A VEGFR2 Antagonist Inhibits Cell Proliferation, Migration, and Invasion by Blocking the PI3K-Akt and MAPK Signaling Pathways in Thyroid Cancer
Abstract Background: Vascular endothelial growth factor receptor-2 (VEGFR2)-mediated signaling cascades are involved in proliferation, migration, survival, and permeability changes in vascular endothelial cells. It was thought that VEGFR2 antagonists exerted their antitumor effects by inhibiting angiogenesis in tumor tissues. However, some recent studies have found that they have significant direct antitumor effects in some tumors. The aim of this study was to explore the antitumor effects and mechanisms of VEGFR2 antagonists in thyroid cancer (TC).Methods: The antitumor efficacy of a VEGFR2 antagonist (apatinib) in TC cells was evaluated through a series of in vitro experiments, and xenograft models were used to test its in vivo antitumor activity. The antitumor mechanisms of the VEGFR2 antagonist were explored using western blotting and immunohistochemistry.Results: Compared with that in the normal human thyroid cell line HTori3, the expression of VEGFR2 in TC cell lines (including IHH4, BCPAP, TPC-1, C643, K1, and 8305C) was significantly increased, especially in the C643 and 8305C cell lines. VEGFR2 antagonist inhibited the proliferation of C643 and 8305C cells in a dose-dependent manner, significantly reduced the invasion and migration of these cells, induced G0/G1 phase arrest and promoted cancer cell apoptosis. Additionally, the antiproliferative effect of the VEGFR2 antagonist was significantly reduced after KDR gene knockdown. In vivo experiments showed that tumor growth in nude mice was significantly inhibited in response to apatinib. The western blot and immunohistochemistry results showed that the VEGFR2 antagonist significantly reduced the expression and phosphorylation of VEGFR2 and further inhibited the phosphorylation of the downstream molecules Akt and ERK1/2.Conclusions: The VEGFR2 antagonist inhibited cell proliferation, invasion and migration in TC by inhibiting the PI3K/Akt and MAPK signaling pathways and exerted direct antitumor effects. Thus, directly targeting VEGFR2 can be an effective strategy for TC expressing VEGFR2.