In addition, it has been reported that TGF-β, as one of the most important immunosuppressive cytokines secreted by M2 cells, can promote tumor metastasis and chemotherapy resistance by inducing the expression of PD-L1 [97], and secretion of TGF-β and up-regulation of PD-L1 are key factors for tumor immune escape and progress [98]. Here, TGFB1 is linked to neoplasm.