In this study, we show that CD9P-1 expression is essential for angiogenesis, and a truncated form of CD9P-1, GS-168AT2, inhibited dose-dependently human endothelial cell (hEC) proliferation, migration and in vitro and in vivo angiogenesis as well as the in vivo tumour growth, probably by downregulating of CD9 and CD151 at the cell surface. The gene discussed is PTGFRN; the disease is neoplasm.