Department of Neurotoxicology, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
J Neurochem. 2012 Nov;123(3):428-36. doi: 10.1111/j.1471-4159.2012.07917.x. Epub 2012 Sep 21.
O(6)-methylguanine-DNA methyltransferase (MGMT) is a DNA-repair protein promoting resistance of tumor cells to alkylating chemotherapeutic agents. Glioma cells are particularly resistant to this class of drugs which include temozolomide (TMZ) and carmustine (BCNU). A previous study using the RNA microarray technique showed that decrease of MGMT mRNA stands out among the alterations in gene expression caused by the cell growth-depressing transfection of a T98G glioma cell line with liver-type glutaminase (LGA) [Szeliga et al. (2009) Glia, 57, 1014]. Here, we show that stably LGA-transfected cells (TLGA) exhibit decreased MGMT protein expression and activity as compared with non-transfected or mock transfected cells (controls). However, the decrease of expression occurs in the absence of changes in the methylation of the promoter region, indicating that LGA circumvents, by an as yet unknown route, the most common mechanism of MGMT silencing. TLGA turned out to be significantly more sensitive to treatment with 100-1000 μM of TMZ and BCNU in the acute cell growth inhibition assay (MTT). In the clonogenic survival assay, TLGA cells displayed increased sensitivity even to 10 μM TMZ and BCNU. Our results indicate that enrichment with LGA, in addition to inhibiting glioma growth, may facilitate chemotherapeutic intervention.
O(6)-甲基鸟嘌呤-DNA 甲基转移酶（MGMT）是一种 DNA 修复蛋白，可促进肿瘤细胞对烷化化疗药物的耐药性。神经胶质瘤细胞对包括替莫唑胺（TMZ）和卡莫司汀（BCNU）在内的这一类药物特别具有耐药性。先前使用 RNA 微阵列技术的研究表明，在 L 型谷氨酸酶（LGA）转染 T98G 神经胶质瘤细胞系引起的基因表达改变中，MGMT mRNA 的减少尤为突出[Szeliga 等人（2009）Glia，57，1014]。在这里，我们表明与未转染或 mock 转染的细胞（对照）相比，稳定转染 LGA 的细胞（TLGA）表现出 MGMT 蛋白表达和活性降低。然而，表达的降低发生在启动子区域的甲基化没有变化的情况下，表明 LGA 通过一种未知的途径绕过了 MGMT 沉默的最常见机制。在急性细胞生长抑制测定（MTT）中，TLGA 对 100-1000 μM 的 TMZ 和 BCNU 的治疗表现出显著的敏感性增加。在集落形成存活测定中，TLGA 细胞甚至对 10 μM 的 TMZ 和 BCNU 显示出更高的敏感性。我们的结果表明，除了抑制神经胶质瘤生长外，LGA 的富集还可能促进化疗干预。
