PECAM1 and neoplasm: Smad3 deficiency protected mice against tumour growth, invasion and metastasis, where a markedly reduction in angiogenesis (CD31, VEGF), invasion and metastasis (MMPs), and immunosuppression (decrease in Foxp3+ Treg but increase in NKp46+ NK cells) were found in the Smad3‐KO mice compared to the wildtype mice, revealing the important role of Smad3 signalling in the protumoural TME.21