Bulk RNA sequencing of WT and Pim1 -/- bone-marrow-derived myeloid-derived suppressor cells. Bulk RNA sequencing of WT and Pim1 -/- bone-marrow-derived myeloid-derived suppressor cells

There is a strong correlation between myeloid derived suppressor cells (MDSCs) and resistance to immune checkpoint blockade (ICB), but the detailed underlying this correlation are largely unknown. Using single-cell RNA-seq analysis in a bilateral tumor model, we found that immunosuppressive myeloid cells with characteristics of fatty acid oxidative metabolism dominate the immune-cell landscape in ICB-resistant subjects. In addition, we uncovered a previously underappreciated role of a serine/threonine kinase, PIM1, in regulating lipid oxidative metabolism via PPARγ-mediated activities. Enforced PPARγ expression sufficiently rescued metabolic and functional defects of Pim1-/- MDSCs. Consistent with this, pharmacological inhibition of PIM kinase by AZD1208 treatment significantly disrupted myeloid cell–mediated immunosuppression microenvironment and unleashed CD8+ T cell–mediated antitumor immunity, which enhanced PD-L1 blockade in preclinical cancer models. PIM kinase inhibition also sensitized non-responders to PD-L1 blockade by selectively targeting suppressive myeloid cells. Overall, we have identified PIM1 as a metabolic modulator in MDSCs that is associated with ICB resistance and can be therapeutically targeted to overcome ICB resistance. Overall design: Bulk RNA sequencing, 2 samples (WT and Pim1-/- MDSC), 3 biological replicates per sample, from bone-marrow-derived myeloid-derived suppressor cells

髓系来源抑制细胞（myeloid derived suppressor cells, MDSCs）与免疫检查点阻断（immune checkpoint blockade, ICB）耐药性之间存在显著相关性，但该关联背后的具体机制仍未完全阐明。本研究通过双侧肿瘤模型中的单细胞RNA测序（single-cell RNA-seq）分析，发现具有脂肪酸氧化代谢特征的免疫抑制性髓系细胞，在免疫检查点阻断耐药受试者的免疫细胞图谱中占据主导地位。此外，本研究还揭示了丝氨酸/苏氨酸激酶PIM1此前未被充分认知的调控功能：其可通过过氧化物酶体增殖物激活受体γ（PPARγ）介导的信号通路调控脂质氧化代谢。强制过表达PPARγ可完全挽救Pim1基因敲除（Pim1-/-）髓系来源抑制细胞的代谢与功能缺陷。与此一致，通过AZD1208对PIM激酶进行药理学抑制，可显著破坏髓系细胞介导的免疫抑制微环境，激活CD8+ T细胞介导的抗肿瘤免疫，从而在临床前癌症模型中增强程序性死亡受体配体1（PD-L1）阻断治疗的效果。PIM激酶抑制还可通过选择性靶向抑制性髓系细胞，使免疫检查点阻断治疗无应答者对PD-L1阻断治疗产生敏感性。综上，本研究证实PIM1是髓系来源抑制细胞中的代谢调控因子，其与免疫检查点阻断耐药性相关，且可作为治疗靶点以克服免疫检查点阻断耐药。总体实验设计：批量RNA测序，共2组样本（野生型（wild type, WT）与Pim1基因敲除（Pim1-/-）髓系来源抑制细胞），每组设置3次生物学重复，样本取自骨髓来源的髓系来源抑制细胞。