CUB domain-containing protein 1 (CDCP1) is a transmembrane protein that is highly expressed in stem cells and frequently overexpressed and tyrosine phosphorylated in cancer. CDCP1 promotes cancer cell metastasis. However, the mechanisms that regulate CDCP1 are not well defined. Studies from our laboratory revealed a biochemical pathway by which CDCP1 participates in the activation of Src-family kinase (SFK) members and the coupling of SFK-activation to the phosphorylation and regulation of protein kinase C-delta (PKC-δ). Here we show that hypoxia induces CDCP1 expression and tyrosine phosphorylation in a HIF-2α, but not HIF-1α, dependent fashion. shRNA knockdown of CDCP1 impairs cancer cell migration under hypoxic conditions, while overexpression of HIF-2α promotes the growth of tumor xenografts in association with enhanced CDCP1 expression and tyrosine phosphorylation, as well as, significantly promotes lung metastases in NOD/SCID mice. To investigate the relationship between HIF-2α and CDCP1 expression, we performed a correlation analysis in the largest up-to-date collection (Sanger Cell Line Project) of cancer cell line microarray data (n=732). We found a dramatic concordance in the expression of HIF-2α and CDCP1 (Pearson's correlation, P <1x10-20), indicating that cancers with high HIF-2α expression tend to have high levels of CDCP1 expression. We next asked whether other known HIF-2α target genes also correlate in this expression analysis. Remarkably, MET and EGFR, which are hypoxia regulated and known HIF-2α target genes, also displayed a strong correlation with HIF-2α and CDCP1 expression. Immunohistochemistry analysis of tissue microarray samples from tumors of patients with clear cell renal cell carcinoma (ccRCC) shows that increased CDCP1 expression correlates with decreased overall survival. Interestingly, high-grade ccRCCs (G3, G4) expressed significantly higher (P = 0.03, t-test) levels of CDCP1 protein compared to lower grade tumors (G1, G2), suggesting that CDCP1 expression increases progressively with higher ccRCC tumor grade. Furthermore, hypoxia activates Src signaling and the Src inhibitor (Dasatinib) prevents the hypoxia-induced phosphorylation of CDCP1. Thereby, reinforcing that CDCP1 is an SFK-associated receptor, which promotes migration and metastasis and suggests that hypoxia-induced CDCP1 signaling may further stimulate a more aggressive cancer phenotype. Together, these data support a critical role for CDCP1 as a unique HIF-2α target gene involved in the regulation of cancer metastasis, and suggest that therapeutic approaches targeting CDCP1, such as monoclonal antibodies, could be beneficial in the treatment of metastatic cancers.
Supported by NIH grant 5R01GM056203-15 to L.C.C and Dana Farber/Harvard Cancer Center Career Development Award to B.M.E.
Citation Format: Brooke M. Emerling, Cyril Benes, Eric Bell, George Poulogiannis, Kevin Courtney, Hui Lui, Rayman Choo-Wing, Gary Bellinger, Stephen Soltoff, Lewis Cantley. Identification of CDCP1 as a HIF-2α target gene involved in the regulation of cancer cell migration and metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4588. doi:10.1158/1538-7445.AM2013-4588