The p38-MK2-HuR pathway potentiates EGFRvIII–IL-1β-driven IL-6 secretion in glioblastoma cells
作者:F M S Gurgis、Y T Yeung、M X M Tang、B Heng、M Buckland、A J Ammit、J Haapasalo、H Haapasalo、G J Guillemin、T Grewal、L Munoz
DOI:10.1038/onc.2014.225
日期:2015.5.28
The microenvironment of glioblastoma (GBM) contains high levels of inflammatory cytokine interleukin 6 (IL-6), which contributes to promote tumour progression and invasion. The common epidermal growth factor receptor variant III (EGFRvIII) mutation in GBM is associated with significantly higher levels of IL-6. Furthermore, elevated IL-1β levels in GBM tumours are also believed to activate GBM cells and enhance IL-6 production. However, the crosstalk between these intrinsic and extrinsic factors within the oncogene-microenvironment of GBM causing overproduction of IL-6 is poorly understood. Here, we show that EGFRvIII potentiates IL-1β-induced IL-6 secretion from GBM cells. Importantly, exacerbation of IL-6 production is most effectively attenuated in EGFRvIII-expressing GBM cells with inhibitors of p38 mitogen-activated protein kinase (p38 MAPK) and MAPK-activated protein kinase 2 (MK2). Enhanced IL-6 production and increased sensitivity toward pharmacological p38 MAPK and MK2 inhibitors in EGFRvIII-expressing GBM cells is associated with increased MK2-dependent nuclearâcytoplasmic shuttling and accumulation of human antigen R (HuR), an IL-6 mRNA-stabilising protein, in the cytosol. IL-1β-stimulated activation of the p38 MAPKâMK2-HuR pathway significantly enhances IL-6 mRNA stability in GBM cells carrying EGFRvIII. Further supporting a role for the p38 MAPKâMK2-HuR pathway in the development of inflammatory environment in GBM, activated MK2 is found in more than 50% of investigated GBM tissues and correlates with lower grade and secondary GBMs. Taken together, p38 MAPKâMK2-HuR signalling may enhance the potential of intrinsic (EGFRvIII) and extrinsic (IL-1β) factors to develop an inflammatory GBM environment. Hence, further improvement of brain-permeable and anti-inflammatory inhibitors targeting p38 MAPK, MK2 and HuR may combat progression of lower grade gliomas into aggressive GBMs.
胶质母细胞瘤(GBM)的微环境中含有高水平的炎症细胞因子白细胞介素6(IL-6),这有助于促进肿瘤进展和侵袭。GBM中常见的表皮生长因子受体变异体III(EGFRvIII)突变与更高的IL-6水平显著相关。此外,GBM肿瘤中升高的IL-1β水平也被认为能激活GBM细胞并增强IL-6的产生。然而,导致IL-6过度产生GBM中的致癌基因-微环境中的这些内在和外在因素之间的相互作用在很大程度上仍未得到理解。在这里,我们展示了EGFRvIII增强了IL-1β诱导的GBM细胞中的IL-6分泌。重要的是,在表达EGFRvIII的GBM细胞中,p38促分裂原活化蛋白激酶(p38 MAPK)和MAPK活化蛋白激酶2(MK2)的抑制剂最有效地减弱了IL-6的产生。在表达EGFRvIII的GBM细胞中,增强的IL-6产生和对药物p38 MAPK和MK2抑制剂的增加的敏感性与增加的依赖MK2的核质穿梭和IL-6 mRNA稳定蛋白——人抗原R(HuR)在胞质的积累相关。IL-1β刺激的p38 MAPK-MK2-HuR途径的激活在携带EGFRvIII的GBM细胞中显著增强了IL-6 mRNA的稳定性。进一步支持p38 MAPK-MK2-HuR途径在GBM炎症环境发展中的作用,在超过50%的被调查的GBM组织中发现了激活的MK2,并且与较低级别和继发性GBM相关。总的来说,p38 MAPK-MK2-HuR信号可能增强内在(EGFRvIII)和外在(IL-1β)因素发展GBM炎症环境的潜力。因此,进一步改进针对p38 MAPK、MK2和HuR的脑渗透和抗炎抑制剂可能有助于阻止低级别胶质瘤进展为侵袭性GBM。