Pharmacological inhibition of CDK4/6 augments long-term anti-tumor immunity through the induction of T cell memory [01_mouse_TIL]

Small molecule inhibitors of cyclin dependent kinases 4 and 6 (CDK4/6) are an approved treatment for hormone receptor-positive breast cancer and are currently under evaluation across hundreds of clinical trials for other cancer types. The clinical success of these inhibitors is largely attributed to well-defined tumor-intrinsic cytostatic mechanisms, while their emerging role as immunomodulatory agents is less understood. Using integrated epigenomic, transcriptomic and proteomic analyses, we demonstrated a novel action of CDK4/6 inhibitors in promoting the phenotypic and functional acquisition of immunological T cell memory. Short-term priming with a CDK4/6 inhibitor promoted long-term endogenous anti-tumor T cell immunity in mice, enhanced the persistence and therapeutic efficacy of chimeric antigen receptor (CAR)-T cells, and induced an RB-dependent T cell phenotype supportive of favorable responses to immune checkpoint blockade in melanoma patients. Taken together, these mechanistic insights significantly broaden the prospective utility of CDK4/6 inhibitors as clinical tools to boost anti-tumor T cell immunity. T cells were isolated from MC38-OVA tumors of mice that had been treated for one week with vehicle or palbociclib. Isolated T cells were labelled with oligo-tagged antibodies specific for PD1, Tim3, CD4 and CD8 (antibody-derived tags; ADT) and oligo-barcoded hashtagging antibodies (HTO). Labelled cells were then captured for single-cell sequencing of RNA (GEX), ADT and HTO. Two samples per treatment group (a total of four samples) were hashtagged and pooled for a single capture reaction. Each hashtagged sample is representative of 8 tumors pooled.

细胞周期蛋白依赖性激酶4和6（CDK4/6）的小分子抑制剂是已获批的激素受体阳性乳腺癌治疗药物，目前另有数百项针对其他癌种的临床试验正在评估其应用潜力。这类抑制剂的临床成功很大程度上归因于已明确的肿瘤内在增殖抑制机制，但其作为免疫调节制剂的新兴作用尚鲜为人知。本研究通过整合表观基因组学、转录组学与蛋白质组学分析，揭示了CDK4/6抑制剂的全新作用：可促进免疫性T细胞记忆的表型与功能成熟。在小鼠模型中，短期使用CDK4/6抑制剂预刺激可诱导长期内源性抗肿瘤T细胞免疫应答，增强嵌合抗原受体（chimeric antigen receptor, CAR）-T细胞的存续能力与治疗效果，并诱导成视网膜细胞瘤蛋白（RB）依赖的T细胞表型，该表型可助力黑色素瘤患者对免疫检查点阻断治疗产生良好应答。综上，这些机制层面的研究发现显著拓展了CDK4/6抑制剂作为增强抗肿瘤T细胞免疫的临床工具的潜在应用范围。研究人员从经溶剂对照或帕博西尼（palbociclib）处理一周的小鼠的MC38-OVA肿瘤组织中分离T细胞。将分离得到的T细胞用针对PD1、Tim3、CD4及CD8的寡核苷酸标记抗体（抗体衍生标签，antibody-derived tags, ADT）以及寡核苷酸条形码标记的哈希抗体（hashtagging antibodies, HTO）进行标记。随后对标记后的细胞进行捕获，以开展RNA测序（GEX）、ADT及HTO的单细胞测序。每个处理组设置两份样本（总计四份样本），均经HTO标记后混合，进行单次捕获反应。每份经HTO标记的样本均对应8份混合的肿瘤组织。