Inhibition of α4 integrin mediated adhesion was involved in the reduction of B16-F10 melanoma cells lung colonization in C57BL/6 mice treated with Gambogic acid

Gambogic acid, the major active ingredient of gamboge, has been shown to exhibit anti-cancer activity both in vivo and in vitro. However, its potential activity in tumor metastasis remains unclear. In the present study, we found that Gambogic acid strongly inhibited the adhesion of highly metastatic mouse melanoma B16-F10 cells in vitro. Gambogic acid also exhibited significant anti-metastasis activity on the development of in vivo artificial metastases (i.e. following tail vein i.v. injection of the B16-F10 melanoma tumor cells in C57BL/6 mice). Flow cytometric analysis and Western blot showed that Gambogic acid inhibited the cell surface expression of α4 integrin, while exhibited negligible effects on the expression of α5 and β1 integrin. Thus we concluded for the first time that Gambogic acid could inhibit the adhesion and migration of B16-F10 cells in vitro and in vivo, in which down-regulation of α4 integrin expression was involved.