Molecular classification of non-muscle-invasive bladder cancer (pTa low-grade, pT1 low-grade, and pT1 high-grade subgroups) using methylation of tumor-suppressor genes

Abstract

The role of epigenetics in distinguishing pathological and clinical subgroups in bladder cancer is not fully characterized. We evaluated whether methylation of tumor-suppressor genes (TSGs) would classify non-muscle-invasive (NMI) bladder cancer subgroups and predict outcome. A retrospective design included the following paraffin-embedded primary NMI tumor types (n = 251): pTa low grade (LG) (n = 79), pT1LG (n = 81), and pT1 high grade (HG) (n = 91). Methylation of 25 TSGs was measured using methylation-specific, multiplex, ligation-dependent probe amplification. The TSGs most frequently methylated in the overall series were STK11 (96.8%), MGMT2 (64.5%), RARB (63.0%), and GATA5 (63.0%). TSG methylation correlated to clinicopathological variables in each subgroup and in the overall NMI series. Methylation of RARB, CD44, PAX5A, GSTP1, IGSF4 (CADM1), PYCARD, CDH13, TP53, and GATA5 classified pTa versus pT1 tumors whereas RARB, CD44, GSTP1, IGSF4, CHFR, PYCARD, TP53, STK11, and GATA5 distinguished LG versus HG tumors. Multivariate analyses indicated that PAX5A, WT1, and BRCA1 methylation independently predicted recurrence in pTaLG, PAX6, ATM, CHFR, and RB1 in pT1LG disease; PYCARD, in pT1HG disease; and PAX5A and RB1, in the overall series. Methylation of TSGs provided a molecular classification of NMI disease according to clinicopathological factors. Furthermore, TSG methylation predicted recurrence in NMI subgroups.