由相同初始致癌驱动因素引起的鳞状细胞癌中预先存在的不同免疫谱导致对免疫检查点抑制剂的不同反应。

BACKGROUND: While immune checkpoint inhibitors (ICI) were approved for head and neck squamous cell carcinomas (HNSCCs), the response rate remains relatively low. Mechanisms underlying ICI unresponsiveness versus sensitivity are not fully understood. METHOD: To better delineate differential responses to ICI treatment, we employed mouse SCC models, termed KPPA tumors that were caused by deleting p53 and hyperactivating PIK3CA, two most frequently mutated genes in human HNSCCs. We transplanted two KPPA tumor lines (TAb2 versus TCh3) into C57BL/6 recipients and examined the immune tumor microenvironment using flow cytometry. Furthermore, we employed single-cell RNA sequencing to identify the difference in tumor infiltrating lymphocytes (TILs). RESULTS: We found that different KPPA tumors exhibited heterogeneous immune profiles pre-existing treatment that dictated their sensitivity or unresponsiveness to anti-PD-L1. Unresponsive TAb2 tumors were highly enriched with functional tumor-associated macrophages (TAMs), especially M2-TAMs. In contrast, sensitive TCh3 tumors contained more CD8 TILs with better effector functions. TAb2 tumor cells drastically expanded F4/80 TAMs from bone marrow precursors, requiring CSF1 and VEGF. Consistently, a higher combined expression of VEGF-C and CSF1 predicts worse survival in PIK3CA/TP53 HNSCC patients. Unresponsive TAb2 tumors upregulated distinct signaling pathways that correlate with aggressive tumor phenotypes. While anti-PD-L1 did not affect the TME of TAb2 tumors, it significantly increased the number of CD8 TILs in TCh3 tumors. CONCLUSIONS: We uncovered tumor-intrinsic differences that may underlie the differential responses to ICI by establishing and employing two SCC tumor lines, TAb2 vs. TCh3, both of which harbor TP53 deletion and PIK3CA hyperactivation. Our study indicates the limitation of stratifying cancers according to their genetic alterations and suggests that evaluating HNSCC tumor-intrinsic cues along with immune profiles in the TME may help better predict ICI responses. Our experimental models may provide a platform for pinpointing tumor-intrinsic differences underlying an immunosuppressive TME in HNSCCs and for testing combined immunotherapies targeting either tumor-specific or TAM-specific players to improve ICI efficacy.

背景：尽管免疫检查点抑制剂（ICI）已被批准用于头颈部鳞状细胞癌（HNSCC），但其反应率仍相对较低。ICI 无应答与敏感的机制尚不完全清楚。

方法：为了更好地描绘对 ICI 治疗的不同反应，我们使用了两种小鼠 SCC 模型，称为 KPPA 肿瘤，其由 p53 缺失和 PIK3CA 过度激活引起，这两种基因是人类 HNSCC 中最常发生突变的基因。我们将两种 KPPA 肿瘤系（TAb2 与 TCh3）移植到 C57BL/6 受体中，并使用流式细胞术检查肿瘤免疫微环境。此外，我们还采用单细胞 RNA 测序来鉴定肿瘤浸润淋巴细胞（TIL）的差异。

结果：我们发现，不同的 KPPA 肿瘤表现出预先存在的治疗的异质性免疫特征，这些特征决定了它们对抗 PD-L1 的敏感性或无应答性。无应答性 TAb2 肿瘤富含功能肿瘤相关巨噬细胞（TAMs），特别是 M2-TAMs。相比之下，敏感的 TCh3 肿瘤含有更多具有更好效应功能的 CD8 TIL。TAb2 肿瘤细胞从骨髓前体中剧烈扩增 F4/80 TAMs，这需要 CSF1 和 VEGF。一致地，VEGF-C 和 CSF1 的联合高表达预测 PIK3CA/TP53 HNSCC 患者的预后更差。无应答性 TAb2 肿瘤上调了与侵袭性肿瘤表型相关的独特信号通路。虽然抗 PD-L1 不影响 TAb2 肿瘤的 TME，但它显著增加了 TCh3 肿瘤中 CD8 TIL 的数量。

结论：我们通过建立和使用两种 SCC 肿瘤系（TAb2 与 TCh3）来揭示肿瘤内在差异，这些肿瘤均具有 TP53 缺失和 PIK3CA 过度激活，这可能是导致对 ICI 不同反应的基础。我们的研究表明，根据癌症的遗传改变对癌症进行分层存在局限性，并表明评估 HNSCC 肿瘤内在线索以及 TME 中的免疫特征可能有助于更好地预测 ICI 反应。我们的实验模型可能为确定 HNSCC 中免疫抑制性 TME 背后的肿瘤内在差异提供一个平台，并为测试针对肿瘤特异性或 TAM 特异性靶点的联合免疫疗法提供平台，以提高 ICI 的疗效。