Dong Y, Wang Z, Mao F, et al. - Given oral squamous cell carcinoma (OSCC) represents one of the most common cancers in the head and neck with a poor prognosis, and there is lack of evidence for T cell exhaustion during oral carcinogenesis, researchers obtained clinical specimens from healthy donors as well as patients with oral leukoplakia (OLK) or OSCC, for immunohistochemical staining with PD-L1, CD86, CD8, PD-1 and CTLA-4 antibodies. They assessed efficacy of PD-1 blockade with or without cisplatin treatment on the mice in precancerous as well as OSCC stages. The human OLK and OSCC tissues exhibited higher expression of PD-1 vs the normal, while low expression CTLA-4 was observed in all oral mucosa tissues. Per findings, a crucial role of T cell exhaustion in oral carcinogenesis was evident, and the progression of oral carcinogenesis can be prevented by PD-1 blockade.