DJ-1/FGFR-1 Signaling Pathway Contributes to Sorafenib Resistance in Hepatocellular Carcinoma

Sorafenib is the first-line therapeutic regimen targeting against advanced or metastatic stage of hepatocellular carcinoma (HCC). However, HCC patients at these stages will eventually fail sorafenib treatment due to the drug resistance. At present, molecular mechanisms underlying sorafenib resistance are not completely understood. Our past studies have shown that DJ-1 is upregulated in HCC, while DJ-1 knockdown inhibits HCC xenograft-induced tumor growth and regeneration, implying that DJ-1 may be a potential target in for HCC treatment. However, whether DJ-1 plays a regulatory role between tumor cells and vascular endothelial cells and whether DJ-1 contributes to sorafenib resistance in HCC cells are largely unclear. To address these questions, we have performed a series of experiments in the current study, and we found that (1) DJ-1, one of the molecules secreted from HCC cells, promoted angiogenesis and migration of vascular endothelial cells (i.e., ECDHCC-1), by inducing phosphorylation of fibroblast growth factor receptor-1 (FGFR-1), phosphorylation of mTOR, phosphorylation of ERK, and phosphorylation of STAT3; (2) downregulation of FGFR1 inhibited tube formation and migration of ECDHCC-1 cells stimulated by DJ-1; (3) FGFR1 knockdown attenuated the phosphorylation of FGFR1 and impaired the activity of Akt, ERK, and STAT3 signals induced by DJ-1 in ECDHCC-1 cells; (4) knocking down FGFR1 led to the elevated expression of proapoptotic molecules but deceased level of antiapoptotic molecules in sorafenib-resistant HCC cells; and (5) Downregulation of FGFR1 suppressed tumor growth and angiogenesis of sorafenib-resistant HCC cells in vivo. Altogether, our results hinted that DJ-1 plays vital roles in tumor microenvironment in HCC development, and DJ-1/FGFR1 signaling pathway may be a therapeutic target for overcoming sorafenib resistance in treating HCC patients at the late stage.