title: The CAG repeat polymorphism of androgen receptor gene and prostate cancer: a meta-analysis.
abstract: The association between the polymorphic CAG repeat in androgen receptor gene (AR) and prostate cancer susceptibility has been studied extensively. However, the results are contradictory. The purpose of our meta-analysis was to investigate whether CAG repeat related to prostate cancer risk and had genetic heterogeneity across different geographic regions and study designs. Random-effects model was performed irrespective of between-study heterogeneity. Data and study quality were assessed in duplicate. Publication bias was assessed by the fail-safe number and Egger's test. There were 16 (patients/controls: 2972/3792), 19 (3835/4908) and 12 (3372/2631) study groups for comparisons of ≥ 20, 22 and 23 repeats of CAG sequence, respectively. Compared with CAG repeat <20, 22 or 23, carriers of ≥ 20, 22 or 23 repeats had 21% (95% CI: 0.61-1.02; P = 0.076), 5% (95% CI: 0.81-1.11; P = 0.508) and 5% (95% CI: 0.76-1.20; P = 0.681) decreased risk of prostate cancer. After classifying studies by geographic areas, carriers of ≥ 20 repeats had 11% decreased risk in populations from USA, 53% from Europe, and 20% from Asia (P > 0.05), whereas comparison of ≥ 23 repeats with others generated a significant prediction in European populations (OR = 1.17; P = 0.039). Stratification by study designs revealed no material changes in risk estimation. Meta-regression analysis found no significant sources of between-study heterogeneity for age, study design and geographic region for all comparisons. There was no identified publication bias. Taken together, our results demonstrated that AR CAG repeat polymorphism with ≥ 20 repeats might confer a protective effect among the prostate cancer patients with 45 years older but not all the prostate cancer patients.
authors.affiliation: Key Laboratory of Genome Science and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Mingliang
authors.initials: M
authors.lastname: Gu
authors.forename: Xiaoqun
authors.initials: X
authors.lastname: Dong
authors.forename: Xuezhi
authors.initials: X
authors.lastname: Zhang
authors.forename: Wenquan
authors.initials: W
authors.lastname: Niu
mesh_terms: D000367:Age Factors; D003710:Demography; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D008297:Male; D015233:Models, Statistical; D011110:Polymorphism, Genetic / Q000235:genetics*; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D017594:Publication Bias; D011944:Receptors, Androgen / Q000235:genetics*; D012044:Regression Analysis; D012107:Research Design; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: D011944:Receptors, Androgen