Non-canonical HIF-2α function drives autonomous breast cancer cell growth via an AREG-EGFR/ErbB4 autocrine loop

Tumor progression is intrinsically tied to the clonal selection of tumor cells with acquired phenotypes allowing to cope with a hostile microenvironment. Hypoxia-inducible factors (HIFs) master the transcriptional response to local tissue hypoxia, a hallmark of solid tumors. Here, we report significantly longer patient survival in breast cancer with high levels of HIF-2 alpha. Amphiregulin (AREG) and WNT1-inducible signaling pathway protein-2 (WISP2) expression was strongly HIF-2 alpha-dependent and their promoters were particularly responsive to HIF-2 alpha. The endogenous AREG promoter recruited HIF-2 alpha in the absence of a classical HIF-DNA interaction motif, revealing a novel mechanism of gene regulation. Loss of AREG expression in HIF-2 alpha-depleted cells was accompanied by reduced activation of epidermal growth factor (EGF) receptor family members. Apparently opposing results from patient and in vitro data point to an HIF-2 alpha-dependent auto-stimulatory tumor phenotype that, while promoting EGF signaling in cellular models, increased the survival of diagnosed and treated human patients. Our findings suggest a model where HIF-2 alpha-mediated autocrine growth signaling in breast cancer sustains a state of cellular self-sufficiency, thereby masking unfavorable microenvironmental growth conditions, limiting adverse selection and improving therapy efficacy. Importantly, HIF-2 alpha/AREG/WISP2-expressing tumors were associated with luminal tumor differentiation, indicative of a better response to classical treatments. Shifting the HIF-1/2 alpha balance toward an HIF-2-dominated phenotype could thus offer a novel approach in breast cancer therapy. Oncogene (2012) 31, 2283-2297; doi:10.1038/onc.2011.417; published online 19 September 2011