Objective  To analyze the expression and clinical significance of stimulator of interferon genes (STING), C-C motif chemokine ligand 5 (CCL5), interferon regulatory factor 3 (IRF3) and programmed death ligand-1 (PDL1) in squamous cell lung cancer.

Methods  A total of 56 patients with squamous cell lung cancer were enrolled. Resected tumor tissues and adjacent non-tumor tissues (located more than 5 cm from the tumor margin) were collected. Immunohistochemical staining was performed to detect the expression of STING, CCL5, IRF3 and PDL1. The correlations of STING, CCL5, IRF3 and PDL1 with clinical data were analyzed. The relationship between the expression of STING, CCL5, IRF3 and PDL1 in lung squamous cell carcinoma tissues and prognosis was also evaluated. The prognostic factors of patients with lung squamous cell carcinoma were analyzed.

Results  The positive rate of STING expression in lung squamous cell carcinoma tissues was significantly lower than that in adjacent non-tumor tissues, whereas the positive rates of CCL5, IRF3 and PDL1 were significantly higher (P < 0.05). The expression levels of STING, CCL5, IRF3 and PDL1 were associated with tumor diameter, TNM stage, lymph node metastasis and differentiation degree (P < 0.05). The 3-year survival rate of STING positive expression patients was significantly higher than that of STING negative expression patients (P < 0.05). The 3-year survival rate of CCL5 positive, IRF3 positive and PDL1 positive expression patients was significantly lower than that of CCL5 negative, IRF3 negative and PDL1 negative expression patients (P < 0.05). STING, CCL5, IRF3 and PDL1 were identified as prognostic factors for patients with squamous cell lung cancer (P < 0.05).

Conclusion  In squamous cell lung cancer tissues, STING is expressed at low levels, while CCL5, IRF3 and PDL1 are expressed at high levels. These findings have significant clinical value in assessing the prognosis of patients with squamous cell lung cancer.