Quantitative methylation analysis of BCL2, hTERT, and DAPK promoters in urine sediment for the detection of non-muscle-invasive urothelial carcinoma of the bladder: a prospective, two-center validation study

Abstract

Objectives: Urinary hypermethylation of BCL2, hTERT, and DAPK promoters has been previously demonstrated as an accurate biomarker for the detection of urothelial carcinoma of the bladder (UCB) in patients undergoing radical cystectomy. In the present study, we investigated with a validation intent the frequency and levels of methylation of the same 3 genes in tumor tissue and urine sediment of patients undergoing transurethral resection (TUR) for non-muscle-invasive (NMI) UCB.

Materials and methods: A total of 108 consecutive patients with NMI UCB and 105 controls with no genitourinary malignancies were enrolled in this prospective study conducted in 2 tertiary referral academic urological departments with an advanced molecular laboratory. The frequency and levels of methylated BCL2, hTERT, and DAPK promoters were evaluated with quantitative methylation-specific real-time polymerase chain reaction in DNA extracted from tumor tissue and paired normal bladder mucosa retrieved at the time of TUR in patients, and from urine in patients and controls.

Results: In tumor tissue, at least 1 gene was hypermethylated in 91% patients (BCL2 in 62%, hTERT in 53%, DAPK in 48%). Methylation of hTERT was significantly correlated with tumor grade (P = 0.026). In urine sediment sensitivity and specificity were 76% and 98%, respectively, using BCL2 and hTERT. The number of methylated genes was highly correlated with tumor grade (P = 0.005). Methylated BCL2 and hTERT in urine sediment were highly correlated with those of the corresponding bladder tumor qualitatively (P < 0.001), and only BCL2 also quantitatively (P = 0.005). Methylation levels of BCL2 and hTERT were variably associated with tumor grade and stage, but were significantly correlated with patient age (P = 0.004 and P = 0.027, respectively).

Conclusions: These findings suggest that quantitative methylation analysis of BCL2 and hTERT, but not DAPK, in urine sediment may be a useful tool in the diagnosis of NMI UCB, deserving future applicability studies.