Abstract: Objective To investigate the expression of IDO1 in different stages of lung squamous cell carcinoma and its relationship with prognosis. Methods Patients with lung squamous cell carcinoma who underwent radical surgery in the Department of thoracic surgery of Xingtai People’s Hospital Affiliated to Hebei Medical University from January 2017 to January 2019 were included. Intraoperative cancer tissue samples were taken. The expression level of IDO1 was detected by immunohistochemical staining, and the patients were followed up after operation. Results IDO1 protein was expressed in lung squamous cell carcinoma, and the number of positive cells in clinical stages Ⅱ ~ Ⅲ was significantly higher than that in stage I. By the end of the follow-up, 28 of the 30 patients had survived, 2 died, 22 had stable disease (73. 3 % ), and 8 had disease progression (26. 7 % ). The progression free survival (PFS) ofido1high expression group andido1low expression group were 26 months and 40 months respectively (P < 0. 05). The PFS of higher clinical stage and lower clinical stage were 33 months and 40 months respectively (P < 0. 05). Conclusion The expression level of IDO1 in lung squamous cell carcinoma was related to the clinical stage. The higher the clinical stage, the higher the expression level, and the worse the prognosis of patients. IDO1 expression level can be used to guide the clinical staging and prognosis in lung squamous cell carcinoma. 

Key words: lung squamous cell carcinoma, indoleamine-2, 3-dioxygenase 1, clinical stage, PFS