Tumor‐Intrinsic Forkhead Box A2 Regulates the Lymph Node Metastasis of Papillary Thyroid Carcinoma by Regulating T‐Cell Apoptosis

ABSTRACT Background Lymph node metastasis is a significant indicator of recurrence and mortality in thyroid carcinoma and often guides treatment decisions. However, the characteristics and specific mechanisms of various cancer cells that metastasize to lymph nodes are not clear. This study aims to characterize the cellular heterogeneity and transcriptomic dynamics of thyroid cancer. We further seek to elucidate the role of the key transcription factor FOXA2 in orchestrating a pro‐metastatic and immunosuppressive program, specifically its regulation of T‐cell activity and apoptosis. Our ultimate goal is to identify potential therapeutic strategies for thyroid cancer with lymph node metastasis. Methods Using single‐cell RNA‐seq analyses, we investigated the dynamic of cellular heterogeneity transcriptome regulation and microenvironmental factors in 15,591 single cells from paired samples of primary and lymph node‐metastasized tumors. The function of key factor was further investigated using data from public database and in vitro experiments. Results We found that among all the six subclusters identified, the cancer cells (cluster 3) with higher tumor different ability (tumor different score) evolved into metastatic clusters infiltrating into lymph nodes. We also showed that the immune response‐activating cell surface receptor signaling pathway is enriched in malignant cells of the metastatic lymph node. The interactions between T cells and other cells were weakened, and CCLs‐mediated signals out/income T‐cells are more likely to affect the interactions. Tumor‐intrinsic forkhead box A2 (FOXA2) orchestrated the thyroid cancer cell immunologic/metastatic signature and its expression is related to prognosis. FOXA2 knockdown promoted thyroid cancer cell migration, proliferation, and T‐cell apoptosis. Moreover, its expression significantly influenced T‐cell activity by the CCL2/LCN2‐mediated signal pathway. Conclusions These findings reveal that FOXA2 regulates cancer cell immunity by influencing T‐cell apoptosis in thyroid cancer. Our results provide a potential pharmacological strategy for immune therapy in thyroid cancer with lymph node metastasis.