Apatinib inhibits VEGF signaling and promotes apoptosis in intrahepatic cholangiocarcinoma

Abstract

Tumor cells co-express vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) that interact each other to support a self-sustainable cell growth. So far, this autocrine VEGF loop is not reported in human intrahepatic cholangiocarcinoma (ICC). Apatinib is a highly selective VEGFR2 inhibitor, but its effects on ICC have not been investigated. In this study, we reported that VEGF and phosphorylated VEGFR2 were expressed at a significantly high level in ICC patient tissues (P<0.05). In vitro, treating ICC cell lines RBE and SSP25 with recombinant human VEGF (rhVEGF) induced phosphorylation of VEGFR1 (pVEGFR1) and VEGFR2 (pVEGFR2); however, only the VEGFR2 played a role in the anti-apoptotic cell growth through activating a PI3K-AKT-mTOR anti-apoptotic signaling pathway which generated more VEGF to enter this autocrine loop. Apatinib inhibited the anti-apoptosis induced by VEGF signaling, and promoted cell death in vitro. In addition, Apatinib treatment delayed xenograft tumor growth in vivo. In conclusion, the autocrine VEGF/VEGFR2 signaling promotes ICC cell survival. Apatinib inhibits anti-apoptotic cell growth through suppressing the autocrine VEGF signaling, supporting a potential role for using Apatinib in the treatment of ICC.