p53 regulates epithelial-mesenchymal transition induced by transforming growth factor β

Epithelial plasticity characterizes embryonic development and diseases such as cancer. Epithelial-mesenchymal transition (EMT) is a reversible and guided process of plasticity whereby embryonic or adult epithelia acquire mesenchymal properties. Multiple signaling pathways control EMT, and the transforming growth factor β (TGFβ) pathway plays a central role as its inducer. Here, we analyzed the role of the tumor suppressor protein p53 in TGFβ-induced EMT in a well-established mammary epithelial cell model. We found that diploid NMuMG mammary cells bi-allelically express a wild type and a missense mutant (R277C) form of p53. Global reduction of both forms of p53 led to an enhanced EMT response to TGFβ. Conversely, stabilization of wild type p53 using the compound nutlin had a negative impact on EMT. After silencing both p53 forms, rescue experiments using either wild type or R277C mutant p53 revealed that wild type p53 inhibited, whereas the R277C mutant did not significantly affect, the TGFβ-driven EMT response. Under serum-free culture conditions, silencing of total p53 levels led to higher numbers of mammospheres characterized by larger size. Rescue of the silenced endogenous p53 with R277C mutant p53, in contrast, suppressed both size and numbers of the mammospheres. This work proposes that wild type p53 controls the efficiency by which mammary epithelial cells undergo EMT in response to TGFβ.