A variant actin (βm) reduces metastasis of mouse B16 melanoma

Abstract

We recently reported an acidic actin co‐expressed with β and γ actin in mouse B16 melanoma, whose expression was inversely correlated with the metastatic potential. The cDNA for this actin is slightly different from the hitherto recognized mouse β actin cDNA, and we designated it βm actin. In order to directly investigate the effects of βm actin on metastasis, we transfected the βm actin cDNA into a re‐cloned B16‐BL6 cell line which is more invasive than the highly metastatic cell line, B16‐F10; we have already reported the suppressive effect of pm actin on the invasiveness of B16 F10. Here we report on the decline in the metastatic ability of βm‐transfected cells. In the pm‐transfected B16‐BL6 cell line, we observed an increase in the organization of actin stress fibers, accompanied by a decrease in metastasis to the lung, in the invasion of collagen gels, in In vivo invasive‐ness, and in cell migration on a glass plate covered with colloidal gold particles. We observed no correlation of pm actin expression either with cell attachment to Matrigel, or with type‐IV collagenase expression. These results suggest that βm actin can play a role in reducing the invasiveness of mouse B16 melanoma, most probably through decreasing cell motility, which may thus result in suppression of the metastatic ability of cells.