Modulation of Chemotherapy Sensitivity of Breast Cancer Cells through Transforming Growth Factor-beta Pathway-mediated Alterations in DNA Damage Response.

Chemotherapeutic drugs, like cisplatin, function by damaging genomic DNA, thus inducing cell apoptosis. Cancer cells can enhance their DNA repair capacity, leading to chemotherapeutic resistance. Nucleotide excision repair (NER) involves repairing DNA adducts and crosslinks caused by chemotherapeutic agents. Transforming growth factor-beta (TGF-β) pathway contributes to carcinogenesis, DNA repair alteration, and chemoresistance. However, the connection between TGF-β pathway, NER function alteration, and resistance to cisplatin therapy remains elusive. Therefore, the objective of current study was to fill this gap by assessing the impact of TGF-β inhibition and activation on cisplatin-induced antiproliferation, apoptosis, and DNA damage using the MTT assay, flow cytometry analysis, and COMET assay, respectively. Four NER genes, XPA, XPB, XPC, and XPF, were measured using Real-time Polymerase Chain Reaction (qPCR). MDA-MB-231 cell line was utilized as a model of breast cancer. Blockade of the TGF-β pathway strengthened cisplatin cytotoxicity, whereas induction of the TGF-β pathway suppressed cisplatin cytotoxicity. In cisplatin-treated breast cancer cells, DNA damage significantly increased upon the TGF-β pathway inhibition. Conversely, cisplatin-induced DNA damage decreased significantly upon TGF-β pathway stimulation. Finally, cisplatin caused an overexpression of the four NER genes which was curtailed and augmented by TGF-β inhibition and stimulation, respectively. Overall, this study presented evidence of the impact exerted by TGF-β pathway on NER and cisplatin sensitivity of breast cancer cells.