:1 was synergistic in MCF-7 cells and MCF-7-MS. Moreover, the enhanced internalization of nanoparticles was observed in MCF-7 cells and MCF-7-MS. Furthermore, the cytotoxicity of NSD against both MCF-7 cells and MCF-7-MS was stronger than the cytotoxicity of any single treatment in vitro. Significantly, NSD could prolong the circulation time and maintain the synergistic ratio of SAL to DTX in vivo for 24 h, thus exhibiting superior tumor targeting and anti-tumor activity compared to other treatments.. Co-encapsulation of SAL and DTX in PLGA/TPGS nanoparticles could maintain the synergistic ratio of drugs in vivo in a better manner; thus, providing a promising strategy for synergistic inhibition of breast cancer.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Docetaxel; Drug Delivery Systems; Drug Liberation; Female; Humans; Liposomes; Male; MCF-7 Cells; Mice, Inbred BALB C; Nanoparticles; Neoplastic Stem Cells; Polylactic Acid-Polyglycolic Acid Copolymer; Pyrans; Rats, Sprague-Dawley; Tissue Distribution; Vitamin E; Xenograft Model Antitumor Assays

To study the effects of the overexpression of autophagy-related gene 3 (ATG3) on autophagy and salinomycin-induced apoptosis in breast cancer cells and explore the underlying mechanisms.. We used the lentivirus approach to establish a breast cancer cell line with stable overexpression of ATG3. Western blotting, immunofluorescence staining and transmission electron microscopy were used to analyze the effect of ATG3 overexpression on autophagy in breast cancer MCF-7 cells. Using the AKT/mTOR agonists SC79 and MHY1485, we analyzed the effect of AKT/mTOR signal pathway activation on ATG3 overexpression-induced autophagy. Western blotting and flow cytometry were used to analyze the effect of autophagy on apoptosis of the ATG3-overexpressing cells treated with salinomycin and 3-MA (an autophagy inhibitor).. In ATG3-overexpressing MCF-7 cells, ATG3 overexpression obviously promoted autophagy, inhibited the AKT/mTOR signaling pathway, significantly weakened salinomycin-induced apoptosis (. ATG3 overexpression promotes autophagy possibly by inhibiting the AKT/mTOR signaling pathway to decrease salinomycin-induced apoptosis in MCF-7 cells, suggesting that autophagy induction might be one of the mechanisms of drug resistance in breast cancer cells.

Topics: Acetates; Apoptosis; Autophagy; Autophagy-Related Proteins; Benzopyrans; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Female; Gene Expression Regulation; Humans; MCF-7 Cells; Morpholines; Proto-Oncogene Proteins c-akt; Pyrans; TOR Serine-Threonine Kinases; Triazines; Ubiquitin-Conjugating Enzymes

Cancer is a complex disease wherein cells begin to divideabnormally and spread into surrounding tissues. Angiogenesis plays a crucial role in tumor progression as it is required for sustained growth and metastasis, therefore targeting angiogenesis is a promising therapeutic approach for breast cancer management. Salinomycin (SAL) has been reported to exhibit anticancer response on various types of cancer. In the present study, we explored the antiangiogenic and anticancer efficacy of the polyether ionophore SAL in the breast cancer model. It effectively inhibited cell proliferation, invasion, and migration. It also inhibited the expression of pro-angiogenic cell surface marker CD31 in HUVEC, thereby interrupting the endothelial tubulogenesis. It decreased the HIF-1α transcription factor DNA binding activity to HRE sequence in HUVEC and human breast cancer cells. Further, corresponding to our in vitro findings, SAL suppressed neovascularization in the chick chorioallantoic membrane and the Matrigel plug implanted mice model. Bioluminescence and immunofluorescence imaging revealed that SAL treatment in mice inhibits breast cancer growth and tumor angiogenesis. SAL also suppressed the serum VEGFA level in tumor-bearing mice and induced caspase-dependent apoptosis in breast cancer cells. Taken together our findings suggested that SAL inhibits VEGF induced angiogenesis and breast cancer growth via interrupting HIF-1α/VEGF signalling and could be used as a promising antiangiogenic agent for breast cancer treatment.

Topics: Angiogenesis Inhibitors; Animals; Breast Neoplasms; Chick Embryo; Disease Progression; Dose-Response Relationship, Drug; Drug Delivery Systems; Female; HEK293 Cells; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; MCF-7 Cells; Mice; Mice, Inbred BALB C; Pyrans; Tumor Burden; Vascular Endothelial Growth Factor A

The preparation of multinuclear metal complexes offers a route to novel anticancer agents and delivery systems. The potency of a novel triangular multinuclear complex containing three platinum atoms, Pt-3, towards breast cancer stem cells (CSCs) is reported. The trinuclear platinum(II) complex, Pt-3 exhibits selective toxicity towards breast CSCs over bulk breast cancer cells and non-tumorigenic breast cells. Remarkably, Pt-3 inhibits the formation, size, and viability of mammospheres to a better extent than salinomycin, an established CSC-potent agent, and cisplatin and carboplatin, clinically used platinum drugs. Mechanism of action studies show that Pt-3 effectively enters breast CSCs, penetrates the nucleus, induces genomic DNA damage, and prompts caspase-dependent apoptosis. To the best of our knowledge, Pt-3 is the first multinuclear platinum complex to selectively kill breast CSCs over other breast cell types.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cadherins; Carboplatin; Caspases; Cell Line, Tumor; Cisplatin; Coordination Complexes; Crystallography, X-Ray; Female; Humans; Molecular Conformation; Neoplastic Stem Cells; Platinum; Pyrans; RNA Interference; RNA, Small Interfering

The residual tumor cells after chemotherapy, even in very small numbers, are generally drug-resistant and invasive, which might result in the progress of tumor metastasis and recurrence. In this research, a new combination chemotherapy strategy of salinomycin (SL) that could selectively inhibit multidrug-resistant tumor cells and a traditional broad-spectrum antitumor drug, doxorubicin (DOX), based on redox-degradable nano-micelles was developed to overcome drug resistance in vitro. The results in vitro indicated that DOX + SL co-loaded nano-micelles could not only escape from the drug efflux of adriamycin-resistant MCF-7 cells (A/MCF-7) but also penetrated and infiltrated into 3D-cultured MCF-7 and 4T1 tumor spheres in vitro more effectively, resulting in a strong antiproliferative effect. In the allogeneic metastatic 4T1 tumor model, the combination chemotherapy of DOX + SL encapsulated in nano-micelles effectively suppressed tumor growth with no splenomegaly and no other major tissue damage, and reversed the EMT progress, and inhibited tumor recurrence and metastasis more effectively after drug withdrawal.

Topics: Animals; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Apoptosis; Breast Neoplasms; Cell Proliferation; Doxorubicin; Drug Delivery Systems; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Drug Therapy, Combination; Female; Humans; Mice; Mice, Inbred BALB C; Micelles; Nanoparticles; Pyrans; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

The polyether ionophore salinomycin has recently captured much interest due to its potent activity against multi-drug resistant cancer cells and cancer stem cells. Previous studies have shown that either acylation of the C20 position or esterification/amidation of the C1 carboxylate moiety is beneficial in terms of biological properties. In this paper, we present the first analogs combining such modifications. Evaluation of the anti-proliferative activity against a series of cancer cell lines showed that acylation of the C20 hydroxyl group improves the activity of salinomycin C1 amides but not of the corresponding C1 esters. Importantly, the activity of several of the doubly modified analogs surpasses that of commonly used cytostatic drugs cisplatin and doxorubicin in the LoVo/DX multi-drug resistant cell line. All analogs were tested against primary acute lymphoblastic leukemia cells in standard cell viability assays; three were more potent than salinomycin. Further studies revealed that selected analogs induced characteristics of apoptotic cell death and increased expression of p53. Additionally, using an ex vivo model of breast tumor, tumor cell viability significantly decreased after treatment with salinomycin or its double-modified derivative (3a) in a time-dependent manner. The present findings indicate that double-modified salinomycin derivatives constitute promising lead compounds for targeting various types of cancer.

Topics: Aged; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Female; Humans; Neoplasms; Pyrans; Tumor Cells, Cultured

The breast cancer stem cell (CSC) and bulk breast cancer cell potency of a series of metallopeptides containing dichloro(1,10-phenanthroline)copper(II) and various organelle-targeting peptide sequences is reported. The mitochondria-targeting metallopeptide 1 exploits the higher mitochondrial load in breast CSCs over the corresponding non-CSCs and the vulnerability of breast CSCs to mitochondrial damage to potently and selectively kill breast CSCs. Strikingly, 1 reduces the formation and size of mammospheres to a greater extent than salinomycin, an established CSC-potent agent. Mechanistic studies show that 1 enters CSC mitochondria, induces mitochondrial dysfunction, generates reactive oxygen species (ROS), activates JNK and p38 pathways, and prompts apoptosis. To the best of our knowledge, 1 is the first metallopeptide to selectivity kill breast CSCs in vitro.

Topics: Apoptosis; Breast Neoplasms; Cell Line, Tumor; Chromatography, High Pressure Liquid; Coordination Complexes; Female; Humans; Inhibitory Concentration 50; MAP Kinase Kinase 4; Metalloproteins; Mitochondria; Neoplastic Stem Cells; p38 Mitogen-Activated Protein Kinases; Peptides; Phenanthrolines; Pyrans; Reactive Oxygen Species; Spectrometry, Mass, Electrospray Ionization; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Chemotherapy is a critical option for cancer treatment. However, consistent exposure to chemotherapeutic drugs promotes chemoresistance in cancer cells through diverse mechanisms. Accordingly, we investigated whether salinomycin, a monocarboxylic ionophore, could induce apoptosis in aggressive breast cancer cells or not, as well as its underlying mechanism.. Using salinomycin on two breast cancer cell lines, MCF-7 cells and MDA-MB-231 cells, cell viability, annexin V/propidium iodide staining, acridine orange staining, caspase-3/9 activity, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were assayed.. In this study, salinomycin induced apoptosis and autophagy in MDA-MB-231 cells. Salinomycin-mediated ROS production led to mitochondrial dysfunction in MDA-MB-231 cells. Interestingly, treatment of N-acetyl-L-cysteine (NAC), a scavenger of ROS, attenuated salinomycin-induced apoptosis and autophagy. Moreover, autophagy inhibition is involved in acceleration of apoptosis induced by salinomycin.. Salinomycin induced apoptosis and ROS production, that were blocked by autophagy, thus resulting in protecting cancer cells. This crosstalk of two different physiological responses (autophagy and apoptosis) induced by salinomycin might play pivotal roles in the relationship between autophagy and apoptosis of cancer cells.

