Induction of Monocyte Chemoattractant Protein-1 and Interleukin-10 by TGFβ1 in Melanoma Enhances Tumor Infiltration and Immunosuppression

Melanoma progression is associated with the expression of different growth factors, cytokines, and chemokines. Because TGF beta 1 is a pleiotropic cytokine involved not only in physiologic processes but also in cancer development, we analyzed in A375 human melanoma cells, the effect of TGF beta 1 on monocyte chemoattractant protein-1 (MCP-1) and interleukin-10 (IL-10) expression, two known factors responsible for melanoma progression. TGFb1 increased the expression of MCP-1 and IL-10 in A375 cells, an effect mediated by the cross-talk between Smad, PI3K (phosphoinositide 3-kinase)/AKT, and BRAF-MAPK (mitogen activated protein kinase) signaling pathways. Supernatants from TGF beta 1-treated A375 cells enhanced MCP-1-dependent migration of monocytes, which, in turn, expressed high levels of TGF, beta 1, bFGF, and VEGF mRNA. Moreover, these supernatants also inhibited functional properties of dendritic cells through IL-10-dependent mechanisms. When using in vitro, the TGF beta 1-blocking peptide P144, TGF beta 1-dependent Smad3 phosphorylation, and expression of MCP-1 and IL-10 were inhibited. In vivo, treatment of A375 tumor-bearing athymic mice with P144 significantly reduced tumor growth, associated with a lower macrophage infiltrate and decreased intratumor MCP-1 and VEGF levels, as well as angiogenesis. Finally, in C57BL/6 mice with B16-OVA melanoma tumors, when administered with immunotherapy, P144 decreased tumor growth and intratumor IL-10 levels, linked to enhanced activation of dendritic cells and natural killer cells, as well as anti-OVA T-cell responses. These results show new effects of TGF beta 1 on melanoma cells, which promote tumor progression and immunosuppression, strongly reinforcing the relevance of this cytokine as a molecular target in melanoma. Cancer Res; 71(3); 812-21. (C)2011 AACR.