TGFB1 and melanoma: We demonstrate that Tregs can expedite melamona metastasis through a mechanism that involves cell-to-cell contact; direct cell-to-cell interactions between Tregs and melanoma cells elevated the TGF-β expression level in melanoma cells and subsequently promoted their migration and invasion (Figure 1, Figure 2, Figure 4A, and Figure 5), whereas inhibition of contact prevented Treg-mediated induction of TGF-β expression in melanoma cells (Figure 2B).