In situ radioimmunotherapy to maximize the engagement of conventional type 1 dendritic cells against non-T cell-inflamed tumors

众所周知，放射治疗(RT)对肿瘤细胞具有直接的细胞毒作用；然而，最近的研究是 揭示其对肿瘤免疫原性的影响，从而影响RT的整体结局。而RT 单独使用通常不足以克服免疫抑制的肿瘤微环境(TME)，策略 RT的增强免疫刺激作用正在深入研究中。到目前为止，人们的大部分注意力都集中在 在RT后进行免疫调节，特别是与免疫检查点抑制剂联合使用。小才是 了解放疗前操作TME对免疫原性和治疗效果的影响 RT.越来越多的证据表明，依赖于BATF3的常规1型树突状细胞(CDc1)很少 发现在肿瘤髓系腔内具有交叉呈现肿瘤相关的重要能力 抗原(TAA)与CD8 T细胞结合，在癌症中充当T细胞反应的“主调节器”。我们假设 CDC1的原位诱导和激活增强了RT的治疗效果和免疫原性。至 为了验证这一假设，我们开发了一种组合原位放射免疫疗法，包括原位给药 目的：1)Flt3L动员cDc1到TME；2)RT促进肿瘤细胞免疫原性死亡和成熟 3)TLR3/CD40双重刺激激活抗原负载的CDC1以启动肿瘤特异性CD8 T 细胞。我们使用免疫原性低的多个同种原位小鼠肿瘤模型的新数据 对抗PD-L1治疗不敏感提示原位放射免疫治疗可引起从头开始的适应性T细胞反应 具有新的克隆型和干细胞样的Tcf1Slamf6表型，使肿瘤产生反应 抗PD-L1抗体，介导持久的完全反应，并形成肿瘤特异性系统 免疫记忆。令人信服的证据表明，RT的免疫原性可以通过原位增强 CDC1的诱导和激活；然而，原位放射免疫治疗的免疫调节作用 远处转移的肿瘤仍不清楚。CDC1启动CD4T细胞以及CD8T细胞，但CD4的作用 T细胞原位放射免疫治疗仍然难以捉摸。此外，目前仍不清楚是否在现场 放射免疫疗法克服了人类非T细胞炎症性肿瘤中T细胞浸润不良的问题。在本建议书中 我们将阐明CD4T细胞在增强原位放射免疫治疗(AIM)抗肿瘤效果中的作用 1)。此外，我们还将寻求更好地了解其免疫调节作用的机制。 以非放疗远处转移肿瘤为靶点的原位放射免疫治疗(目标2)。最后，在目标3中，我们将 探讨不能切除和转移性乳腺癌患者外周血中TME的变化 接受原位放射免疫治疗。这些研究将增加对RT如何进行必要的机械理解 和免疫系统相互作用，并提供对原位放射免疫治疗的临床潜力的洞察 抗PD-L1治疗不敏感的非T细胞炎性肿瘤。

Radiation therapy (RT) is known to exert direct cytotoxic effects on tumor cells; however, recent research is revealing its influence on the immunogenicity of tumors, thus affecting the overall outcome of RT. While RT alone is usually insufficient to overcome the immunosuppressive tumor microenvironment (TME), strategies to boost immune-stimulating effects of RT are under intensive investigation. To date, most of the focus has been placed on immunomodulation after RT, in particular in combination with immune checkpoint inhibitors. Little is known about how manipulation of the TME before RT can impact on immunogenicity and therapeutic efficacy of RT. A growing body of evidence reveals that Batf3-dependent conventional type 1 dendritic cells (cDC1) rarely found within the tumor myeloid compartment have the important capacity of cross-presenting tumor-associated antigens (TAA) to CD8+ T cells, and act as `master regulators' for the T cell response in cancer. We hypothesize that in situ induction and activation of cDC1 enhances the therapeutic efficacy and immunogenicity of RT. To test this hypothesis, we developed a combinatorial in situ radioimmunotherapy comprised of in situ administration of: 1) Flt3L to mobilize cDC1 to the TME; 2) RT to promote immunogenic death of cancer cells and maturation of DC; and 3) dual TLR3/CD40 stimulation to activate antigen-loaded cDC1 for priming of tumor-specific CD8+ T cells. Our new data using multiple syngeneic orthotopic murine models of poorly immunogenic tumors insensitive to anti-PD-L1 therapy reveal that in situ radioimmunotherapy elicits de novo adaptive T cell responses that are characterized by novel clonotypes and stem-like Tcf1+ Slamf6+ phenotypes, renders tumors responsive to anti-PD-L1 antibody, mediates durable complete responses, and develops tumor-specific systemic immunological memory. Compelling evidence suggests that immunogenicity of RT can be enhanced by in situ induction and activation of cDC1; however, immunomodulatory effect of in situ radioimmunotherapy against distant metastatic tumors remains unclear. cDC1 prime CD4+ T cells as well as CD8+ T cells, but the role of CD4+ T cells in in situ radioimmunotherapy remains elusive. In addition, it remains unknown whether in situ radioimmunotherapy overcomes poor T-cell infiltration in human non-T cell-inflamed tumors. In this proposal we will elucidate the roles of CD4+ T cells in augmenting antitumor efficacy of in situ radioimmunotherapy (Aim 1). Additionally, we will seek to better understand the mechanisms underlying the immunomodulatory effect of in situ radioimmunotherapy targeting non-irradiated distant metastatic tumors (Aim 2). Finally, in Aim 3, we will seek to determine the alteration of the human TME in patients with unresectable and metastatic breast cancer treated with in situ radioimmunotherapy. These studies will add essential mechanistic understanding to how RT and the immune system interact, and provide insight into the clinical potential of in situ radioimmunotherapy against non-T cell-inflamed tumors insensitive to anti-PD-L1 therapy.