Topics: Anti-Bacterial Agents; Apoptosis; Autophagy; Blotting, Western; Breast Neoplasms; Cell Proliferation; Female; Fluorescent Antibody Technique; Humans; Membrane Potential, Mitochondrial; Pyrans; Reactive Oxygen Species; Tumor Cells, Cultured

Resveratrol is a dietary compound that has been widely reported for its anticancer activities. However, successful extrapolation of its effects to pre-clinical studies is met with limited success due to inadequate bioavailability. We investigated the potential of combination therapy to improve the efficacy of resveratrol in a more physiologically relevant dose range.. The effect of resveratrol on canonical Wnt signaling was evaluated by Western blotting. Wnt modulators HLY78 (activator) and salinomycin (inhibitor) were evaluated in combination with resveratrol for their effect on breast cancer cell viability (MTT assay), cell cycle progression and apoptosis (Western blotting). Bliss independency model was used to evaluate combinatorial effects of resveratrol-salinomycin combination.. Resveratrol downregulated canonical Wnt signaling proteins in treated breast cancer cells (MCF-7, MDA-MB-231 and MDA-MB-468) in the dose range of 50-200μM, which also affected cellular viability. However, at very low doses (0-50μM), resveratrol exhibited no cellular toxicity. Co-treatment with salinomycin significantly potentiated the anti-cancer effects of resveratrol, whereas HLY78 co-treatment had minimal effect. Bliss independency model revealed that Wnt inhibition synergistically potentiates the effects of resveratrol in MCF-7 and BT474 cells. Significantly downregulated canonical Wnt signaling proteins and marker of epithelial-mesenchymal transition (EMT), vimentin were observed in cells treated with resveratrol-salinomycin combination. Cell cycle arrest, caspase activation and apoptosis induction in cells treated with resveratrol-salinomycin combination further confirmed the efficacy of the combination.. We report a novel resveratrol-salinomycin combination for targeting ER-positive breast cancer cells and present evidence for successful pre-clinical implementation of resveratrol.

Topics: Anti-Bacterial Agents; Antineoplastic Agents, Phytogenic; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Drug Therapy, Combination; Female; Gene Expression Regulation, Neoplastic; Humans; Pyrans; Receptors, Estrogen; Resveratrol; Signal Transduction; Stilbenes; Wnt Proteins

Salinomycin is a monocarboxylic polyether ionophore isolated from Streptomyces albus. It has been widely used as an antibiotic in veterinary medicine in poultry. A recent study demonstrated that salinomycin selectively inhibits human breast cancer stem cells; one possible mechanism of tamoxifen resistance. Our results show that salinomycin is effective in inhibiting MCF-7/LCC2 and MCF-7/LCC9 cell lines which are well-established endocrine resistant cells and has a synergistic effect in combination with tamoxifen using MTT proliferation assay. The inhibitory effect of salinomycin on the reduction of critical ER co-activator; amplified breast 1 (AIB1) mRNA and protein expression is overcoming tamoxifen resistance. Moreover, salinomycin significantly inhibits cell invasion in Matrigel invasion assay. The effect was mediated at least in part by the decrease of matrix metalopeptidase 9 (MMP-9) which is one critical enzyme facilitated in the cell invasion process. In conclusion, salinomycin should be developed as a novel agent used alone or in combination for endocrine-resistant breast cancer.

Topics: Apoptosis; Breast Neoplasms; Cell Movement; Drug Resistance, Neoplasm; Drug Synergism; Gene Expression Regulation, Neoplastic; Humans; Matrix Metalloproteinase 9; MCF-7 Cells; Neoplasm Invasiveness; Nuclear Receptor Coactivator 3; Pyrans; RNA, Messenger; Tamoxifen

Resveratrol (RES) is a natural polyphenol having anti-proliferative activity against breast cancer cells. RES in combination with other chemo modulatory agents, minimizes toxicity and increases efficacy of the treatment. Salinomycin (SAL), a monocarboxylic polyether ionophore is known for selectively targeting breast cancer stem cells. Purpose of the present study was to investigate whether RES in combination with SAL exerts synergistic anti-proliferative activity on breast cancer cells. We further evaluated the molecular mechanism behind SAL and RES mediated cell death. Cytotoxicity assay was performed to determine 50% inhibitory concentration (IC50) of SAL and RES in different human breast cancer cells (HBCCs). Drug synergism and combination index (CI) were calculated using CompuSyn software and effects of synergistic combinations (CI < 1) involving lower doses of SAL and RES were selected for further studies. This combination significantly induced apoptosis in HBCCs without affecting non tumorigenic human breast epithelial cells MCF-10A. Co-treatment enhanced apoptosis in MCF-7 cells via reactive oxygen species (ROS) mediated mitochondrial dysfunction. Oxidative stress disrupt redox homeostasis which altered antioxidant enzymes viz. CuZn Superoxide dismutase (SOD), MnSOD and catalase. Additionally, combination altered nuclear morphology, enhanced PARP cleavage and led to caspase activation. SAL and RES also synergistically modulated MAPK pathway. Study suggests that SAL and RES offer a novel combination approach for the treatment of breast cancer.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Drug Synergism; Female; Flow Cytometry; Humans; Inhibitory Concentration 50; MAP Kinase Signaling System; MCF-7 Cells; Pyrans; Reactive Oxygen Species; Resveratrol; Stilbenes; Tumor Stem Cell Assay

Most studies on new cancer drugs are based on population-derived data, where the absence of response of a small population may pass unnoticed. Thus, individual longitudinal tracking of cells is important for the future development of efficient cancer treatments. We have used digital holographic microscopy to track individual JIMT-1 human breast cancer cells and L929 mouse fibroblast cultivated in normoxia or hypoxia. In addition, JIMT-1 cells were treated with salinomycin, a cancer stem cell targeting compound. Three-day time-lapse movies were captured and individual cells were analysed with respect to cell division (cell cycle length) and cell movement. Comparing population-doubling time derived from population-based growth curves and individual cell cycle time data from time-lapse movies show that the former hide a sub-population of dividing cells. Salinomycin treatment increased the motility of cells, however, this motility did not result in an increased distant migration i.e. the cells increased their local movement. MCF-7 breast cancer cells showed similar motility behaviour as salinomycin-treated JIMT-1 cells. We suggest that combining features, such as motility and migration, can be used to distinguish cancer cells with mesenchymal (JIMT-1) and epithelial (MCF-7) features. The data clearly emphasize the importance of longitudinal cell tracking to understand the biology of individual cells under different conditions.

Topics: Breast Neoplasms; Cell Division; Cell Line, Tumor; Cell Movement; Cell Proliferation; Female; Humans; Hypoxia; Neoplastic Stem Cells; Pyrans

Cancer stem cells (CSCs) represent a subset of cells within tumours that exhibit self-renewal properties and the capacity to seed tumours. CSCs are typically refractory to conventional treatments and have been associated to metastasis and relapse. Salinomycin operates as a selective agent against CSCs through mechanisms that remain elusive. Here, we provide evidence that a synthetic derivative of salinomycin, which we named ironomycin (AM5), exhibits a more potent and selective activity against breast CSCs in vitro and in vivo, by accumulating and sequestering iron in lysosomes. In response to the ensuing cytoplasmic depletion of iron, cells triggered the degradation of ferritin in lysosomes, leading to further iron loading in this organelle. Iron-mediated production of reactive oxygen species promoted lysosomal membrane permeabilization, activating a cell death pathway consistent with ferroptosis. These findings reveal the prevalence of iron homeostasis in breast CSCs, pointing towards iron and iron-mediated processes as potential targets against these cells.

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Proliferation; Cell Survival; Drug Screening Assays, Antitumor; Female; Homeostasis; Humans; Iron; Lysosomes; Molecular Conformation; Neoplastic Stem Cells; Pyrans; Reactive Oxygen Species

Breast cancer stem cells (CSCs) are responsible for the initiation, recurrence, and metastasis of breast cancer. Sufficient evidence has established that breast cancer cells can spontaneously turn into breast CSCs. Thus, it is essential to simultaneously target breast CSCs and cancer cells to maximize the efficacy of breast cancer therapy. HER2 has been found to be overexpressed in both breast CSCs and cancer cells. We developed salinomycin-loaded polymer-lipid hybrid anti-HER2 nanoparticles (Sali-NP-HER2) to target both HER2-positive breast CSCs and cancer cells.. The antitumor activity of Sali-NP-HER2 constructed by conjugating anti-HER2 antibodies to polymer-lipid salinomycin nanoparticles was evaluated in vitro and in vivo.. Sali-NP-HER2 efficiently bound to HER2-positive breast CSCs and cancer cells, resulting in enhanced cytotoxic effects compared with non-targeted nanoparticles or salinomycin. In mice bearing breast cancer xenografts, administration of Sali-NP-HER2 exhibited superior efficacy in inhibiting tumor growth. Sali-NP-HER2 reduced the breast tumorsphere formation rate and the proportion of breast CSCs more effectively than non-targeted nanoparticles or salinomycin alone.. Sali-NP-HER2 represents a promising approach in treating HER2-positive breast cancer by targeting both breast CSCs and cancer cells.

