Tandem CAG repeats of the androgen receptor gene and prostate cancer risk in black and white men

The most common malignancy in men worldwide is cancer of the prostate. Andr ogens play a direct role in normal and malignant growth of prostate cells v ia the androgen receptor (AR). This study analyzed the polymorphic CAG repe at sequence in exon 1 of the AR gene to determine if the number of repeats might be an indicator of prostate cancer risk or aggressive disease. DNA wa s extracted from blood samples of 20 black and 20 white men with well-docum ented prostate cancer and 40 healthy controls (20 blacks and 20 whites). PC R amplification was followed by gel electrophoresis and DNA sequencing. Thi s region normally contains between 9 and 29 repeats. Patients an controls b oth had minor variations in the number Of repeats, which ranged from 13 to 27 with 21 being the most frequent allele. Black controls and patients both had a mean of 20 +/- 3 repeats; in whites the mean was significantly lower in patients than controls (21 +/- 2 versus 23 +/- 2; p = 0.004). Combined black and white patients also had a lower number than the combined group of controls (20 +/- 3 versus 22 +/- 3; p = 0.02). Similarly, black and white patients with aggressive disease had a lower number than patients whose dis ease was more slowly progressive (19 +/- 2 versus 22 +/- 3; p = 0.02). We c onclude that the small differences in the number of CAG repeats in both bla ck and white patients do not appear to be a strong indicator of risk or agg ressive disease but that this size polymorphism may be one of many genetic and environmental risk factors involved in prostate cancer.