Michael E. French

Exposure to ultraviolet radiation: association with susceptibility and age at presentation with prostate cancer

A positive association between latitude and prostate cancer mortality has been interpreted to indicate that ultraviolet radiation (UVR) protects against development of this cancer. We aimed to examine this hypothesis. We compared exposure between 210 cases and 155 controls. Childhood sunburn (odds ratio 0.18, 95% CI 0.08-0.38), regular foreign holidays(0.41, 0.25-0.68), sunbathing score (0.83, 0.76-0.89), and low exposure to UVR (3.03, 1.59-5.78) were associated with development of prostate cancer. Furthermore, cases with low UVR exposure developed cancer at a younger median age (67.7 years, IQR 61.5-74.6) than cases with higher exposure (72.1 years, 67.5-76.4); p=0.006. These findings are compatible with UVR having a protective role against prostate cancer.

Prostate cancer risk and exposure to ultraviolet radiation: further support for the protective effect of sunlight

Recent studies have suggested that exposure to ultraviolet (UV) radiation may be protective to some internal cancers including that in the prostate. We describe a confirmatory study in 212 prostatic adenocarcinoma and 135 benign prostatic hypertrophy patients designed to determine whether previous findings showing a protective effect for UV exposure could be reproduced. We used a validated questionnaire to obtain data on aspects of lifetime exposure to UV. The data confirmed that higher levels of cumulative exposure, adult sunbathing, childhood sunburning and regular holidays in hot climates were each independently and significantly associated with a reduced risk of this cancer.

Prostate cancer risk: associations with ultraviolet radiation, tyrosinase and melanocortin-1 receptor genotypes.

Exposure to ultraviolet radiation may reduce prostate cancer risk, suggesting that polymorphism in genes that mediate host pigmentation will be associated with susceptibility to this cancer. We studied 210 prostate cancer cases and 155 controls to determine whether vitamin D receptor (VDR, Taql and Fokl variants), tyrosinase (TYR, codon 192 variant) and melanocortin-1 receptor (MC1R, Arg151Cys, Arg160Trp, Val92Met, Asp294His and Asp84Glu variants) genotypes are associated with risk. UV exposure was determined using a questionnaire. MC1R Arg160/Arg160 homozygotes were at increased risk (P = 0.027, odds ratio = 1.94) while TYR A2/A2 homozygotes were at reduced risk of prostate cancer (P = 0.033, odds ratio = 0.48). These associations remained significant after correction for UV-exposure. Stratification of cases and controls by quartiles of exposure, showed that the protective effect of TYR A1A2 (P = 0.006, odds ratio 0.075) and A2A2 (P = 0.003, odds ratio 0.055) was particularly strong in subjects who had received the greatest exposure. Our data show for the first time, that allelism in genes linked with skin pigment synthesis is associated with prostate cancer risk possibly because it mediates the protective effects of UV. Importantly, susceptibility is associated with an interaction between host predisposition and exposure.

Associations between prostate cancer susceptibility and parameters of exposure to ultraviolet radiation.

Low sunlight exposure confers increased prostate cancer risk. In a study conducted in northern England, we investigated how combinations of exposure measures affect this risk. Recursive partitioning was used to identify combinations of exposure parameters that distinguished 453 prostate cancers from 312 benign hypertrophy patients. Sunbathing score most significantly defined cancer patients; 78.7% men with low scores (</=3.0) and 40.2% men with high scores (>8.0) had cancer. These subgroups were stratified by childhood sunburning, holidays in a hot climate and skin type such that subgroups with a 13.0-fold increased risk of cancer were identified.

Associations Between G/A1229, A/G3944, T/C30875, C/T48200 and C/T65013 Genotypes and Haplotypes in the Vitamin D Receptor Gene, Ultraviolet Radiation and Susceptibility to Prostate Cancer

Ultraviolet radiation (UVR) may protect against prostate cancer via a mechanism involving vitamin D. Thus, the vitamin D receptor (VDR) gene is a susceptibility candidate, though published data are discrepant. We studied the association of prostate cancer risk with five VDR single nucleotide polymorphisms (SNPs): G/A1229 (SNP 1), A/G3944 (SNP 2), T/C30875 (SNP 3), C/T48200 (SNP 4) and C/T65013 (SNP 5), in 430 cancer and 310 benign prostatic hypertrophy (BPH) patients. The SNP 2 GG genotype frequency was lower in cancer than BPH patients (odds ratio = 0.63, 95% CI = 0.41–0.98, p = 0.039). SNPs 1 and 2, and SNPs 4 and 5, were in linkage disequilibrium. Two copies of haplotypes comprising SNPs 1‐2, G‐G (odds ratio = 0.63, p = 0.039), SNPs 2‐3 G‐C (odds ratio = 0.45, p = 0.008) and SNPs 1‐2‐3 G‐G‐C (odds ratio = 0.44, p = 0.006), but not SNPs 1‐3, G‐C (odds ratio = 0.81, p = 0.34), were associated with reduced risk (reference, no copies of the haplotypes). These associations were observed after stratification of subjects by extent of UVR exposure. These data show that SNP 2 GG genotype mediates prostate cancer risk, complementing studies reporting this allele is protective in malignant melanoma pathogenesis. They further suggest that published associations of risk with SNP 1 may result from linkage disequilibrium with SNP 2.

Glutathione S-transferase GSTP1 genotypes are associated with response to androgen ablation therapy in advanced prostate cancer

We determined whether the glutathione S-transferase GSTP1 Ile105 --> Val105 substitution is associated with response to androgen ablation therapy in patients with advanced prostate cancer. As response may be associated with tumor grade, Gleason score, clinical T stage and presence of metastases we also determined if GSTP1 genotypes were associated with these prognostic parameters. We speculated that GSTP1 Ile105/Ile105 would be linked with good response to androgen ablation therapy and, low/moderate tumor grade, 1/2 clinical T-stage, Gleason score < 6 and, no metastases. Genotype frequencies in cases and controls were not significantly different (P = 0.70) indicating that allelism in GSTP1 is not associated with susceptibility. There was no association between GSTP1 (Ile105/Ile105 versus Ile105/Val105 and Val105/Val105) and grade (P = 0.28, OR = 0.92), Gleason score (P = 0.84, OR = 0.94) or metastatic state (P = 0.68, OR = 0.88) though the frequency of GSTP1 Ile105/Ile105 was higher in cases with stage 1/2 tumors than those with stage 3/4 tumors (P = 0.03, OR = 1.89). GSTP1 Val105/Val105 was also associated with response to hormone ablation therapy. Thus, the GSTP1 Ile105/Ile105 frequency was significantly higher in 86/118 patients who demonstrated a good response than in those with poor response (P = 0.03, OR = 2.70). We speculate that the association of GSTP1 with response results from an effect of the gene product early in carcinogenesis.