Topics: Animals; Antibodies, Monoclonal; Breast Neoplasms; Cell Line, Tumor; Drug Delivery Systems; Female; Humans; Lipids; Mice; Nanoparticles; Neoplastic Stem Cells; Polymers; Pyrans; Receptor, ErbB-2; Xenograft Model Antitumor Assays

Chemoresistance is a major challenge for the successful therapy of breast cancer. The discovery of salinomycin as an anticancer stem cell drug provides progress in overcoming chemoresistance. However, it remains to be elucidated whether salinomycin treatment is able to sensitize cancer cells to chemotherapeutic drugs. In the present study, we consecutively treated epithelial MCF-7 and BT-474 breast cancer cells as well as mesenchymal MDA-MB 231 and MDA-MB 436 cells with salinomycin, and analyzed the gene expression of the two prominent multiple drug resistance (MDR) genes, MDR1 and BCRP1. We found that repeated treatment with salinomycin generated resistance against this drug in all cell lines and increased the chemosensitivity towards doxorubicin. Drug efflux pump gene expression and pump activity of MDR1 and BCRP1 were downregulated in almost all cell lines, except for MDR1 in the MDA-MB 231 cells. Consequently, the intracellular doxorubicin accumulation was increased compared to the respective parental cells. Our findings suggest a novel treatment option for MDR tumors by sensitizing these tumors via salinomycin pretreatment.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Breast Neoplasms; Cell Line, Tumor; Doxorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Humans; MCF-7 Cells; Neoplasm Proteins; Pyrans

Targeting breast cancer and more specifically cancer stem cell (CSC) subpopulation, responsible for tumor growth, resistance and self-renewal, using combination of therapeutic drugs selectively delivered via biocompatible nanocarriers, provides a novel approach for effective therapy. Here, we propose to evaluate the potential therapeutic efficacy of combining Paclitaxel and Salinomycin drugs actively targeted to both breast cancer and CSCs in xenograft murine model after conjugation with biocompatible CD44 antibody conjugated SWCNTs via hydrazone linker allowing pH-responsive release mechanism near the acidic tumor microenvironment. Both in vitro investigations on MDA-MB-231, sorted CSC negative or CSC positive fractions and in vivo evaluations on tumor-bearing mice using noninvasive bioluminescence and magnetic resonance imaging confirmed the enhanced therapeutic effect of the combined therapy compared to treatment with individual drug-conjugated nanocarriers or free drug suspensions. Thus, confirmed the great promise of the developed SWCNTs drug delivery system for effective breast cancer treatment by targeting and eradicating both whole tumor cells and CSCs populations.

Topics: Animals; Antibodies; Antigens, Tumor-Associated, Carbohydrate; Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Drug Carriers; Female; Humans; Hyaluronan Receptors; Hydrazones; Mice, Inbred BALB C; Mice, Nude; Mucin-1; Nanotubes, Carbon; Neoplastic Stem Cells; Paclitaxel; Pyrans; Tumor Burden

Epithelial-to-mesenchymal transition (EMT) is the major cause of breast cancer to initiate invasion and metastasis. Salinomycin (Sal) has been found as an effective chemical compound to kill breast cancer stem cells. However, the effect of Sal on invasion and metastasis of breast cancer is unclear. In the present study, we showed that Sal reversed transforming growth factor-β1 (TGF-β1) induced invasion and metastasis accompanied with down-regulation of MMP-2 by experiments on human breast cancer cell line MCF-7. Sal was able to inhibit TGF-β1-induced EMT phenotypic transition and the activation of key signaling molecules involved in Smad (p-Smad2/3,Snail1) and non-Smad (β-catenin, p-p38 MAPK) signals which cooperatively regulate the induction of EMT. Importantly, in a series of breast cancer specimens, we found strong correlation among E-cadherin expression, β-catenin expression, and the lymph node metastatic potential of breast cancer. Our research suggests that Sal is promised to be a chemotherapeutic drug by suppressing the metastasis of breast cancer.

Topics: Anti-Bacterial Agents; Antineoplastic Agents; Breast Neoplasms; Epithelial-Mesenchymal Transition; Female; Humans; MCF-7 Cells; Neoplasm Invasiveness; Neoplasm Metastasis; Neoplastic Stem Cells; Pyrans; Signal Transduction; Smad Proteins; Transforming Growth Factor beta1

Cancer stem cells (CSCs) have been invoked in resistance, recurrence and metastasis of cancer. Consequently, curative cancer treatments may be contingent on CSC selective approaches. Of particular interest in this respect is the ionophore salinomycin, a natural product shown to be 100-fold more active against CSCs than clinically used paclitaxel. We have previously reported that synthetic salinomycin derivatives display increased activity against breast cancer cell lines. Herein we specifically investigate the CSC selectivity of the most active member in each class of C20-O-acylated analogs as well as a C1-methyl ester analog incapable of charge-neutral metal ion transport.. JIMT-1 breast cancer cells were treated with three C20-O-acylated analogs, the C1-methyl ester of salinomycin, and salinomycin. The effects of treatment on the CSC-related CD44(+)/CD24(-) and the aldehyde dehydrogenase positive (ALDH(+)) populations were determined using flow cytometry. The survival ability of CSCs after treatment was investigated with a colony formation assay under serum free conditions. The effect of the compounds on cell migration was evaluated using wound-healing and Boyden chamber assays. The expression of vimentin, related to mesenchymal traits and expression of E-cadherin and β-catenin, related to the epithelial traits, were investigated using immunofluorescence microscopy.. Treatment with each of the three C20-acylated analogs efficiently decreased the putative CSC population as reflected by reduction of the CD44(+)/CD24(-) and ALDH(+) populations already at a 50 nM concentration. In addition, colony forming efficiency and cell migration were reduced, and the expression of the epithelial markers E-cadherin and β-catenin at the cell surface were increased. In contrast, salinomycin used at the same concentration did not significantly influence the CSC population and the C1-methyl ester was inactive even at a 20 μM concentration.. Synthetic structural analogs of salinomycin, previously shown to exhibit increased activity against cancer cells, also exhibited improved activity against CSCs across several assays even at nanomolar concentrations where salinomycin was found inactive. The methyl ester analog of salinomycin, incapable of charge-neutral metal ion transport, did not show activity in CSC assays, lending experimental support to ionophoric stress as the molecular initiating event for the CSC effects of salinomycin and related structures.

Topics: beta Catenin; Breast Neoplasms; Cadherins; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cell Survival; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Female; Humans; Ionophores; Neoplastic Stem Cells; Pyrans; Vimentin

The search for anticancer drugs has led researchers to study salinomycin, an ionophore antibiotic that selectively destroys cancer stem cells. In this study, salinomycin was assessed in two human cell lines, a breast adenocarcinoma (MCF-7) and a non-tumor breast cell line (HB4a), to verify its selective action against tumor cells. Real-time assessment of cell proliferation showed that HB4a cells are more resistant to salinomycin than MCF-7 tumor cell line, and these data were confirmed in a cytotoxicity assay. The half maximal inhibitory concentration (IC50) values show the increased sensitivity of MCF-7 cells to salinomycin. In the comet assay, only MCF-7 cells showed the induction of DNA damage. Flow cytometric analysis showed that cell death by apoptosis/necrosis was only induced in the MCF-7 cells. The increased expression of GADD45A and CDKN1A genes was observed in all cell lines. Decreased expression of CCNA2 and CCNB1 genes occurred only in tumor cells, suggesting G2/M cell cycle arrest. Consequently, cell death was activated in tumor cells through strong inhibition of the antiapoptotic genes BCL-2, BCL-XL, and BIRC5 genes in MCF-7 cells. These data demonstrate the selectivity of salinomycin in killing human mammary tumor cells. The cell death observed only in MCF-7 tumor cells was confirmed by gene expression analysis, where there was downregulation of antiapoptotic genes. These data contribute to clarifying the mechanism of action of salinomycin as a promising antitumor drug and, for the first time, we observed the higher resistance of HB4a non-tumor breast cells to salinomycin.

Topics: Adenocarcinoma; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Breast Neoplasms; Cell Cycle Proteins; Cell Proliferation; Comet Assay; DNA Damage; Dose-Response Relationship, Drug; Female; Flow Cytometry; Gene Expression Regulation, Neoplastic; Humans; Inhibitory Concentration 50; M Phase Cell Cycle Checkpoints; Mammary Glands, Human; MCF-7 Cells; Pyrans; Reverse Transcriptase Polymerase Chain Reaction; Time Factors

Cancer stem cell (CSC) inhibitors are a new category of investigational drugs to treat metastasis. Salinomycin (Sali) is one of most studied CSC inhibitors and has reached clinical tests. Several drug carriers have been developed to improve efficacy of Sali. However, Sali has not been shown to inhibit metastasis from orthotopic tumors, the gold standard for metastasis. To fill this gap, we developed an immune-tolerant, elastin-like polypeptide (iTEP)-based nanoparticle (iTEP-Sali-ABA NP) that released 4-(aminomethyl)benzaldehyde-modified Sali (Sali-ABA) under acidic conditions. We found that the NP increased the area under the curve (AUC) of Sali-ABA by 30-fold and the tumor accumulation by 3.4-fold. Furthermore, no metastasis was detected in any of the mice given the NP. However, all the mice died of primary tumor burdens. To overcome primary tumor growth and improve the overall survival, we applied a combination therapy consisting of the iTEP-Sali-ABA NP and iTEP NP-delivered paclitaxel. This therapy effectively retarded primary tumor growth, and most importantly, improved the overall survival. In conclusion, delivery of Sali-ABA by the NP, alone or in combination with paclitaxel, was more effective than free Sali-ABA in decreasing metastasis and increasing survival. This iTEP-Sali-ABA NP represents a novel and clinically promising therapy to combat metastasis.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Benzaldehydes; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Elastin; Electrophoresis, Polyacrylamide Gel; Female; Humans; Immune Tolerance; Mice, Inbred BALB C; Nanoparticles; Neoplasm Metastasis; Paclitaxel; Peptides; Pyrans; Tissue Distribution

Sustained autophagy contributes to the metabolic adaptation of cancer cells to hypoxic and acidic microenvironments. Since cells in such environments are resistant to conventional cytotoxic drugs, inhibition of autophagy represents a promising therapeutic strategy in clinical oncology. We previously reported that the efficacy of hydroxychloroquine (HCQ), an autophagy inhibitor under clinical investigation is strongly impaired in acidic tumor environments, due to poor uptake of the drug, a phenomenon widely associated with drug resistance towards many weak bases. In this study we identified salinomycin (SAL) as a potent inhibitor of autophagy and cytotoxic agent effective on several cancer cell lines under conditions of transient and chronic acidosis. Since SAL has been reported to specifically target cancer-stem cells (CSC), we used an established model of breast CSC and CSC derived from breast cancer patients to examine whether this specificity may be associated with autophagy inhibition. We indeed found that CSC-like cells are more sensitive to autophagy inhibition compared to cells not expressing CSC markers. We also report that the ability of SAL to inhibit mammosphere formation from CSC-like cells was dramatically enhanced in acidic conditions. We propose that the development and use of clinically suitable SAL derivatives may result in improved autophagy inhibition in cancer cells and CSC in the acidic tumor microenvironment and lead to clinical benefits.

