Human Papillomavirus (HPV) Infected Epithelial Cells and FBLN1 ⁺ Fibroreticular Cells Govern the Immunogenic Tumor Microenvironment in HPV-Associated Oropharyngeal Squamous Cell Carcinoma

Objective.: Oropharyngeal squamous cell carcinoma (OPSCC) demonstrates distinct clinical behaviors depending on human papillomavirus (HPV) status. HPV-associated OPSCC typically shows a better prognosis and response to therapy compared to non-HPV-associated OPSCC; however, the underlying tumor microenvironment (TME) differences remain unclear. Methods.: To investigate cellular and molecular factors linked to improved outcomes in HPVassociated OPSCC, we performed single-cell RNA sequencing and high-resolution spatial transcriptomics on samples from 2 non-HPV-associated OPSCCs, 5 HPVassociated OPSCCs, and 3 normal tonsils, focusing on fibroreticular cells (FRCs). Results.: We identified four distinct FRC subsets, with FBLN1+ FRCs significantly enriched in HPV-associated OPSCC. These FRCs expressed SLIT2, a molecule involved in immune cell recruitment. Spatial mapping revealed that FBLN1+ FRCs were closely associated with both tumor and immune cells, suggesting a role in promoting a more immunogenic TME. Moreover, HPV-associated OPSCC exhibited higher levels of proliferating epithelial cells and antigen-presentation gene expression compared to non-HPV-associated tumors. Conclusion.: Our findings highlight the role of FBLN1+ FRCs in fostering immune activation within the TME of HPV-associated OPSCC. Enhanced antigen presentation and epithelial proliferation likely facilitate tumor-immune interactions, contributing to better clinical outcomes. This study advances the understanding of TME dynamics in OPSCC and may inform future therapeutic strategies.