The Interplay Between PD-1 Blockade and T cell Development in the Context of Thymic Regeneration in Prostate Cancer

项目总结 免疫疗法，如PD-1阻断，已经显示出前列腺癌的治疗潜力；然而，只有 部分患者有反应，表明耐药机制不明。目前的护理标准 前列腺癌的治疗方法是雄激素剥夺疗法(ADT)，它针对激素敏感的肿瘤细胞。 有趣的是，ADT还导致胸腺再生，并增加新形成的T细胞的胸腺产量 细胞。我们已经证明，由ADT诱导的胸腺再生流量产生的新生成的T细胞 他们可以为肿瘤免疫环境做出贡献的肿瘤。此外，PD-1缺乏或阻断会导致 胸腺调节性T细胞(Tregs)的生成增加，提示PD-1调节 胸腺中的这些细胞，因此，就是Treg谱系。目前尚不清楚PD-1是否限制了Treg的发展 通过抑制T细胞受体信号通路或CD28共刺激通路，但它已经 确定CD28对Treg的发展至关重要。基于这些数据，我假设抑制 PD-1可以扩大可用于前列腺癌的Treg的保留范围，PD-1限制Treg 通过抑制CD28信号进行选择。首先，我将确定肿瘤浸润性Treg谱系的变化 在胸腺再生的背景下，由于PD-1的阻断而导致。ADT去势模型用于诱导 去势和免疫治疗耐药的前列腺癌小鼠模型中的胸腺再生。动物是 用apd-1或对照组处理，检测T细胞谱系。另外，我会检查手术前和手术后 作为正在进行的临床试验的一部分收集的治疗样本，治疗天真的男子被诊断为 晚期前列腺癌患者接受ADT联合APD-1，使我们能够进行实时评估 在胸腺再生过程中阻断PD-1对患者曲谱选择的影响。第二，我会 确定PD-1限制Treg发育的机制。这将通过使用 CRISPR-Cas9系统突变CD28胞质尾部PD-1抑制位点的基序 确定对CD28信号的依赖性。进一步地，下游信号通路的改变是由 PD-1缺乏症将通过转录组学和蛋白质组学研究进行检查。这项提议的结果是 期望揭示PD-1阻断如何在ADT诱导的胸腺背景下影响免疫谱系 再生以确定前列腺癌免疫治疗抵抗的潜在机制。这些研究 也可能导致前列腺癌联合治疗以增加患者数量的新理由 回应检查站封锁。

PROJECT SUMMARY Immunotherapies, such as PD-1 blockade, have shown therapeutic potential in prostate cancer; however, only a portion of patients respond, suggesting unidentified mechanisms of resistance. The current standard of care for prostate cancer is androgen deprivation therapy (ADT), which targets hormone-sensitive tumor cells. Interestingly, ADT also results in regeneration of the thymus and increased thymic output of newly developed T cells. We have shown that newly generated T cells resulting from ADT-induced thymic regeneration traffic to tumors where they can contribute to the tumor immune milieu. Further, PD-1 deficiency or blockade leads to an increase in the generation of thymic regulatory T cells (Tregs), suggesting that PD-1 regulates the selection of these cells in the thymus and, therefore, the Treg repertoire. It is unclear whether PD-1 limits Treg development by inhibiting the T cell receptor signaling pathway or the CD28 costimulatory pathway, but it has already been established that CD28 is critical for Treg development. Based upon these data, I hypothesize that inhibition of PD-1 could broaden the repertoire of Tregs available to traffic to prostate tumors and PD-1 limits Treg selection through inhibition of CD28 signaling. First, I will identify changes in tumor infiltrating Treg repertoire resulting from PD-1 blockade in the context of thymic regeneration. A castration model of ADT is used to induce thymic regeneration in a castration and immunotherapy resistant murine model of prostate cancer. Animals are treated with aPD-1 or control and the T cell repertoire is examined. Additionally, I will examine pre- and post- treatment samples collected as a part of an ongoing clinical trial where treatment-naïve men diagnosed with advanced prostate cancer receive ADT in combination with aPD-1, allowing us to perform real-time evaluation of the impact of PD-1 blockade during thymic regeneration on repertoire selection in patients . Second, I will determine the mechanism by which PD-1 limits Treg development. This will be accomplished through the use of the CRISPR-Cas9 system to mutate motifs in the CD28 cytoplasmic tail that are sites of PD-1 inhibition to determine dependence on CD28 signaling. Further, alterations of downstream signaling pathways resulting from PD-1 deficiency will be examined by transcriptomic and proteomic studies. The outcomes of this proposal are anticipated to reveal the how PD-1 blockade impacts the immune repertoire in the context of ADT-induced thymic regeneration to identify potential mechanisms of immunotherapy resistance in prostate cancer. These studies may also lead to new justifications for combination therapies in prostate cancer to increase the number of patients responding to checkpoint blockade.