n-(n-(3-5-difluorophenacetyl)alanyl)phenylglycine-tert-butyl-ester and Breast-Neoplasms

Adult stem cells are found in numerous tissues of the body and play a role in tissue development, replacement and repair. Evidence shows that breast stem cells are multipotent and can self renew, which are key characteristics of stem cells, and a single cell enriched with cell surface markers has the ability to grow a fully functional mammary gland in vivo. Many groups have extrapolated the cancer stem cell hypothesis from the haematopoietic system to solid cancers, where using in vitro culture techniques and in vivo transplant models have established evidence of cancer stem cells in colon, pancreas, prostate, brain and breast cancers. In the report we describe the evidence for breast cancer stem cells; studies consistently show that stem cell like and breast cancer initiating populations can be enriched using cell surface makers CD44+/CD24- and have upregulated genes which include Notch. Notch signalling has been highlighted as a pathway involved in the development of the breast and is frequently dysregulated in invasive breast cancer. We have investigated the role of Notch in a pre-invasive breast lesion, ductal carcinoma in situ (DCIS), and have found that aberrant activation of Notch signalling is an early event in breast cancer. High expression of Notch 1 intracellular domain (NICD) in DCIS also predicted a reduced time to recurrence 5 years after surgery. Using a non-adherent sphere culture technique we have grown DCIS mammospheres from primary DCIS tissue, where self-renewal capacity, measured by the number of mammosphere initiating cells, were increased from normal breast tissue. A gamma-secretase inhibitor, DAPT, which inhibits all four Notch receptors and a Notch 4 neutralising antibody were shown to reduce DCIS mammosphere formation, indicating that Notch signalling and other stem cell self-renewal pathways may represent novel therapeutic targets to prevent recurrence of pre-invasive and invasive breast cancer.

Topics: Amyloid Precursor Protein Secretases; Animals; Biomarkers, Tumor; Breast Neoplasms; Carcinoma, Intraductal, Noninfiltrating; CD24 Antigen; Dipeptides; Enzyme Inhibitors; Female; Gene Expression Regulation, Neoplastic; Humans; Hyaluronan Receptors; Mammary Glands, Animal; Mammary Glands, Human; Mammary Neoplasms, Experimental; Multipotent Stem Cells; Neoplasm Recurrence, Local; Neoplasm Transplantation; Neoplastic Stem Cells; Receptor, Notch1; Spheroids, Cellular; Up-Regulation

RY10-4, a novel protoapigenone analog, shows potent cytotoxicity against human breast cancer cells. However, breast cancer cell lines overexpressing human epidermal growth factor receptor 2 (HER2), SKBR3 and BT474, showed less sensitivity to RY10-4 when compared to breast cancer cells lines expressing lower levels of HER2, such as MDA-MB-231 and MCF-7 cells. This was associated with aberrant hyperactivity in Notch signaling in cells treated with RY10-4, since treatment with RY10-4 causes an increase in Notch activity by 2-to3.5-fold in SKBR3 and BT474 cell lines. The increase in activity was abrogated with a γ-secretase inhibitor, DAPT, or with Notch1 small-interfering RNA (si-Notch1). Cell proliferation was inhibited more effectively by RY10-4 plus DAPT or si-Notch1 than either agent alone. RY10-4 plus DAPT increases apoptosis in both HER2-overexpressing cell lines by two-fold compared to RY10-4 alone, while DAPT alone has no significant effects on apoptosis. In addition, we previously found RY10-4 could inhibit tumor growth through the PI3K/AKT pathway. Here we report that the combination of RY10-4 and DAPT exhibit additive suppression on AKT phosphorylation, contributing to the anti-cancer effects. In an animal model, this combination therapy inhibits the growth of SKBR3 tumor xenografts in nude mice to a greater extent than treatment with either reagent alone. These results indicate that the aberrant activation of Notch signaling impedes the inhibitory effect of RY10-4 on HER2-amplified cell proliferation. Furthermore, these adverse effects can be prevented by treatment combining RY10-4 with a Notch pathway inhibitor.

