DataSheet_2_Low-density lipoprotein balances T cell metabolism and enhances response to anti-PD-1 blockade in a HCT116 spheroid model.zip

IntroductionThe discovery of immune checkpoints and the development of their specific inhibitors was acclaimed as a major breakthrough in cancer therapy. However, only a limited patient cohort shows sufficient response to therapy. Hence, there is a need for identifying new checkpoints and predictive biomarkers with the objective of overcoming immune escape and resistance to treatment. Having been associated with both, treatment response and failure, LDL seems to be a double-edged sword in anti-PD1 immunotherapy. Being embedded into complex metabolic conditions, the impact of LDL on distinct immune cells has not been sufficiently addressed. Revealing the effects of LDL on T cell performance in tumor immunity may enable individual treatment adjustments in order to enhance the response to routinely administered immunotherapies in different patient populations. The object of this work was to investigate the effect of LDL on T cell activation and tumor immunity in-vitro.
MethodsExperiments were performed with different LDL dosages (LDLlow = 50 μg/ml and LDLhigh = 200 μg/ml) referring to medium control. T cell phenotype, cytokines and metabolism were analyzed. The functional relevance of our findings was studied in a HCT116 spheroid model in the context of anti-PD-1 blockade.
ResultsThe key points of our findings showed that LDLhigh skewed the CD4+ T cell subset into a central memory-like phenotype, enhanced the expression of the co-stimulatory marker CD154 (CD40L) and significantly reduced secretion of IL-10. The exhaustion markers PD-1 and LAG-3 were downregulated on both T cell subsets and phenotypical changes were associated with a balanced T cell metabolism, in particular with a significant decrease of reactive oxygen species (ROS). T cell transfer into a HCT116 spheroid model resulted in a significant reduction of the spheroid viability in presence of an anti-PD-1 antibody combined with LDLhigh.
DiscussionFurther research needs to be conducted to fully understand the impact of LDL on T cells in tumor immunity and moreover, to also unravel LDL effects on other lymphocytes and myeloid cells for improving anti-PD-1 immunotherapy. The reason for improved response might be a resilient, less exhausted phenotype with balanced ROS levels.

引言
免疫检查点的发现及其特异性抑制剂的开发，被视为癌症治疗领域的重大突破。然而，仅有有限数量的患者队列对该治疗表现出充分响应。因此，亟需识别新型检查点与预测性生物标志物，以期克服免疫逃逸与治疗耐药性。低密度脂蛋白（LDL）与治疗响应及治疗失败均存在关联，在抗PD-1免疫治疗中堪称一把双刃剑。由于其嵌入复杂的代谢环境，LDL对不同免疫细胞的影响尚未得到充分研究。阐明LDL对肿瘤免疫中T细胞功能的影响，或可实现个体化治疗调整，从而提升不同患者群体对常规免疫治疗的响应效果。本研究旨在体外探究LDL对T细胞活化及肿瘤免疫的影响。
方法
本实验设置了不同剂量的LDL（低剂量LDLlow=50 μg/ml，高剂量LDLhigh=200 μg/ml），以培养基作为空白对照。对T细胞表型、细胞因子及代谢情况进行了分析。在抗PD-1阻断的研究背景下，通过HCT116球体模型对本研究发现的功能相关性进行了验证。
结果
本研究的核心发现如下：高剂量LDL可将CD4+ T细胞亚群极化为中枢记忆样表型，增强共刺激标志物CD154（CD40L）的表达，并显著降低IL-10的分泌。两种T细胞亚群上的耗竭标志物PD-1与LAG-3均出现下调，表型变化与平衡的T细胞代谢状态相关，尤其是活性氧（reactive oxygen species, ROS）水平显著降低。将T细胞移植至HCT116球体模型后，联合使用抗PD-1抗体与高剂量LDL时，球体存活率显著降低。
讨论
仍需开展进一步研究，以全面阐明LDL对肿瘤免疫中T细胞的影响；此外，还需解析LDL对其他淋巴细胞及髓系细胞的作用，从而优化抗PD-1免疫治疗方案。治疗响应提升的潜在原因，可能是T细胞表型更具韧性、耗竭程度更低，且ROS水平维持平衡。