Impact of senescence on T-cell function and immunotherapeutic response

摘要 以p16 INK 4a持续表达为标志的衰老细胞在衰老组织中增加，并促进衰老的发生。 小鼠的年龄相关疾病。这些观察结果导致p16 INK 4a的广泛临床前和临床应用 作为生物功能衰退的替代标志。然而，与年龄相关的分子事件， p16 INK 4a水平的上升在很大程度上是不确定的，研究还没有确定衰老细胞是否保留任何正常的 生理功能。 使用创新技术同时分析指示T细胞亚型、功能和细胞增殖的mRNA， 在衰老过程中，我们发现p16 INK 4a水平与T细胞耗竭的标志物平行上升。疲惫是一种 由反复免疫刺激催化的T细胞功能障碍的进行性形式。耗尽的T细胞表达 当被外源配体激活时对抗T细胞受体（TCR）信号传导的抑制性受体。电流 新兴的癌症免疫疗法阻断这些受体-配体相互作用，称为免疫检查点， 来恢复肿瘤特异性T细胞的功能。我们观察到p16 INK 4a在外周血中的表达， 来自新诊断的黑色素瘤患者的T淋巴细胞（PBL）与年龄无关， 免疫中止。这些发现支持了我们的总体假设， 是持续抗原刺激的结果，并决定了免疫检查点的结果 黑色素瘤抑制剂治疗。我们提出了一个模型，其中初始T细胞刺激导致瞬态 p16 INK 4a和T细胞耗竭标志物的上调。然而，当TCR反复接合时， 持续的p16 INK 4a表达驱动进入细胞衰老，从而将T细胞锁定在非免疫状态。 免疫疗法不能再为患者提供益处的增殖状态。拟议的研究 将确定T细胞耗竭和细胞凋亡之间的时间、分子和功能关系。 衰老（目的1A，C），鉴定调节TCR下游p16 INK 4a的生理过程 活化（目标1B），并确定免疫检查点抑制剂治疗中T细胞衰老的影响（目标2）。 这项工作将描绘触发T细胞衰老的生理事件并确定其身份， 这些细胞的功能能力，这越来越多地被用作生物老化的替代措施。这些 研究还可能通过证明循环外周血淋巴细胞可以促进癌症免疫治疗方案的发展， 血液标志物可用于预测结果，提高反应率和减少毒性。

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.