Topics: Acidosis; Antineoplastic Agents; Autophagy; Biopsy; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Female; Humans; Neoplastic Stem Cells; Pyrans; Spheroids, Cellular; Tumor Microenvironment; Tumor Stem Cell Assay

Luminal A breast cancer is the most common breast cancer subtype which is usually treated with selective estrogen receptor modulators (SERMS) like tamoxifen. Nevertheless, one third of estrogen receptor positive breast cancer patients initially do not respond to endocrine therapy and about 40% of luminal A breast tumors recur in five years. In this study, we investigated an alternative treatment approach by combining tamoxifen and salinomycin in luminal A breast cancer cell lines. We have found that salinomycin induces an additional cytotoxic effect by inhibiting the ligand independent activation of ERα. Thereby salinomycin increases the intracellular calcium level. This leads to a premature fusion of endosomes with lysosomes and thus to the degradation of Egfr family members. Since this process is essential for luminal A breast cancer cells to circumvent tamoxifen treatment, the combination of both drugs induces cytotoxicity in tamoxifen sensitive as well as resistant luminal A breast cancer cell lines.

Topics: Biological Transport; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Drug Screening Assays, Antitumor; Drug Synergism; Endosomes; Estrogen Receptor alpha; Female; Humans; Inhibitory Concentration 50; Ligands; Lysosomes; MCF-7 Cells; Phenobarbital; Pyrans; Receptor Protein-Tyrosine Kinases; Selective Estrogen Receptor Modulators; Tamoxifen

Ovarian cancer is one of the most important malignancies, and the origin, detection, and pathogenesis of epithelial ovarian cancer remain elusive. Although many cancer drugs have been developed to dramatically reduce the size of tumors, most cancers eventually relapse, posing a critical problem to overcome. Hence, it is necessary to identify possible alternative therapeutic approaches to reduce the mortality rate of this devastating disease. To identify alternative approaches, we first synthesized silver nanoparticles (AgNPs) using a novel bacterium called Bacillus clausii. The synthesized AgNPs were homogenous and spherical in shape, with an average size of 16-20 nm, which are known to cause cytotoxicity in various types of human cancer cells, whereas salinomycin (Sal) is able to kill cancer stem cells. Therefore, we selected both Sal and AgNPs to study their combined effect on apoptosis and autophagy in ovarian cancer cells. The cells treated with either Sal or AgNPs showed a dose-dependent effect with inhibitory concentration (IC)-50 values of 6.0 µM and 8 µg/mL for Sal and AgNPs, respectively. To determine the combination effect, we measured the IC25 values of both Sal and AgNPs (3.0 µM and 4 µg/mL), which showed a more dramatic inhibitory effect on cell viability and cell morphology than either Sal or AgNPs alone. The combination of Sal and AgNPs had more pronounced effect on cytotoxicity and expression of apoptotic genes and also significantly induced the accumulation of autophagolysosomes, which was associated with mitochondrial dysfunction and loss of cell viability. Our data show a strong synergistic interaction between Sal and AgNPs in tested cancer cells. The combination treatment increased the therapeutic potential and demonstrated the relevant targeted therapy for the treatment of ovarian cancer. Furthermore, we provide, for the first time, a mode of action for Sal and AgNPs in ovarian cancer cells: enhanced apoptosis and autophagy.

Topics: Antineoplastic Agents; Apoptosis; Autophagosomes; Autophagy; Bacillus; Biomarkers, Tumor; Breast Neoplasms; Caspase 3; Cell Line, Tumor; Cell Shape; Cell Survival; Female; Gene Expression Regulation, Neoplastic; Humans; Lysosomes; Membrane Potential, Mitochondrial; Metal Nanoparticles; Ovarian Neoplasms; Oxidative Stress; Pyrans; Real-Time Polymerase Chain Reaction; Silver; Up-Regulation

Cyclohexyl thiosemicarbazone derivatives (C1-14) were synthesized, characterized and evaluated against HER-2 over expressed breast cancer cells. The synthesized compounds were screened in vitro against four breast cancer cell lines; SKBr-3, MCF-7, MDA-MB-468 and MDA-MB-231. All the compounds showed activity against HER-2 over expressed SKBr-3 cells with (IC₅₀ = 25.6 ± 0.07 μM-61.6 ± 0.4 μM). The most active compounds inhibit ALDH⁺ breast cancer stem cells more effectively than the cancer stem cells specific agent Salinomycin. Immunohistochemistry staining also confirmed that these compounds inhibit the expression of HER-2 on SKBr-3 cells. Compound C2 significantly inhibited the cell migration and cell adhesion of breast cancer cell lines. Compound C2 was found to most active compound of this series targeting HER-2 over expressed breast cancer cells.

Topics: Breast Neoplasms; Drug Delivery Systems; Female; Gene Expression Regulation, Neoplastic; Humans; MCF-7 Cells; Receptor, ErbB-2; Thiosemicarbazones

Breast cancer tissue contains a small population of cells that have the ability to self-renew, these cells are known as breast cancer stem cells (BCSCs). The Hedgehog signal transduction pathway plays a central role in stem cell development, its aberrant activation has been shown to contribute to the development of breast cancer, making this pathway an attractive therapeutic target. Salinomycin (Sal) is a novel identified cancer stem cells (CSCs) killer, however, the molecular basis for its anticancer effects is not yet clear. In the current study, Sal's ability to modulate the activity of key elements in the Hedgehog pathway was examined in the human breast cancer cell line MCF-7, as well as in a subpopulation of cancer stem cells identified within this cancer cell line. We show here that Sal inhibits proliferation, invasion, and migration while also inducing apoptosis in MCF-7 cells. Interestingly, in a subpopulation of MCF-7 cells with the CD44(+)/CD24(-) markers and high ALDH1 levels indicative of BCSCs, modulators of Hedgehog signaling Smo and Gli1 were significantly down-regulated upon treatment with Sal. These results demonstrate that Sal also inhibits proliferation and induces apoptosis of BCSCs, further establishing it as therapeutically relevant in the context of breast cancers and also indicating that modulation of Hedgehog signaling is one potential mechanism by which it exerts these anticancer effects.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Proliferation; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Hedgehog Proteins; Humans; MCF-7 Cells; Molecular Structure; Neoplastic Stem Cells; Pyrans; Signal Transduction; Structure-Activity Relationship; Transcription Factors; Tumor Cells, Cultured; Zinc Finger Protein GLI1

Salinomycin is a monocarboxylic polyether antibiotic, which is widely used as an anticoccidial agent. The anticancer property of salinomycin has been recognized and is based on its ability to induce apoptosis in human multidrug resistance (MDR). The present study investigated whether salinomycin reverses MDR towards chemotherapeutic agents in doxorubicin-resistant MCF-7/MDR human breast cancer cells. The results demonstrated that doxorubicin-mediated cytotoxicity was significantly enhanced by salinomycin in the MCF-7/MDR cells, and this occurred in a dose-dependent manner. This finding was consistent with subsequent observations made under a confocal microscope, in which the doxorubicin fluorescence signals of the salinomycin-treated cells were higher compared with the cells treated with doxorubicin alone. In addition, flow cytometric analysis revealed that salinomycin significantly increased the net cellular uptake and decreased the efflux of doxorubicin. The expression levels of MDR-1 and MRP-1 were not altered at either the mRNA or protein levels in the cells treated with salinomycin. These results indicated that salinomycin was mediated by its ability to increase the uptake and decrease the efflux of doxorubicin in MCF-7/MDR cells. Salinomycin reversed the resistance of doxorubicin, suggesting that chemotherapy in combination with salinomycin may benefit MDR cancer therapy.

Topics: Antineoplastic Agents; Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Doxorubicin; Drug Resistance, Neoplasm; Female; Humans; MCF-7 Cells; Multidrug Resistance-Associated Proteins; Pyrans

The therapeutic limitations of conventional chemotherapeutic drugs have emerged as a challenge for breast cancer therapy; these shortcomings are likely due, at least in part, to the presence of the cancer stem cells (CSCs). Salinomycin, a polyether antibiotic isolated from Streptomyces albus, has been shown to selectively inhibit cancer stem cells; however, its clinical application has been hindered by the drug's hydrophobility, which limits the available administration routes. In this paper, a novel drug delivery system, cross-linked multilamellar liposomal vesicles (cMLVs), was optimized to allow for the codelivery of salinomycin (Sal) and doxorubicin (Dox), targeting both CSCs and breast cancer cells. The results show that the cMLV particles encapsulating different drugs have similar sizes with high encapsulation efficiencies (>80%) for both Dox and Sal. Dox and Sal were released from the particles in a sustained manner, indicating the stability of the cMLVs. Moreover, the inhibition of cMLV(Dox+Sal) against breast cancer cells was stronger than either single-drug treatment. The efficient targeting of cMLV(Dox+Sal) to CSCs was validated through in vitro experiments using breast cancer stem cell markers. In accordance with the in vitro combination treatment, in vivo breast tumor suppression by cMLV(Dox+Sal) was 2-fold more effective than single-drug cMLV treatment or treatment with the combination of cMLV(Dox) and cMLV(Sal). Thus, this study demonstrates that cMLVs represent a novel drug delivery system that can serve as a potential platform for combination therapy, allowing codelivery of an anticancer agent and a CSC inhibitor for the elimination of both breast cancer cells and cancer stem cells.

