Natural killer cell-dependent suppression of systemic spread of human lung adenocarcinoma cells by monocyte chemoattractant protein-1 gene transfection in severe combined immunodeficient mice.

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine with various biological activities, including augmentation of cytotoxic activity of monocytes and natural killer (NK) cells. The present study was undertaken to determine whether transfection of the MCP-1 gene into lung cancer cells affected their tumorigenicity and metastatic potential by the NK cell-mediated mechanism. The human MCP-1 gene inserted into an expression vector (BCMGSNeo) was transfected into human lung adenocarcinoma (PC-14) cells. There was no difference in in vitro proliferation between MCP-1 gene-transfected PC-14 cells and the parent cells or mock-transfected cells. The tumorigenicity and in vivo tumor growth of MCP-1 gene-transfected PC-14 cells were similar to those of the parent cells or mock-transfected cells when tumor cells were injected into the s.c. space of NK cell-intact severe combined immunodeficient (SCID) mice. Although parent cells and mock-transfected cells inoculated i.v. formed lung metastatic colonies and pleural effusion, MCP-1 gene transfectants reduced the systemic spread in NK cell-intact SCID mice. Interestingly, these modulations in a systemic spread by MCP-1 gene transfection were not observed in NK cell-depleted SCID mice. Decreased survival of MCP-1 gene transfectants in the lung was observed in NK cell-intact SCID mice but not in NK cell-depleted SCID mice. Recombinant MCP-1 or the supernatant of MCP-1 gene transfectants enhanced the cytotoxicity of human CD56+ NK cells and spleen cells of SCID mice against PC-14 cells. These findings suggest that locally produced MCP-1 suppresses tumor progression by a NK cell-mediated mechanism, depending on organ microenvironment.