Lavon Iris, Fuchs Dana, Zrihan Daniel, Efroni Gilat, Zelikovitch Bracha, Fellig Yakov, Siegal Tali
Leslie and Michael Gaffin Center for Neuro-Oncology, Department of Neurology, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
Cancer Res. 2007 Sep 15;67(18):8952-9. doi: 10.1158/0008-5472.CAN-06-3820.
O(6)-Methylguanine-DNA-methyltransferase (MGMT) and nuclear factor kappaB (NF-kappaB) are two key effectors associated with the development of resistance to alkylating agent-based chemotherapy. This prompted us to hypothesize that NF-kappaB might be involved in MGMT regulation. Consistent with this hypothesis, we have discovered two putative NF-kappaB binding sites within the MGMT promoter region and showed a specific and direct interaction of NF-kappaB at each of these sites. Forced expression of the NF-kappaB subunit p65 in HEK293 cells induced an increase in MGMT expression whereas addition of the NF-kappaB super repressor DeltaNIkappaB completely abrogated the induction. We also found a significant correlation between the extent of NF-kappaB activation and MGMT expression in the glioma cell lines and the human glial tumors tested and showed that it was independent of MGMT promoter methylation. Our results are of potential clinical significance because we show that cell lines with ectopic p65 or high constitutive NF-kappaB activity are less sensitive to nitrosourea treatment and that suppression of MGMT activity with O(6)-benzylguanine completely abolishes the chemoresistance acquired by NF-kappaB. The findings of our study strongly suggest that NF-kappaB plays a major role in MGMT regulation and that MGMT is most probably the major player in NF-kappaB-mediated chemoresistance to alkylating agents.
O(6)-甲基鸟嘌呤-DNA甲基转移酶（MGMT）和核因子κB（NF-κB）是与基于烷化剂的化疗耐药性发展相关的两个关键效应因子。这促使我们推测NF-κB可能参与MGMT的调控。与该假设一致，我们在MGMT启动子区域内发现了两个假定的NF-κB结合位点，并显示NF-κB在每个位点都有特异性的直接相互作用。在HEK293细胞中强制表达NF-κB亚基p65可诱导MGMT表达增加，而添加NF-κB超级抑制剂DeltaNIκB则完全消除了这种诱导作用。我们还发现，在所测试的胶质瘤细胞系和人类神经胶质瘤中，NF-κB激活程度与MGMT表达之间存在显著相关性，且表明这与MGMT启动子甲基化无关。我们的结果具有潜在的临床意义，因为我们发现异位表达p65或具有高组成型NF-κB活性的细胞系对亚硝基脲治疗不太敏感，并且用O(6)-苄基鸟嘌呤抑制MGMT活性可完全消除NF-κB获得的化疗耐药性。我们的研究结果强烈表明，NF-κB在MGMT调控中起主要作用，并且MGMT很可能是NF-κB介导的对烷化剂化疗耐药性的主要参与者。
