A functional copy number variation in the WWOX gene is associated with lung cancer risk in Chinese

Lei Yang 3 Bin Liu 2 3 Binfang Huang 2 3 Jieqiong Deng 0 Hongbin Li 5 Bolan Yu 4 Fuman Qiu 3 Mei Cheng 3 Hui Wang 3 Rongrong Yang 3 Xiaorong Yang 3 Yifeng Zhou 0 Jiachun Lu 3 0 Soochow University Laboratory of Cancer Molecular Genetics, Medical College of Soochow University , Suzhou 215123, China 1 The Author 2013. Published by Oxford University Press. All rights reserved 2 Guangzhou No.12 Hospital affiliated to Guangzhou Medical University , 1 Tianqiang Road, Guangzhou 510620, China 3 The Institute for Chemical Carcinogenesis, The State Key Lab of Respiratory Disease, Guangzhou Medical University , 195 Dongfengxi Road, Guangzhou 510182, China 4 The Key Laboratory for Major Obstetric Diseases of Guangdong Province, Third Affiliated Hospital of Guangzhou Medical University , Guangzhou 510150, China 5 Department of Medical Oncology, The Third Affiliated Hospital of Harbin Medical University , Harbin 150040, China WW domain-containing oxidoreductase (WWOX) is a tumor suppressor that has been reported to lose function due to genetic alterations in several cancers. WWOX maps to the common chromosomal fragile site FRA16D and several copy number variations (CNVs) were found within this gene. In this study, we investigated the association between the CNVs of WWOX and lung cancer risk in four independent case - control studies, which are on 2942 lung cancer cases and 3074 cancer-free controls of southern, eastern and northern Chinese. A common CNV-67048 was genotyped by the Taqman real-time PCR, and its biological effect was accessed with protein expression and sequencing assays. We found that in comparison with the common 2-copy genotype, the carriers of loss variant genotypes (1-copy or 0-copy) had a significantly increased risk of lung cancer (adjusted OR 5 1.39, 95% CI 5 1.24 - 1.55, P 5 9.0131029) in a dose - response manner (Ptrend 5 1.12 3 10210), and the WWOX protein expressions in lung cancer tissues were significantly lower (P 5 0.036), accompanying a higher rate of exons absence (P 5 0.021) in subjects with loss genotypes of CNV-67048. Our data suggest that the loss genotypes of CNV-67048 in WWOX predispose their carriers to lung cancer; this might be related with altered WWOX gene expression and exons absence in them. - INTRODUCTION Although an abundance of association studies, especially the genome-wide association studies (GWAS), has reported that a lot of single-nucleotide polymorphisms (SNPs) are associated with risks of various cancers, only a small proportion of cancer heritability can be explained by those SNPs, reflecting that some missing heritability existed (1). Recently, increasing evidence suggests that the copy number variation (CNV) might hold the key to account for a large proportion of the missing heritability (1 3). CNV is a prevalent genetic aberration that covers .1 kb duplication or deletion, which may contribute to phenotypic variations by altering biological functions or genes expression (4,5). Therefore, if CNVs are located in tumor suppressor genes or oncogenes, corresponding to loss-of-function mutations or gain-of-function mutations would possibly alter the predisposition to cancer. Human WW domain-containing oxidoreductase (WWOX) is an identified tumor suppressor gene. As a pro-apoptotic molecule, WWOX regulates several cancer-related signaling pathways and genes (6 8), and it frequently loses function in the initiation of tumorigenesis as well as neoplastic process (9,10). Not only does WWOX directly suppress the carcinogenic effects of oncogenes such as c-Jun, erbB4, MDM2 (11 13), but it also activates tumor suppressor genes such as p53, p73 to induce cell apoptosis (14 16). WWOX knockout mice had increased lung carcinoma susceptibility (10), whereas transfection of WWOX in an animal model caused dramatic suppression of tumorigenesis (17,18). In addition, loss expression of WWOX protein has been found in various tumors (19,20), and WWOX is down-regulated by exposure to environmental carcinogens such as Benzo[a]pyrene diol epoxide (9). The human WWOX gene (OMIM: 605131) is located on chromosome 16q23.3 24.1, a region spanning over the common fragile site 16D (FRA16D). Loss of heterozygosis (LOH), homozygous deletions and chromosomal translocations in WWOX has been reported in several types of cancer (21 24). In lung cancer, a high incidence of exons absence like the familiar deletion of WWOX exons 6 8 was reported (23). However, it is still unclear how these somatic mutations evolve in cancer development. Recently, a germline CNV was found related with LOH in Chr18q22.1 in ileal carcinoid tumor cells (25), implying that the constitutional CNV may induce high frequency of somatic mutations and thus be involved in cancer predisposition. Using bioinformatics analysis, we found that there were several CNVs in WWOX (http://projects.tcag.ca/variation/?source=hg18, date last accessed January 6, 2013), and we hypothesized that the CNVs in WWOX might be associated with lung (...truncated)