Chemoradiotherapy, Cyclophosphamide, Head and neck cancer, Head and neck squamous cell carcinoma, Human papillomavirus (HPV), Immunotherapy, Inducible nitric oxide synthase (iNOS), L-n6-(1-iminoethyl)-lysine (L-NIL), Radiotherapy, Tumor microenvironment, Animals, Antineoplastic Agents, CD8-Positive T-Lymphocytes, Cell Line, Tumor, Chemoradiotherapy, Cyclophosphamide, Head and Neck Neoplasms, Humans, Immunomodulation, Lymphocytes, Tumor-Infiltrating, Lysine, Male, Mice, Inbred C57BL, Neoplasms, Papillomavirus Infections, Squamous Cell Carcinoma of Head and Neck, Tumor Microenvironment