Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Breast Cancer Res Treat. 2012 Jun;133(3):959-68. doi: 10.1007/s10549-011-1871-x. Epub 2011 Nov 20.
Epigenetic biomarkers are emerging as determinants of breast cancer prognosis. Breast cancer cells display unique alterations in major cellular metabolic pathways and it is becoming widely recognized that enzymes that regulate epigenetic alterations are metabolically sensitive. In this study, we used microarray data from the GEO database to compare gene expression for regulators of metabolism and epigenetic alterations among non-invasive epithelial (MCF-7, MDA-MB-361, and T-47D) and invasive mesenchymal (MDA-MB-231, Hs-578T, and BT-549) breast cancer cell lines. The expression of genes, including GLS1, GFPT2, LDHA, HDAC9, MYST2, and SUV420H2, was assessed using RT-PCR. There was differential expression between epithelial and mesenchymal cell lines. MYST2 and SUV420H2 regulate the levels of the epigenetic biomarkers histone H4 lysine 16 acetylation (H4K16ac) and histone H4 lysine 20 trimethylation (H4K20me3), respectively. Reduced amounts of H4K16ac and H4K20me3 correlated with lower levels of MYST2 and SUV420H2 in mesenchymal cells and, along with reduced amounts of histone H3 lysine 9 acetylation (H3K9ac), were found to distinguish epithelial from mesenchymal cells. In addition, both GLS1 and GFPT2 play roles in glutamine metabolism and were observed to be more highly expressed in mesenchymal cell lines, and when glutamine and glutamate levels reported in the NCI-60 metabolomics dataset were compared, the ratio of glutamate/glutamine was found to be higher in mesenchymal cells. Blocking the conversion of glutamine to glutamate using an allosteric inhibitor, Compound 968, against GLS1, increased H4K16ac in T-47D and MDA-MB-231 cells, linking glutamine metabolism to a particular histone modification in breast cancer. These findings support the concept that metabolically sensitive histone modifications and corresponding histone modifying enzymes can be used as diagnostic and prognostic biomarkers for breast cancer. It also further emphasizes the importance of glutamine metabolism in tumor progression and that inhibitors of cellular metabolic pathways may join histone deacetylase inhibitors as a form of epigenetic therapy.
表观遗传生物标志物正逐渐成为乳腺癌预后的决定因素。乳腺癌细胞在主要细胞代谢途径中表现出独特的改变，人们越来越认识到，调节表观遗传改变的酶对代谢敏感。在这项研究中，我们使用 GEO 数据库中的微阵列数据，比较了非侵袭性上皮（MCF-7、MDA-MB-361 和 T-47D）和侵袭性间充质（MDA-MB-231、Hs-578T 和 BT-549）乳腺癌细胞系中代谢和表观遗传改变调节因子的基因表达。使用 RT-PCR 评估包括 GLS1、GFPT2、LDHA、HDAC9、MYST2 和 SUV420H2 在内的基因的表达。上皮细胞系和间充质细胞系之间存在差异表达。MYST2 和 SUV420H2 分别调节表观遗传生物标志物组蛋白 H4 赖氨酸 16 乙酰化（H4K16ac）和组蛋白 H4 赖氨酸 20 三甲基化（H4K20me3）的水平。在间充质细胞中，H4K16ac 和 H4K20me3 的含量减少与 MYST2 和 SUV420H2 的水平降低相关，并且与组蛋白 H3 赖氨酸 9 乙酰化（H3K9ac）的含量减少相关，可将上皮细胞与间充质细胞区分开来。此外，GLS1 和 GFPT2 均在谷氨酰胺代谢中发挥作用，并且在间充质细胞系中表达更高，并且当比较 NCI-60 代谢组学数据集中报告的谷氨酰胺和谷氨酸水平时，发现间充质细胞中的谷氨酸/谷氨酰胺比值更高。使用针对 GLS1 的变构抑制剂 Compound 968 阻断谷氨酰胺向谷氨酸的转化，增加了 T-47D 和 MDA-MB-231 细胞中的 H4K16ac，将谷氨酰胺代谢与乳腺癌中的特定组蛋白修饰联系起来。这些发现支持了这样一种概念，即代谢敏感的组蛋白修饰及其相应的组蛋白修饰酶可作为乳腺癌的诊断和预后生物标志物。它还进一步强调了谷氨酰胺代谢在肿瘤进展中的重要性，并且细胞代谢途径的抑制剂可能与组蛋白去乙酰化酶抑制剂一起作为一种表观遗传治疗形式。
