ABCC4 copy number variation is associated with susceptibility to esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the eighth most common cause of cancer-related death worldwide. However, previous genome-wide single nucleotide polymorphism association analyses have not explained the high heritability associated with ESCC. In this study, we performed genome-wide copy number variation (CNV) analysis on 128 discordant sibling pairs to identify novel genes that contribute to ESCC susceptibility. A total of 57 774 individual CNVs were identified, and an interactive network of common CNV-associated genes was constructed, which showed that several ABC transporter genes contain CNVs in ESCC patients. Independent validation of a CNV at 13q32.1 in 1048 northern Chinese Han subjects demonstrated that the amplification of ABCC4 significantly correlated with ESCC risk [odds ratio: 3.36 (1.65-7.93), P = 0.0013]. Immunohistochemistry staining suggested that high copy numbers correlated with increased protein levels. High expression of ABCC4 was an independent poor prognostic factor for ESCC [relative risk: 1.73 (1.10-2.73), P = 0.0181]. The CNV region showed strong enhancer activity. Furthermore, inhibition of ABCC4 protein in ESCC cells decreased cell proliferation and motility via the inhibition of COX-2, PGE2 receptors and c-Myc expression; AKT, extracellular signal-regulated kinase and cAMP response element-binding protein phosphorylation; and β-catenin nuclear translocation in ESCC cells. In conclusion, the CNV at 13q32.1 is associated with ESCC susceptibility, and a gene within this locus, ABCC4, activates the oncogenic pathways in ESCC and thus facilitates cancer cell development and progression. A direct genetic contribution of ESCC risk through CNV common variants was determined in this study, and ABCC4 might therefore have predictive and therapeutic potential for ESCC.