Single nucleotide polymorphism of the human kallikrein-2 gene highly correlates with serum human kallikrein-2 levels and in combination enhances prostate cancer detection

Purpose: We examined the relationship between a mutant (T) for wild-type (C) allele substitution of the human kallikrein-2 gene (KLK2), circulating human kallikrein-2 (hK2) levels and prostate cancer risk. Patients and Methods: We studied 1,287 consecutive men who underwent prostate biopsies because of an abnormal prostate-specific antigen level. Serum and DNA were obtained before biopsy. Cases were patients with cancer, and controls were patients with no cancer. The mutant and wild-type alteles of the KLK2 gene were designated as the T and C alteles, respectively. Results: Of the 1,297 men, 616 had cancer, and 671 had no cancer. The overall distribution of the CC, CT, and TT KLK2 genotypes was 55.1%, 38.2%, and 6.8%, respectively. The median hK2 levels for men with the CC, CT, and TT genotypes were 0.24, 0.18, and 0.062 ng/mL and correlated with the genotypes, respectively (P = .0001). The adjusted adds ratios for prostate cancer for patients with the TT and CT genotypes compared with patients with the CC genotype, were 2.13 (95% confidence interval [CI], 1.3 to 3.5; P = .004) and 1.51 (95% CI, 1.2 to 2.0; P = .002), respectively. The adjusted odds ratio for prostate cancer for patients in the fourth quartile, of hK2 compared with the first quartite was 4.33 (95% CI, 2.9 to 6.4; P = .001). When combined, the adjusted adds ratio for having prostate cancer was 13.92 (95% CI, 6.6 to 29.2; P = .0001) for patients with high hK2 levels and at least one T allele. Conclusion: The C/T polymorphism of the KLK2 gene and circulating levels of hK2 are correlated and, in combination, are highly predictive for prostate cancer.