Topics: Animals; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Apoptosis; Blotting, Western; Breast Neoplasms; Cell Proliferation; Cross-Linking Reagents; Doxorubicin; Drug Delivery Systems; Drug Therapy, Combination; Female; Flow Cytometry; Humans; Immunoenzyme Techniques; Liposomes; Mice; Mice, Inbred BALB C; Neoplastic Stem Cells; Pyrans; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured

BCSCs (breast cancer stem cells) have been shown to be resistant to chemotherapy. However, the mechanisms underlying BCSC-mediated chemoresistance remain poorly understood. The Hh (Hedgehog) pathway is important in the stemness maintenance of CSCs. Nonetheless, it is unknown whether the Hh pathway is involved in BCSC-mediated chemoresistance. In the present study, we cultured breast cancer MCF-7 cells in suspension in serum-free medium to obtain BCSC-enriched MCF-7 MS (MCF-7 mammosphere) cells. We showed that MCF-7 MS cells are sensitive to salinomycin, but not paclitaxel, distinct from parent MCF-7 cells. The expression of the critical components of Hh pathway, i.e., PTCH (Patched), SMO (Smoothened), Gli1 and Gli2, was significantly up-regulated in MCF-7 MS cells; salinomycin, but not paclitaxel, treatment caused a remarkable decrease in expression of those genes in MCF-7 MS cells, but not in MCF-7 cells. Salinomycin, but not paclitaxel, increased apoptosis, decreased the migration capacity of MCF-7 MS cells, accompanied by a decreased expression of c-Myc, Bcl-2 and Snail, the target genes of the Hh pathway. The salinomycin-induced cytotoxic effect could be blocked by Shh (Sonic Hedgehog)-mediated Hh signalling activation. Inhibition of the Hh pathway by cyclopamine could sensitize MCF-7 MS cells to paclitaxel. In addition, salinomycin, but not paclitaxel, significantly reduced the tumour growth, accompanied by decreased expression of PTCH, SMO, Gli1 and Gli2 in xenograft tumours. Furthermore, the expression of SMO and Gli1 was positively correlated with the expression of CD44+ / CD24-, and the expression of SMO and Gli1 in CD44+ / CD24- tissues was associated with a significantly shorter OS (overall survival) and DFS (disease-free survival) in breast cancer patients receiving chemotherapy.

Topics: Animals; Antineoplastic Agents; Breast Neoplasms; CD24 Antigen; Drug Resistance, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Hedgehog Proteins; Humans; Hyaluronan Receptors; Kaplan-Meier Estimate; Kruppel-Like Transcription Factors; MCF-7 Cells; Mice, Inbred BALB C; Mice, Nude; Neoplastic Stem Cells; Nuclear Proteins; Paclitaxel; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-myc; Pyrans; Receptors, G-Protein-Coupled; Signal Transduction; Smoothened Receptor; Spheroids, Cellular; Transcription Factors; Xenograft Model Antitumor Assays; Zinc Finger Protein GLI1; Zinc Finger Protein Gli2

AZD5363, an inhibitor of protein kinase B (AKT), is currently in clinical trials assessing the potential of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. The purpose of the present study was to identify conditions that increase the sensitivity of cancer cells to AZD5363. Microscopic examination revealed that treatment of cancer cells with a low concentration of salinomycin reduced cellular growth of AZD5363-treated breast cancer cells. Furthermore, fluorescence-activated cell sorting (FACS) analysis, Hoechst staining, and annexin V staining revealed that co-treatment with salinomycin sensitizes AZD5363-treated cancer cells via increased apoptosis with S-phase arrest. These results suggest that salinomycin can be applied to increase treatment efficacy for AZD5363-treated cancer cells. Our findings may contribute to improving the efficacy of the development of AZD5363-based sensitization therapies for patients with cancer.

Topics: Apoptosis; Breast Neoplasms; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Drug Screening Assays, Antitumor; Female; Humans; Pyrans; Pyrimidines; Pyrroles; S Phase

Cancer stem cells (CSCs) play important roles in the formation, growth and recurrence of tumors, particularly following therapeutic intervention. Salinomycin has received recent attention for its ability to target breast cancer stem cells (BCSCs), but the mechanisms of action involved are not fully understood. In the present study, we sought to investigate the mechanisms responsible for salinomycin's selective targeting of BCSCs and its anti-tumor activity. Salinomycin suppressed cell viability, concomitant with the downregulation of cyclin D1 and increased p27(kip1) nuclear accumulation. Mammosphere formation assays revealed that salinomycin suppresses self-renewal of ALDH1-positive BCSCs and downregulates the transcription factors Nanog, Oct4 and Sox2. TUNEL analysis of MDA-MB-231-derived xenografts revealed that salinomycin administration elicited a significant reduction in tumor growth with a marked downregulation of ALDH1 and CD44 levels, but seemingly without the induction of apoptosis. Our findings shed further light on the mechanisms responsible for salinomycin's effects on BCSCs.

Topics: Aldehyde Dehydrogenase 1 Family; Animals; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p27; Down-Regulation; Female; Humans; Hyaluronan Receptors; Isoenzymes; MCF-7 Cells; Mice, Inbred BALB C; Mice, Nude; Neoplastic Stem Cells; Pyrans; Retinal Dehydrogenase; Spheroids, Cellular; Transcription Factors; Xenograft Model Antitumor Assays

Triple-negative breast cancer (TNBC) is an aggressive tumor subtype with an enriched CD44+/CD24- stem-like population. Salinomycin is an antibiotic that has been shown to target cancer stem cells (CSC); however, the mechanisms of action involved have not been well characterized. The objective of the present study was to investigate the effect of salinomycin on cell death, migration, and invasion, as well as CSC-like properties in MDA-MB-231 breast cancer cells. Salinomycin significantly induced anoikis-sensitivity, accompanied by caspase-3 and caspase-8 activation and PARP cleavage, during anchorage-independent growth. Salinomycin treatment also caused a marked suppression of cell migration and invasion with concomitant downregulation of MMP-9 and MMP-2 mRNA levels. Notably, salinomycin inhibited the formation of mammospheres and effectively reduced the CD44+/CD24- stem-like population during anchorage-independent growth. These observations were associated with the inhibition of STAT3 phosphorylation (Tyr705). Furthermore, interleukin-6 (IL-6)-induced STAT3 activation was strongly suppressed by salinomycin challenge. These findings support the notion that salinomycin may be potentially efficacious for targeting breast cancer stem-like cells through the inhibition of STAT3 activation.

Topics: Anoikis; Breast Neoplasms; Cell Line, Tumor; Humans; Hyaluronan Receptors; Interleukin-6; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Neoplasm Proteins; Neoplastic Stem Cells; Pyrans; Sialic Acid Binding Ig-like Lectin 2; STAT3 Transcription Factor

To investigate the inhibitory effect of salinomycin on human breast cancer cells in vitro, and to explore the related molecular mechanism.. Human breast cancer MDA-MB-231 cells were treated with salinomycin at different concentrations and at various time points. The effect of salinomycin on MDA-MB-231 cells proliferation was studied by CCK-8 method. The cell cycle status was examined by flow cytometry. RT-PCR and Western blot were used to detect the expression of Shh, Smo and Gli1 in the Hedgehog pathway at mRNA and protein levels.. Proliferation of MDA-MB-231 cells treated with salinomycin was markedly inhibited in a concentration and time dependent manner. Salinomycin at concentrations of 0, 0.4, 0.8 and 1.6 µmol/L inhibited the growth at the rates of 11.18%, 25.88%, 50.03%, 92.65%, respectively. Salinomycin prevented MDA-MB-231 cells from G1 into S phase. Salinomycin at concentrations of 0, 0.8 and 1.6 µmol/L resulted in S-phase percentage of 25.03%, 11.85% and 35.21%, respectively (P < 0.05). RT-PCR and Western blot showed that the expression of key elements Shh, Smo and Gli1 in the Hedgehog pathway was inhibited by salinomycin in a concentration dependent manner (P < 0.05).. Salinomycin prevents breast cancer cell transition from G1 to S phase through downregulation of the target genes of Hedgehog signaling pathway, leading to an effective inhibition of MDA-MB-231 cells.

Topics: Breast Neoplasms; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Down-Regulation; Female; Hedgehog Proteins; Humans; Pyrans; Signal Transduction; Smoothened Receptor; Time Factors; Zinc Finger Protein GLI1

The present studies determined whether the antibiotic salinomycin interacted with HDAC inhibitors to kill primary human GBM cells. Regardless of PTEN, ERBB1, or p53 mutational status salinomycin interacted with HDAC inhibitors in a synergistic fashion to kill GBM cells. Inhibition of CD95/Caspase 8 or of CD95/RIP-1/AIF signaling suppressed killing by the drug combination. Salinomycin increased the levels of autophagosomes that correlated with increased p62 and LC3II levels; valproate co-treatment correlated with reduced LC3II and p62 expression, and increased caspase 3 cleavage. Molecular inhibition of autophagosome formation was protective against drug exposure. The drug combination enhanced eIF2α phosphorylation and decreased expression of MCL-1 and phosphorylation of mTOR and p70 S6K. Activation of p70 S6K or mTOR promoted cell survival in the face of combined drug exposure. Overexpression of BCL-XL or c-FLIP-s was protective. Collectively our data demonstrate that the lethality of low nanomolar concentrations of salinomycin are enhanced by HDAC inhibitors in GBM cells and that increased death receptor signaling together with reduced mitochondrial function are causal in the combinatorial drug necro-apoptotic killing effect.

Topics: Antineoplastic Agents; Apoptosis; Autophagy; Breast Neoplasms; Cell Line, Tumor; Drug Synergism; Female; Glioblastoma; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Necrosis; Neoplastic Stem Cells; Pyrans; Valproic Acid; Vorinostat

Tumor spreading is the major threat for cancer patients. The recently published anti-cancer drug salinomycin raised hope for an improved treatment by targeting therapy-refractory cancer stem cells. However, an unambiguous role of salinomycin against cancer cell migration and metastasis formation remains elusive.. We report that salinomycin effectively inhibits cancer cell migration in a variety of cancer types as determined by Boyden chamber assays. Additionally, cells were treated with doxorubicin at a concentration causing a comparable low cytotoxicity, emphasizing the anti-migratory potential of salinomycin. Moreover, single-cell tracking by time-lapse microscopy demonstrated a remarkable effect of salinomycin on breast cancer cell motility. Ultimately, salinomycin treatment significantly reduced the metastatic tumor burden in a syngenic mouse tumor model.. Our findings clearly show that salinomycin can strongly inhibit cancer cell migration independent of the induction of cell death. We furthermore demonstrate for the first time that salinomycin treatment reduces metastasis formation in vivo, strengthening its role as promising anti-cancer therapeutic.

Topics: Animals; Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Female; Humans; Mice; Mice, Inbred BALB C; Microscopy, Fluorescence; Neoplasm Metastasis; Pyrans; Tumor Burden

Cancer stem cells (CSCs) have been identified in a variety of cancers and emerged as a new target for cancer therapy. CSCs are resistant to many current cancer treatments, including chemotherapy and radiation therapy. Therefore, eradication of this cell population is a primary objective in cancer therapy. Here, we report gold nanorods (AuNRs) mediated photothermal treatment can selectively eliminate CSCs in MCF-7 breast cancer cells. It significantly reduced the aldehyde dehydrogenase positive (ALDH(+)) cells subpopulation and the mammosphere formation ability of treated cells. Also, the gene expression of stem cell markers was decreased. Cellular uptake assay revealed that polyelectrolyte conjugated AuNRs could be internalized by CSCs much more and faster than non cancer stem cells (NCSCs), which might be the main reason for the selective elimination of CSCs. We further loaded salinomycin (SA), a CSCs inhibitor with polyelectrolyte conjugated AuNRs to get a synergistic CSCs inhibition. Enhanced inhibition of CSCs was obtained by NIR light triggered drug release and hyperthermia. This CSCs-targeted thermo-chemotherapy platform provides a new combinatorial strategy for efficient inhibition of CSCs, which is promising to improve cancer treatment and may overcome the chemoresistance and recurrence of cancer.

