296. Effective Suppression of Breast Cancer by Downregulation of VEGF Signaling

Abstract

Blocking tumor angiogenesis may be an effective approach to suppress tumor metastasis. Vascular endothelial growth factor (VEGF) plays a pivotal role in tumor angiogenesis. The degree of tumor malignancy correlates with the expression of VEGF and the inverse expression of tumor suppressor gene p16. To examine whether p16 decreases VEGF gene expression and inhibits tumor angiogenesis and metastasis in breast cancer cells, human breast cancer cell line MDA-MB-231, MCF-7 and mouse breast cancer cell line JygMC(A) were used as models for studies. To facilitate induction of p16 expression, a replication-defective recombinant adenovirus expressing human wild-type p16 (AdRSVp16) has been generated. Our study showed that adenoviral-mediated p16 expression downregulated VEGF expression and VEGF receptor activation in breast cancer cells. AdRSVp16 inhibited in vitro cell growth of MDA-MB-231, MCF-7 and JygMC(A) at 50.4%, 58.3% and 38.5%, respectively, attenuated in vivo angiogenesis induced by MDA-MB-231 cells in Matrigel plug assay and in a dorsal air sac model, and had a 53% reduction of metastases of JygMC(A) in nude mice after subcutaneous injection when compared to control group. In addition, the effects of p16 on expression of proliferation marker PCNA, neovascularization marker CD31 and apoptosis inside the tumors were also analyzed. These results demonstrate that p16 downregulates VEGF gene expression, inhibits angiogenesis, and suppresses tumor growth and metastasis in breast cancer cells. This study suggests that viral vector-based p16 gene therapy may have clinical potentials to suppress breast cancer growth and metastasis.