Low intra-tumor heterogeneity (ITH) correlates with increased patient survival and immunotherapy response. However, even highly homogeneous tumors are variably aggressive, and the immunological factors impacting aggressiveness remain understudied. Here, we analyzed the mechanisms underlying immune escape in murine tumors with low ITH. We used immunophenotyping and single-cell RNA sequencing to compare the temporal growth of in-vivo transplanted, genetically similar rejected vs. non-rejected single-cell clones. Non-rejected clones showed high infiltration of tumor-associated macrophages (TAMs), lower T-cell infiltration, and increased T-cell exhaustion compared to rejected clones. Comparative analysis of rejection-associated gene expression programs, combined with in-vivo CRISPR knockout screens of candidate regulators, identified Mif (macrophage migration inhibitory factor) as a major contributor to immune rejection. Mif knockout resulted in smaller tumors and reduced TAM infiltration. These results were validated in melanoma patient data. Overall, our homogeneous tumor system can uncover factors regulating growth variability and identifies Mif as critical in aggressive melanoma.

中文翻译：

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同质肿瘤模型的时间基因组分析揭示了黑色素瘤免疫逃避的关键调节因子


低肿瘤内异质性 （ITH） 与患者生存率和免疫治疗反应增加相关。然而，即使是高度同质的肿瘤也具有可变的侵袭性，影响侵袭性的免疫因素仍未得到充分研究。在这里，我们分析了低 ITH 小鼠肿瘤免疫逃逸的潜在机制。我们使用免疫表型分析和单细胞 RNA 测序来比较体内移植的、遗传相似的排斥细胞克隆与非排斥细胞克隆的时间生长。与排斥克隆相比，非排斥克隆显示肿瘤相关巨噬细胞 （TAM） 的高浸润、较低的 T 细胞浸润和 T 细胞耗竭增加。排斥相关基因表达程序的比较分析，结合候选调节因子的体内 CRISPR 敲除筛选，确定 Mif（巨噬细胞迁移抑制因子）是免疫排斥的主要因素。Mif 敲除导致肿瘤变小并减少 TAM 浸润。这些结果在黑色素瘤患者数据中得到了验证。总体而言，我们的同质肿瘤系统可以发现调节生长变异性的因素，并确定 Mif 在侵袭性黑色素瘤中至关重要。