Targeting GSK3B in refractory B-cell malignancies

摘要 GSK 3E作为E-catenin的重要负调节因子发挥作用，而E-catenin的积累代表了一个中心的调节因子。 致癌驱动基因在实体瘤中，E-连环蛋白与TCF 7因子形成复合物，用于转录 MYC 1 -5的激活。与实体瘤形成鲜明对比的是，我们发现B细胞白血病和淋巴瘤不是 仅免于活化E-连环蛋白损伤，但对E-连环蛋白积聚高度敏感， 通过GSK 3E介导的降解对其负调控：与其他癌症类型不同，E- B细胞恶性肿瘤中的连环蛋白抑制MYC表达并迅速诱导细胞死亡。代替 转录激活因子TCF 7，我们在B细胞恶性肿瘤中的相互作用组研究表明，E-连环蛋白形成了一个转录激活因子TCF 7。 与淋巴特异性Ikaros锌指（IKZF）6-8因子的抑制复合物。E-而不是MYC激活 连环蛋白组装的淋巴特异性Ikaros因子和抑制性核小体的多个成员 重塑和去乙酰化（NuRD）9-10复合物用于MYC的转录抑制。 GSK 3E磷酸化E-连环蛋白外显子3中的S/T残基，以启动E-连环蛋白降解。利用 淋巴特异性抑制性E-连环蛋白复合物作为以前未认识到的治疗脆弱性，我们 检查了GSK 3E小分子抑制剂。引人注目的是，目前在临床上使用的已确立的GSK 3E抑制剂 用于神经系统疾病和实体瘤的试验，在B细胞中的低纳摩尔浓度下有效。 恶性肿瘤，诱导大量积累的E-连环蛋白，抑制MYC和急性细胞死亡。临床前 基于患者来源的异种移植物的实验验证了小分子GSK 3E抑制剂用于靶向 参与淋巴特异性抑制性E-连环蛋白复合物克服难治性B- 体内细胞恶性肿瘤。 基于这一发现，该提案的中心目标是将GSK 3E抑制剂重新用于靶向治疗。 在难治性B细胞恶性肿瘤中抑制性E-连环蛋白复合物的参与。鉴于四个GSK 3E- 抑制剂已经进行了全面的临床开发，并在以下方面显示出良好的安全性特征： 通过18项临床试验，我们预计这种强大的新方法可以迅速发展，使患者受益 难治性B细胞恶性肿瘤，并在未来进一步扩展到T细胞恶性肿瘤。我们提出了两 目的是（1）阐明E-连环蛋白介导的肿瘤抑制的机制基础和（2）发展概念 利用E-连环蛋白-Ikaros复合物的靶向活化用于难治性B细胞 恶性肿瘤。

Abstract GSK3E functions as essential negative regulator of E-catenin, while E-catenin accumulation represents a central oncogenic driver in cancer. In solid tumors, E-catenin forms complexes with TCF7-factors for transcriptional activation of MYC1-5. In striking contrast to solid tumors, we found that B-cell leukemias and lymphomas are not only exempt from activating E-catenin lesions but highly sensitive to E-catenin accumulation and critically depend on its negative regulation by GSK3E-mediated degradation: Unlike other cancer types, inducible activation of E- catenin in B-cell malignancies suppressed MYC-expression and rapidly induced cell death. Instead of the transcriptional activator TCF7, our interactome studies in B-cell malignancies revealed that E-catenin formed a repressive complex with lymphoid-specific Ikaros zinc finger (IKZF)6-8 factors. Instead of MYC-activation, E- catenin assembled lymphoid-specific Ikaros factors and multiple members of the repressive nucleosome remodeling and deacetylation (NuRD)9-10 complex for transcriptional repression of MYC. GSK3E phosphorylates S/T-residues in E-catenin exon 3, to initiate E-catenin- degradation. To leverage lymphoid-specific repressive E-catenin-complexes as previously unrecognized therapeutic vulnerability, we examined GSK3E small molecule inhibitors. Strikingly, established GSK3E-inhibitors that are currently in clinical trials for the neurological disorders and solid tumors, were effective at low nanomolar concentrations in B-cell malignancies, induced massive accumulation of E-catenin, repression of MYC and acute cell death. Preclinical experiments based on patient-derived xenografts validated small molecule GSK3E-inhibitors for targeted engagement of lymphoid-specific repressive E-catenin-complexes to overcome drug-resistance in refractory B- cell malignancies in vivo. Based on this discovery, the central goal of this proposal is to repurpose GSK3E-inhibitors for targeted engagement of repressive E-catenin-complexes in refractory B-cell malignancies. Given that four GSK3E- inhibitors have already undergone full clinical development and demonstrated favorable safety profiles in eighteen clinical trials, we anticipate that this powerful new approach can rapidly be developed to benefit patients with refractory B-cell malignancies and be further extended to T-cell malignancies in the future. We propose two Aims to (1) elucidate the mechanistic basis of E-catenin-mediated tumor suppression and to (2) develop concepts to leverage targeted activation of E-catenin-Ikaros complexes for therapeutic intervention in refractory B-cell malignancies.