去甲基化药物地西他滨通过调控CD4效应T细胞活性增强霍奇金淋巴瘤PD-1抗体反应性的临床及机制研究

Anti-programmed death-1 (PD-1) antibody induces more than 80% clinical response in relapsed/refractory classical Hodgkin's lymphoma (R/R cHL), but less than 30% complete remission (CR) is observed. Improving the CR rate of anti-PD-1 antibody and disease prognosis is still a significant issue to be solved urgently. It is demonstrated that de novo DNA methylation promoted T-cell exhaustion and limited the effect of anti-PD-1 antibody. We first have registered the clinical trial in the ClinicalTrials.gov database to determine the safety and efficacy of low-dose decitabine-plus-anti-PD-1 antibody in patients with R/R cHL. Preliminary results showed that the addition of decitabine could significantly improve the CR rate of anti-PD-1 antibody, enhance the activity of CD3+ T cells and increase the ratio of CD4/CD8 in peripheral blood. CHL is characterized by an abundance of CD4+ T cells in tumor microenvironment, and the expression of major histocompatibility complex class I (MHC I) in RS tumor cells is frequently absent, suggesting that non-CD8 T cells are also involved in the immune response induced by anti-PD-1 antibody. Therefore, we propose the hypothesis that decitabine enhances the effect of anti-PD-1 antibody by regulating CD4 effector T cells activation, and aim to explore the effect of decitabine, anti-PD-1 antibody as well as combined regimen on the proliferation, activation, differentiation, cytotoxicity and exhaustion of CD4 T cells, to investigate the molecular mechanism of T cells activation by the combined therapy, and to establish optimized regimen of low-dose demethylating agent combined with an-PD-1 antibody in R/R cHL patients.

PD-1抗体的诞生使超过80%复发难治性经典型霍奇金淋巴瘤（r/r CHL）患者临床获益，但不足30%的完全缓解（CR）率仍难以给患者良好预后。研究表明DNA甲基化会导致T细胞耗竭，限制PD-1抗体疗效。本团队率先注册开展了低剂量DNA去甲基化药物地西他滨联合PD-1抗体治疗r/r cHL临床试验，前期结果表明此联合方案能够显著提高PD-1抗体的CR率，患者外周T细胞活性增强，且发现联合治疗后CD4/CD8比值升高。霍奇金淋巴瘤具有独特的肿瘤微环境，CD4 T细胞大量富集且RS肿瘤细胞I型MHC分子表达频繁缺失，提示非CD8 T细胞也参与PD-1抗体诱导的免疫应答。因此，我们提出地西他滨通过调控CD4效应T细胞活性而增强PD-1抗体临床疗效的假说，并将从细胞水平、动物模型及临床样本多层面探讨地西他滨、PD-1抗体及二者联合对CD4 T细胞的调控效应，建立预后评估体系。

PD-1抗体的诞生使超过80%复发难治性经典型霍奇金淋巴瘤（r/r CHL）患者临床获益，但不足30%的完全缓解（CR）率仍难以给患者良好预后。研究表明DNA甲基化会导致T细胞耗竭，限制PD-1抗体疗效。本团队率先注册开展了低剂量DNA去甲基化药物地西他滨联合PD-1抗体治疗r/r cHL临床试验，证实此联合方案能够显著提高PD-1抗体的CR率。除了高CR率，我们还检测到表观免疫联合方案可获得较长无进展生存期。在此基础上，我们提出了PD-1抗体免疫治疗能否实现cHL治愈的新问题，即探讨巩固治疗方式及停药后患者复发情况。通过对96例PD-1抗体（单药或联合）治疗获得CR的r/r CHL患者长期随访，研究发现，对于免疫治疗获CR患者，3至4周巩固治疗优于6-12周巩固治疗方式，基于PD-1抗体治疗达到1年CR后可停药，且停药2年时80%以上患者依然处于CR状态。此外，鉴于地西他滨与PD-1抗体联合治疗后患者外周T细胞活性增强，且CD4/CD8比值升高，我们进而探讨了地西他滨对CD4+ T细胞的调控作用。低剂量地西他滨在体外能够直接调控CD4+ T细胞，促进Th1细胞增殖和激活，具体机制为通过增加E3泛素连接酶β-TRCP的表达，地西他滨处理促进IκBα泛素化降解，从而激活NF-κB信号，进而增加IFN-γ合成，促进IFN-γ+CD4+ Th1细胞分化。本项目针对团队构建的表观免疫联合治疗临床方案，在r/r CHL中获得突破，提出免疫治疗长效持久性潜能，并在体外细胞水平初步探讨了DNA去甲基化药物对CD4+ T细胞调控作用。