Enhanced oral versus flank lymph node T cell response parallels anti-PD1 efficacy in head and neck cancer

Objectives Understanding head and neck tissue specific immune responses is important for elucidating immunotherapy resistance mechanisms to head and neck squamous cell carcinoma (HNSCC). In this study, we aimed to investigate HNSCC-specific immune response differences between oral and subcutaneous flank tumor transplantation in preclinical models. Materials and methods The MOC1 syngeneic mouse oral carcinoma cell line or versions expressing either the H2Kb-restricted SIINFEKL peptide from ovalbumin (MOC1OVA) or ZsGreen (MOC1ZsGreen) were inoculated into mouse oral mucosa (buccal space) or subcutaneous flank and compared for immune cell kinetics in tumors and tumor-draining lymph nodes (TDLNs) and for anti-PD1 response. Results Compared to subcutaneous flank tumors, orthotopic oral MOC1OVA induced a higher number of OVA-specific T cells, PD1 + or CD69 + activated OVA-specific T cells in both primary tumors and TDLNs. Tumors were also larger in the flank site and CD8 depletion eliminated the difference in tumor weight between the two sites. Oral versus flank SIINFEKL peptide vaccination showed enhanced TDLN lymphocyte response in the former site. Notably, cDC1 from oral TDLN showed enhanced antigen uptake and co-stimulatory marker expression, resulting in elicitation of an increased antigen specific T cell response and increased activated T cells. Parental MOC1 in the oral site showed increased endogenous antigen-reactive T cells in TDLNs and anti-PD1 blockade rejected oral MOC1 tumors but not subcutaneous flank MOC1. Conclusion Collectively, we find distinct immune responses between orthotopic oral and heterotopic subcutaneous models, including priming by cDC1 in TDLN, revealing important implications for head and neck cancer preclinical studies.