P38alpha Blockade Inhibits Colorectal Cancer Growth in Vivo by Inducing a Switch from HIF1alpha- to FoxO-dependent Transcription

Colorectal cancer cell (CRC) fate is governed by an intricate network of signaling pathways, some of which are the direct target of DNA mutations, whereas others are functionally deregulated. As a consequence, cells acquire the ability to grow under nutrients and oxygen shortage conditions. We earlier reported that p38alpha activity is necessary for proliferation and survival of CRCs in a cell type-specific manner and regardless of their phenotype and genotype. Here, we show that p38alpha sustains the expression of HIF1alpha target genes encoding for glycolytic rate-limiting enzymes, and that its inhibition causes a drastic decrease in ATP intracellular levels in CRCs. Prolonged inactivation of p38alpha triggers AMPK-dependent nuclear localization of FoxO3A and subsequent activation of its target genes, leading to autophagy, cell cycle arrest and cell death. In vivo, pharmacological blockade of p38alpha inhibits CRC growth in xenografted nude mice and azoxymethane-treated Apc(Min) mice, achieving both a cytostatic and cytotoxic effect, associated with high nuclear expression of FoxO3A and increased expression of its target genes p21 and PTEN. Hence, inhibition of p38alpha affects the aerobic glycolytic metabolism specific of cancer cells and might be taken advantage of as a therapeutic strategy targeted against CRCs.