Signature-guided therapy for mismatch repair defective cancers

在DNA复制过程中，当DNA聚合酶的校对能力受到损害时，会发生单碱基对错配和1-4碱基对错配的索引。这些错误通过完整错配修复（MMR）途径修复。DNA MMR缺陷与躯体癌（包括子宫内膜癌（30%）和结直肠癌（15-17%））以及使个体易患癌症的各种生殖系疾病有关。MMR缺陷（MMRD）子宫内膜癌和结直肠癌对常规辅助化疗具有高度耐药性，迫切需要新的治疗方法。为此，我们产生了一个稳健的基因标记，可以忠实地预测MMRD癌症，并基于该标记，我们进一步在体外和体内鉴定了MLN4924是一种有效的药物，可以降低MMRD细胞的细胞活力。MLN4924是NEDD8激活酶E1亚单位1 （NAE1）抑制剂，可阻止肿瘤抑制因子的需要酰化。与泛素化类似，在蛋白质底物上添加NEDD8片段，使其通过蛋白酶体降解。有趣的是，我们发现在MMRD与MMR完整子宫内膜样细胞和结肠癌细胞系中，整体泛素化修饰增加，而MLN4924治疗抑制了这种增加。这些数据表明，MMRD癌细胞中的高突变负担可能导致MMRD癌症中错误折叠突变蛋白的过度聚集和蛋白毒性应激水平升高；MLN4924进一步增加蛋白毒性应激并杀死MMRD癌细胞。此外，由于蛋白毒性应激诱导促炎反应，MLN4924可能增强免疫检查点疗法，这种疗法已被大量研究用于治疗MMRD结直肠癌。所有这些有希望的发现都有力地支持了MLN4924可以通过增加蛋白毒性应激特异性靶向MMRD癌症，从而增强促炎反应和增强PD-1免疫治疗效果的假设。这些假设将通过三个特定目的进行验证：(1)确定MLN4924治疗是否会抑制结肠癌和子宫内膜样癌中MMRD患者来源的异种移植物（PDX）的致瘤性。我们将建立皮下和原位子宫内膜样和结肠PDX模型，以严格评估MLN4924对MMRD癌症的治疗效果；(2)确定抑制MLN4924治疗MMRD癌症疗效的潜在机制。我们将研究MLN4924如何机械地杀死MMRD癌细胞；(3)确定MLN4924是否会增强PD-1免疫治疗在MMRD肿瘤中的作用。我们将建立同基因子宫内膜和结肠小鼠模型，以评估使用MLN4924和抗小鼠PD-1抗体的单药治疗和联合治疗。所有拟议的研究将导致开发新颖有效的基于mln4924的单药和联合疗法，以有效治疗MMRD癌症。

Single base pair mismatches, and indels of between 1-4 base pair mismatches, occur during DNA replication when DNA polymerase’s proofreading abilities are compromised. These errors are repaired via an intact mismatch repair (MMR) pathway. Deficiencies in DNA MMR are associated with somatic cancers, including endometrial (30%) and colorectal cancers (15-17%), and in various germline diseases that predispose individuals to cancer development. MMR defect (MMRD) endometrial and colorectal cancers are highly resistant to conventional adjuvant chemotherapy and thus novel therapies are urgently needed for the treatment of MMRD cancers. To this end, we have generated a robust gene signature that can faithfully predict MMRD cancer, and based on this signature, we further identified MLN4924 as an effective drug that diminishes cell viability of MMRD cells in vitro and in vivo. MLN4924 is a NEDD8 Activating Enzyme E1 Subunit 1 (NAE1) inhibitor, which prevents ned-dylation of tumor suppressors. Similar to ubiquitination, the addition of a NEDD8 moiety to protein substrates targets them for degradation via the proteasome. Intriguingly, we found that global neddylation increases in MMRD versus MMR intact endometrioid and colon carcinoma cell lines, which is suppressed with MLN4924 treatment. These data suggest that a high mutational burden in MMRD cancer cells may lead to the excessive aggregation of misfolded mutant proteins and elevated proteotoxic stress levels in MMRD cancers; MLN4924 further increases proteotoxic stress and kills MMRD cancer cells. Moreover, because proteotoxic stress induces pro-inflammatory responses, MLN4924 may enhance the immune checkpoint therapies that have been heavily investigated for the treatment of MMRD colorectal cancer. All of these promising findings strongly support the hypothesis that MLN4924 can specifically target MMRD cancers by increasing proteotoxic stress, thereby potentiating the pro-inflammatory response and enhancing the effects of PD-1 immunotherapy. These hypotheses will be tested via three specific aims: (1) to determine if MLN4924 treatment will inhibit the tumorigenicity of MMRD patient-derived xenografts (PDX) in colon and endometrioid carcinomas. We will establish both subcutaneous and orthotopic endometrioid and colon PDX models to critically evaluate the therapeutic effect of MLN4924 on MMRD cancers; (2) to determine the underlying mechanisms for the therapeutic efficacy of MLN4924 inhibition in MMRD cancers. We will investigate how MLN4924 mechanistically kills MMRD cancer cells; and (3) to determine if MLN4924 will potentiate the effects of PD-1 immunotherapy in MMRD tumors. We will establish syngeneic endometrial and colon mouse models to evaluate the monotherapies and combination therapies using MLN4924 and an anti-mouse PD-1 antibody. All of the proposed studies will lead to the development of novel and effective MLN4924-based mono- and combination therapies to effectively treat MMRD cancers.