ABSTRACT
Changes in DNA methylation of tumor suppressors can occur early in carcinogenesis and are potentially important early indicators of cancer. The objective of this study was to assess the methylation of 25 tumor suppressor genes in bladder cancer using a methylation-specific (MS) multiplex ligation-dependent probe amplification assay (MLPA). Initial analyses in bladder cancer cell lines (n = 14) and fresh-frozen primary bladder tumor specimens (n = 31) supported the panel of genes selected being altered in bladder cancer. The process of MS-MLPA was optimized for its application in body fluids using two independent training and validation sets of urinary specimens (n = 146), including patients with bladder cancer (n = 96) and controls (n = 50). BRCA1 (71.0%), WT1 (38.7%), and RARB (38.7%) were the most frequently methylated genes in bladder tumors, with WT1 methylation being significantly associated with tumor stage (P = 0.011). WT1 and PAX5A were identified as methylated tumor suppressors. In addition, BRCA1, WT1, and RARB were the most frequently methylated genes in urinary specimens. Receiver operating characteristic curve analyses revealed significant diagnostic accuracies in both urinary sets for BRCA1, RARB, and WT1. The novelty of this report relates to applying MS-MLPA, a multiplexed methylation technique, for tumor suppressors in bladder cancer and body fluids. Methylation profiles of tumor suppressor genes were clinically relevant for histopathological stratification of bladder tumors and offered a noninvasive diagnostic strategy for the clinical management of patients affected with uroepithelial neoplasias.
Subject(s)
DNA Methylation/genetics , Genes, Tumor Suppressor , Urinary Bladder Neoplasms/genetics , Aged , Aged, 80 and over , Biomarkers, Tumor/genetics , Cell Line, Tumor , Female , Humans , Ligase Chain Reaction , Male , Middle Aged , Molecular Diagnostic Techniques , Neoplasm Staging , ROC Curve , Reproducibility of Results , Sensitivity and Specificity , Urinary Bladder Neoplasms/diagnosis , Urinary Bladder Neoplasms/pathologyABSTRACT
PURPOSE: Polyamines are important regulators of cell growth and death. The polyamine modulated factor-1 (PMF-1) is involved in polyamine homeostasis. After identifying an enriched CpG island encompassing the PMF1 promoter, we aimed at evaluating the clinical relevance of PMF1 methylation in bladder cancer. EXPERIMENTAL DESIGN: The epigenetic silencing of PMF1 by hypermethylation was tested in bladder cancer cells (n = 11) after azacytidine treatment. PMF1 methylation status was evaluated in 507 bladder tumors and 118 urinary specimens of bladder cancer patients and controls. PMF1 protein expression was analyzed by immunohistochemistry on tissue arrays containing bladder tumors for which PMF1 methylation was assessed (n = 218). RESULTS: PMF1 hypermethylation was associated with gene expression loss, being restored in vitro by a demethylating agent. An initial set of 101 primary frozen bladder tumors served to identify PMF1 hypermethylation in 88.1% of the cases. An independent set of 406 paraffin-embedded tumors also revealed a high PMF1 methylation rate (77.6%). PMF1 methylation was significantly associated with increasing stage (P = 0.025). Immunohistochemical analyses revealed that PMF1 methylation was associated with cytoplasmic PMF1 expression loss (P = 0.032). PMF1 protein expression patterns were significantly associated with stage (P < 0.001), grade (P < 0.001), and poor overall survival using univariate (P < 0.001) and multivariate (P = 0.011) analyses. Moreover, PMF1 methylation in urinary specimens distinguished bladder cancer patients from controls (area under the curve = 0.800). CONCLUSION: PMF1 was identified to be epigenetically modified in bladder cancer. The association of PMF1 methylation with tumor progression and its diagnostic ability using urinary specimens support including PMF1 assessment for the clinical management of bladder cancer patients.
