SAMHD1 沉默通过 IFI16-STING 通路与放疗协同增强肺腺癌的抗肿瘤免疫。

BACKGROUND: Sterile alpha motif domain and histidine-aspartate domain-containing protein 1 (SAMHD1) is a DNA end resection factor, which is involved in DNA damage repair and innate immunity. However, the role of SAMHD1 in anti-tumor immunity is still unknown. This study investigated the effects of SAMHD1 on stimulator of interferon genes (STING)-type I interferon (IFN) pathway and radiation-induced immune responses. METHODS: The roles of SAMHD1 in the activation of cytosolic DNA sensing STING pathway in lung adenocarcinoma (LUAD) cells were investigated with flow cytometry, immunofluorescence, immunoblotting and qPCR. The combined effects of SAMHD1 silencing and radiation on tumor cell growth and STING pathway activation were also evaluated with colony formation and CCK8 assay. The Lewis lung cancer mouse model was used to evaluate the combined efficiency of SAMHD1 silencing and radiotherapy in vivo. Macrophage M1 polarization and cytotoxic T cell infiltration were evaluated with flow cytometry. RESULTS: The single-stranded DNA (ssDNA) accumulated in the cytosol of SAMHD1-deficient lung adenocarcinoma (LUAD) cells, accompanied by upregulated DNA sensor IFN-γ-inducible protein 16 (IFI16) and activated STING pathway. The translocation of IFI16 from nucleus to cytosol was detected in SAMHD1-deficient cells. IFI16 and STING were acquired in the activation of STING-IFN-I pathway in SAMHD1-deficient cells. SAMHD1 silencing in LUAD cells promoted macrophage M1 polarization in vitro. SAMHD1 silencing synergized with radiation to activate ssDNA-STING-IFN-I pathway, inhibit proliferation, promote apoptosis and regulate cell cycle. SAMHD1 silencing cooperated with radiotherapy to inhibit tumor growth and increase CD86MHC-II M1 proportion and CD8 T cell infiltration in vivo. CONCLUSIONS: SAMHD1 deficiency induced IFN-I production through cytosolic IFI16-STING pathway in LUAD cells. Moreover, SAMHD1 downregulation and radiation cooperated to inhibit tumor growth and enhance anti-tumor immune responses through macrophage M1 polarization and CD8 T cell infiltration. Combination of SAMHD1 inhibition and radiotherapy may be a potentially therapeutic strategy for LUAD patients.

背景：无菌α基序域和天冬氨酸-组氨酸富含域蛋白 1（SAMHD1）是一种 DNA 末端切除因子，参与 DNA 损伤修复和固有免疫。然而，SAMHD1 在抗肿瘤免疫中的作用尚不清楚。本研究探讨了 SAMHD1 对干扰素基因刺激物（STING）-I 型干扰素（IFN）途径和辐射诱导免疫反应的影响。

方法：通过流式细胞术、免疫荧光、免疫印迹和 qPCR 研究了 SAMHD1 在肺腺癌（LUAD）细胞中激活胞质 DNA 感应 STING 途径的作用。还通过集落形成和 CCK8 测定评估了 SAMHD1 沉默和辐射对肿瘤细胞生长和 STING 途径激活的联合作用。使用 Lewis 肺癌小鼠模型评估 SAMHD1 沉默和放疗在体内的联合效率。通过流式细胞术评估巨噬细胞 M1 极化和细胞毒性 T 细胞浸润。

结果：SAMHD1 缺陷的肺腺癌细胞（LUAD）细胞中积累了单链 DNA（ssDNA），同时 DNA 传感器 IFN-γ诱导蛋白 16（IFI16）上调并激活了 STING 途径。在 SAMHD1 缺陷细胞中检测到 IFI16 从核到细胞质的易位。IFI16 和 STING 在 SAMHD1 缺陷细胞中 STING-IFN-I 途径的激活中被获得。在体外，SAMHD1 沉默促进了 LUAD 细胞中巨噬细胞 M1 极化。SAMHD1 沉默与辐射协同激活 ssDNA-STING-IFN-I 途径，抑制增殖，促进凋亡并调节细胞周期。SAMHD1 沉默与放疗协同抑制肿瘤生长，并增加体内 CD86MHC-II M1 比例和 CD8 T 细胞浸润。

结论：SAMHD1 缺陷通过 LUAD 细胞中的胞质 IFI16-STING 途径诱导 IFN-I 产生。此外，SAMHD1 下调与辐射协同抑制肿瘤生长并通过巨噬细胞 M1 极化和 CD8 T 细胞浸润增强抗肿瘤免疫反应。SAMHD1 抑制与放疗的联合可能是 LUAD 患者的一种潜在治疗策略。