Prognostic value of RASSF1 promoter methylation in prostate cancer.

PURPOSE: Patients with prostate cancer who have biochemical recurrence after curative therapy are at higher risk for distant metastasis and cancer specific death. Assessment of aberrant DNA methylation in urine might complement currently used clinical prognostic factors and serve as a noninvasive tool for early prediction of biochemical recurrence after radical prostatectomy. MATERIALS AND METHODS: Promoter methylation of 7 genes was evaluated by methylation sensitive polymerase chain reaction in 149 prostate cancer tissues, 37 noncancerous prostate tissues and 17 benign prostatic hyperplasia samples. Quantitative polymerase chain reaction was used for DNA methylation analysis of the urine of 253 patients with prostate cancer and 32 with benign prostatic hyperplasia. RESULTS: In prostate cancer tissue the most frequently methylated genes were RASSF1, GSTP1 and RARB, which combined were positively identified in 85% of cases. These genes were also methylated in the urine of 60% of patients with prostate cancer. RASSF1 was methylated in 45% of prostate cancer urine samples with methylation intensity significantly higher in prostate cancer than in benign prostatic hyperplasia cases (p = 0.018). In a univariate model RASSF1 methylation and the total number of methylated genes in prostate cancer tissue were predictive of time to biochemical recurrence (p = 0.019 and 0.043, respectively). On multivariate analysis RASSF1 methylation together with pathological stage was the most significant predictor of biochemical recurrence in patients with Gleason score 6 tumors when analyzed in tissue and urine (p ≤0.001). CONCLUSIONS: Hypermethylation of RASSF1 in cancerous tissue and urine from patients with prostate cancer correlated with biochemical recurrence after radical prostatectomy. The prognostic potential of this biomarker deserves further investigation.

Tumor suppressor gene ZAC/PLAGL1: altered expression and loss of the nonimprinted allele in pheochromocytomas.

ZAC/PLAGL1 is a novel imprinted tumor suppressor gene encoding an important inducer of cell cycle arrest and apoptosis, and found to be lost during tumorigenesis. We analyzed the significance of ZAC in the development of a rare, usually benign tumor of the adrenal gland: pheochromocytoma (PCC). Twenty-four PCCs were analyzed for the loss of the active nonimprinted allele of ZAC, and nine of the twenty-four PCCs were also assayed for expression of the protein. In thirteen of the cases, a paired nonmalignant tissue was available for analysis. Methylation-specific polymerase chain reaction revealed frequent (15 of 23, 65%) loss of unmethylated DNA in the imprinting control region of ZAC. Immunohistochemistry identified reduced ZAC expression in 56% (5 of 9) of the subset cases. Four of the five PCC cases where reduced expression of ZAC was observed were also positive for the loss of the active ZAC allele. Additionally, the loss of ZAC expression was also found to be frequent in a series of capillary hemangioblastomas and gliomas (6 of 6, 100%, and 17 of 27, 63%, respectively) examined for comparison. In conclusion, our study suggests the involvement of the imprinted ZAC gene in the pathogenesis of PCC.