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Genetic Variation in the Inhibin Pathway and Risk of Testicular Germ Cell Tumors

¹ Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Department of Health and Human Services, Bethesda, Maryland; ² National Cancer Institute Core Genotyping Facility, NIH, Department of Health and Human Services, Gaithersburg, Maryland; ³ U.S. Army Center for Health Promotion and Preventive Medicine, Washington, District of Carolina; and ⁴ Walter Reed Army Institute of Research, Forest Glen, Maryland

Requests for reprints: Mark Purdue, Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Department of Health and Human Services, EPS-8009, 6120 Executive Boulevard, Rockville, MD 20892, 7234. Phone: 301-451-5036; Fax: 301-402-1819; E-mail: purduem{at}mail.nih.gov.

Key Words: inhibin • INHA • polymorphisms • case control study • testicular cancer • USA

Gene-knockout studies in mice suggest that INHA, encoding a subunit of gonadotropin-regulating proteins known as inhibins, is a tumor suppressor for testicular stromal cell tumors. It is not known whether genetic variation in the inhibin pathway also influences susceptibility to testicular germ cell tumors (TGCT), the most common testicular cancer in young men. To address this question, we conducted a case-control analysis (577 cases; 707 controls) of single-nucleotide polymorphisms (SNP) in genes in the inhibin pathway among participants in the U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants Study. Thirty-eight tagging SNPs in six genes (INHA, INHBA, INHBB, INHBC, INHBE, and SMAD4) were genotyped. Odds ratios (OR) and 95% confidence intervals (CI) relating variant genotypes to TGCT risk were calculated using unconditional logistic regression. Among White subjects, an elevated risk of TGCT was observed for carriers of the T allele of the INHA variant rs2059693 (CT genotype: OR, 1.33; 95% CI, 1.04–1.71; TT: OR, 1.60; 95% CI, 1.01–2.52; P_trend = 0.008). The association with rs2059693 was stronger for nonseminomas, and for teratomas and teratocarcinomas in particular (N = 58; CT: OR, 1.63; 95% CI, 0.89–2.99; TT: OR, 4.54; 95% CI 2.00–10.3; P_trend = 0.0008). We found no evidence of association with variants in the other investigated genes. These findings suggest that genetic variation in the INHA locus influences TGCT development. [Cancer Res 2008;68(8):3043–8]