Medical Oncology, Hunter Holmes McGuire VA Medical Center, Richmond, Virginia, USA.
Anesthesiology, University of Colorado Denver - Anschutz Medical Campus, Aurora, Colorado, USA.
J Immunother Cancer. 2020 Apr;8(1). doi: 10.1136/jitc-2019-000441.
Programmed death 1/programmed death ligand 1 (PD-1/PD-L1) targeted immunotherapy affords clinical benefit in ~20% of unselected patients with lung cancer. The factor(s) that determine whether a tumor responds or fails to respond to immunotherapy remains an active area of investigation. We have previously defined divergent responsiveness of two KRAS-mutant cell lines to PD-1/PD-L1 blockade using an orthotopic, immunocompetent mouse model. Responsiveness to PD-1/PD-L1 checkpoint blockade correlates with an interferon gamma (IFNγ)-inducible gene signature and major histocompatibility complex class II (MHC II) expression by cancer cells. In the current study, we aim to identify therapeutic targets that can be manipulated in order to enhance cancer-cell-specific MHC II expression.
Responsiveness to IFNγ and induction of MHC II expression was assessed after various treatment conditions in mouse and human non-small cell lung cancer (NSCLC) cell lines using mass cytometric and flow cytometric analysis.
Single-cell analysis using mass and flow cytometry demonstrated that IFNγ consistently induced PD-L1 and MHC class I (MHC I) across multiple murine and human NSCLC cell lines. In contrast, MHC II showed highly variable induction following IFNγ treatment both between lines and within lines. In mouse models of NSCLC, MHC II induction was inversely correlated with basal levels of phosphorylated extracellular signal-regulated kinase (ERK) 1/2, suggesting potential mitogen-activated protein (MAP) kinase-dependent antagonism of MHC II expression. To test this, cell lines were subjected to varying levels of stimulation with IFNγ, and assessed for MHC II expression in the presence or absence of mitogen-activated protein kinase kinase (MEK) inhibitors. IFNγ treatment in the presence of MEK inhibitors significantly enhanced MHC II induction across multiple lung cancer lines, with minimal impact on expression of either PD-L1 or MHC I. Inhibition of histone deacetylases (HDACs) also enhanced MHC II expression to a more modest extent. Combined MEK and HDAC inhibition led to greater MHC II expression than either treatment alone.
These studies emphasize the active inhibitory role that epigenetic and ERK signaling cascades have in restricting cancer cell-intrinsic MHC II expression in NSCLC, and suggest that combinatorial blockade of these pathways may engender new responsiveness to checkpoint therapies.
程序性死亡受体 1/配体 1（PD-1/PD-L1）靶向免疫疗法为约 20%未经选择的肺癌患者提供了临床获益。决定肿瘤对免疫治疗是否有反应或无反应的因素仍然是一个活跃的研究领域。我们之前使用过一种原位免疫功能正常的小鼠模型，定义了两种 KRAS 突变细胞系对 PD-1/PD-L1 阻断的不同反应性。对 PD-1/PD-L1 检查点阻断的反应性与干扰素 γ（IFNγ）诱导的基因特征和癌细胞主要组织相容性复合体 II（MHC II）表达相关。在本研究中，我们旨在确定可用于增强癌细胞特异性 MHC II 表达的治疗靶点。
使用质谱流式细胞术和流式细胞术分析，在小鼠和人非小细胞肺癌（NSCLC）细胞系中，评估各种处理条件下 IFNγ对 MHC II 表达的诱导作用。
使用质谱和流式细胞术的单细胞分析表明，IFNγ在多种小鼠和人 NSCLC 细胞系中一致诱导 PD-L1 和 MHC I（MHC I）。相比之下，IFNγ 处理后 MHC II 的诱导在不同细胞系之间和细胞系内具有高度的可变性。在 NSCLC 的小鼠模型中，MHC II 的诱导与基础磷酸化细胞外信号调节激酶（ERK）1/2 水平呈负相关，表明潜在的有丝分裂原激活蛋白（MAP）激酶依赖性 MHC II 表达拮抗作用。为了验证这一点，细胞系接受不同水平的 IFNγ刺激，并在存在或不存在丝裂原激活蛋白激酶激酶（MEK）抑制剂的情况下评估 MHC II 表达。在 MEK 抑制剂存在下进行 IFNγ 处理可显著增强多种肺癌细胞系的 MHC II 诱导，对 PD-L1 或 MHC I 的表达影响最小。组蛋白去乙酰化酶（HDACs）抑制剂也在一定程度上增强了 MHC II 的表达。MEK 和 HDAC 联合抑制导致 MHC II 的表达比单独任何一种治疗都更强。
这些研究强调了表观遗传和 ERK 信号级联在限制 NSCLC 中癌细胞内在 MHC II 表达方面的积极抑制作用，并表明这些途径的组合阻断可能会引发对检查点治疗的新反应。
