thiourea and Triple-Negative-Breast-Neoplasms

Unlike other breast cancer subtypes that may be treated with a variety of hormonal or targeted therapies, there is a need to identify new, effective targets for triple-negative breast cancer (TNBC). It has recently been recognized that membrane potential is depolarized in breast cancer cells. The primary objective of the study is to explore whether hyperpolarization induced by opening potassium channels may provide a new strategy for treatment of TNBC.. Breast cancer datasets in cBioPortal for cancer genomics was used to search for ion channel gene expression. Immunoblots and immunohistochemistry were used for protein expression in culture cells and in the patient tissues. Electrophysiological patch clamp techniques were used to study properties of BK channels in culture cells. Flow cytometry and fluorescence microscope were used for cell viability and cell cycle studies. Ultrasound imaging was used to study xenograft in female NSG mice.. In large datasets of breast cancer patients, we identified a gene, KCNMA1 (encoding for a voltage- and calcium-dependent large-conductance potassium channel, called BK channel), overexpressed in triple-negative breast cancer patients. Although overexpressed, 99% of channels are closed in TNBC cells. Opening BK channels hyperpolarized membrane potential, which induced cell cycle arrest in G2 phase and apoptosis via caspase-3 activation. In a TNBC cell induced xenograft model, treatment with a BK channel opener significantly slowed tumor growth without cardiac toxicity.. Our results support the idea that hyperpolarization induced by opening BK channel in TNBC cells can become a new strategy for development of a targeted therapy in TNBC.

Topics: Animals; Apoptosis; Breast; Caspase 3; Cell Line, Tumor; Datasets as Topic; Female; G2 Phase Cell Cycle Checkpoints; Humans; Intravital Microscopy; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Membrane Potentials; Mice; Oxadiazoles; Patch-Clamp Techniques; Tetrazoles; Thiourea; Triple Negative Breast Neoplasms

Topics: Antineoplastic Agents; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Drug Design; Drug Screening Assays, Antitumor; Humans; Models, Molecular; Molecular Structure; p21-Activated Kinases; Protein Kinase Inhibitors; Structure-Activity Relationship; Thiourea; Triple Negative Breast Neoplasms

Mutation of the key tumour suppressor p53 defines a transition in the progression towards aggressive and metastatic breast cancer (BC) with the poorest outcome. Specifically, the p53 mutation frequency exceeds 50% in triple-negative BC. Key regulators of mutant p53 that facilitate its oncogenic functions are potential therapeutic targets. We report here that the MDM4 protein is frequently abundant in the context of mutant p53 in basal-like BC samples. Importantly, we show that MDM4 plays a critical role in the proliferation of these BC cells. We demonstrate that conditional knockdown (KD) of MDM4 provokes growth inhibition across a range of BC subtypes with mutant p53, including luminal, Her2

Topics: Anthracenes; Carcinogenesis; Cell Cycle Proteins; Cell Line; Cell Proliferation; Female; Gene Knockdown Techniques; Humans; Mutation; Nuclear Proteins; Proto-Oncogene Proteins; Thiourea; Triple Negative Breast Neoplasms; Tumor Suppressor Protein p53

Blocking dephosphorylation of eukaryotic translation initiation factor 2α (eIF2α) is reported to alter proliferation and differentiation of various cells. Using salubrinal and guanabenz as an inhibitory agent of dephosphorylation of eIF2α, we addressed a question whether an elevated level of phosphorylated eIF2α attenuates malignant phenotypes of triple negative breast cancer cells (TNBCs) that lack estrogen receptor, progesterone receptor and human epidermal growth factor receptor-2. We determined effects of salubrinal and guanabenz on in vitro phenotype of 4T1 mammary tumor cells and MDA-MB-231 human breast cancer cells and evaluated their effects on in vivo tumor growth using BALB/c mice injected with 4T1 cells. The results revealed that these agents block the proliferation and survival of 4T1 and MDA-MB-231 cells, as well as their invasion and motility. Silencing eIF2α revealed that eIF2α is involved in the reduction in invasion and motility. Furthermore, salubrinal-driven inactivation of Rac1 was suppressed in the cells treated with eIF2α siRNA, and treatment with Rac1 siRNA reduced cell invasion and motility. In vivo assay revealed that subcutaneous administration of salubrinal reduced the volume and weight of tumors induced by 4T1 cells. Collectively, the results indicate that these agents can attenuate malignant phenotype and tumor growth of breast cancer cells through the eIF2α-mediated Rac1 pathway. Since salubrinal and guanabenz are known to inhibit bone resorption, this study provides a potential use of eIF2α-mediated Rac1 regulation in suppressing the growth and metastasis of breast cancer.

Topics: Animals; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cinnamates; Dose-Response Relationship, Drug; Eukaryotic Initiation Factor-2; Female; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Guanabenz; Humans; Mammary Neoplasms, Experimental; Mice; Mice, Inbred BALB C; rac1 GTP-Binding Protein; Signal Transduction; Thiourea; Triple Negative Breast Neoplasms; Xenograft Model Antitumor Assays