Given that transforming growth factor-β (TGF-β) is involved in Trem cell activation [123] and exosomal PDL1 secretion [73], it is likely that a metastasis-prone condition such as the induction of the epithelial-to-mesenchymal transition or the tumor-nested condition is formed in the tumor microenvironment elicited by TGF-β [124], though this mechanism is not yet fully understood. The gene discussed is TGFB1; the disease is neoplasm.