The expression of immune checkpoint proteins PD-L1 and TIM3 in mouse and human head and neck squamous cell carcinoma

The aim of this study was to examine the expression of programmed death-ligand 1 (PD-L1) and of T cell immunoglobulin and mucin domain-containing protein (TIM3) in oral epithelial dysplasia and head and neck squamous cell carcinoma (HNSCC). Mouse HNSCC was induced with 4-nitroquinoline-1 oxide (4NQO). Oral epithelial dysplastic lesions, carcinoma in situ and HNSCC lesions were stained with anti-PD-L1 and TIM3 antibodies. The expression of PD-L1 and TIM3 in tumor cells and immune cells was semiquantitatively measured and compared. In parallel, human dysplasia and HNSCC were stained with anti-PD-L1 and anti-TIM3. The expression pattern of PD-L1⁺ and TIM3⁺ cells was further compared. In human and mouse samples both PD-L1 and TIM3 were found to be expressed in neoplastic and immune cells in HNSCC, but not in dysplasia. There was no significant difference in PD-L1 and TIM3 expression between metastatic and nonmetastatic HNSCC. We conclude that the 4NQO-induced mouse HNSCC model may be an excellent preclinical model for immune checkpoint therapy.