REDUCED INVASIVE AND METASTATIC POTENTIALS OF KAI1-TRANSFECTED MELANOMA-CELLS

KAI1 is a metastasis suppressor gene for human prostate cancer. To rev eal the effect of KAI1 on the in vivo metastasis of tumors other than prostatic cancer, we transfected a human KAI1 cDNA into highly metasta tic B16-BL6 murine melanoma cells and established stable transfectant clones with different expression levels of KAI1 message. The following results were obtained with the use of those transfectants. (1) Cell a ggregation assay revealed a significantly enhanced Ca2+-independent ag gregation of B16-BL6 cells by KAI1 cDNA transfection compared with moc k transfectants (P<0.01). (2) The in vivo phagokinetic activity and in vasive ability of KAI1 transfectants were clearly decreased as compare d with those of mock transfectants (P<0.01). There was no significant effect of KAI1 expression on the in vitro or in vivo proliferation of B16-BL6 cells. (3) Lung colony formation of intravenously injected KAI 1 transfectants in nude mice was significantly reduced as compared wit h mock transfectants or parental B16-BL6 cells (P<0.01). These data su ggest that KAI1 expression gives rise to the suppression of invasive a nd metastatic potentials of B16-BL6 cells.