ΔNp63α Promotes Breast Cancer Cell Motility through the Selective Activation of Components of the Epithelial-to-Mesenchymal Transition Program

Cell identity signals influence the invasive capability of tumor cells, as demonstrated by the selection for programs of epithelialto-mesenchymal transition (EMT) during malignant progression. Breast cancer cells retain canonical epithelial traits and invade collectively as cohesive groups of cells, but the signaling pathways critical to their invasive capabilities are still incompletely understood. Here we report that the transcription factor DNp63a drives the migration of basal-like breast cancer (BLBC) cells by inducing a hybrid mesenchymal/epithelial state. Through a combination of expression analysis and functional testing across multiple BLBC cell populations, we determined that DNp63a induces migration by elevating the expression of the EMT program components Slug and Axl. Interestingly, DNp63a also increased the expression of miR-205, which can silence ZEB1/2 to prevent the loss of epithelial character caused by EMT induction. In clinical specimens, co-expression of various elements of the DNp63a pathway confirmed its implication in motility signaling in BLBC. We observed that activation of the DNp63a pathway occurred during the transition from noninvasive ductal carcinoma in situ to invasive breast cancer. Notably, in an orthotopic tumor model, Slug expression was sufficient to induce collective invasion of E-cadherin- expressing BLBC cells. Together, our results illustrate how DNp63a can drive breast cancer cell invasion by selectively engaging promigratory components of the EMT program while, in parallel, still promoting the retention of epithelial character. (C) 2015 AACR.