Sorafenib is used for treating advanced hepatocellular carcinoma (HCC), but some patients acquire sorafenib resistance. We investigated the mechanisms underlying acquired sorafenib resistance in HCC cells and targeted them to re-sensitize them to sorafenib. In silico analysis indicated that toll-like receptor (TLR)-9 was significantly overexpressed, and that miRNA (hsa-miR-30a-5p) was downregulated in sorafenib-resistant HCC cells, which modulated HCC cell proliferation, oxidative stress, and apoptosis. TLR9 overexpression increased HCC cell proliferation, whereas TLR9 inhibition from hydroxychloroquine (HCQ) decreased HCC cell proliferation, tumor growth, oxidative stress marker (SOD1), and the formation of autophagosome bodies (reduced ATG5 and Beclin-1 expression). Moreover, HCQ treatment reduced epithelial-mesenchymal transition, leading to decreased clonogenicity, migratory ability, and invasiveness. HCQ targeted and reduced the self-renewal capacity phenotype by inhibiting tumorsphere generation. Both in vitro and in vivo results demonstrated the synergistic effect of the HCQ-sorafenib combination on sorafenib-resistant HCC (Huh7-SR) cells, increasing their sensitivity to treatment by modulating TLR9, autophagy (ATG5 and Beclin-1), oxidative stress (SOD1), and apoptosis (c-caspase3) expression and thus overcoming the drug resistance. This study's findings indicate that TLR9 overexpression occurs in sorafenib-resistant HCC cells and that its downregulation aids HCC suppression. Moreover, HCQ treatment significantly increases sorafenib's effect on sorafenib-resistant HCC cells.
Keywords: HCQ; TLR9; autophagy; hepatocellular carcinoma; oxidative stress; sorafenib resistance.