Identifying tumor antigen-specific T cells from cancer patients has important implications for immunotherapy diagnostics and therapeutics.,Here, we show that CD103+CD39+ tumor-infiltrating CD8 T cells (CD8 TIL) are enriched for tumor-reactive cells both in primary and metastatic tumors.,This CD8 TIL subset is found across six different malignancies and displays an exhausted tissue-resident memory phenotype.,CD103+CD39+ CD8 TILs have a distinct T-cell receptor (TCR) repertoire, with T-cell clones expanded in the tumor but present at low frequencies in the periphery.,CD103+CD39+ CD8 TILs also efficiently kill autologous tumor cells in a MHC-class I-dependent manner.,Finally, higher frequencies of CD103+CD39+ CD8 TILs in patients with head and neck cancer are associated with better overall survival.,Our data thus describe an approach for detecting tumor-reactive CD8 TILs that will help define mechanisms of existing immunotherapy treatments, and may lead to future adoptive T-cell cancer therapies.,Identifying and enumerating tumor-specific CD8 T cells are important for assessing cancer prognosis and therapy efficacy.,Here the authors show that CD39 and CD103 mark a subset of tumor-infiltrating CD8 T cells that are tumor-reactive and exhibit characteristics of exhausted or tissue-resident memory T cells.
Melanoma is the most fatal skin cancer, but the etiology of this devastating disease is still poorly understood.,Recently, the transcription factor Sox10 has been shown to promote both melanoma initiation and progression.,Reducing SOX10 expression levels in human melanoma cells and in a genetic melanoma mouse model, efficiently abolishes tumorigenesis by inducing cell cycle exit and apoptosis.,Here, we show that this anti-tumorigenic effect functionally involves SOX9, a factor related to SOX10 and upregulated in melanoma cells upon loss of SOX10.,Unlike SOX10, SOX9 is not required for normal melanocyte stem cell function, the formation of hyperplastic lesions, and melanoma initiation.,To the contrary, SOX9 overexpression results in cell cycle arrest, apoptosis, and a gene expression profile shared by melanoma cells with reduced SOX10 expression.,Moreover, SOX9 binds to the SOX10 promoter and induces downregulation of SOX10 expression, revealing a feedback loop reinforcing the SOX10 low/SOX9 high ant,m/ii-tumorigenic program.,Finally, SOX9 is required in vitro and in vivo for the anti-tumorigenic effect achieved by reducing SOX10 expression.,Thus, SOX10 and SOX9 are functionally antagonistic regulators of melanoma development.