Immunostaining of Increased Expression of Enhancer of Zeste Homolog 2 (EZH2) in Diffuse Midline Glioma H3K27M-Mutant Patients with Poor Survival

Abstract

<b><i>Introduction:</i></b> The interaction of K27M mutation in histone H3 (H3K27M mutation) with polycomb repressive complex 2 (PRC2) is facilitated by the enhancer of zeste homolog 2 (EZH2). Subsequently, this interaction leads to the global reduction level of H3K27me3. We analyzed the EZH2 expression level in H3K27M mutation-positive tumors and revealed the association of high EZH2 expression with poor survival. <b><i>Methods:</i></b> Our study included 12 patients, with an age range of 6–56 years and treated between 2007 and 2016. All patients underwent MRI study for nonenhanced T1, T2, diffusion, gadolinium-enhanced T1-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). Immunohistochemical staining was performed against H3K27M, H3K27me3, EZH2, EED, mutant isocitrate dehydrogenase 1 (IDH1), α-thalassemia X-linked intellectual disability (ATRX), p53, O6-methylguanine-DNA methyltransferase (MGMT), and Ki-67 antibodies. <b><i>Results:</i></b> All patients were negative for IDH1R132H and H3K27me3, but H3K27M-positive. Staining against EZH2 was negative in all histological features of grade II cases (3/12) and positive in grade III and IV cases; EZH2 positivity is associated with poor prognosis (<i>p</i> = 0.0082). EZH2 positivity was not associated with EED positivity. Retained ATRX staining was found mostly in grade III and IV cases (6/12). P53 was predominantly positive in cases of astrocytoma and glioblastoma (8/12). The labeling index of Ki-67 was 1.2–31.4% for grade II and III histological features and 11.2–24.8% for grade IV. <b><i>Conclusion:</i></b> We suggest that the expression of EZH2 is not associated with the PRC2 pathway and increases in patients with H3K27M-mutant diffuse midline glioma and a poor prognosis. Further studies are necessary to understand the mechanism involved.

Radiological and Immunostaining Characteristics of H3.3 G34R-Mutant Glioma: A Report of 3 Cases and Review of the Literature

“…In addition, other immunohistochemistry staining results in our cases also gave more perspective. The ATRX and p53 immunostaining positive cutoff values were both 10% nuclear staining as described previously [16]. All of our cases showed consistent results with previous reports of ATRX-negative immunostaining expressions [11,17].…”

Immune system‑associated genes increase malignant progression and can be used to predict clinical outcome in patients with hepatocellular carcinoma

“…EZH2 is expression is low in the normal liver, and is associated with methylation of histone H3K27 and recruitment of methyltransferases, which are involved in DNA replication for cancer progression, and stem cell maintenance and differentiation of other cell lineages, such as immune cells (32,33). Several studies have confirmed its prognostic value and importance in various types of cancer, including lymphoma, glioma, head and neck carcinoma, and cervical neoplasia (34)(35)(36)(37)(38). Novel therapeutic methods have been developed to target EZH2, although high expression of EZH2 is not always correlated with the malignancy of a cancer, such as in colorectal cancer (39)(40)(41).…”

Midline Glioma in Adults: Clinicopathological, Genetic, and Epigenetic Analysis

“…We reviewed eight articles and 187 cases (including the 23 cases in this study) of adult diffuse midline glioma. 13,[18][19][20][21][22][23][24] The prognosis was examined by the presence or absence of K27M or by histological grade in 171 or 164 cases, respectively. When the prognosis was examined based on the presence or absence of K27M mutation, cases that did not determine K27M mutation status were excluded and we reviewed 171 cases.…”