Characterization of the dynamic change in the immunological landscape during malignant transformation from precancerous lesions to cancerous lesions in squamous cell carcinoma (SCC) is critical for the application of immunotherapy. Here, we performed single-cell RNA-Seq (scRNA-Seq) of 131,702 cells from 13 cancerous tissues of oral squamous cell carcinoma (OSCC), 3 samples of precancerous oral leukoplakia, and 8 adjacent normal samples. We found that tumor-infiltrating CD4⁺ and CD8⁺ T cells were functionally inhibited by immunosuppressive ligands expressed on various types of myeloid cells or neutrophils in the process of oral carcinogenesis. Notably, we identified a subset of myofibroblasts that exclusively expressed tryptophan 2,3-dioxygenase (TDO2). These TDO2⁺ myofibroblasts were located distally from tumor nests, and both CD4⁺ and CD8⁺ T cells were enriched around them. Functional experiments revealed that TDO2⁺ myofibroblasts were more likely to possess the ability for chemotaxis toward T cells but induced the transformation of CD4⁺ T cells into Tregs and caused CD8⁺ T cell dysfunction. We further showed that use of the TDO2 inhibitor LM10 attenuated the inhibitory states of T cells, restored the T cell antitumor response, and prevented the progression of OSCC malignant transformation in murine models. Our study reveals a multistep transcriptomic landscape of OSCC and demonstrates that TDO2⁺ myofibroblasts are potential targets for immunotherapy.

中文翻译：

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TDO2+肌成纤维细胞介导鳞状细胞癌恶性转化中的免疫抑制

表征鳞状细胞癌 (SCC) 从癌前病变向癌性病变的恶性转化过程中免疫学景观的动态变化对于免疫治疗的应用至关重要。在这里，我们对来自 13 个口腔鳞状细胞癌 (OSCC) 癌组织、3 个癌前口腔白斑样本和 8 个相邻正常样本的 131,702 个细胞进行了单细胞 RNA-Seq (scRNA-Seq)。我们发现，在口腔癌变过程中，肿瘤浸润性 CD4 ⁺和 CD8 ⁺ T 细胞受到在各种类型的骨髓细胞或中性粒细胞上表达的免疫抑制配体的功能抑制。值得注意的是，我们确定了一个专门表达色氨酸 2,3-双加氧酶 (TDO2) 的肌成纤维细胞子集。这些 TDO2 ⁺肌成纤维细胞位于肿瘤巢的远端，CD4 ⁺和 CD8 ⁺ T 细胞在它们周围富集。功能实验表明，TDO2 ⁺肌成纤维细胞更可能具有对 T 细胞趋化的能力，但会诱导 CD4 ⁺ T 细胞转化为 Tregs 并导致 CD8 ⁺ T 细胞功能障碍。我们进一步表明，TDO2 抑制剂 LM10 的使用减弱了 T 细胞的抑制状态，恢复了 T 细胞的抗肿瘤反应，并阻止了小鼠模型中 OSCC 恶性转化的进展。我们的研究揭示了 OSCC 的多步骤转录组学格局，并证明 TDO2 ⁺肌成纤维细胞是免疫治疗的潜在靶点。