CXCL16 Producing Tumor Clones Are Shaping Immunosuppressive Microenvironment in Squamous Cell Carcinoma via CXCR6...

Cutaneous squamous cell carcinoma (cSCC) and basal cell carcinoma (BCC) are the most prevalent types of nonmelanoma skin cancer (NMSC) and exhibit significant inter- and intra-tumor heterogeneity. cSCC has a higher metastatic potential than BCC, accompanied by a considerable mortality rate. However, the detailed mechanisms of tumor evolution in cSCC have not yet been described.

We performed single-cell RNA sequencing (scRNA-seq) and T cell receptor (TCR) clonal analysis of skin biopsies from five BCCs, three squamous cell carcinomas in situ (SCCIS), and two invasive squamous cell carcinomas (SCC). Independent SCC specimens were used for spatial transcriptomic (ST) analysis using GeoMx Digital Spatial Profiler (DSP).

Using scRNA-seq, we analyzed a total of 117,663 cells. We distinguished cancer cells using copy number variation and identified SCC-specific genes that potentially contribute to tumor progression. Analysis of tumor clones revealed SCC-specific COL6A1+/ITGA5+ carcinoma cells which produce CXCL16. We also annotated CXCR6+ regulatory T cells (Tregs) which potentially move toward the tumor site by CXCL16, shaping the immunosuppressive TME. ST analysis supported these clones were located at the invasion site of SCC.

We suggest COL6A1 and ITGA5 promote the invasive and metastatic property of SCC. We also uncovered how SCC recruits Tregs via the CXCL16/CXCR6 axis to create a TME favorable for its survival. These molecules can be used as potential therapeutic targets for treatment of SCC.