Topics: Aldehyde Dehydrogenase; Breast Neoplasms; Cell Line, Tumor; Female; Gold; Humans; Hyperthermia, Induced; Nanotubes; Neoplastic Stem Cells; Phototherapy; Pyrans

Salinomycin, a naturally occurring polyether ionophore was recently found to selectively reduce the proportion of CD44(+)/CD24(-) cells, a phenotype associated with breast cancer stem cells. Subsequent studies from our group showed that chemical modification of the allylic C20 hydroxyl of salinomycin, located at the C-ring, can enhance the activity of derivatives against breast cancer cells over 5-fold compared to the native structure. Access to C-ring-modified salinomycin analogues is thus of interest from both a mechanistic and a synthetic perspective. Here, we report efficient strategies for gram scale synthesis of the natural product SY-1 (20-deoxy salinomycin), and a saturated analogue, 18,19-dihydro SY-1, for a comparative in vitro investigation of the biological profiles of these compounds with that of salinomycin. Across several assays, the deoxygenated structures required higher concentrations to elicit similar cellular responses to that of salinomycin. Similarly to salinomycin, SY-1 or 18,19-dihydro SY-1 treatment was found to reduce the proportion of CD44(+)/CD24(-) cells with essentially complete selectivity up to ∼IC25. Importantly, the proportion of CD44(+)/CD24(-) cells showed a pronounced U-shaped dose response curve for salinomycin and its derivatives, but not for paclitaxel. The concentration for maximum response in this assay followed differences in IC50 for salinomycin and its analogues, which emphasizes the importance of taking concentration dependence into account when comparing effects on the CD44(+)/CD24(-) phenotype. Small differences in the global conformation within the triad of compounds investigated together with differences in activity across assays emphasize the importance of substitution at C20 for the activity of salinomycin and its derivatives.

Topics: Antineoplastic Agents; Breast; Breast Neoplasms; CD24 Antigen; Cell Line, Tumor; Cell Proliferation; Female; Humans; Hyaluronan Receptors; Ionophores; Models, Molecular; Neoplastic Stem Cells; Pyrans

Emerging evidence indicates that activation of Wnt/β-catenin signaling at the cell surface results in inhibition of glycogen synthase kinase 3β (GSK3β), leading to activation of mTORC1 signaling in cancer cells. The low density lipoprotein receptor-related protein-6 (LRP6) is an essential Wnt co-receptor for Wnt/β-catenin signaling. Salinomycin is a novel small molecule inhibitor of LRP6. In the present study, we found that LRP6 overexpression induced mTORC1 signaling activation in cancer cells, and that salinomycin was not only a potent Wnt/β-catenin signaling inhibitor, but also a strong mTORC1 signaling antagonist in breast and prostate cancer cells. Mechanistically, salinomycin activated GSK3β in cancer cells. Moreover, salinomycin was able to suppress the expression of cyclin D1 and survivin, two targets of both Wnt/β-catenin and mTORC1 signaling, in prostate and breast cancer cells, and displayed remarkable anticancer activity. Our results present novel mechanisms underlying salinomycin-mediated cancer cell death.

Topics: Anti-Bacterial Agents; Apoptosis; beta Catenin; Breast; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin D1; Enzyme Activation; Female; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; HEK293 Cells; Humans; Inhibitor of Apoptosis Proteins; Low Density Lipoprotein Receptor-Related Protein-6; Male; MCF-7 Cells; Mechanistic Target of Rapamycin Complex 1; Multiprotein Complexes; Prostate; Prostatic Neoplasms; Pyrans; Survivin; TOR Serine-Threonine Kinases; Wnt Proteins; Wnt Signaling Pathway

Salinomycin (Sali) has selective toxicity to cancer stem cells (CSCs), a subpopulation of cancer cells that have been recently linked with tumor multidrug resistance (MDR). To utilize its selective toxicity for cancer therapy, we sought to devise a nanoparticle (NP) carrier to deliver Sali to solid tumors through the enhanced permeability and retention effect and, hence, to increase its exposure to CSCs. First, hydrophobic Sali was conjugated to a hydrophilic, immune-tolerant, elastin-like polypeptide (iTEP); the amphiphilic iTEP-Sali conjugates self-assemble into NPs. Next, free Sali was encapsulated into the NPs alone or with two additives, N,N-dimethylhexylamine (DMHA) and α-tocopherol. The coencapsulation significantly improved the loading efficiency and release profile of Sali. The resulting NPs of the coencapsulation, termed as iTEP-Sali NP3s, have an in vitro release half-life of 4.1 h, four times longer than iTEP-Sali NP2s, the NPs that have encapsulated Sali only. Further, the NP3 formulation increases the plasma area under curve and the tumor accumulation of Sali by 10 and 2.4 times, respectively. Lastly, these improved pharmacokinetic and tumor accumulation profiles are consistent with a boost of CSC-elimination effect of Sali in vivo. In NP3-treated 4T1 orthotopic tumors, the mean CSC frequency is 55.62%, a significant reduction from the mean frequencies of untreated tumors, 75.00%, or free Sali-treated tumors, 64.32%. The CSC-elimination effect of the NP3 can further translate to a delay of tumor growth. Given the role of CSCs in driving tumor MDR and recurrence, it could be a promising strategy to add the NP3 to conventional cancer chemotherapies to prevent or reverse the MDR.

Topics: alpha-Tocopherol; Amines; Animals; Breast Neoplasms; Drug Carriers; Drug Delivery Systems; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Elastin; Female; Mice; Mice, Inbred BALB C; Nanomedicine; Nanoparticles; Neoplasm Transplantation; Neoplastic Stem Cells; Pyrans; Time Factors; Tissue Distribution

Treatment resistance significantly inhibits the efficiency of targeted cancer therapies in drug-sensitive genotypes. In the current work, we studied mechanisms for rapidly occurring, adaptive resistance in targeted therapy-sensitive lung, breast, and melanoma cancer cell lines. The results show that in ALK translocated lung cancer lines H3122 and H2228, cells with cancer stem-like cell features characterized by high expression of cancer stem cell markers and/or in vivo tumorigenesis can mediate adaptive resistance to oncogene ablative therapy. When pharmacological ablation of ALK oncogene was accompanied with PI3K inhibitor or salinomycin therapy, cancer stem-like cell features were reversed which was accompanied with decreased colony formation. Furthermore, co-targeting was able to block the formation of acquired resistance in H3122 line. The results suggest that cells with cancer stem-like cell features can mediate adaptive resistance to targeted therapies. Since these cells follow the stochastic model, concurrent therapy with an oncogene ablating agent and a stem-like cell-targeting drug is needed for maximal therapeutic efficiency.

Topics: Aldehyde Dehydrogenase; Anaplastic Lymphoma Kinase; Animals; Antineoplastic Agents; Breast Neoplasms; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Cell Transformation, Neoplastic; Drug Resistance, Neoplasm; Drug Synergism; Female; Humans; Lung Neoplasms; MCF-7 Cells; Melanoma; Mice; Mice, Inbred NOD; Mice, SCID; Molecular Targeted Therapy; Neoplasms; Oxidoreductases Acting on CH-NH Group Donors; Phosphoinositide-3 Kinase Inhibitors; Pyrans; Receptor Protein-Tyrosine Kinases; Xenograft Model Antitumor Assays

Cancer stem cells (CSCs), a small and elusive population of undifferentiated cancer cells within tumors that drive tumor growth and recurrence, are believed to resemble normal stem cells. Although surrogate markers have been identified and compelling CSC theoretical models abound, actual proof for the existence of CSCs can only be had retrospectively. Hence, great store has come to be placed in isolating CSCs from cancers for in-depth analysis. On the other hand, although induced pluripotent stem cells (iPSCs) hold great promise for regenerative medicine, concern exists over the inadvertent co-transplantation of partially or undifferentiated stem cells with tumorigenic capacity. Here we demonstrate that the introduction of defined reprogramming factors (OCT4, SOX2, Klf4 and c-Myc) into MCF-10A nontumorigenic mammary epithelial cells, followed by partial differentiation, transforms the bulk of cells into tumorigenic CD44(+)/CD24(low) cells with CSC properties, termed here as induced CSC-like-10A or iCSCL-10A cells. These reprogrammed cells display a malignant phenotype in culture and form tumors of multiple lineages when injected into immunocompromised mice. Compared with other transformed cell lines, cultured iCSCL-10A cells exhibit increased resistance to the chemotherapeutic compounds, Taxol and Actinomycin D, but higher susceptibility to the CSC-selective agent Salinomycin and the Pin1 inhibitor Juglone. Restored expression of the cyclin-dependent kinase inhibitor p16INK4a abrogated the CSC properties of iCSCL-10A cells, by inducing cellular senescence. This study provides some insight into the potential oncogenicity that may arise via cellular reprogramming, and could represent a valuable in vitro model for studying the phenotypic traits of CSCs per se.

