Indole-3-carbinol as a radiosensitizer and modulator of IR-dependent stemness in triple-negative breast cancer

Abstract

ABSTRACT Breast cancer (BC) is one of the most common malignant tumors among women worldwide that contributes to the high mortality rate among other malignancies. The resistance developed by cancer cells against different treatment strategies such as radiotherapy, inspired the researchers to use other products such as phytochemicals to sensitize cancer cells to therapy. This study is designed to evaluate the anti-cancer and/or radio-sensitizing effect of Indole-3-carbinol (I3C) on the triple negative breast cancer (TNBC) cell line MDA-MB-231. The concentration of I3C that is used as a radio-sensitizing dose was assessed using an MTT assay. Treatment of MDA-MB-231 cells with I3C and/or ionizing radiation led to significant downregulation at cell proliferation which was indicated by the decrease at colony formation ratio and reduction in Ki67 expression. The combined treatment showed upregulation of Bax and downregulation of Bcl-2 gene expression. Wound healing assay indicated the significant effect of combined treatment in reducing MDA-MB-231 cell motility, which was molecularly validated by significant downregulation at CD44, MMP-9 and VEGF transcripts levels. The combined therapy led to a significant reduction at the antioxidant enzyme levels as well as the Epithelial-mesenchymal transition indicated by downregulation of IR-dependent vimentin upregulation. The stemness markers Nanog and Sox2 were significantly downregulated in combined therapy compared to IR-only treatment. In conclusion, synchronized therapy showed a potential role in enhancing the cell responsiveness to IR therapy by ceasing cell proliferation, survival, metastasis and reversing IR-dependent induction of EMT, and stemness in TNBC cell line MDA-MB-231.