S-phase arrest and apoptosis in human breast adenocarcinoma MCF-7 cells via mitochondrial dependent pathway induced by tricyclohexylphosphine gold (I) n-mercaptobenzoate complexes

We have previously reported the inhibition of thioredoxin reductase (TrxR) and invasion by tricyclohexylphosphine gold (I) n-mercaptobenzoate (n = 2, 3, 4) labeled as 1-3 towards MCF-7 cells, in vitro. Nevertheless, the mode of death and its apoptotic pathway has yet to be revealed. The main aim of this study is to investigate the anti-neoplastic activity of this phosphanegold (I) thiolates against breast adenocarcinoma cells, MCF-7. Herein, we explored the role of gold(I) series, 1-3 for their apoptosis-inducing ability against MCF-7 cells. They were scrutinized for their antiproliferative activities which exhibited their IC50 values of 8.14 μM ± 0.10, 7.26 μM ± 0.33, and 9.03 μM ± 0.69, respectively, and indicated better cytotoxicities than that of cisplatin (positive control). Further, the mechanisms of their actions were studied by analyzing the status of ROS generation (by DCFH-DA), cytochrome c release (by ELISA), and activation of caspases 3/7, 8, 9, and 10, annexin V staining and cell cycle analysis by flow cytometry, respectively. It was observed that the compounds, 1-3 can promote ROS generation, cytochrome c release, and activation of caspases 3/7, caspase 8, caspase 9, and caspase 10 on MCF-7 cells. In addition, the compounds are shown to induce MCF-7 cell arrest at S-phase. Gene analysis via PCR array further clarified their effects by modulating the related genes upon the compounds' treatment. Further investigation on other breast cancer cells as well as in vivo studies on these compounds will further increase their potential as anti-breast cancer agents.