E‐cadherin polymorphism −160 C/A and prostate cancer

Dear Sir, We read with interest the report of Verhage et al.,1 “Single nucleotide polymorphism in the E-cadherin gene promoter modifies the risk of prostate cancer. ” They studied C/A polymorphism at 160 bp relative to the transcription-start site for E-cadherin gene. They genotyped 82 PCa patients and 188 controls and found significant differences in frequencies of alleles between cases and controls, and a higher relative risk of PCa for A-allele carriers (OR 3.6) compared to C-only carriers. Genotype frequencies among PCa patients were 3.7% AA, 70.7% CA, 25.6% CC; among controls 4.8% AA, 40.0% CA, 55.3% CC. The promising nature of their results prompted us to complement their findings with data from our SlovenianCaucasian population and our group of PCa patients. The availability of commercial test has made it easier to determine the genotype for particular polymorphism and this was evaluated simultaneously. Genotyping was carried out on DNA samples from 183 patients with histologically proven (sporadic) PCa, 168 women blood donors to estimate the frequencies of alleles in the general population and 30 patients with histologically verified benign prostatic hyperplasia. Our study was approved by competent ethical review board committee. DNA was extracted from peripheral blood samples using a standard salt-precipitation technique. Genotyping was carried out using pre-developed TaqMan assay reagents for allelic discrimination (Assay on Demand, part number C_11934298_10, Applied Biosystems, Applera Corporation, Foster City, CA) according to the manufacturer’s instructions, using a reaction volume of 5 l in 384-well plates on a sequence detection system AbiPrism 7900HT. The frequencies of genotypes and alleles in controls are presented in Table I, and those among PCa patients are presented in Table II. Allele frequencies in all groups (including patients and all subgroups of patients) were in Hardy-Weinberg equilibrium. The frequency of AA homozygotes was higher in patients than in controls, although the difference was not statistically significant (11.5% vs. 6.1%). Separating patients into 2 groups according to age ( 70 years old and 70 years and older) showed noticeable differences in the frequency of AA homozygotes with age (15.9% vs. 7.4%, p 0.07). There was a significant difference in genotype frequency between controls and patients with PCa younger than 70 years ( ,2 p 0.024). The relative risks for individual genotypes were as follows (using CC as the reference): AC, 1.11 (p 0.69, 95% CI 0.66–1.89); and AA, 2.92 (p 0.014, 95% CI 1.25–6.82). Carriers of A allele had an increased, though not statistically significant, relative risk of PCa (1.42, 95% CI 0.86–2.35). There were no significant differences in frequencies of genotypes in groups according to Gleason score or WHO grade. When limiting the analysis to 91 patients (age 63 6.3 years, mean SD), who underwent radical prostatectomy (confined disease), the distribution was 11% AA, 36.3% AC and 52.7% CC, which is not different from that in other patient groups. The frequencies of alleles in the general population in our study agree with findings in the Dutch population of the cited study,1 which was as expected because both study populations are Caucasian. Our results also confirm findings from the first investigation1 into the importance of C/A SNP as a novel risk factor for PCa. Our results differ from the results of Verhage et al.1 concerning their finding that heterozygote genotype (CA) is at higher risk compared to a high risk homozygote (AA). It was also not possible to confirm the magnitude of allele A influence, which may be due to the larger data set used in our present study. Although our study included patients with different stages of disease (confined, locally advanced and metastatic), subgroup analyses confirmed this finding. We did not find a significant correlation between stage of disease and genotype or identify differences between stages. These findings supplement results from the cited study, which included only patients with confined disease. Perhaps due to the larger sample, all of our groups were in Hardy-Weinberg equilibrium. In this series only patients with sporadic PCa were included. Family history of PCa was excluded by interview, although some elderly patients may not recall diseases of their firstdegree relatives correctly. We believe that this does not affect the validity of our results because Verhage et al.1 evaluated this aspect and did not find differences in the frequencies of the concerned polymorphism between patients with sporadic and familial PCa. This is further supported by recent findings of no differences in clinical presentation and epidemiological features when comparing familial and sporadic PCa, indicating that the 2 entities are the same disease.2 It was expected to find correlation between stage of disease or histological aggressiveness and genotype because of the important role of E-cadherin in cell adhesion, epithelial devel-