Recruitment of melanoma-specific CD4+ T cells

摘要 在抗肿瘤治疗策略的设计中，CD4T细胞是一个未被充分研究但却很重要的靶点 旨在重塑肿瘤微环境，增强抗肿瘤CTL功能。最近几年 已经看到免疫疗法的实施，通过 体内肿瘤特异性CTL的激活和/或挽救。虽然这些方法很有希望，但响应率 都很低。CD4T细胞在控制肿瘤生长方面也发挥着关键作用。肿瘤的生长在 CD4T细胞的缺失和抗肿瘤CD4T细胞反应的诱导可以显著增强 肿瘤特异性CTL的功能和存活率。因此，它们代表着一种未被开发的替代方案。 治疗目标，关于他们对目前检查站封锁的反应知之甚少 免疫疗法。我们的初步数据表明，在黑色素瘤的小鼠模型中，肿瘤特异性 CD4T细胞的募集对抗原水平非常敏感。低水平的肿瘤抗原无法重新招募 即使是亲和力相对较高的CD4T细胞也能进入抗肿瘤反应，表明这是调节的一个关键因素 T辅助细胞对肿瘤的反应是TCR亲和力和随后的T细胞募集。这些发现让我们 假设旨在降低CD4T细胞TCR激活阈值的策略将增强其 募集成反应及其抗肿瘤功能。我们将通过两种方式检验这一假设。首先，我们 将测试低TCR亲和力T辅助细胞是否被招募到抗黑色素瘤反应中，以及 确定常规检查站封锁(抗PD-1和/或抗CTLA-4)对其招募的影响 和功能。其次，我们将确定靶向SHP-1，一种调节活性的磷酸酶 多种TCR近端信号级联，将诱导较低的CD4T细胞激活阈值 与检查点封锁相结合，对黑色素瘤做出反应并改善其效应器功能。在我们的 在之前发表的研究中，我们已经开发出强大的工具，使我们能够分析CD4T细胞 在逐个克隆的基础上作出反应，包括一个分析CD4TCR曲目开发的模型系统 和进化，使用逆转录病毒表达载体和这两种方法产生TCR“逆转录基因”小鼠的方法 常规TCR转基因小鼠，两者对同一抗原有特异性，但TCR亲和力不同。我们 预计这里提出的实验将为黑色素瘤的设计提供重要的基础 针对T辅助细胞的免疫治疗策略。

Summary CD4+ T cells represent an understudied yet important target in the design of anti-tumor therapeutic strategies aimed at re-shaping the tumor microenvironment and enhancing the function of anti-tumor CTL. Recent years have seen the implementation of immunotherapies for the treatment of melanoma and other cancers via the activation and/or rescue of tumor-specific CTLs in vivo. While these approaches are promising, response rates are low. CD4+ T cells also play a critical role in the control of tumor growth. Tumor growth is accelerated in the absence of CD4+ T cells, and the induction of anti-tumor CD4+ T cell responses can dramatically enhance the function and survival of tumor-specific CTL. Therefore, they represent an underexplored alternative therapeutic target, and little is known regarding their response to current checkpoint blockade immunotherapies. Our preliminary data indicate that in a mouse model of melanoma, tumor-specific recruitment of CD4+ T cells is acutely sensitive to the level of antigen. Low levels of tumor antigen fail to recruit even relatively high avidity CD4+ T cells into the anti-tumor response, indicating that one key factor regulating the T helper response to tumors is TCR avidity and subsequent T cell recruitment. These findings have led us to hypothesize that strategies aimed at lowering TCR activation threshold of CD4+ T cells will enhance their recruitment into the response and their anti-tumor function. We will test this hypothesis in two ways. First, we will test whether low TCR avidity T helper cells are recruited into the anti-melanoma response, as well as determine the impact of conventional checkpoint blockade (anti-PD-1 and/or anti-CTLA-4) on their recruitment and function. Second, we will determine whether targeting of Shp-1, a phosphatase that regulates the activity of a variety of TCR proximal signaling cascades, will induce lower CD4+ T cell activation thresholds in response to melanoma and improve their effector function in combination with checkpoint blockade. In our previously published studies, we have developed powerful tools that will allow us to analyze the CD4+ T cell response on a clone-by-clone basis, including a model system for analyzing CD4+ TCR repertoire development and evolution, methods for generating TCR “retrogenic” mice using retroviral expression vectors and the two conventional TCR transgenic mice, both specific for the same antigen but with different TCR avidity. We anticipate that experiments proposed here will provide an important foundation for the design of melanoma immunotherapeutic strategies that target T helper cells.