Host-Derived MCP-1 and MIP-1 alpha Regulate Protective Anti-Tumor Immunity to Localized and Metastatic B16 Melanoma

Leukocytic infiltration into malignant melanoma lesions is tightly regulated by chemokines. To assess the role of the CC chemokines monocyte chemotactic protein-1 (MCP-1/chemokine ligand 2) and macrophage inflammatory protein-1 alpha (MIP-1 alpha/chemokine ligand 3) in this process, s.c. primary and metastatic B16 F10 melanoma a tumor growth levels were examined in mice lacking MCP-1 or MIP-1 alpha. Primary s.c. B16 F10 melanoma growth was augmented by loss of MCP-1 or MIP-1 alpha. Similarly, lung metastasis was enhanced by the deficiency of MCP-1 or MIP-1 alpha. Enhanced tumor outgrowth was associated with decreased percentages of infiltrating CD4(+) T cells, CD8(+) T cells, and natural killer cells. In the absence of MCP-1 or MIP-1 alpha, melanoma outgrowth was correlated with reduced local expression of interferon-gamma, IL-6, tumor necrosis factor-alpha, and transforming growth factor-beta. Among these cytokines, reduced expression levels of interferon-gamma and tumor necrosis factor-alpha on leukocytes from the spleen were associated with the development of lung metastasis in chemokine-deficient mice. The local s.c. administration of these four cytokines significantly augmented another chemokine's expression and suppressed primary melanoma growth in mice deficient for MCP-1 or MIP-1 alpha. The s.c. injection of MCP-1 or MW-la significantly inhibited the primary tumor growth in wild-type mice. These results indicate that host-derived MCP-1 and MIP-1 alpha regulate protective anti-tumor immunity to B16 F10 melanoma by promoting lymphocyte infiltration into the tumor and subsequent cytokine production. (Am J Pathol 2012, 180: 365-374; DOI: 10.1016/j.ajpath.2011.09.005)