Tumor-educated VEGFR-3 lymphatics augment PD-1 resistance in HPV-negative HNSCC

The human papillomavirus (HPV) status is closely related to the response to immune checkpoint inhibitors (ICIs) in head and neck squamous cell carcinoma (HNSCC), yet the mechanisms of immunotherapy resistance in HPV-negative disease remain unclear. We integrated single-cell transcriptomics datasets to investigate the underlying driving factors of ICI resistance in HPV-negative HNSCC. The ecosystem of HPV-negative tumors exhibited a lymphocyte-deficient pattern. Further analyses revealed that this lymphocyte exclusion was driven by aberrantly infiltrated lymphatic endothelial cells (LECs) in HPV-negative microenvironments. Mechanistically, LECs release the excess homing cytokine CCL21, which strongly attracts immune cells via the CCL21‒CCR7 axis and eventually excludes them from the HPV-negative microenvironment. We discovered that HPV-negative tumor cells presented relatively high VEGFC expression, which accelerated the growth of LECs via the VEGF-C‒VEGFR-3 axis. Furthermore, VEGFR-3 blockade significantly facilitated ICI therapy in in vivo models by restoring the infiltration of lymphocytes, mainly CD8+ T cells. These results delineate a tumor-LEC-immune axis that deserts antitumoral lymphocytes and highlight VEGFR-3 blockade as a highly desirable target in HPV-negative HNSCC and other ICI-refractory subpopulations.