Molecular biological investigation of telomerase inhibitor bibr1532 agent effect in breast cancer and breast cancer stem cells

It is emphasized that the cancer stem cells (CSC) forming the subpopulation of tumor cells are responsible for tumor growth, metastasis, cancer drug resistance and telomerase enzyme may be effective in the treatment of CSC. Inadequate response to conventional therapy in breast cancer leads researchers to find new treatment methods and literature surveys which support cancer stem cell studies. A selective anti-cancer agent BIBR1532 inhibits the telomerase enzyme. Many of the general chemotherapeutic drugs used in clinical trials have harmful effects but the advantage of telomerase-based inhibitors are less toxic to normal tissues. In the presence of this inhibitor, it is planned to minimize the therapeutic drug damage. It is known that PI3K/Akt/mTOR pathway is common in breast cancer and important in regenerating cancer stem cell in anti-cancer drug resistance. It is emphasized that the interaction between the mTOR and hTERT pathways is essential for the survival of cancer cells. In our study, we applied the BIBR1532 inhibitor on MCF-7, breast cancer stem cell (BCSC) and control normal breast epithelial cell MCF10A. Cytotoxic, apoptotic effects in cells were evaluated and cell cycle analysis was performed. In addition, the 84 gene expression changes in the mTOR pathway and hTERT gene expression changes were analyzed by RT-qPCR and the changes in HIF1α/PKM2 proteins were examined by ELISA (Enzyme-Linked ImmunoSorbent Assay). The IC50 doses for the 48th hour of the BIBR1532 agent were detected 34,59 μM in the MCF-7 cell line, 29,91 μM in the BCSC line and 29,07 μM in the MCF10A cell line. It has been observed that this agent induces apoptosis in the BCSC and MCF-7 cell lines but no induction of apoptosis has been observed in the MCF10A control cell. According to the results of cell cycle analysis, G2/M phase accumulation was observed in BCSC and MCF-7 cell lines. It has also been shown that the agent BIBR1532 suppresses telomerase activity in BCSC and MCF-7 cell lines. The cytotoxic activity of BIBR1532 was first investigated in BCSC and MCF10A cell lines and BIBR1532 agent induced apoptosis effectively on BCSC and MCF-7 cell lines. It has been observed that the BIBR1532 agent did not cause a significant apoptotic effect on the MCF10A cell line. The effect of BIBR1532 on the mTOR signaling pathway has been investigated for the first time in this study. It is thought that the telomerase inhibitor may bring a new approach to treatment, since the breast cancer observation's positive effects on mTOR signaling pathway. We observed that HIF-1α/PKM2 protein level decreased in BCSC and MCF-7 cell lines treated with BIBR1532. We think that the decrease in HIF-1α/PKM2 protein levels is related to hTERT when the literature is considered.