EGFR‐mediated hyperacetylation of tubulin induced docetaxel resistance by downregulation of HDAC6 and upregulation of MCAK and PLK1 in prostate cancer cells

Abstract

AbstractDocetaxel‐based chemotherapy has generally been considered as one of the effective treatments for castration‐resistant prostate cancer (PCa). However, clinical treatment with docetaxel often encounters a number of undesirable effects, including drug resistance. Tubulin isoforms have been previously examined for their resistance to docetaxel in many cancers, but their real mechanisms remained unclear. In this study, a series of docetaxel‐resistant PC/DX cell sublines were established by chronically exposing PC3 to progressively increased concentrations of docetaxel. Western blotting results showed significantly higher expression of acetyl‐tubulin, α‐tubulin, β‐tubulin, γ‐tubulin, and βIII‐tubulin in PC/DX25 than in parental PC3 cells. PC/DX25 with greater resistance to docetaxel had higher levels of acetyl‐tubulin and mitotic centromere‐associated kinesin (MCAK) than PC3 cells. This study found that docetaxel induced the expression of acetyl‐tubulin and MCAK in PC3 cells at a dose‐ and time‐dependent manner. Both mRNA and protein levels of histone deacetylase 6 (HDAC6) were significantly decreased in PC/DX25 compared with PC3 cells. PC3 increased the resistance to docetaxel by HDAC6 knockdown and Tubastatin A (HDAC6 inhibitor). Conversely, PC/DX25 reversed the sensitivity to docetaxel by MCAK knockdown. Notably, flow cytometry analysis revealed that MCAK knockdown induced significantly sub G1 fraction in PC/DX cells. Overexpression of polo‐like kinase‐1 increased the cell survival rate and resistance to docetaxel in PC3 cells. Moreover, epidermal growth factor receptor (EGFR) activation induced the upregulation of acetyl‐tubulin in docetaxel‐resistant PCa cells. These findings demonstrated that the EGFR‐mediated upregulated expression of acetyl‐tubulin played an important role in docetaxel‐resistant PCa.