Effect of the telomerase and mitochondria inhibition on breast cancer stem cells and incombination therapy with NK cells

Abstract

Introduction: Triple Negative Breast Cancers (TNBC) is known as lethal and the most invasive breast cancers. TNBC exhibits the properties of cancer stem cells (CSCs) such as less differentiated, high metastasis, and recurrence. Also, they are resistance to conventional therapy. In recent years, novel therapies such as targeted therapy and immunotherapy have been considered. High telomerase activity involved in breast cancer tumorigenesis. Telomerase, especially hTERT subunit, displays several oncogenic functions such as the effect on mitochondria function, gene expression, and apoptosis except telomere protection. Therefore, we assessed the effect of telomerase and mitochondria inhibition on apoptosis and DNMT3a, TET2, and ALDH expression in TNBC.Moreever, Natural killer cells act as the first line of defense of the immune system against the tumor. NK cellular activity is regulated by the balance between activation and inhibitory signals expressed at the cell surface. Inhibitory receptors are part of the immunoglobulin receptor (KIR) complex. KIRs are expressed on the surface of NK cells and recognize MHC class I proteins (HLA-A, B, C). There is heterogeneity of KIR expression among different individuals. Therefore, in this study, we investigated the effect of NKcell KIR on BC cells. Materials and methods: MDA-MB-231 and MDA-MB-468 cells were treated with BIBR1532, Tigcycline, and combination of them. Then, MTT assay, Annexin V/7AAD were measured. Also, telomere length, the expression of DNMT3a, TET2, and hTERT were studied. Finally, apoptosis-related proteins and genes were analyzed. In addition, NK cells were co-cultured with breast cancer cells and the cytotoxic effect was evaluated with CD107, INFɣ. Results: The present results showed that IC50 level of telomerase and mitochondria inhibition induced apoptosis but had no significant effect on telomere length. Data also proposed that telomerase inhibition induced extrinsic apoptosis in MDA-MB-231 while, caused intrinsic apoptosis in MDA-MB-468 cells. Furthermore, it was found that the expression of p53 decreased following telomerase and mitochondria inhibition and was ineffective on the apoptosis of cells. The expressions of DNMT3a and TET2 were increased in cells flowing treatment with IC50 level of telomerase and mitochondria inhibition. In addition, combination treatment was better than BIBR1532 and Tigcycline alone. In addition, NK cells were co-cultured with breast cancer cells and the cytotoxic effect was evaluated with CD107, INFɣ. Conclusion: The inhibition of telomerase and mitochondria caused intrinsic and extrinsic apoptosis and increased DNMT3a and TET2 expression. NK KIR + cells increase cytotoxicity and can be useful in the treatment of TNBC breast cancer cells.