Topics: Amyloid Precursor Protein Secretases; Animals; Apoptosis; Blotting, Western; Breast Neoplasms; Cell Proliferation; Dipeptides; Drug Therapy, Combination; Female; Gene Amplification; Humans; Immunoenzyme Techniques; Mice; Mice, Inbred BALB C; Mice, Nude; Pyrones; Real-Time Polymerase Chain Reaction; Receptor, ErbB-2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Voltage-gated sodium channel (VGSC) activity enhances cell behaviors related to metastasis, such as motility, invasion, and oncogene expression. Neonatal alternative splice form of Nav1.5 isoform is expressed in metastatic breast cancers. Furthermore, aberrant Notch signaling pathway can induce oncogenesis and may promote the progression of breast cancers. In this study, we aimed to analyze the effect of the nNav1.5 inhibitor phenytoin and Notch signal inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine-t-butyl ester (DAPT) on triple negative breast cancer cell line (MDA-MB-231) via inhibition of nNav1.5 VGSC activity and Notch signaling, respectively. In order to determine the individual and combined effects of these inhibitors, the 4-[3-(4-iyodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) test, wound healing assay, and zymography were performed to detect the proliferation, lateral motility, and matrix metalloproteinase-9 (MMP9) activity, respectively. The expressions of nNav1.5, Notch4, MMP9, and tissue inhibitor of metalloproteinases-1 (TIMP1) were also detected by quantitative real-time reverse transcriptase-polymerase chain reaction. DAPT caused an antiproliferative effect when the doses were higher than 10 µM, whereas phenytoin showed no inhibitory action either alone or in combination with DAPT on the MDA-MB-231 cells. Furthermore, it was found that the lateral motility was inhibited by both inhibitors; however, this inhibitory effect was partially rescued when they were used in combination. Meanwhile, the results showed that the MMP9 activity and the ratio of MMP9 mRNA to TIMP1 mRNA were only decreased by DAPT. Thus, we conclude that the combined effect of DAPT and phenytoin is not as beneficial as using DAPT alone on MDA-MB-231 breast cancer cells.

Topics: Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Dipeptides; Drug Interactions; Female; Humans; In Vitro Techniques; Matrix Metalloproteinase 9; NAV1.5 Voltage-Gated Sodium Channel; Phenytoin; Proto-Oncogene Proteins; Receptor, Notch4; Receptors, Notch; RNA, Messenger; Tissue Inhibitor of Metalloproteinase-1

We have previously reported that the major isoform of Flt1/VEGFR-1 expressed in MDA-MB-231 breast cancer cells was a truncated intracellular isoform transcribed from intron 21 (i21 Flt1). This isoform upregulated the active form of Src and increased breast cancer cell invasiveness. Since expression of the transmembrane and soluble Flt1 isoforms of HUVEC is activated by Notch signaling, we wondered whether the expression of the intracellular isoform i21 Flt1 was also dependent on Notch activation. We report here that the expression of i21 Flt1 in HUVEC and MDA-MB-231 cells is downregulated by the γ-secretase inhibitor DAPT. In addition, treatment of MDA-MB-231 cells with siRNA specific for Notch-1 and Notch-3 downregulates the expression of i21 Flt1. In agreement with these findings, HUVEC and MDA-MB-231 breast cancer cells, cultured on dishes coated with recombinant human Dll4 extracellular domain, express higher levels of i21 Flt1. In cancer cells, Flt1 is a target of the micro RNA family miR-200. In MDA-MB-231 breast cancer cells, the truncated intracellular isoform i21 Flt1 is also negatively regulated by miR-200c. Retinoic acid interferes i21 Flt1 expression by downregulating Notch-3 and upregulating miR-200 expression. Treatment of MDA-MB-231 breast cancer cells with both a γ-secretase inhibitor and retinoic acid suppresses the expression of i21 Flt1, providing a new mechanism to explain the effectiveness of this therapeutic approach.

Topics: Adaptor Proteins, Signal Transducing; Amyloid Precursor Protein Secretases; Breast Neoplasms; Calcium-Binding Proteins; Cell Line, Tumor; Dipeptides; Down-Regulation; Female; Gene Expression Regulation, Neoplastic; Human Umbilical Vein Endothelial Cells; Humans; Intercellular Signaling Peptides and Proteins; MicroRNAs; Protein Isoforms; Receptor, Notch1; Receptor, Notch3; Receptors, Notch; Tretinoin; Up-Regulation; Vascular Endothelial Growth Factor Receptor-1

