However, activated platelets can release vascular endothelial growth factor (VEGF) which is able to inhibit the differentiation and development of dendritic cells (DCs), and finally lead to the immune tolerance of CTLs.[34] Further, platelet-derived TGF-β can induce the low-level expression of MHC class II in tumor cells thereby sheltering tumor cells from the cytotoxic effect.[35] Collectively, to form distant metastases, surviving tumor cells also need the assistance of platelets. This evidence concerns the gene TGFB1 and neoplasm.