Hydroxychloroquine potentiates the anti-cancer effect of bevacizumab on glioblastoma via the inhibition of autophagy

Bevacizumab (BEV) is widely used for the treatment of patients with recurrent glioblastoma (GBM), but recent evidence demonstrated that BEV induced cytoprotective autophagy, which allows tumor cells to survive. Hydroxychloroquine (HCQ) inhibits lysosomal acidification and blocks autophagy via influencing autophago-some fusion and degradation. HCQ is often used to enhance the efficacy of chemoradiotherapy. However, whether HCQ sensitizes GBM cells to BEV and the molecular mechanism of this effect are not clear. We showed that high concentrations of BEV increased the LC3-II/LC3-I ratio and caused the degradation of Beclin1 in the LN18 and LN229 cell lines, indicating that high concentrations of BEV induced the autophagy of the LN18 and LN229 cells. However, BEV (100 mu g/ml) did not influence the autophagy of the LN18 and LN229 cells, and HCQ at less than 5 mu g/ml significantly accumulated LC3B-II and p62 proteins and blocked the autophagy process. Importantly, we found that HCQ (5 mu g/ml) potentiated the anti-cancer effect of BEV (100 mu g/ml). Therefore, HCQ is a novel strategy that may augment the efficacy of BEV for GBM via the inhibition of autophagy.