Gallbladder cancer (GC) is a relatively uncommon cancer with higher incidence in certain areas including Japan. Because of the difficulty in diagnosis, prognosis of GC is very poor. To identify genetic determinants of GC, we conducted a genome-wide association study (GWAS) in 41 GC patients and 866 controls. Association between each single-nucleotide polymorphism (SNP) with GC susceptibility was evaluated by multivariate logistic regression analysis conditioned on age and gender of subjects. SNPs that showed suggestive association (Po1脗10 脌4 ) with GC were further examined in 30 cases and 898 controls. SNP rs7504990 in the DCC (deleted in colorectal cancer, 18q21.3) that encodes a netrin 1 receptor achieved a combined P-value of 7.46脗10 脌8 (OR录6.95; 95% CI录3.43-14.08). Subsequent imputation analysis identified multiple SNPs with similarly strong associations in an adjacent genomic region, where loss of heterozygosity was reported in GC and other cancers. Reduced expression of DCC was indicated to be associated with the poorly differentiated histological type, increased proliferation and metastasis through loss of adhesiveness. However, due to the limited sample size investigated here, further replication study and functional analysis would be necessary to further confirm the result of the association.
INTRODUCTIONGallbladder cancer (GC) is the most common malignancy of the biliary tract and the fifth most common cancer of the gastrointestinal tract. 1 With an overall 5-year survival rate of o5%, GC is a highly lethal malignancy with very poor prognosis. 2 Most of GCs were diagnosed at a very late stage because of the lack of symptoms and non-specific symptoms of early-stage tumors. 1,3 Although the incidence of GC is relatively rare compared with other cancers, higher incidences of GC have been reported in certain geographical regions including India, Pakistan, Ecuador, Korea and Japan. 4 In addition, the prevalence of GC is known to be three times higher in women than in men. 5 Although several clinical risk factors of GC such as gallstones, cholecystitis, porcelain gallbladder, gallbladder polyps, anomalous panreatobiliary duct junction and obesity have been indicated, 1,6 etiology of GC is largely unknown. Only few somatic genetic changes including mutations in K-ras, TP53 and p16 Ink4 /CDKN2 as well as loss of heterozygosity at several chromosomal regions harboring known or putative tumor-suppressor genes have been reported in GCs. 5,7 Hence, identification of novel genetic factors associated with susceptibility to GC should