Identification of CDCP1 as a hypoxia-inducible factor 2α (HIF-2α) target gene that is associated with survival in clear cell renal cell carcinoma patients

Abstract

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. Here we show that hypoxia induces CDCP1 expression and tyrosine phosphorylation in hypoxia-inducible factor (HIF)-2α-, but not HIF-1α-, dependent fashion. shRNA knockdown of CDCP1 impairs cancer cell migration under hypoxic conditions, whereas overexpression of HIF-2α promotes the growth of tumor xenografts in association with enhanced CDCP1 expression and tyrosine phosphorylation. Immunohistochemistry analysis of tissue microarray samples from tumors of patients with clear cell renal cell carcinoma shows that increased CDCP1 expression correlates with decreased overall survival. 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 CDCP1 is a biomarker and potential therapeutic target for metastatic cancers.kidney cancer | oxygen deprivation C UB domain-containing protein 1 (CDCP1), also known as transmembrane and associated with SRC kinase (TRASK) and subtractive immunization M + HEp3-associated 135-kDa protein (SIMA135), is a substrate and binding protein for the Src-family tyrosine kinases (SFKs). CDCP1 is overexpressed and highly tyrosine-phosphorylated in multiple cancers (1, 2), predominantly renal (3, 4), breast (2), colon (2, 5, 6), pancreatic (7), and lung cancers (2). At present, the functional importance of CDCP1 has been reported in patients with metastatic carcinomas as well as in a number of epithelial cancer cell lines (3,6,(8)(9)(10)(11)(12)(13)(14). However, mechanisms regulating CDCP1 are not well-defined. Studies from our laboratory revealed a biochemical pathway by which CDCP1 participates in the activation of Src-family members and the coupling of SFK activation to phosphorylation and regulation of protein kinase C delta (PKC-δ) (15).Importantly, a recent study shows that CDCP1 plays a critical role in the process of metastasis and in the survival of cells at distant sites of metastasis (16). Here we demonstrate a unique role for CDCP1 under conditions of oxygen deprivation (hypoxia).Hypoxia triggers the elevation of hypoxia-inducible factors HIF-1α and HIF-2α by blocking von Hippel Lindau (VHL)-dependent HIF-α degradation (17)(18)(19). HIF is a heterodimer of two basic helix-loop-helix/PAS proteins, HIF-α and the aryl hydrocarbon nuclear translocator (ARNT or HIF-β) (20). HIF-α and ARNT subunits are ubiquitously expressed; however, the α-subunit is labile under conditions of normal oxygen (5-21% O 2 ). Under hypoxic conditions (0.5-5% O 2 ) the HIF-α subunit is stabilized, dimerizes with ARNT, translocates to the nucleus, and subsequently binds to hypoxia response elements (HREs) within target genes. Among HIF transcription targets are genes involved in glucose metabolism, angiogenesis, and metastasis (21), thereby tigh...

EGF inhibits constitutive internalization and palmitoylation-dependent degradation of membrane-spanning procancer CDCP1 promoting its availability on the cell surface

“…Our data showing that CDCP1 is up-regulated via the EGFR system is supported by a recent report demonstrating that levels of the encoding transcripts are highly correlated across 732 cancer cell lines (9). Interestingly, high correlation across this large cell line dataset was also seen between CDCP1 mRNA, and transcripts encoding the transcription factor hypoxiainducible factor (HIF)-2α and the receptor tyrosine kinase Met, indicating that cancers with high HIF-2α or Met expression will likely have high CDCP1 levels (9).…”

“…Interestingly, high correlation across this large cell line dataset was also seen between CDCP1 mRNA, and transcripts encoding the transcription factor hypoxiainducible factor (HIF)-2α and the receptor tyrosine kinase Met, indicating that cancers with high HIF-2α or Met expression will likely have high CDCP1 levels (9). Consistently, recent papers have linked HIF-2α and CDCP1 (9, 10).…”

“…EGF increases the lifespan of CDCP1 promoting its availability on the cell surface where our data indicate it is available to mediate pro-cancer phenotypes such as cell migration. Based on published analysis of patient cohorts and animal models, antibody targeting of CDCP1 has been proposed for cancer treatment (9,10,18,20). This is supported by molecular analysis demonstrating that CDCP1 is pro-cancerous in vivo by promoting cell survival via pathways involving Src, PKCδ, FAK, PI3K and Akt (14,18,19), and that anti-CDCP1 antibodies efficiently block survival, inducing apoptosis (18)(19)(20)22).…”

“…In addition, data from 732 cancer cell lines reveals high concordance in CDCP1 and EGFR mRNA expression suggesting that cancers dependent on EGFR will have elevated CDCP1 (9). Here we examine EGFR mechanisms regulating CDCP1 with our data demonstrating the first example of the EGFR system functioning to increase the lifespan and cell surface availability of a protein.…”

Elevated CDCP1 predicts poor patient outcome and mediates ovarian clear cell carcinoma by promoting tumor spheroid formation, cell migration and chemoresistance

“…In several tumor types that commonly metastasize via vascular routes, including lung, kidney, pancreas and colon cancer, elevated or cell-surface expression of CDCP1 is associated with poor patient outcome. [12][13][14][15][16][17] Consistent with a role in hematogenous metastasis, in animal models of vascular dissemination, survival of cancer cells undergoing extravasation is markedly enhanced by a mechanism involving serine protease cleavage to generate 70 kDa CDCP1. This initiates pro-survival signaling via focal adhesion kinase 1 and phosphoinositide 3-kinase (PI3K) dependent protein kinase B (Akt) activation resulting in suppression of poly (ADP-ribose) polymerase 1 (PARP1) mediated apoptosis.…”