Major efforts are underway to identify agents that can potentiate effects of immune checkpoint inhibition. Here, we show that ascorbic acid (AA) treatment caused genomewide demethylation and enhanced expression of endogenous retroviral elements in lymphoma cells. AA also increased 5-hydroxymethylcytosine (5hmC) levels of CD8+ T cells and enhanced their cytotoxic activity in a lymphoma coculture system. High-dose AA treatment synergized with anti-PD1 therapy in a syngeneic lymphoma mouse model, resulting in marked inhibition of tumor growth compared with either agent alone. Analysis of the intratumoral epigenome revealed increased 5hmC with AA treatment, consistent with in vitro findings. Analysis of the tumor immune microenvironment revealed that AA strikingly increased intratumoral infiltration of CD8+ T cells and macrophages, suggesting enhanced tumor immune recognition. The combination treatment markedly enhanced intratumoral infiltration of macrophages and CD8+ T lymphocytes, granzyme B production by cytotoxic cells (cytotoxic T cells and natural killer cells), and interleukin 12 production by antigen-presenting cells compared with single-agent anti-PD1. These data indicate that AA potentiates anti-PD1 checkpoint inhibition through synergistic mechanisms. The study provides compelling rationale for testing combinations of high-dose AA and anti-PD1 agents in patients with aggressive B cell lymphoma as well as in preclinical models of other malignancies.

中文翻译：

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在淋巴瘤小鼠模型中，高剂量抗坏血酸与抗 PD1 药物具有协同作用。

目前正在努力寻找能够增强免疫检查点抑制作用的药物。在这里，我们发现抗坏血酸（AA）治疗导致淋巴瘤细胞中全基因组去甲基化并增强内源性逆转录病毒元件的表达。AA 还增加了 CD8+ T 细胞的 5-羟甲基胞嘧啶 (5hmC) 水平，并增强了淋巴瘤共培养系统中的细胞毒活性。在同基因淋巴瘤小鼠模型中，高剂量 AA 治疗与抗 PD1 治疗协同作用，与单独使用任一药物相比，可显着抑制肿瘤生长。瘤内表观基因组分析显示，AA 治疗后 5hmC 增加，与体外研究结果一致。对肿瘤免疫微环境的分析表明，AA 显着增加了 CD8+ T 细胞和巨噬细胞的瘤内浸润，表明肿瘤免疫识别能力增强。与单药抗PD1相比，联合治疗显着增强了巨噬细胞和CD8+T淋巴细胞的瘤内浸润、细胞毒性细胞（细胞毒性T细胞和自然杀伤细胞）产生的颗粒酶B以及抗原呈递细胞产生的白细胞介素12。这些数据表明 AA 通过协同机制增强抗 PD1 检查点抑制作用。该研究为在侵袭性 B 细胞淋巴瘤患者以及其他恶性肿瘤的临床前模型中测试高剂量 AA 和抗 PD1 药物的组合提供了令人信服的理由。