INTRODUCTION
Oral squamous cell carcinoma (OSCC) is a major type of head and neck cancer, accounting for ~2%–4%of all incident cancer cases per year.1 Because of the high rate of metastasis to cervical lymph nodes at early stages, OSCC is regarded as an aggressive type of cancer. Although the treatment of OSCC has evolved from surgical resection to surgery-based comprehensive therapy including radiation and chemotherapy in the past few decades,2 the current average 5-year overall survival (OS) rate is only ~65% in the world.3 In recent years, immune checkpoint blockade therapy, which reinvigorates antitumour CD8+ T cells by blocking programmed cell death protein 1 (PD-1) or programmed cell death ligand 1 (PD-L1), has provided a novel approach for cancer therapy;4 however, the response rate of OSCC is only ~13%.5 Therefore, given the poor prognosis of OSCC, it is imperative to select and identify a marker with good diagnostic and prognostic value. However, until now, no specific markers have met the requirements for OSCC treatment.