Cytoplasmic pattern recognition receptors (PRRs) for double-stranded RNA (RIG-I/MDA5) are key mediators of anti-viral responses. PRR agonists, such as dsRNA oncolytic Reovirus type 3 Dearing (Rt3D), potently activate RNA sensors. We used an unbiased cytotoxicity screen to reveal synergistic drug-virotherapy combinations and found potent effects of Rt3D combined with the CDK4/6 inhibitor, palbociclib. The combination augmented oncolytic virus-induced endoplasmic reticulum (ER) stress/unfolded protein response (UPR) and the expression and activation/signaling of RNA sensors. Combined Rt3D-palbociclib treatment potently increased interferon production and signaling, and knockdown studies implicated key UPR proteins and the RNA sensor, RIG-I, as essential to the phenotype observed. Further experiments, using canonical RIG-I agonists and an ER stress inducer, thapsigargin, confirmed cross-talk between RNA sensing and ER stress pathways that augmented cancer cell death and interferon production. Combined Rt3D-palbociclib also increased innate immune activation within tumour cells and IFN-induced HLA expression. Analysis of the immunopeptidome revealed changes to HLA-captured peptides with Rt3D-palbociclib, including altered expression of peptides from cancer/testis antigens (CTA) and endogenous retroviral elements (ERVs). Our findings highlight cross-talk between UPR signaling and RNA-mediated PRR activation as a means of enhancing anti-cancer efficacy with potential pro-immunogenic consequences. This has implications for future clinical development of PRR agonists and oncolytic viruses, and broadens the therapeutic remit of CDK4/6 inhibitors to include roles as both ER stress and dsRNA PRR sensitizers.

中文翻译：

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CDK4/6 抑制和 dsRNA 传感器激动作用通过 ER 应激和肿瘤细胞的免疫调节共同增强抗癌作用

双链 RNA (RIG-I/MDA5) 的细胞质模式识别受体 (PRR) 是抗病毒反应的关键介质。PRR 激动剂，如 dsRNA 溶瘤呼肠孤病毒 3 型 Dearing (Rt3D)，可有效激活 RNA 传感器。我们使用无偏见的细胞毒性筛选来揭示协同药物-病毒疗法组合，并发现 Rt3D 与 CDK4/6 抑制剂 palbociclib 联合的有效作用。该组合增强了溶瘤病毒诱导的内质网 (ER) 应激/未折叠蛋白反应 (UPR) 以及 RNA 传感器的表达和激活/信号传导。联合 Rt3D-palbociclib 治疗有效地增加了干扰素的产生和信号传导，并且敲低研究表明关键的 UPR 蛋白和 RNA 传感器 RIG-I 对于观察到的表型至关重要。进一步的实验，使用经典的 RIG-I 激动剂和 ER 应激诱导剂毒胡萝卜素，证实了 RNA 传感和 ER 应激途径之间的串扰，从而增加了癌细胞的死亡和干扰素的产生。联合 Rt3D-palbociclib 还增加了肿瘤细胞内的先天免疫激活和 IFN 诱导的 HLA 表达。免疫肽组分析揭示了 Rt3D-palbociclib 对 HLA 捕获肽的变化，包括来自癌症/睾丸抗原 (CTA) 和内源性逆转录病毒元件 (ERV) 的肽表达改变。我们的研究结果强调了 UPR 信号和 RNA 介导的 PRR 激活之间的交叉对话，作为增强抗癌功​​效的一种手段，具有潜在的促免疫原性后果。这对 PRR 激动剂和溶瘤病毒的未来临床开发具有重要意义，