1875 METHYLATION OF TUMOR SUPPRESSOR GENES PREDICT RECURRENCE AND SUBCLASSIFY NON MUSCLE-INVASIVE DISEASE: PTA LOW GRADE VERSUS PT1 LOW GRADE AND PT1 HIGH GRADE BLADDER TUMORS

Abstract

INTRODUCTION AND OBJECTIVES: Genetic and epigenetic factors are involved in tumorigenesis and bladder cancer progression. The role of epigenetic factors at distinguishing pathological and clinical subgroups is not well defined. We aimed at evaluating the role of methylation of 25 tumor suppressor genes (TSG) to subclassify nonmuscle invasive (NMI) bladder tumor subtypes and as clinical outcome prognosticators. METHODS: A retrospective design included paraffin-embedded tumors (n 251) of patients with primary NMI disease: pTa Low Grade (LG)(n 79), PT1LG(n 81), and PT1 High Grade (HG) (n 91). Methylation of 25 TSG was measured using a methylation-specific multiplex ligation-dependent probe amplification assay (MS-MLPA). Recurrence, progression into muscle invasive tumors and diseasespecific survival (DSS) rates were analyzed using competing risks regression analysis. RESULTS: The TSGs most frequently methylated in the overall series were STK11 (96.8%), MGMT2 (64.5%), RARB (63.0%) and GATA5 (63.0%). TSGs methylation significantly correlated to clinicopathological variables within each specific subgroup and the overall series. Methylation of RARB (p 0.027), CD44 (p 0.002), PAX5A (p 0.018), GSTP1 (p 0.001), IGSF4 (p 0.001), PYCARD (p 0.001), CDH13 (p 0.028), TP53 (p 0.001) and GATA5 (p 0.001) allowed classification of PTa versus PT1 tumors while RARB (p 0.001), CD44 (p 0.001), GSTP1 (p 0.001), IGSF4 (p 0.005), CHFR (p 0.032), PYCARD (p 0.001), TP53 (p 0.001), STK11 (p 0.028) and GATA5 (p 0.001) distinguished LG vs HG tumors. Multivariate analyses indicated that PAX5A (p 0.019), WT1 (p 0.042) and BRCA1 (p 0.023) methylation independently predicted recurrence in pTaLG lesions, PAX6 (p 0.044), ATM (p 0.004), CHFR (p 0.035) and RB1 (p 0.007) in pT1LG tumors, and PYCARD (p 0.035) in pT1HG disease, and PAX5A (p 0.01) and RB1 (p 0.008) in the overall NMI series. CONCLUSIONS: Methylation of TSG distinguished NMI bladder tumors depending on their clinicopathological phenotypes. Methylation of TSG correlated to patient outcome and behaved as independent prognosticators of recurrence. Methylation of TSG may select NMI patients who may require closer surveillance and more aggressive therapeutic interventions.