Identification of pY654-β-catenin as a critical co-factor in hypoxia-inducible factor-1α signaling and tumor responses to hypoxia

Abstract

Hypoxia is linked to epithelial mesenchymal transition (EMT) and tumor progression in numerous carcinomas. Responses to hypoxia are thought to operate via hypoxia-inducible factors (HIFs), but the importance of co-factors that regulate HIF signaling within tumors is not well understood. Here we elucidate a signaling pathway that physically and functionally couples tyrosine phosphorylation of β-catenin to hypoxia-inducible factor-1α (HIF1α) signaling and HIF1α-mediated tumor EMT. Primary human lung adenocarcinomas accumulate pY654-β-catenin and HIF1α. All pY654-β-catenin, and only the tyrosine phosphorylated form, was found complexed with HIF1α and active Src, both within human tumors and in lung tumor cell lines exposed to hypoxia. Phosphorylation of Y654, generated by hypoxia mediated, reactive oxygen species (ROS)-dependent Src kinase activation, was required for β-catenin to interact with HIF1α and Src, to promote HIF1α transcriptional activity, and for hypoxia-induced EMT. Mice bearing hypoxic pancreatic islet adenomas, generated by treatment with anti-vascular endothelial growth factor antibodies, accumulate HIF1α/pY654-β-catenin complexes and develop an invasive phenotype. Concurrent administration of the ROS inhibitor N-acetylcysteine abrogated β-catenin/HIF pathway activity and restored adenoma architecture. Collectively, the findings implicate accumulation of pY654-β-catenin specifically complexed to HIF1α and Src kinase as critically involved in HIF1α signaling and tumor invasion. The findings also suggest that targeting ROS-dependent aspects of the pY654-β-catenin/ HIF1α pathway may attenuate untoward biological effects of anti-angiogenic agents and tumor hypoxia.

Utility of a bacterial infection model to study epithelial–mesenchymal transition, mesenchymal–epithelial transition or tumorigenesis

“…Consistent with hypoxia being a frequent feature of the microenvironment of infected tissues due to activation of the hypoxia-inducible factor and NF-κB pathways, 18,19 CR-infection-induced Hif-1α expression that coincided with relative increases in Hif-1α levels during hypoxia, in addition to induction of HDAC3, β-catenin, Slug and Snail (Supplementary Figure 2A). During wound-healing assay, N-acetylcysteine, an inhibitor of reactive oxygen species activity that is elevated during hypoxia, 44 inhibited CR-induced cell migration under normoxic conditions [Figure 3e(i), e(ii)]. During hypoxia, although CR-induced cell migration was recorded within 6 h, CR only partially rescued N-acetylcysteine-induced inhibition of cell migration [Figure 3f(i), f(ii)] due in part to decreases in β-catenin, Slug and Snail (Supplementary Figure 2A).…”

“…55–57 We now provide evidence of CR-induced EMT of immortalized, but primary, epithelial cells that promotes cell migration and intriguingly exhibits responses that mimic changes recorded during hypoxia. Given that hypoxia/Hif-1α regulates metastatic processes, especially EMT by directly interacting with β-catenin 44,58 or Notch intracellular domain, 59 it is not surprising that CR infection that mimics hypoxia and is associated with activation of the Wnt/β-catenin 30,34 and Notch 35,36 pathways, promotes neoplasia in response to a second hit. 36,45 Finally, several recent studies have shown that it is not unprecedented for EMT to generate cells with many of the properties of self-renewing stem cells (7–9).…”

Nuclear Signaling from Cadherin Adhesion Complexes

“…The best evidence for the aforementioned model involves a tyrosine phosphorylation in β-catenin at residue 654, which leads to reduced E-cadherin binding both in vitro (Roura et al, 1999) and in vivo (van Veelen et al, 2011), and enhanced nuclear signaling activity (Jean et al, 2009; Kim et al, 2009; Piedra et al, 2001; van Veelen et al, 2011; Xi et al, 2013). Activation of a number of kinases is associated with phosphorylation of β-catenin at Y654, including EGFR (Jean et al, 2009), HGF (David et al, 2008), TGFβ (Kim et al, 2009), and Src downstream of a variety of signals (Condello, Cao, & Matei, 2013; Lee et al, 2013; Sumiyoshi, Takahashi, Obata, Sugimoto, & Kohara, 2011; Xi et al, 2013).…”

“…Activation of a number of kinases is associated with phosphorylation of β-catenin at Y654, including EGFR (Jean et al, 2009), HGF (David et al, 2008), TGFβ (Kim et al, 2009), and Src downstream of a variety of signals (Condello, Cao, & Matei, 2013; Lee et al, 2013; Sumiyoshi, Takahashi, Obata, Sugimoto, & Kohara, 2011; Xi et al, 2013). In most of these cases, pY654 β-catenin shows reduced association with cadherin contacts as well as enhanced nuclear accumulation and target-gene activation.…”

Downregulation of FOXO3a Promotes Tumor Metastasis and Is Associated with Metastasis-Free Survival of Patients with Clear Cell Renal Cell Carcinoma

“…Thus, FOXO3a might suppress EMT of ccRCC cells and thereby inhibited metastasis. We searched for a panel of key regulators of EMT, including TWIST1, HIF1a, SNAIL1, and YBX1 (20)(21)(22)(23). These genes were all transcription factors that regulated EMT.…”