Autocrine vascular endothelial growth factor signaling promotes cell proliferation and modulates sorafenib treatment efficacy in hepatocellular carcinoma.
Tumor cells express vascular endothelial growth factor (VEGF) that can activate VEGF receptors (VEGFRs) on or within tumor cells to promote growth in an angiogenesis-independent fashion; however, this autocrine VEGF pathway has not been reported in hepatocellular carcinoma (HCC). Sorafenib, an angiogenic inhibitor, is the only drug approved for use in advanced HCC patients. Yet the treatment efficacy is diverse and the mechanism behind it remains undetermined. Our aims were to study the molecular mechanisms underlying autocrine VEGF signaling in HCC cells and evaluate the critical role of autocrine VEGF signaling on sorafenib treatment efficacy. By immunohistochemistry, we found robust nuclear and cytoplasmic staining for active, phosphorylated VEGF receptor 1 (pVEGFR1) and phosphorylated VEGF receptor 2 (pVEGFR2), and by western blotting we found that membrane VEGFR1 and VEGFR2 increased in HCC tissues. We showed that autocrine VEGF promoted phosphorylation of VEGFR1 and VEGFR2 and internalization of pVEGFR2 in HCC cells, which was both pro-proliferative through a protein lipase C-extracellular kinase pathway and self-sustaining through increasing VEGF, VEGFR1, and VEGFR2 mRNA expressions. In high VEGFR1/2-expressing HepG2 cells, sorafenib treatment inhibited cell proliferation, reduced VEGFR2 mRNA expression in vitro, and delayed xenograft tumor growth in vivo. These results were not found in low VEGFR1/2-expressing Hep3B cells. In an advanced HCC population on sorafenib treatment for postoperative recurrence, we found that the absence of VEGFR1 or VEGFR2 expression in resected tumor tissues before sorafenib treatment was associated with poorer overall survival.


CONCLUSIONS
Autocrine VEGF signaling directly promotes HCC cell proliferation and affects the sorafenib treatment outcome in vitro and in vivo, which may enable better stratification for clinical treatment decisions.
Department of Gastroenterology and Hepatology.
Sui
S
Peng
Ye
Y
Wang
Hong
H
Peng
Dong
D
Chen
Shunli
S
Shen
Baogang
B
Peng
Minhu
M
Chen
Riccardo
R
Lencioni
Ming
M
Kuang
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D019898:Autocrine Communication / Q000502:physiology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000401:mortality / Q000503:physiopathology*; D049109:Cell Proliferation / Q000502:physiology*; D004195:Disease Models, Animal; D005260:Female; D064593:Heterografts; D006801:Humans; D053208:Kaplan-Meier Estimate; D008099:Liver / Q000503:physiopathology; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000401:mortality / Q000503:physiopathology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D010671:Phenylurea Compounds / Q000627:therapeutic use*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000502:physiology; D000077157:Sorafenib; D015996:Survival Rate; D016896:Treatment Outcome; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*
D000970:Antineoplastic Agents; D010671:Phenylurea Compounds; D042461:Vascular Endothelial Growth Factor A; D009536:Niacinamide; D000077157:Sorafenib; D040262:Receptors, Vascular Endothelial Growth Factor