Role of aven in apoptotic response following paclitaxel and docetaxel treatment in mda-mb231 breast cancer cells

Clinically useful, taxane group of drugs paclitaxel and docetaxel act by stabilizing microtubules and disrupting microtubular dynamics, which are important for cell cycle progression, leading to cell cycle arrest and apoptosis. Among numerous proteins involved in this response, Aven was shown have an anti apoptotic role, therefore, our study aimed at elucidating the role of Aven in apoptotic response to taxane treatment in p53 deficient and estrogen receptor (-) MDA-MB231 breast cancer cell line. Our results demonstrated that Aven is regulated in response to 50 nM paclitaxel and docetaxel treatments in a time dependent manner according to western blot and Real-Time analysis. Aven was upregulated in early time points 2-4 hours, with a similar pattern of expression of Bcl-2, Apaf-1, caspase-9, Puma and Parp-1 but not with Bcl-xl or Bax. Aven expression was downregulated after 24 hours coinciding with a major decrease in cell viability measured by MTT assay in response to drug treatments. It was also shown that when Aven was silenced by siRNA treatment endogenous levels of Bcl-2 and Bax was upregulated. Furthermore in overexpression studies Bcl-2 was found to be downregulated. The effect of Aven silencing and overexpression on cell death was also investigated. Aven overexpression did not protect MDA-MB231 cells from taxane induced apoptosis; however Aven silencing increased vulnerability of these cells to docetaxel treatment. Finally, Aven was shown to be immunoprecipitated by phospho-tyrosine antibody indicating that it is phosphorylated on its tyrosine residue(s)