PECAM1 and neoplasm: To further examine whether tylophorine could suppress tumor growth by inhibiting angiogenesis, tumor tissues were stained with specific antibodies against CD31, P-VEGFR2 (Tyr 1175), P-AKT, and P-Erk in Figure 7E. CD31 is a widely used endothelial marker for quantifying angiogenesis by calculating microvessel density (MVD) [42].