Inhibition of MBTPS1 reprograms cold into inflamed tumors and potentiates anti-PD-1 immunotherapy

Despite notable advancements in cancer immunotherapy, the overall response rate among cancer patients remains low. Therefore, exploring strategies combining immunotherapy with adjuvant approaches to augment adaptive immune responses, such as by boosting the infiltration of T lymphocytes, is an attractive strategy. To pinpoint key regulators of tumor immunity, we developed a focused single guide RNA (sgRNA) library targeting membrane and secreted protein genes. Utilizing this library, we conducted an in vivo clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 screen in colorectal cancer mice model. We revealed that the loss of MBTPS1 in tumor cells enhanced anti-tumor immunity and synergized with anti-PD-1 therapy. Mechanistic studies uncovered that tumor cell-intrinsic MBTPS1 could compete with USP13 for binding with STAT1, thereby disrupting the USP13-dependent deubiquitination and stabilization of STAT1. MBTPS1 deficiency induced CXCR3+ CD8+ T cells infiltration in the tumor microenvironment by upregulating mRNA levels of Cxcl9, Cxcl10 and Cxcl11 transcribed by STAT1. Our study revealed that targeting MBTPS1 in cancer cells could turn cold tumors into inflamed ones, thereby enhancing the efficacy of anti-PD-1 blockade. To investigate the function of MBTPS1 in cancer immunotherapy regulation, we conducted gene expression profiling analyses utilizing Mbtps1 knockout and control MC38 cells, with each group comprising 3 replicates. Furthermore, we performed sequencing on C57BL/6 wild-type mice implanted with either MBTPS1 knockdown or control MC38 cells, with each group consisting of 5 replicates.尽管癌症免疫治疗领域已取得显著进展，但癌症患者的整体应答率仍处于较低水平。因此，探索将免疫治疗与辅助手段相结合以增强适应性免疫应答的策略（例如促进T淋巴细胞浸润），成为极具吸引力的研究方向。为精准定位肿瘤免疫的关键调控因子，我们构建了靶向膜蛋白及分泌蛋白编码基因的聚焦型单引导RNA（single guide RNA, sgRNA）文库。利用该文库，我们在结直肠癌小鼠模型中开展了体内成簇规律间隔短回文重复序列（clustered regularly interspaced short palindromic repeats, CRISPR）-Cas9筛选实验。研究发现，肿瘤细胞中MBTPS1的缺失可增强抗肿瘤免疫，并与抗PD-1治疗产生协同效应。机制研究揭示，肿瘤细胞内源性MBTPS1可与USP13竞争性结合STAT1，从而阻断USP13依赖的STAT1去泛素化与稳定化过程。MBTPS1缺失可通过上调STAT1转录的Cxcl9、Cxcl10及Cxcl11的mRNA水平，诱导肿瘤微环境中CXCR3+ CD8+ T细胞浸润。本研究表明，靶向肿瘤细胞中的MBTPS1可将“冷肿瘤”转化为“热肿瘤”，从而提升抗PD-1免疫检查点阻断治疗的疗效。为探究MBTPS1在癌症免疫治疗调控中的功能，我们利用Mbtps1基因敲除MC38细胞及对照MC38细胞开展了基因表达谱分析，每组设置3个生物学重复。此外，我们对植入MBTPS1基因敲低MC38细胞或对照MC38细胞的C57BL/6野生型小鼠进行了测序实验，每组设置5个生物学重复。