Paclitaxel (PAC) is the first-line chemotherapy drug for most breast cancer patients, but clinical studies showed that some breast cancer patients were insensitive to PAC, which led to chemotherapy failure. It was reported that Notch1 signaling participated in drug resistance of breast cancer. Here, we show whether Notch1 expression is related to PAC sensitivity of breast cancer.. We employed Notch1 siRNA and Notch1 inhibitor, N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester (DAPT), to down regulate Notch1 expression in human breast cancer cells MDA-MB-231, and detected the inhibition effect by Western blotting and reverse trans cription-polymerase chain reaction, respectively. After 24 hours exposure to different concentration of PAC (0, 1, 5, 10, 15, 20, and 25 µg/ml), the viability of the control group and experimental group cells was tested by MTT. We also examined the expression of Notch1 in PAC sensitive and nonsensitive breast cancer patients, respectively by immunohistochemistry (IHC). The PAC sensitivity of breast cancer patients were identified by collagen gel droplet embedded culture-drug sensitivity test (CD-DST).. Down regulation of Notch1 expression by Notch1siRNA interference or Notch1 inhibitor increased the PAC sensitivity in MDA-MB-231 cells (P < 0.05). Also, the expression of Notch1 in PAC sensitive patients was much lower than that of PAC non-sensitive patients (P < 0.01).. Notch1 expression has an effect on PAC sensitivity in breast cancer patients, and the inhibition of Notch1 increases paclitaxel sensitivity to human breast cancer.

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Dipeptides; Humans; Immunohistochemistry; Paclitaxel; Receptor, Notch1; Reverse Transcriptase Polymerase Chain Reaction

Breast cancer is the most common tumor among women with inherited mutations in the p53 gene (Li-Fraumeni syndrome). The tumors represent the basal-like subtype, which has been suggested to originate from mammary stem/progenitor cells. In mouse mammary epithelium, mammosphere-forming potential was increased with decreased dosage of the gene encoding the p53 tumor suppressor protein (Trp53). Limiting dilution transplantation also showed a 3.3-fold increase in the frequency of long-term regenerative mammary stem cells in Trp53-/- mice. The repression of mammospheres by p53 was apparent despite the absence of apoptotic responses to radiation indicating a dissociation of these two activities of p53. The effects of p53 on progenitor cells were also observed in TM40A cells using both mammosphere-forming assays and the DsRed-let7c-sensor. The frequency of long-term label-retaining epithelial cells was decreased in Trp53-/- mammary glands indicating that asymmetric segregation of DNA is diminished and contributes to the expansion of the mammary stem cells. Treatment with an inhibitor of γ-secretase (N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester) reduced the number of Trp53-/- mammospheres to the level found in Trp53+/+ cells. These results demonstrate that basal levels of p53 restrict mammary stem/progenitor cells through Notch and that the Notch pathway is a therapeutic target to prevent expansion of this vulnerable pool of cells.

Topics: Amyloid Precursor Protein Secretases; Animals; Apoptosis; Breast Neoplasms; Cells, Cultured; Dipeptides; Epithelial Cells; Female; Genes, p53; Humans; Li-Fraumeni Syndrome; Mammary Glands, Human; Mice; Mice, Inbred BALB C; Receptors, Notch; Stem Cell Transplantation; Stem Cells

The Notch pathway displays several functions related to tumor progression. Breast carcinomas commonly express Notch1, Notch2, Notch3 and Notch4 at variable levels and these are mainly involved in differentiation, proliferation and survival. Notch1 can also induce the invasion of breast cancer cells. However, the precise role and mechanism of Notch1 in tumor invasion remains unclear. In this report, we used small interference RNA technology to knock down the expression of Notch1, resulting in reduced migration and invasion of breast cancer cells. Meanwhile, F-actin polymerization, which is essential for cellular generation of the forces needed for motility, was also impaired in Notch1 knockdown cells. We further investigated the expression of extracellular matrix metalloproteinase inducer (EMMPRIN), matrix metalloproteases-2 (MMP-2) and MMP-9, and found that the expression of functional EMMPRIN and MMP-2 was significantly decreased in Notch1 knockdown cells, while the expression of MMP-9 was constant. Additionally, the silencing of Notch1 expression likewise impaired cell-to-matrix and cell-to-cell adhesion. Western blotting results showed that reduction of Notch1 levels impacted the phosphorylation of PAK, phosphorylation of Akt, phosphorylation of FAK, the phosphorylation of integrin β1, ICAM-1 and β-catenin. Collectively, these findings suggest that targeting Notch1 has important therapeutic value in breast cancer.

