PAX5α Enhances the Epithelial Behavior of Human Mammary Carcinoma Cells

Deregulated PAX5 expression has been associated with metastatic mammary carcinoma, although the precise role of PAX5 in cancer progression is unclear. Stable forced expression of PAX5α in the mammary carcinoma cell lines MCF-7 and MDA-MB-231 reduced cell cycle progression, cell survival, and anchorage-independent cell growth. In xenograft studies, forced expression of PAX5α was associated with a significant reduction in tumor volume. Furthermore, forced expression of PAX5α in mammary carcinoma cells resulted in altered cell morphology with resultant enhancement of epithelial cell characteristics. Morphologic changes were associated with localization of β-CATENIN at cell-cell junctions and with altered mRNA expression of mesenchymal markers in mammary carcinoma cells. In addition, forced expression of PAX5α in MCF-7 and MDA-MB-231 cells significantly reduced cell migration and invasion. Concomitantly, small interfering RNA–mediated depletion of PAX5α increased MCF-7 total cell number, cell motility, migration, and invasion. These studies show that PAX5α enhances the epithelial characteristics of mammary carcinoma cells, reminiscent of mesenchymal to epithelial transition. Mol Cancer Res; 8(3); 444–56