Association of tissue promoter methylation levels of APC, TGFβ2, HOXD3 and RASSF1A with prostate cancer progression

Aberrant promoter methylation is known to silence tumor-suppressor genes in prostate cancer (PCa). We correlated quantitative promoter methylation levels of APC, TGF beta 2 and RASSF1A in 219 radical prostatectomies diagnosed between 1998 and 2001 with clinicopathological follow-up data available including Gleason Pattern (GP), Gleason Score (GS) and pathological stage and explored their potential in predicting biochemical recurrence using univariate and multivariate analyses. We observed that the average methylation levels of APC increased significantly from GS <= 6 to GS7, and pT2 to pT3a, and that of TGF beta 2 increased from GS <= 6 to GS7, but not for RASSF1A. PCa samples were also stratified into high methylation (HM) and low methylation (LM) groups based on the PMR scores of all cases analyzed for each marker. The HM frequency of APC was greater in pT3a than pT2, and in GS >= 8 than GS <= 6. The HM frequency also increased significantly from GP3 to GP4 for APC, TGF beta 2 and RASSF1A. APC methylation level was a significant predictor of biochemical recurrence in univariate analysis (p-value = 0.028). Finally, we combined methylation data of these three genes with the previously reported novel methylation biomarker HOXD3. Quantitative methylation assessment of a multiplex panel of markers, consisting of APC, HOXD3 and TGF beta 2, outperforms any single marker for the prediction of biochemical recurrence (p-value = 0.017). Our study demonstrated that quantitative increase in promoter methylation levels of APC, HOXD3 and TGF beta 2 are associated with PCa progression.