Topics: Breast Neoplasms; Cell Adhesion; Cell Growth Processes; Cell Line, Tumor; Cell Movement; Dipeptides; Female; Humans; Neoplasm Invasiveness; Receptor, Notch1

Basal-like breast cancers (BLBC) are highly aggressive, yet selective therapies targeting the specific oncoproteins driving these tumors have not been developed. These cancers frequently express epidermal growth factor receptor (EGFR), with resistance to its inhibition being well documented, albeit poorly understood. Notch pathway activation is also common in this breast cancer subtype and can be suppressed by gamma-secretase inhibitors, which effectively block receptor cleavage and activation. Herein, we show that although inhibition of either EGFR or Notch signaling alone is insufficient to suppress basal-like breast tumor cell survival and proliferation, simultaneous inhibition uncovers a synthetic lethal relationship between these two oncogenic pathways. This lethality is due in part to significant decreases in AKT activation caused by combined EGFR and Notch inhibition. Expression of the activated form of Notch1 restores AKT activity and enables cells to overcome cell death after dual-pathway blockade. Combined pathway inhibition is also dramatically more effective at suppressing tumor growth in mice than blocking EGFR or Notch signaling alone. Thus, we show that Notch pathway activation contributes to resistance to EGFR inhibition, and provide a novel treatment strategy for BLBCs.

Topics: Amyloid Precursor Protein Secretases; Animals; Antineoplastic Agents; Benzodiazepinones; Breast Neoplasms; Cell Growth Processes; Cell Line, Tumor; Cell Survival; Dipeptides; Enzyme Activation; ErbB Receptors; Female; Gefitinib; Humans; Mice; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Quinazolines; Receptors, Notch; Signal Transduction; Xenograft Model Antitumor Assays

Notch is a family of transmembrane protein receptors whose activation requires proteolytic cleavage by gamma-secretase. Since aberrant Notch signaling can induce mammary carcinomas in transgenic mice and high expression levels of Notch receptors and ligands correlates with overall poor clinical outcomes, inhibiting gamma-secretase with small molecules may be a promising approach for breast cancer treatment. Consistent with this hypothesis, two recent papers reported that gamma-secretase inhibitor I (GSI I), Z-LLNle-CHO, is toxic to breast cancer cells both in vitro and in vivo. In this study, we compared the activity and cytotoxicity of Z-LLNle-CHO to that of two highly specific GSIs, DAPT and L-685,458 and three structurally unrelated proteasome inhibitors, MG132, lactacystin, and bortezomib in order to study the mechanism underlying the cytotoxicity of Z-LLNle-CHO in breast cancer cells.. Three estrogen receptor (ER) positive cell lines, MCF-7, BT474, and T47D, and three ER negative cell lines, SKBR3, MDA-MB-231, and MDA-MB-468, were used in this study. Both SKBR3 and BT474 cells also overexpress HER2/neu. Cytotoxicity was measured by using an MTS cell viability/proliferation assay. Inhibition of gamma-secretase activity was measured by both immunoblotting and immunofluorescent microscopy in order to detect active Notch1 intracellular domain. Proteasome inhibition was determined by using a cell-based proteasome activity assay kit, by immunoblotting to detect accumulation of polyubiquitylated protein, and by immunofluorescent microscopy to detect redistribution of cellular ubiquitin.. We found that blocking gamma-secretase activity by DAPT and L-685,458 had no effect on the survival and proliferation of a panel of six breast cancer cell lines while Z-LLNle-CHO could cause cell death even at concentrations that inhibited gamma-secretase activity less efficiently. Furthermore, we observed that Z-LLNle-CHO could inhibit proteasome activity and the relative cellular sensitivity of these six breast cancer cell lines to Z-LLNle-CHO was the same as observed for three proteasome inhibitors. Finally, we found that the cell killing effect of Z-LLNle-CHO could be reversed by a chemical that restored the proteasome activity.. We conclude that the cytotoxicity of Z-LLNle-CHO in breast cancer cells is mediated by proteasome inhibition, not by gamma-secretase inhibition.

Topics: Adenocarcinoma; Amyloid Precursor Protein Secretases; Breast Neoplasms; Carbamates; Cell Line, Tumor; Dipeptides; Drug Delivery Systems; Estrogens; Female; Humans; Neoplasm Proteins; Neoplasms, Hormone-Dependent; Oligopeptides; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Receptor, Notch1; Receptors, Estrogen