Human T cells interacting with HNSCC-derived mesenchymal stromal cells acquire tissue-resident memory like properties.

Tissue-resident memory (Trm) cells are specialized components of both CD4+ and CD8+ T cell subsets that persist in peripheral nonlymphoid tissues following infections and provide fast response in case of a secondary invasion by the same pathogen. Trm cells express the surface markers CD69, CD103, and the immune checkpoint molecule PD-1. Trm cells develop not only in the context of infections but also in tumors, where they can provide a line of defense as suggested by the positive correlation between the frequency of tumor-infiltrating Trm cells and patients' survival. Trm cells persistence in peripheral tissues depends on their adaptation to the local microenvironment and the presence of survival factors, mainly IL-7, IL-15, and Notch ligands. However, the cell sources of these factors are largely unknown, especially in the context of tumors. Here, we show that head-neck squamous cell carcinoma (HNSCC) is enriched in CD4+ and CD8+ T cells with a Trm phenotype. Moreover, we show that mesenchymal stromal cells that accumulate in HNSCC are a source of survival factors and allow proper expression of Trm-typical markers in a VCAM1-dependent manner.