The identification of novel therapeutic strategies to overcome resistance to the MEK inhibitor trametinib in mutant KRAS lung adenocarcinoma (LUAD) is a challenge. This study analyzes the effects of trametinib on Id1 protein, a key factor involved in the KRAS oncogenic pathway, and investigates the role of Id1 in the acquired resistance to trametinib as well as the synergistic anticancer effect of trametinib combined with immunotherapy in KRAS-mutant LUAD. We evaluated the effects of trametinib on KRAS-mutant LUAD by Western blot, RNA-seq and different syngeneic mouse models. Genetic modulation of Id1 expression was performed in KRAS-mutant LUAD cells by lentiviral or retroviral transductions of specific vectors. Cell viability was assessed by cell proliferation and colony formation assays. PD-L1 expression and apoptosis were measured by flow cytometry. The anti-tumor efficacy of the combined treatment with trametinib and PD-1 blockade was investigated in KRAS-mutant LUAD mouse models, and the effects on the tumor immune infiltrate were analyzed by flow cytometry and immunohistochemistry. We found that trametinib activates the proteasome-ubiquitin system to downregulate Id1 in KRAS-mutant LUAD tumors. Moreover, we found that Id1 plays a major role in the acquired resistance to trametinib treatment in KRAS-mutant LUAD cells. Using two preclinical syngeneic KRAS-mutant LUAD mouse models, we found that trametinib synergizes with PD-1/PD-L1 blockade to hamper lung cancer progression and increase survival. This anti-tumor activity depended on trametinib-mediated Id1 reduction and was associated with a less immunosuppressive tumor microenvironment and increased PD-L1 expression on tumor cells. Our data demonstrate that Id1 expression is involved in the resistance to trametinib and in the synergistic effect of trametinib with anti-PD-1 therapy in KRAS-mutant LUAD tumors. These findings suggest a potential therapeutic approach for immunotherapy-refractory KRAS-mutant lung cancers.

中文翻译：

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Trametinib 通过 Id1 下调使 KRAS 突变肺腺癌肿瘤对 PD-1/PD-L1 轴阻断敏感

确定新的治疗策略来克服突变型 KRAS 肺腺癌 (LUAD) 对 MEK 抑制剂曲美替尼 (Trametinib) 的耐药性是一项挑战。本研究分析曲美替尼对KRAS致癌通路关键因子Id1蛋白的影响，探讨Id1在曲美替尼获得性耐药中的作用以及曲美替尼联合免疫治疗在KRAS突变型LUAD中的协同抗癌作用。我们通过蛋白质印迹、RNA-seq 和不同的同基因小鼠模型评估了曲美替尼对 KRAS 突变 LUAD 的影响。通过特定载体的慢病毒或逆转录病毒转导，在 KRAS 突变 LUAD 细胞中对 Id1 表达进行遗传调节。通过细胞增殖和集落形成测定来评估细胞活力。通过流式细胞术测量PD-L1表达和细胞凋亡。在 KRAS 突变 LUAD 小鼠模型中研究曲美替尼联合 PD-1 阻断的抗肿瘤疗效，并通过流式细胞术和免疫组化分析对肿瘤免疫浸润的影响。我们发现 Trametinib 激活蛋白酶体泛素系统，下调 KRAS 突变 LUAD 肿瘤中的 Id1。此外，我们发现 Id1 在 KRAS 突变 LUAD 细胞中对曲美替尼治疗的获得性耐药中发挥着重要作用。使用两种临床前同基因 KRAS 突变 LUAD 小鼠模型，我们发现曲美替尼与 PD-1/PD-L1 阻断剂具有协同作用，可阻碍肺癌进展并提高生存率。这种抗肿瘤活性依赖于曲美替尼介导的 Id1 减少，并与免疫抑制较少的肿瘤微环境和肿瘤细胞上 PD-L1 表达增加有关。我们的数据表明，Id1 表达与 Trametinib 耐药以及 Trametinib 与抗 PD-1 疗法在 KRAS 突变 LUAD 肿瘤中的协同作用有关。这些发现为免疫治疗难治性 KRAS 突变肺癌提供了一种潜在的治疗方法。