Global histone modification patterns as prognostic markers to classify glioma patients

Abstract

Background: An altered pattern of epigenetic modifications is central to the development and progression of various tumors. We studied epigenetic changes involving multiple modifications of histones to better predict prognosis of glioma patients. Methods: Immunohistochemistry was done to investigate global histone modification expression of histone 3 lysine 4 dimethylation (H3K4diMe), histone 4 arginine 3 monomethylation (H4R3monoMe), histone 4 lysine 20 trimethylation (H4K20triMe), and acetylation of histone 3 lysine 9 (H3K9Ac), histone 3 lysine 18 (H3K18Ac), histone 4 lysine 12 (H4K12Ac), and histone 4 lysine 16 (H4K16Ac) in resected tumor samples of 230 glioma patients. Data were analyzed using a recursive partitioning analysis (RPA). Results: RPA classified the patients into 10 distinct prognostic groups based on WHO grade, histology, and histone modifications: H3K9Ac (<88% or ≥88% tumor cells), H3K4diMe (<64% or ≥64% tumor cells), H3K18Ac (<74% or ≥74% tumor cells), and H4K20triMe (<75% or ≥75% tumor cells). The 10 groups were associated with significantly different progression-free (P < 0.0001) and overall survival (P < 0.0001). Cox proportional hazards models including age, sex, WHO grade, histology, extent of tumor resection, Karnofsky performance status score, and RPA groups retained age and RPA groups as the sole independent factors significantly influencing overall survival. For progression-free survival, RPA grouping was the only independent prognostic factor. Conclusions: Multiple histone modifications seem to have prognostic relevance in glioma. Impact: Further evaluation of histone modifications as prognostic markers of treatment and predictors of chemotherapy response using histone deacetylase inhibitors is warranted. ©2010 AACR.