Methylation patterns of Lys9 and Lys27 on histone H3 correlate with patient outcome and tumor progression in lung cancer

Abstract

BackgroundsHistone methylation is recognized as an important component of the epigenetic mechanisms of cancer initiation and progression. Previous studies have demonstrated that aberrant alterations in histone methylation are associated with lung cancer. However, novel and specific epigenetic biomarkers for monitoring lung adenocarcinoma remain unknown. MethodsA retrospective clinicopathological analysis was performed on 71 lung adenocarcinoma (LUAD) patients who received complete ablative surgical treatment. Tissue arrays were made from the paraffin-embedded LUAD tumor tissues, and these, together with corresponding normal tissues, were examined through immunohistochemistry for several markers: histone 3 lysine 9 di-methylation (H3K9me2), histone 3 lysine 9 tri-methylation (H3K9me3), and histone 3 lysine 27 tri-methylation (H3K27me3). The expression level of each marker was analyzed according to the histological classification and clinical prognosis data. ResultsCompared with peri-cancerous tissues, cancerous tissues distinctly expressed higher proportions of H3K9me2, H3K9me3, and H3K27me3. A higher expression pattern of H3K27me3 was associated with the poorly differentiation and unfavorable prognosis in LUAD. Based on histological types, it was found that the H3K27me3 level of patients with micropapillary type is high, and it is related to worse prognosis. ConclusionsThe findings of this study show that the H3K27me3 and micropapillary type are malignant clinical factors of LUAD. H3K27me3 reduction is a novel epigenetic biomarker for defining high-risk LUAD and predicting worse prognosis. Immunohistochemical evaluation of H3K27me3 expression is an economic, easily available, and readily adaptable method.