Investigation of the effects of telomerase inhibitor ''BIBR1532'' on epithelial mesenchymal transition on breast cancer and breast cancer stem cells

Cancer stem cells (CSCs) are a subgroup of cells that are involved in tumor tissue as a subpopulation and are capable of forming tumors and cause treatment resistance. CSCs, which contribute to tumor heterogeneity, are now considered as one of the reasons why cancer treatment is not fully successful. It is an attractive issue to target these cells to increase the efficiency of cancer therapies. CSCs which have the common features of high telomerase activity and high migration and invasion capabilities are accepted as the initiator of metastasis. The fact that chemotherapeutic agents damage healthy tissue and CSCs are resistant to standard treatment raises the need for new therapeutic targets. BIBR1532, a selective small molecule inhibitor, enables effective targeting of cancer cells by inhibiting telomerase. Moreover, recent studies have suggested that telomerase is associated with epithelial mesenchymal transition (EMT). EMT program, which causes epithelial cells to acquire a mesenchymal morphology, is known to play a role in cancer metastasis. The hypothesis of our study is that suppression of telomerase in breast cancer cells would result in interruption of EMT mechanism. In our study, the cytotoxicity of telomerase inhibitor BIBR1532 was found in breast cancer cells MDA-MB-231 and MCF-7, breast cancer stem cells and breast epithelial stem cells and the effects of the substance on apoptosis were investigated. The effect of BIBR1532 on the migration rate of cells was examined by wound healing test and sphere forming capacities were observed with hanging drop test. Finally, the expression of 84 EMT-related genes was analyzed by real-time qPCR. The IC50 values for the MDA-MB-231 and BESCs of the active substance BIBR1532 were calculated as 18.04 and 38.71 μl at 72 hours, respectively. While the apoptotic effects of the active substance on MDA-MB-231 and MCF-7 cells were not observed, apoptosis was found in BCSCs and BESCs as 26.5% and 32.2%, respectively. The effect of the active substance on BESCs was investigated for the first time and the drug had an apoptotic effect on stem cells. The sphere structures examined by the hanging drop test which showed that sphere areas were reduced in stem cells treated with BIBR1532 compared to the control group. In wound healing assay, we observed that active substance decreased the migration rate of stem cells more efficiently than cancer cells. The regulation of EMT-related genes in BIBR1532-treated cell lines indicated that telomerase inhibition affects the EMT mechanism. The targeted elimination of CSCs by telomerase inhibition in cancer treatment may limit the mobility and stemness of cancer cells due to the EMT mechanism. In breast cancer which is correlated with high telomerase activity, it can be a promising step in preventing metastasis and preventing cancer recurrence.