General control nonderepressible 2 (GCN2) is an environmental sensor controlling transcription and translation in response to nutrient availability. Although GCN2 is a putative therapeutic target for immuno-oncology, its role in shaping the immune response to tumors is poorly understood. Here, we used mass cytometry, transcriptomics, and transcription factor-binding analysis to determine the functional impact of GCN2 on the myeloid phenotype and immune responses in melanoma. We found that myeloid-lineage deletion of GCN2 drives a shift in the phenotype of tumor-associated macrophages and myeloid-derived suppressor cells (MDSCs) that promotes antitumor immunity. Time-of-flight mass cytometry (CyTOF) and single-cell RNA sequencing showed that this was due to changes in the immune microenvironment with increased proinflammatory activation of macrophages and MDSCs and interferon-γ expression in intratumoral CD8+ T cells. Mechanistically, GCN2 altered myeloid function by promoting increased translation of the transcription factor CREB-2/ATF4, which was required for maturation and polarization of macrophages and MDSCs in both mice and humans, whereas targeting Atf4 by small interfering RNA knockdown reduced tumor growth. Last, analysis of patients with cutaneous melanoma showed that GCN2-dependent transcriptional signatures correlated with macrophage polarization, T cell infiltrates, and overall survival. Thus, these data reveal a previously unknown dependence of tumors on myeloid GCN2 signals for protection from immune attack.

中文翻译：

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GCN2在肿瘤微环境中驱动巨噬细胞和MDSC功能以及免疫抑制。

通用控制不可抑制2（GCN2）是一种环境传感器，可根据营养状况控制转录和翻译。尽管GCN2是免疫肿瘤学的假定治疗靶标，但其在塑造对肿瘤的免疫反应中的作用知之甚少。在这里，我们使用了细胞计数，转录组学和转录因子结合分析来确定GCN2对黑色素瘤的骨髓表型和免疫反应的功能影响。我们发现，GCN2的髓系谱系缺失驱动肿瘤相关巨噬细胞和髓系抑制细胞（MDSCs）的表型转变，从而促进抗肿瘤免疫力。飞行时间质谱（CyTOF）和单细胞RNA测序表明，这是由于免疫微环境的改变，伴随着肿瘤内CD8 + T细胞中巨噬细胞和MDSC的促炎激活增加以及干扰素-γ表达。从机制上讲，GCN2通过促进转录因子CREB-2 / ATF4的翻译增加而改变了髓样功能，CREB-2 / ATF4是小鼠和人类中巨噬细胞和MDSC的成熟和极化所必需的，而通过小的干扰RNA敲低靶向Atf4则降低了肿瘤的生长。最后，对皮肤黑色素瘤患者的分析表明，依赖GCN2的转录特征与巨噬细胞极化，T细胞浸润和总体存活率相关。因此，