Effects of Hypoxia, Surrounding Fibroblasts, and p16 Expression on Breast Cancer Cell Migration and Invasion.

Cancer cell migration and invasion play essential roles in the metastatic cascade that transforms the local, noninvasive confined tumor cells to the motile, metastatic cancer cells moving through the extracellular matrix and basement into the circulation. Accumulated evidences suggest that intratumoral hypoxia, a characteristic of fast-growing solid tumors, promotes cancer cell motile and invasive abilities. In this study, we investigated the effects of hypoxia, surrounding fibroblasts, and p16 expression on the migration and invasion of breast cancer cells. We found that hypoxia promoted breast cancer cell migration and invasion, and cocultured fibroblasts stimulated invasiveness of breast cancer cells. Moreover, by using a Tet-on inducible system, we found that p16 is capable of inhibiting hypoxia-induced cell migration and invasion of breast cancer cells, and suppressing cocultured fibroblast-stimulated invasiveness of breast cancer cells. These results suggest that p16, in addition to its well-known anti-tumor proliferation function, has novel anti-cancer properties capable of suppressing hypoxia-mediated cancer cell migration and invasion. This study may provide important validation for p16-mediated cancer therapy either by gene therapy or pharmacological activation of internal p16 gene that is usually inactive due to hypermethylation in the tumor cells.