Characterization of a liver metastatic variant of murine K1735M2 melanoma cells

Intraportal vein injection of highly metastatic K1735M2L5 cells consistently resulted in liver metastases (increases in the number of tumor nodules in the liver), whereas inoculation of K1735M2 cells rarely did so. K1735M2L5 cells invaded the basement membrane Matrigel in greater numbers than did K1735M2 cells, suggesting that the metastatic potential of K1735M2L5 cells is partly related to enhanced invasive properties. The adhesion to Matrigel- and laminin-coated substrates was enhanced in K1735M2L5 cells. The up-regulated expression of VLA-4 and VLA-6 on the surface of K1735M2L5 cells was detected by flow cytometry. The RT-PCR and gelatin zymography study revealed that the secretion of MMP-2 was higher in K1735M2L5 cells than in K1735M2 cells. These results indicate that the invasive ability of K1735M2L5 cells may also be attributed to enhanced gelatinolytic activity as well as adhesiveness. K1735M2L5 cells grew more rapidly than K1735M2 cells and showed fibroblastoid morphology with loose cell-cell contacts as compared with K1735M2 cells. Thus, experimental models using highly metastatic K1735M2L5 cells would be useful for analyzing the molecular mechanism of tumor metastasis and for evaluating the efficacy of treatments for metastases which may have already occurred at the time of the diagnosis.