Repression of p63 and induction of EMT by mutant RAS in mammary epithelial cells

Abstract

The p53-related transcription factor p63 is required for maintenance of epithelial cell differentiation. We found that activated forms of the Harvey Rat Sarcoma Virus GTPase (H-RAS) and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) oncogenes strongly repress expression of ΔNp63α, the predominant p63 isoform in basal mammary epithelial cells. This regulation occurs at the transcriptional level, and a short region of the ΔNp63 promoter is sufficient for repression induced by H-RasV12. The suppression of ΔNp63α expression by these oncogenes concomitantly leads to an epithelial-tomesenchymal transition (EMT). In addition, the depletion of ΔNp63α alone is sufficient to induce EMT. Both H-RasV12 expression and ΔNp63α depletion induce individual cell invasion in a 3D collagen gel in vitro system, thereby demonstrating how Ras can drive the mammary epithelial cell state toward greater invasive ability. Together, these results suggest a pathway by which RAS and PIK3CA oncogenes induce EMT through regulation of ΔNp63α.