Vulnerabilities of MMR-deficient glioblastoma

胶质母细胞瘤（GBM）是最常见和致命的脑癌，具有对所有肿瘤的固有或适应性抗性。 现有的治疗。GBM对替莫唑胺产生耐药性的一个重要机制是， 在其治疗中使用的一线化疗，源于基因突变，如MSH 6和MSH 2关键 在DNA错配修复（MMR）-结肠癌和其他癌症中发现的机制。这些MMR缺陷 GBM变得高度突变，特别具有侵袭性，并且对许多化疗具有抗性， 迫切需要确定对它们有效的疗法。虽然最近的一份报告描述了 2例儿童MMR缺陷、高度突变的GBM对免疫检查点有反应 抑制剂，我们自己和其他人的临床经验一致表明，在成人患者中缺乏反应 用这些药物治疗的MMR缺陷、高度突变的GBM。这项建议测试新的治疗 方法MMR缺陷，超突变GBM，并使用独特的工具来做到这一点。我们的初步研究 扩展先前的报告，表明钙通道抑制对MMR缺陷的可能活性 首次表明，将不同钙通道的抑制剂--羧氨基三唑 (CAI)米贝拉地尔和维拉帕米-对MMR缺陷GBM系具有优先和协同活性 与父母的关系此外，我们的初步结果进一步表明，TGF-β作为一个潜在的目标，在这一点上， 化疗药物伊立替康和抗胆固醇他汀类药物可以被重新利用为TGF-β。 对MMR缺陷型GBM具有优先活性的β抑制剂。这些治疗策略正在接受测试 针对GBM系的匹配组，所述GBM系各自包括亲本系和由其衍生的MMR缺陷系， 以及自发产生MMR缺陷的GBM系组和对照GBM系组。MMR- 缺陷系各自具有来源于继发于体内代谢的突变的MSH 6或MSH 2不足 替莫唑胺治疗或稳定表达shRNA。该提案将使用这些匹配的 亲本/MMR缺陷GBM系，以测试钙通道阻断剂组合和TGF-β的作用 体外和体内抑制。此外，考虑到MMR缺陷和超突变以及治疗性 方法可能会影响抗GBM免疫应答，我们还将开发一种免疫活性 MMR缺陷GBM小鼠模型来测试这些作用。既有针对性又无偏见的机制研究 将进行，包括评估两种治疗策略之间的联系， 磷酸蛋白质组学和RNA-seq分析。拟议的研究将产生新的生物和治疗 这些见解可能会迅速影响MMR缺陷，超突变GBM和其他癌症的治疗。

Glioblastoma (GBM) is the most common and lethal brain cancer, with inherent or adaptive resistance to all existing treatments. One important mechanism by which GBM develops resistance to temozolomide, the frontline chemotherapy used in its treatment, stems from mutations in genes such as MSH6 and MSH2 critical in DNA mismatch repair (MMR)—a mechanism found in colon and other cancers as well. These MMR-deficient GBMs become hypermutated and particularly aggressive as well as resistant to many chemotherapies, and there is a pressing need to identify therapies that are effective against them. While a recent report describes two cases of pediatric MMR-deficient, hypermutated GBM that responded to immunotherapeutic checkpoint inhibitors, our own and others’ clinical experience has uniformly indicated a lack of responses in adult patients with MMR-deficient, hypermutated GBM treated with these agents. This proposal tests novel therapeutic approaches to MMR-deficient, hypermutated GBMs and uses unique tools to do so. Our preliminary studies expand on prior reports suggesting possible activity of calcium channel inhibition against MMR-deficient cancers to show for the first time that combining inhibitors of different calcium channels—carboxyamidotriazole (CAI), mibefradil, and verapamil—has preferential and synergistic activity against MMR-deficient GBM lines versus parental lines. In addition, our preliminary results further suggest TGF-β as a potential target in this setting, and that the chemotherapy drug irinotecan and the anti-cholesterol statins can be repurposed as TGF- β inhibitors with preferential activity against MMR-deficient GBM. These therapeutic strategies are being tested against matched sets of GBM lines that each include a parental line and an MMR-deficient line derived from it, as well as sets of GBM lines that spontaneously developed MMR deficiency and control GBM lines. The MMR- deficient lines each have MSH6 or MSH2 insufficiency derived either from mutations secondary to in vivo temozolomide treatment or from stable expression of shRNA. This proposal will use these matched parental/MMR-deficient GBM lines to test the effects of calcium channel blockade combinations and TGF-β inhibition in vitro and in vivo. In addition, given that MMR deficiency and hypermutation and both therapeutic approaches are likely to impact the anti-GBM immune response, we will also develop an immunocompetent mouse model of MMR-deficient GBM to test these effects. Both targeted and unbiased studies of mechanism will be performed, including assessing connections between the two therapeutic strategies and phosphoproteomic and RNA-seq analyses. The proposed studies will yield new biologic and therapeutic insights that could rapidly impact the treatment of MMR-deficient, hypermutated GBM and other cancers.