Topics: Animals; Breast Neoplasms; CD24 Antigen; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Cellular Reprogramming; Cellular Senescence; Cyclin-Dependent Kinase Inhibitor p16; Dactinomycin; Drug Resistance, Neoplasm; Epithelial Cells; Female; Gene Expression Regulation, Neoplastic; Humans; Hyaluronan Receptors; Induced Pluripotent Stem Cells; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Mammary Glands, Human; MCF-7 Cells; Mice; Mice, Inbred BALB C; Mice, Nude; Naphthoquinones; Neoplastic Stem Cells; Octamer Transcription Factor-3; Paclitaxel; Proto-Oncogene Proteins c-myc; Pyrans; SOXB1 Transcription Factors; Spheroids, Cellular

Breast cancer tissue contains a small population of cells that have the ability to self-renew; these cells are known as cancer stem-like cells (CSCs). We have recently shown that autophagy is essential for the tumorigenicity of these CSCs. Salinomycin (Sal), a K (+) /H (+) ionophore, has recently been shown to be at least 100 times more effective than paclitaxel in reducing the proportion of breast CSCs. However, its mechanisms of action are still unclear. We show here that Sal blocked both autophagy flux and lysosomal proteolytic activity in both CSCs and non-CSCs derived from breast cancer cells. GFP-LC3 staining combined with fluorescent dextran uptake and LysoTracker-Red staining showed that autophagosome/lysosome fusion was not altered by Sal treatment. Acridine orange staining provided evidence that lysosomes display the characteristics of acidic compartments in Sal-treated cells. However, tandem mCherry-GFP-LC3 assay indicated that the degradation of mCherry-GFP-LC3 is blocked by Sal. Furthermore, the protein degradation activity of lysosomes was inhibited, as demonstrated by the rate of long-lived protein degradation, DQ-BSA assay and measurement of cathepsin activity. Our data indicated that Sal has a relatively greater suppressant effect on autophagic flux in the ALDH (+) population in HMLER cells than in the ALDH (-) population; moreover, this differential effect on autophagic flux correlated with an increase in apoptosis in the ALDH (+) population. ATG7 depletion accelerated the proapoptotic capacity of Sal in the ALDH (+) population. Our findings provide new insights into how the autophagy-lysosomal pathway contributes to the ability of Sal to target CSCs in vitro.

Topics: Acridine Orange; Aldehyde Dehydrogenase; Apoptosis; Autophagy; Autophagy-Related Protein 7; Breast Neoplasms; Cell Proliferation; Down-Regulation; Female; Green Fluorescent Proteins; Humans; Lysosomes; MCF-7 Cells; Membrane Fusion; Microtubule-Associated Proteins; Models, Biological; Neoplastic Stem Cells; Phagosomes; Proteolysis; Pyrans; Recombinant Fusion Proteins; Staining and Labeling; Ubiquitin-Activating Enzymes

The molecular mechanism of Salinomycin's toxicity is not fully understood. Various studies reported that Ca(2+), cytochrome c, and caspase activation play a role in Salinomycin-induced cytotoxicity. Furthermore, Salinomycin may target Wnt/β-catenin signaling pathway to promote differentiation and thus elimination of cancer stem cells. In this study, we show a massive autophagic response to Salinomycin (substantially stronger than to commonly used autophagic inducer Rapamycin) in prostrate-, breast cancer cells, and to lesser degree in human normal dermal fibroblasts. Interestingly, autophagy induced by Salinomycin is a cell protective mechanism in all tested cancer cell lines. Furthermore, Salinomycin induces mitophagy, mitoptosis and increased mitochondrial membrane potential (∆Ψ) in a subpopulation of cells. Salinomycin strongly, and in time-dependent manner decreases cellular ATP level. Contrastingly, human normal dermal fibroblasts treated with Salinomycin show some initial decrease in mitochondrial mass, however they are largely resistant to Salinomycin-triggered ATP-depletion. Our data provide new insight into the molecular mechanism of preferential toxicity of Salinomycin towards cancer cells, and suggest possible clinical application of Salinomycin in combination with autophagy inhibitors (i.e. clinically-used Chloroquine). Furthermore, we discuss preferential Salinomycins toxicity in the context of Warburg effect.

Topics: Adenosine Triphosphate; Animals; Anti-Bacterial Agents; Autophagy; Breast Neoplasms; Cell Line, Tumor; Cytotoxins; Dermis; Female; Fibroblasts; Humans; Male; Membrane Potential, Mitochondrial; Mice; Mice, Knockout; Mitochondria; Mitophagy; Prostatic Neoplasms; Pyrans; Wnt Signaling Pathway

Expression of cyclin E proteolytic cleavage products, low-molecular weight cyclin E (LMW-E), is associated with poor clinical outcome in patients with breast cancer and it enhances tumorigenecity in mouse models. Here we report that LMW-E expression in human mammary epithelial cells induces an epithelial-to-mesenchymal transition phenotype, increases the CD44(hi)/CD24(lo) population, enhances mammosphere formation, and upregulates aldehyde dehydrogenase expression and activity. We also report that breast tumors expressing LMW-E have a higher proportion of CD44(hi)/CD24(lo) tumor cells as compared with tumors expressing only full-length cyclin E. In order to explore how LMW-E enriches cancer stem cells in breast tumors, we conducted a protein microarray analysis that identified the histone acetyltransferase (HAT) Hbo1 as a novel cyclin E/CDK2 substrate. The LMW-E/CDK2 complex phosphorylated Hbo1 at T88 without affecting its HAT activity. When coexpressed with LMW-E/CDK2, wild-type Hbo1 promoted enrichment of cancer stem-like cells (CSC), whereas the T88 Hbo1 mutant reversed the CSC phenotype. Finally, doxorubicin and salinomycin (a CSC-selective cytotoxic agent) synergized to kill cells expressing LMW-E, but not full-length cyclin E. Collectively, our results suggest that the heightened oncogenecity of LMW-E relates to its ability to promote CSC properties, supporting the design of therapeutic strategies to target this unique function.

Topics: Anti-Bacterial Agents; Antibiotics, Antineoplastic; Apoptosis; Blotting, Western; Breast Neoplasms; CD24 Antigen; Cell Proliferation; Cyclin E; Cyclin-Dependent Kinase 2; Doxorubicin; Drug Synergism; Drug Therapy, Combination; Epithelial-Mesenchymal Transition; Female; Flow Cytometry; Fluorescent Antibody Technique; Histone Acetyltransferases; Humans; Hyaluronan Receptors; Immunoprecipitation; Molecular Weight; Neoplastic Stem Cells; Phosphorylation; Protein Array Analysis; Pyrans; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Tumor Cells, Cultured

Salinomycin has found renewed interest as an agent for prevention of cancer recurrence through selectively targeting cancer stem cells. Strategies for generation of improved salinomycin analogs by individual modification of its hydroxyl groups are presented. An evaluation of the dose-response effects of the resulting library on breast cancer cell lines shows that acylation of the C20 hydroxyl can be used to improve IC50 values down to one fifth that of salinomycin.

Topics: Acylation; Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Dose-Response Relationship, Drug; Female; Humans; Inhibitory Concentration 50; Molecular Structure; Pyrans

The use of conventional chemotherapeutic drugs was emerged as challenging for breast cancer therapy, because breast cancer stem cells cannot be destroyed due to their great nature of drug resistance. In this study, a novel nanoparticulate system of Herceptin (HER)-immobilized salinomycin (SAL)-encapsulated poly(lactic-co-glycolic acid) (PLGA) (HER-SAL-PLGA) nanoparticles were constructed and investigated for breast cancer targeting. SAL-encapsulated PLGA nanoparticles were characterized for their particle size, morphology, structural and thermal properties, and drug-encapsulation efficiency. HER-SAL-PLGA nanoparticles were characterized via particle size, surface chemistry, and herceptin-immobilization efficiency. In vitro release studies were performed for both nontargeting and targeting SAL-PLGA nanoparticles, which demonstrated a controlled release of SAL from nanoparticles. Cellular uptake of the HER-SAL-PLGA nanoparticles was assessed by fluorescence and optical microscopy and flow cytometry, which showed that the HER-SAL-PLGA nanoparticles were successfully uptaken by MCF7 cells. In conclusion, this novel drug-delivery system, HER-SAL-PLGA, was suggested as a promising targeting system for breast cancer therapy.

Topics: Anti-Bacterial Agents; Antibodies, Monoclonal, Humanized; Breast Neoplasms; Cell Line, Tumor; Delayed-Action Preparations; Drug Delivery Systems; Female; Humans; Lactic Acid; Nanoparticles; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Pyrans; Receptor, ErbB-2; Trastuzumab

Nutrient deprivation and reactive oxygen species (ROS) play an important role in breast cancer mitochondrial adaptation. Adaptations to these conditions allow cells to survive in the stressful microenvironment of the tumor bed. This study is directed at defining the consequences of High Nitric Oxide (HNO) exposure to mitochondria in human breast cancer cells. The breast cancer cell line BT-20 (parent) was adapted to HNO as previously reported, resulting in the BT-20-HNO cell line. Both cell lines were analyzed by a variety of methods including MTT, LDH leakage assay, DNA sequencing, and Western blot analysis. The LDH assay and the gene chip data showed that BT-20-HNO was more prone to use the glycolytic pathway than the parent cell line. The BT-20-HNO cells were also more resistant to the apoptotic inducing agent salinomycin, which suggests that p53 may be mutated in these cells. Polymerase chain reaction (PCR) followed by DNA sequencing of the p53 gene showed that it was, in fact, mutated at the DNA-binding site (L194F). Western blot analysis showed that p53 was significantly upregulated in these cells. These results suggest that free radicals, such as nitric oxide (NO), pressure human breast tumor cells to acquire an aggressive phenotype and resistance to apoptosis. These data collectively provide a mechanism by which the dysregulation of ROS in the mitochondria of breast cancer cells can result in DNA damage.

Topics: Adaptation, Physiological; Anaerobiosis; Anti-Bacterial Agents; Apoptosis; Binding Sites; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Female; Gene Dosage; Gene Expression Regulation, Neoplastic; Glycolysis; Humans; Mitochondria; Nitric Oxide; Phenotype; Pyrans; Reactive Oxygen Species; Sequence Analysis, DNA; Tumor Suppressor Protein p53

In the present study, we investigated the effect of Salinomycin on the survival of three human breast cancer cell lines MCF-7, T47D and MDA-MB-231 grown in adherent culture conditions.. Cell viability was measured by Cell Titer-Glo and Trypan blue exclusion assay. Apoptosis was determined by caspase 3/7 activation, PARP cleavage and Annexin V staining. Cell cycle distribution was assessed by propidium iodide flow cytometry. Senescence was confirmed by measuring the senescence-associated β-galactosidase activity. Changes in protein expression and histone hyperacetylation was determined by western blot and confirmed by immunofluorescence assay.. Salinomycin was able to inhibit the growth of the three cell lines in time- and concentration-dependent manners. We showed that depending on the concentrations used, Salinomycin elicits different effects on the MDA-MB-231 cells. High concentrations of Salinomycin induced a G2 arrest, downregulation of survivin and triggered apoptosis. Interestingly, treatment with low concentrations of Salinomycin induced a transient G1 arrest at earlier time point and G2 arrest at later point and senescence associated with enlarged cellmorphology, upregulation of p21 protein, increase in histone H3 and H4 hyperacetylation and expression of SA-β-Gal activity. Furthermore, we found that Salinomycin was able to potentiate the killing of the MCF-7 and MDA-MB-231 cells, by the chemotherapeutic agents, 4-Hydroxytamoxifen and frondo side A, respectively.. Our data are the first to link senescence and histone modifications to Salinomycin.. This study provides a new insight to better understand the mechanism of action of Salinomycin, at least in breast cancer cells.

