Clusterin knockdown sensitizes prostate cancer cells to taxane by modulating mitosis

Clusterin (CLU) is a stress-activated molecular chaperone that confers treatment resistance to taxanes when highly expressed. While CLU inhibition potentiates activity of taxanes and other anti-cancer therapies in preclinical models, progression to treatment resistant disease still occurs implicating additional compensatory survival mechanisms. Taxanes are believed to selectively target cells in mitosis, a complex mechanism controlled in part by balancing antagonistic roles of Cdc25C and Wee1 in mitosis progression. Our data indicate that CLU silencing induces a constitutive activation of Cdc25C, which delays mitotic exit and hence sensitizes cancer cells to mitotic-targeting agents such taxanes. Unchecked Cdc25C activation leads to mitotic catastrophe and cell death unless cells upregulate protective mechanisms mediated through the cell cycle regulators Wee1 and Cdc2. In this study we show that CLU silencing induces a constitutive activation of Cdc25C via the phosphatase PP2A but leads to relief of negative feedback inhibition and activation of Wee1-Cdc2 to promote survival and limit therapeutic efficacy. Simultaneous inhibition of CLU-regulated cell cycle effectors, like PP2A and Wee1, may improve synergistic responses of biologically rational combinatorial regimens using taxanes and CLU inhibitors Biological triplicate of PC3 treated with siClusterin were compared to biological trplicate of PC3 treated with siScramblein