The role of stem-like CD8 T-cells in the abscopal response

项目摘要 诊断为局部晚期黑色素瘤的患者预后差。生存结局得到改善 在新辅助、辅助和不可切除的情况下使用检查点阻断。双重检查站封锁 进一步增强结果，但通常以显著的临床毒性为代价。尽管取得了这些进展， 超过40%的患者没有反应，结果仍然令人沮丧。显然需要发展 创新的治疗方法，具有更高的反应率和更低的毒性。辐射（RT）具有免疫- 刺激活性，其能够在照射的细胞内外诱导抗肿瘤CD 8 + T细胞应答， 场-远位效应。在临床前和临床研究中，RT的免疫刺激活性与 检查点阻断（αPD-1），以显著改善肿瘤控制，毒性有限。尽管 RT + αPD-1的临床潜力令人鼓舞，但远位效应仍仅发生在少数患者中。到 确定创新的方法，以提高远位效应，我们评估了肿瘤导向RT的影响， 不同的CD 8 + T细胞亚群在鼠模型中。艾哈迈德实验室已经显示出一个耗尽的PD-1+ T细胞亚群， 干细胞样CD 8 + TCF-1+ T细胞是稳健的αPD-1应答所必需的。树突状细胞（DC）提供肽- MHC和共刺激沿着αPD-1刺激干细胞样T细胞扩增和分化为终末细胞 能够杀死肿瘤的效应细胞。我已经展示了这种干细胞样亚群主要位于肿瘤中- 引流淋巴结（TDLN）。引人注目的是，肿瘤定向RT单独刺激DC的成熟和增殖 在TDLN中的子集。RT后的这种增殖反应，不依赖于αPD-1，提示了一种新的 RT诱导的T细胞再生机制可能完全依赖于DC。值得注意的是，对于当地 晚期或高危黑色素瘤患者，通常给予免疫刺激治疗（RT和/或αPD-1） 肿瘤和TDLN切除后。这种目前的方法降低了免疫刺激潜力， 治疗相比，他们的管理与完整的TDLN。重要的是，联合术前αPD-1 和RT尚未在局部晚期或高危黑色素瘤中进行研究。基于这些初步 结果，我们的中心假设是TDLN中的干细胞样CD 8 + T细胞是肿瘤的重要介质， RT刺激的抗肿瘤远位效应。为了验证这一假设，我们将：（1）确定类干细胞的作用， （2）确定树突状细胞介导的刺激是否是RT的关键 在TDLN中诱导干细胞样T细胞扩增;（3）确定αPD-1的新辅助肿瘤-RT是否 与飞行员局部晚期黑色素瘤中干细胞样CD 8 + T细胞浸润增加相关 study.这项提议的结果可能会确定一种克服T细胞耗竭的新机制， 免疫毒性小，抗肿瘤效果增强。在临床上，它可能会重新定义标准方法 由于淋巴结在远端反应中的重要性，手术切除或照射TDLN。

PROJECT SUMMARY Prognosis is poor for patients diagnosed with locally advanced melanoma. Survival outcomes are improved with checkpoint blockade in the neoadjuvant, adjuvant and unresectable setting. Dual checkpoint blockade further enhances outcomes, but often at the cost of significant clinical toxicity. Despite this progress, for the more than 40% of patients who do not respond, outcomes remain dismal. There is a clear need to develop innovative treatment approaches with higher response rates and less toxicity. Radiation (RT) has immuno- stimulatory activity capable of inducing an anti-tumor CD8+ T cell response within and outside of the irradiated field - an abscopal effect. In preclinical and clinical studies, RT’s immuno-stimulatory activity synergizes with checkpoint blockade (αPD-1) to significantly improve tumor control with limited toxicity. Despite the encouraging clinical potential of RT + αPD-1, the abscopal effect still only occurs in a minority of patients. To determine innovative methods to enhance the abscopal effect, we evaluated tumor-directed RT’s impact on different CD8+ T-cell subsets in a murine model. The Ahmed lab has shown an exhausted PD-1+ T cell subset, stem-like CD8+ TCF-1+ T cells, are essential for robust αPD-1 responses. Dendritic cell (DC) provided peptide- MHC and co-stimulation along with αPD-1 stimulate stem-like T cell expansion and differentiation into terminal effector cells capable of tumor killing. I have shown this stem-like subset is primarily localized to the tumor- draining lymph node (TDLN). Strikingly, tumor-directed RT alone stimulates maturation of DCs and proliferation of this subset in the TDLN. This proliferative response following RT, independent of αPD-1, suggests a novel RT induced mechanism for T-cell reinvigoration which may be exclusively DC dependent. Notably, for locally advanced or high-risk melanoma patients, immunostimulatory therapy (RT and/or αPD-1) are typically given following tumor and TDLN removal. This current approach reduces the immuno-stimulatory potential of either treatment compared to their administration with an intact TDLN. Importantly, combination pre-operative αPD-1 and RT have not been investigated in locally advanced or high-risk melanoma. Based on these preliminary results, our central hypothesis is that the stem-like CD8+ T cells in the TDLN are important mediators of the Tumor- RT stimulated anti-tumor abscopal effect. To test this hypothesis, we will: (1) determine the role of the stem-like CD8+ T cells in the abscopal effect; (2) determine whether dendritic cell mediated stimulation is critical for RT induced stem-like T cell expansion in the TDLN; (3) determine whether neoadjuvant Tumor-RT with αPD-1 is associated with increased stem-like CD8+ T cell infiltration in locally advanced melanoma in a pilot human study. Results of this proposal may identify a novel mechanism for overcoming T-cell exhaustion which has less immunologic toxicity with increased anti-tumor efficacy. Clinically, it may redefine the standard approach of surgical removal or irradiation of the TDLN due to the lymph node’s importance in the abscopal response.