Aberrant differential expression of EZH2 and H3K27me3 in extranodal NK/T-cell lymphoma, nasal type, is associated with disease progression and prognosis.

Enhancer of zeste homolog 2 (EZH2), an H3K27-specific histone methyltransferase, has been shown to be frequently overexpressed in various human cancers including lymphoma. Here we investigate the expression and functionality of EZH2 and H3K27me3 in extranodal NK/T-cell lymphoma, nasal type (ENKTL). Results of NanoString analysis revealed that EZH2 and related histone H3 families were up-regulated genes in ENKTL tissues. Results of immunohistochemistry demonstrated that EZH2 and trimethylation of Lys-27 in histone (H3K27me3) were highly expressed in 55.2% and 78.0% of patients with ENKTL, respectively. EZH2 overexpression was significantly associated with higher tumor cell proliferation (r = 0.582, P = .000), advanced stage (P = .012), and predicted poorer overall survival (P = .016) in ENKTL. H3K27me3-positive expression was correlated with lower tumor cell proliferation (r = -0.623, P = .036), earlier stage (P = .043), and predicted better overall survival (P = .020). In addition, EZH2 and H3K27me3 showed inverse correlations (r = -0.652, P = .002) in clinical samples by immunohistochemistry. Furthermore, inhibition of EZH2 by 3-deazaneplanocin A significantly suppressed tumor cell growth. Interestingly, pharmacologic suppression of the JAK3/STAT3 pathway effectively reduced EZH2 and enhanced H3K27me3 in NK/T tumor cell lines. Our data suggest that EZH2 and H3K27me3 are important prognostic markers and potential therapeutic targets in ENKTL.
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