We investigated the expression of microRNAs (miRNAs) associated with replicative senescence in human primary keratinocytes. A cohort of miRNAs up-regulated in senescence was identified by genome-wide miRNA profiling, and their change in expression was validated in proliferative versus senescent cells. Among these, miRNA (miR)-138, -181a, -181b, and -130b expression increased with serial passages. miR-138, -181a, and -181b, but not miR130b, overexpression in proliferating cells was sufficient per se to induce senescence, as evaluated by inhibition of BrdU incorporation and quantification of senescence-activated β-galactosidase staining. We identified Sirt1 as a direct target of miR-138, -181a, and -181b, whereas ΔNp63 expression was inhibited by miR-130b. We also found that ΔNp63α inhibits miR-138, -181a, -181b, and -130b expression by binding directly to p63-responsive elements located in close proximity to the genomic loci of these miRNAs in primary keratinocytes. These findings suggest that changes in miRNA expression, by modulating the levels of regulatory proteins such as p63 and Sirt1, strongly contribute to induction of senescence in primary human keratinocytes, thus linking these two proteins. Our data also indicate that suppression of miR-138, -181a, -181b, and -130b expression is part of a growth-promoting strategy of ΔNp63α in epidermal proliferating cells.

SignificanceExpression in cancer cells of novel proteins generated by mutations in the TP53 gene is an important prognostic factor; however, how p53 mutants promote cancer progression is largely unknown. Here, we describe a molecular mechanism of gain-of-function by mutant p53 in hypoxic non-small cell lung cancer (NSCLC) cells. We identified the existence of a hypoxia-inducible factor-1 (HIF-1)/mutant p53 complex, exerting transcriptional control of a specific subset of protumorigenic genes, codifying for extracellular matrix (ECM) components. Employing in vivo cancer models and analyzing clinical material, we demonstrate that these ECM components substantially contribute to the synergistic protumorigenic activity of p53 mutants and HIF-1. Our data indicate that HIF-1/mutant p53 cross-talk is an innovative potential therapeutic target to treat advanced NSCLC.