Topics: Acetylation; Anti-Bacterial Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cellular Senescence; Cyclin-Dependent Kinase Inhibitor p21; Cytoskeletal Proteins; Female; G2 Phase; Glycosides; Histones; Humans; Inhibitor of Apoptosis Proteins; Pyrans; Survivin; Triterpenes

Tumor stem cells have emerged as the new targets for anti-cancer therapy, besides tumor cells themselves. To eradicate both breast cancer cells and breast cancer stem cells which can not be eliminated by the conventional chemotherapy, octreotide (Oct)-modified paclitaxel (PTX)-loaded PEG-b-PCL polymeric micelles (Oct-M-PTX) and salinomycin (SAL)-loaded PEG-b-PCL polymeric micelles (M-SAL) were developed and investigated in combination. In this study, Oct that targets somatostatin receptors (SSTR) overexpressed in tumors including breast cancer, was coupled to the PEG end of PEG-b-PCL, and all the micelles were prepared using thin film hydration method. Results showed that the particle size of all the micelles was approximately 25-30 nm, and the encapsulation efficiency was >90%. Quantitative and qualitative analysis demonstrated that Oct facilitates the uptake of micelles in SSTR overexpressed breast cancer MCF-7 cells while free Oct inhibited cellular uptake of Oct-modified micelles, revealing the mechanism of receptor-mediated endocytosis. Breast cancer stem cells (side population cells, SP cells) were sorted from MCF-7 cells and identified with the CD44+/CD24- phenotype. M-SAL was capable of decreasing the proportion of SP cells, and its suppression was more potent in SP cells than that in cancer cells. As compared to PTX-loaded micelles (M-PTX), the inhibition of Oct-M-PTX against MCF-7 cells was stronger while such effect significantly increased when applying Oct-M-PTX in combination with M-SAL. In the MCF-7 xenografts, the combination therapy with Oct-M-PTX plus M-SAL produced the strongest antitumor efficacy, in accord with the combination treatment in vitro. Compared with free SAL, M-SAL was found to be more effective in suppressing breast cancer stem cells in vivo. Thus, this combination therapy may provide a strategy to improve treatment of breast cancers for eradication of breast cancer cells together with breast cancer stem cells.

Topics: Animals; Antineoplastic Agents, Hormonal; Antineoplastic Agents, Phytogenic; Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Cell Line, Tumor; Female; Flow Cytometry; Gene Expression Regulation, Neoplastic; Humans; Lactones; Mice; Mice, Inbred BALB C; Mice, Nude; Micelles; Microscopy, Confocal; Neoplastic Stem Cells; Octreotide; Paclitaxel; Polyethylene Glycols; Polymers; Pyrans

A major obstacle in the successful treatment of cancer is the occurrence of chemoresistance. Cancer cells surviving chemotherapy and giving rise to a recurrence of the tumor are termed cancer stem cells and can be identified by elevated levels of certain stem cell markers. Eradication of this cell population is a priority objective in cancer therapy. Here, we report elevated levels of stem cell markers in MCF-7 mammospheres. Likewise, an upregulation of HER2 and its differential expression within individual cells of mammospheres was observed. Sorting for HER2(high) and HER2(low) cells revealed an upregulation of stem cell markers NANOG, OCT4 and SOX2 in the HER2(low) cell fraction. Accordingly, HER2(low) cells also showed reduced proliferation, ductal-like outgrowths and an increased number of colonies in matrigel. Xenografts from subcutaneously injected HER2(low) sorted cells exihibited earlier onset but slower growth of tumors and an increase in stem cell markers compared to tumors developed from the HER2(high) fraction. Treatment of mammospheres with salinomycin reduced the expression of SOX2 indicating a selective targeting of cancer stem cells. Trastuzumab however, did not reduce the expression of SOX2 in mammospheres. Furthermore, a combinatorial treatment of mammospheres with trastuzumab and salinomycin was superior to single treatment with each drug. Thus, targeting HER2 expressing tumors with anti-HER2 therapies will not necessarily eliminate cancer stem cells and may lead to a more aggressive cancer cell phenotype. Our study demonstrates efficient killing of both HER2 positive cells and cancer stem cells, hence opening a possibility for a new combinatorial treatment strategy.

Topics: Antibodies, Monoclonal, Humanized; Antineoplastic Combined Chemotherapy Protocols; Base Sequence; Breast Neoplasms; Cell Line, Tumor; DNA Primers; Female; Humans; Neoplastic Stem Cells; Pyrans; Real-Time Polymerase Chain Reaction; Receptor, ErbB-2; Trastuzumab

Salinomycin is a polyether ionophore antibiotic that has recently been shown to induce cell death in human cancer cells displaying multiple mechanisms of drug resistance. The underlying mechanisms leading to cell death after salinomycin treatment have not been well characterized. We therefore investigated the role of salinomycin in caspase dependent and independent cell death in colon cancer (SW480, SW620, RKO) and breast cancer cell lines (MCF-7, T47D, MDA-MB-453).. We detected features of apoptosis in all cell lines tested, but the executor caspases 3 and 7 were only strongly activated in RKO and MDA-MB-453 cells. MCF-7 and SW620 cells instead presented features of autophagy such as cytoplasmic vacuolization and LC3 processing. Caspase proficient cell lines activated autophagy at lower salinomycin concentrations and before the onset of caspase activation. Salinomycin also led to the formation of reactive oxygen species (ROS) eliciting JNK activation and induction of the transcription factor JUN. Salinomycin mediated cell death could be partially inhibited by the free radical scavenger N-acetyl-cysteine, implicating ROS formation in the mechanism of salinomycin toxicity.. Our data indicate that, in addition to its previously reported induction of caspase dependent apoptosis, the initiation of autophagy is an important and early effect of salinomycin in tumor cells.

Topics: Antineoplastic Agents; Apoptosis; Autophagy; Breast Neoplasms; Caspases; Cell Line, Tumor; Cell Survival; Colonic Neoplasms; Female; Humans; MCF-7 Cells; Pyrans; Reactive Oxygen Species; Signal Transduction; Tumor Stem Cell Assay

Salinomycin (Sal) has recently been shown to inhibit various cancer stem cells. Here, we investigated whether Sal could sensitize cancer cells to the effects of doxorubicin (DOX) or etoposide (ETO).. Using the Comet assay, immunocytochemistry and Western blot analysis, we assessed the ability of Sal to increase DNA breakage. We performed a cell proliferation assay to determine cell viability, cellular detachment, increased pre-G1 region, Annexin V staining and TUNEL assay to measure the ability of Sal to increase apoptosis.. Sal increased DNA breakage and phosphorylated levels of p53 and H2AX. Sal also induced the formation of DNA foci with pH2AX and 53BP1. Furthermore, Sal increased the sensitivity of cancer cells to the apoptotic effects of DOX or ETO. We found that pH2AX, pBRCA1, p53BP1 and pChk1 levels were greatly increased after co-treatment of Sal with DOX or ETO. The level of anti-apoptotic p21 protein was increased by DOX or ETO but decreased by Sal, which increased proteasome activity.. This is the first study to report that Sal increases DNA damage, and this effect plays an important role in the increased apoptosis caused by Sal. Overall, we demonstrated that the ability of Sal to sensitize cancer cells to the effects of DOX or ETO is associated with an increase in DNA damage and a decrease in anti-apoptotic protein p21 levels. These results may contribute to the development of Sal-based chemotherapy for cancer patients receiving DOX or ETO treatment.

Topics: Annexin A5; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Comet Assay; Cyclin-Dependent Kinase Inhibitor p21; DNA Damage; Doxorubicin; Drug Resistance, Neoplasm; Etoposide; Female; Hep G2 Cells; Humans; In Situ Nick-End Labeling; Proteasome Endopeptidase Complex; Pyrans; Sarcoma; Uterine Neoplasms

Curative eradication of all cells within carcinomas is seldom achievable with chemotherapy alone. This limitation may be partially attributable to tumor cell subpopulations with intrinsic resistance to current drugs. Within squamous cell carcinoma (SCC) cell lines, we previously characterized a subpopulation of mesenchymal-like cells displaying phenotypic plasticity and increased resistance to both cytotoxic and targeted agents. These mesenchymal-like (Ecad-lo) cells are separable from epithelial-like (Ecad-hi) cells based on loss of surface E-cadherin and expression of vimentin. Despite their long-term plasticity, both Ecad-lo and Ecad-hi subsets in short-term culture maintained nearly uniform phenotypes after purification. This stability allowed testing of segregated subpopulations for relative sensitivity to the cytotoxic agent cisplatin in comparison to salinomycin, a compound with reported activity against CD44(+)CD24(-) stem-like cells in breast carcinomas. Salinomycin showed comparable efficacy against both Ecad-hi and Ecad-lo cells in contrast to cisplatin, which selectively depleted Ecad-hi cells. An in vivo correlate of these mesenchymal-like Ecad-lo cells was identified by immunohistochemical detection of vimentin-positive malignant subsets across a part of direct tumor xenografts (DTXs) of advanced stage SCC patient samples. Cisplatin treatment of mice with established DTXs caused enrichment of vimentin-positive malignant cells in residual tumors, but salinomycin depleted the same subpopulation. These results demonstrate that mesenchymal-like SCC cells, which resist current chemotherapies, respond to a treatment strategy developed against a stem-like subset in breast carcinoma. Further, they provide evidence of mesenchymal-like subsets being well-represented across advanced stage SCCs, suggesting that intrinsic drug resistance in this subpopulation has high clinical relevance.

Topics: Animals; Breast Neoplasms; Carcinoma, Squamous Cell; Cell Culture Techniques; Cell Line, Tumor; Cisplatin; Drug Resistance, Neoplasm; Humans; Mesenchymal Stem Cells; Mice; Pyrans; Transplantation, Heterologous