The Research Institute of the McGill University Health Centre, 1625 Pine Avenue West, Montreal, Quebec, H3G 1A4, Canada.
Mol Cancer Ther. 2012 Nov;11(11):2440-50. doi: 10.1158/1535-7163.MCT-11-0977. Epub 2012 Sep 17.
The dismal prognosis of glioblastoma multiforme (GBM) is mostly due to the high propensity of GBM tumor cells to invade. We reported an inverse relationship between GBM angiogenicity and expression of the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT), which has been extensively characterized for its role in resistance to alkylating agents used in GBM treatment. In the present study, given the major role of angiogenesis and invasion in GBM aggressiveness, we aimed to investigate the relationship between MGMT expression and GBM invasion. Stable overexpression of MGMT in the U87MG cell line significantly decreased invasion, altered expression of invasion-related genes, decreased expression of α(5)β(1) integrin and focal adhesion kinase, and reduced their spindle-shaped morphology and migration compared with the empty vector control. Conversely, short hairpin RNA-mediated stable knockdown of MGMT or its pharmacologic depletion in the MGMT-positive T98G cell line were required for increased invasion. The inverse relationship between MGMT and invasion was further validated in primary GBM patient-derived cell lines. Using paraffin-embedded tumors from patients with newly diagnosed GBM (n = 59), tumor MGMT promoter hypermethylation (MGMT gene silencing) was significantly associated with increased immunohistochemical expression of the proinvasive matricellular protein secreted protein acidic and rich in cysteine (SPARC; P = 0.039, χ(2) test). Taken together, our findings highlight for the first time the role of MGMT as a negative effector of GBM invasion. Future studies are warranted to elucidate the role of SPARC in the molecular mechanisms underlying the inverse relationship between MGMT and GBM invasion and the potential use of MGMT and SPARC as biomarkers of GBM invasion.
多形性胶质母细胞瘤（GBM）预后不佳，主要是由于 GBM 肿瘤细胞侵袭的高倾向。我们报道了 GBM 血管生成与 DNA 修复蛋白 O(6)-甲基鸟嘌呤-DNA 甲基转移酶（MGMT）表达之间的反比关系，MGMT 因其在抵抗用于 GBM 治疗的烷化剂方面的作用而得到广泛研究。在本研究中，鉴于血管生成和侵袭在 GBM 侵袭性中的主要作用，我们旨在研究 MGMT 表达与 GBM 侵袭之间的关系。在 U87MG 细胞系中稳定过表达 MGMT 可显著降低侵袭性，改变侵袭相关基因的表达，降低 α(5)β(1)整联蛋白和粘着斑激酶的表达，并降低其纺锤形形态和迁移，与空载体对照相比。相反，在 MGMT 阳性 T98G 细胞系中，通过短发夹 RNA 介导的 MGMT 稳定敲低或其药物耗竭，需要增加侵袭性。在原发性 GBM 患者来源的细胞系中进一步验证了 MGMT 与侵袭之间的反比关系。使用新诊断为 GBM 的患者的石蜡包埋肿瘤（n = 59），肿瘤 MGMT 启动子甲基化（MGMT 基因沉默）与富含半胱氨酸的酸性分泌蛋白（SPARC）的促侵袭免疫组织化学表达显著相关，这表明基质细胞蛋白（P = 0.039，X(2)检验）。总之，我们的研究结果首次强调了 MGMT 作为 GBM 侵袭的负效应物的作用。未来的研究需要阐明 SPARC 在 MGMT 和 GBM 侵袭之间的反比关系的分子机制中的作用，以及 MGMT 和 SPARC 作为 GBM 侵袭的生物标志物的潜在用途。
