The downregulation of ΔNp63 in p53-deficient mouse epidermal tumors favors metastatic behavior

The TP63 gene codes for two major isoform types, TAp63 and Delta Np63, with probable opposite roles in tumorigenesis. The Delta Np63a protein is frequently amplified and overexpressed in different epithelial tumors. Accordingly, it has been considered a potential oncogene. Nonetheless, a possible metastatic suppressor activity has also been suggested based on the experimental observation that its expression is reduced or even absent in advanced invasive tumors. Such metastatic suppressor activities are often related to tumors bearing point mutated TP53 gene. However, its potential roles in TP53-deficient tumors are poorly characterized. Here we show that in spontaneous tumors, induced by the epidermal-specific Trp53 ablation, the reduction of Delta Np63 expression is an early event, whereas it is re-expressed in the lung metastatic lesions. Using knock down and ectopic expression approaches, we show that Delta Np63 expression opposes the epithelial-mesenchymal transition and reduces the metastatic potential of the cells. This process occurs through the modulation of Delta Np63-dependent downstream targets (including transcription factors and microRNAs) likely to play metastatic roles. Further, Delta Np63 also favors the expression of factors involved in iPS reprogramming, thus suggesting that it can also modulate specific stem cell traits in mouse epidermal tumor cells. Overall, our data assign antimetastatic roles to Delta Np63 in the context of p53 deficiency and epidermis.