Enokida H et al. (2005) Ethnic group-related differences in CpG hypermethylation of the GSTP1 gene promoter among African-American, Caucasian and Asian patients with prostate cancer. Int J Cancer 116: 174–181

Glutathione S-transferase pi (GSTP1) has been the subject of several cancer studies. Recent work by Enokida and colleagues has investigated the role of inactivation of GSTP1 by CpG hypermethylation in prostate cancer pathogenesis, and has asked whether this differs among ethnic groups.

Using a methylation-specific polymerase-chain-reaction technique, the team recorded the methylation status of the GSTP1 promoter in 291 prostate cancer tissue samples. 170 samples were obtained from Asian patients, 44 from African-Americans, and 77 from Caucasians. The results were compared with those from 172 benign prostatic hyperplasia samples (96 from Asian patients, 38 from African-Americans, and 38 from Caucasians). As expected, this analysis showed that GSTP1 hypermethylation was more common in prostate cancer than in benign prostatic hyperplasia (65.6% vs 24.5%, P <0.0001), across all ethnic groups. The difference was most pronounced among the African-American samples, however, and the authors suggest that GSTP1 methylation is a useful biomarker for prostate cancer in this ethnic group.

Next, GSTP1 methylation was correlated with pathologic stage and Gleason score. In both cases, the frequency of methylation was positively associated with the pathologic findings, suggesting a role for GSTP1 methylation in tumor progression. Among the individual ethnic groups, however, this association was statistically significant only for the Asian patients.

In summary, the study indicates that GSTP1 methylation is important in prostate cancer pathogenesis and that this epigenetic event differs among ethnic groups.