Effect of Autophagy Inhibitor Hydroxychloroquine on Chemosensitivity of Castration-resistant Prostate Cancer

  Objective  To determine the effects of autophagy inhibitor hydroxychloroquine (HCQ) on chemosensitivity of castration-resistant prostate cancer 22RV1 cell line in vitro and in vivo, and changes in its mRNA expressions of autophagy gene Bcelin-1, autophagy specific substrate P62 gene, pro-apoptotic gene Bax.

  Methods  22RV1 cells were cultured in vitro and divided into blank control (no drug), DOC, and HCQ (20 μmol/L)+DOC groups. The concentration of DOC was set at 10^-6 mol/L, 10^-7 mol/L, and 10^-8 mol/L in the tests. Cell proliferation activities were detected by CCK-8 method 72 h after drug treatments. The 22RV1 cell suspension was injected subcutaneously into nude mice to establish transplanted tumor. The successfully modeled mice were randomly divided into three groups (five each) treated by physiological saline, DOC and HCQ+DOC (injected intraperitoneally for 4 weeks), respectively. Changes in growth of the transplanted tumor were observed. The mRNA expressions of Beclin-1, P62, and Bax were detected by qPCR. The protein expressions of Beclin-1, LC3B, and Bax were detected by Western blot.

  Results  In vitro: compared with the blank control, the DOC and HCQ+DOC groups showed decrease proliferation of cells(P<0.05); HCQ further lowered cell proliferation in the presence of DOC (P<0.05), resulting in reduced half maximal inhibitory concentration (IC₅₀) of DOC. In vivo: compared with the model mice, the DOC and HCQ+DOC groups had decreased volume of transplanted tumor. HCQ slowed the weekly growth of tumor in the presence of DOC (P<0.05), most obvious at the 4th week. In vitro and in vivo, HCQ+DOC upregulated the mRNA and protein expressions of Beclin-1, P62 and Bax (P<0.05).

  Conclusion  HCQ can interfere with the autophagy of castration-resistant prostate cancer cells, inhibiting its proliferation and enhancing its sensitivity to chemotherapeutic drugs.