Association of Vitamin D Receptor Polymorphisms With the Risk of Nonmelanoma Skin Cancer in Adults

Abstract

Protective effects of UV-B radiation against nonmelanoma skin cancer (NMSC) are exerted via signaling mechanisms involving the vitamin D receptor (VDR). Recent studies have examined single-nucleotide polymorphisms (SNPs) in the VDR, resulting in contradictory findings as to whether these polymorphisms increase a person's risk for NMSC. To examine whether the polymorphisms in the VDR gene are associated with the development of NMSC and the demographic characteristics of the participants. This case-control study recruited 100 individuals who received a diagnosis of and were being treated for basal cell carcinoma or squamous cell carcinoma (cases) and 100 individuals who were receiving treatment of a condition other than skin cancer (controls) at the dermatology clinics at the Kirklin Clinic of the University of Alabama at Birmingham Hospital between January 1, 2012, and December 31, 2014. All participants completed a questionnaire that solicited information on skin, hair, and eye color; skin cancer family history; and sun exposure history, such as tanning ability and number of severe sunburns experienced throughout life. Blood samples for DNA genotyping were collected from all participants. Polymorphisms in the VDR gene (ApaI, BsmI, and TaqI) were assessed to determine the association of polymorphisms with NMSC development and demographic characteristics. χ2 Analysis was used to determine whether genotype frequencies deviated significantly from Hardy-Weinberg equilibrium. Logistic regression was used to calculate odds ratios (ORs) and associated 95% CIs for the identification of factors associated with NMSC diagnosis. A model was created to predict NMSC diagnoses using known risk factors and, potentially, VDR SNPs. A total of 97 cases and 100 controls were included. Of the 97 cases, 68 (70%) were men and 29 (30%) were women, with a mean (SD) age of 70 (11) years. Of the 100 controls, 46 (46%) were men and 54 (54%) were women, with a mean (SD) age of 63 (9) years. All participants self-identified as non-Hispanic white. A model including age, sex, and skin color was created to most effectively predict the incidence of skin cancer. Risk factors that significantly increased the odds of an NMSC diagnosis were light skin color (OR, 5.79 [95% CI, 2.79-11.99]), greater number of severe sunburns (OR, 2.59 [95% CI, 1.31-5.10]), light eye color (OR, 2.47 [95% CI, 1.30-4.67]), and less of an ability to tan (OR, 2.35 [95% CI, 1.23-4.48]). The risk factors of family history of NMSC (OR, 1.66 [95% CI, 0.90-3.07]) and light hair color (OR, 1.17 [95% CI, 0.51-2.71]) did not reach statistical significance. Participants with the BsmI SNP were twice as likely to develop NMSC than participants with no mutation (OR, 2.04 [95% CI, 1.02-4.08]; P = .045). The results of this study are especially useful in the early treatment and prevention of NMSC with chemopreventive agents (for those with the BsmI SNP). A screening for the BsmI SNP may emphasize the importance of sun protection and facilitate skin cancer prevention and, therefore, decrease the skin cancer burden.