Impact of senescence on T-cell function and immunotherapeutic response

摘要 以p16INK4a持续表达为标志的衰老细胞在衰老组织中增加，并促进 小鼠的年龄相关疾病。这些观察结果导致了p16INK4a在临床前和临床上的广泛应用。 作为生物功能衰退的替代标记。然而，与年龄相关的分子事件导致 P16INK4a水平的上升在很大程度上是未知的，研究尚未确定衰老细胞是否保持正常 生理功能。 使用一种创新技术同时分析指示T细胞亚型、功能和细胞的mRNAs 在衰老过程中，我们发现p16INK4a水平与T细胞衰竭的标志物平行上升。精疲力竭是一种 反复免疫刺激导致的进行性T细胞功能障碍。疲惫的T细胞表达 当被外源配体激活时，反对T细胞受体(TCR)信号的抑制性受体。当前 新兴的癌症免疫疗法阻止了这些受体-配体的相互作用，即所谓的免疫检查点， 以恢复肿瘤特异性T细胞的功能。我们观察到p16INK4a在外周血中的表达 新诊断的黑色素瘤患者的T淋巴细胞(PBTL)与年龄无关，似乎可以预测 停止免疫治疗。这些发现支持我们的总体假设，即T细胞衰老 是持续抗原刺激的结果，并决定了免疫检查点的结果 黑色素瘤的抑制剂治疗。我们提出了一个模型，在这个模型中，最初的T细胞刺激导致了瞬时 P16INK4a和T细胞耗竭标志物均上调。然而，当TCR被重复占用时， 持续的p16INK4a表达促使细胞进入衰老，从而将T细胞锁定在非 免疫治疗不再能给患者带来益处的增殖性状态。建议进行的研究 将决定T细胞耗竭和细胞功能之间的时间、分子和功能关系 衰老(目标1A，C)，确定调节TCR下游p16INK4a的生理过程 激活(目标1B)，并确定T细胞衰老在免疫检查点抑制剂治疗中的影响(目标2)。 这项工作将描绘触发T细胞衰老的生理事件，并建立身份和 这些细胞的功能能力，越来越多地被用作生物老化的替代指标。这些 研究还可能通过证明循环中的外周血细胞来推进癌症免疫治疗方案。 血液标记物可用于预测结果，提高应答率，并将毒性降至最低。

ABSTRACT Senescent cells, marked by persistent p16INK4a expression, increase in aging tissues and promote the onset of age-related disease in mice. These observations have led to widespread pre-clinical and clinical use of p16INK4a as a surrogate marker of declining biological function. However, the age-related molecular events that cause p16INK4a levels to rise are largely undefined and studies have yet to determine if senescent cells retain any normal physiological functions. Using an innovative technique to simultaneously profile mRNAs indicative of T-cell subtype, function and cellular senescence, we find that p16INK4a levels rise in parallel with markers of T-cell exhaustion. Exhaustion is a progressive form of T-cell dysfunction catalyzed by repeated immune stimulation. Exhausted T-cells express inhibitory receptors that oppose T-cell receptor (TCR) signaling when activated by exogenous ligands. Current and emerging cancer immunotherapies block these receptor-ligand interactions, known as immune checkpoints, to restore the function of tumor-specific T-cells. We observe that the expression of p16INK4a in peripheral blood T-lymphocytes (PBTLs) from newly diagnosed melanoma patients is age-independent and appears to predict immunotherapeutic discontinuation. These findings support our overarching hypothesis that T-cell senescence is a consequence of continued antigenic stimulation and dictates the outcome of immune checkpoint inhibitor therapy in melanoma. We propose a model wherein initial T-cell stimulation leads to the transient upregulation of both p16INK4a and markers of T-cell exhaustion. However, when the TCR is repeatedly engaged, sustained p16INK4a expression drives entry into cellular senescence, thereby locking T-cells into a non- proliferative state in which immunotherapies can no longer provide benefit to the patient. The proposed studies will determine the chronologic, molecular and functional relationship between T-cell exhaustion and cellular senescence (Aim 1A, C), identify the physiological processes that regulate p16INK4a downstream of TCR activation (Aim 1B) and define the impact of T-cell senescence in immune checkpoint inhibitor therapy (Aim 2). This work will delineate the physiological events that trigger T-cell senescence and establish the identity and functional capacity of these cells, which are increasingly used as a surrogate measure of biological aging. These studies are also likely to advance cancer immunotherapy regimens by demonstrating that a circulating peripheral blood marker could be used to predict outcome, improve response rates and minimize toxicity.