Expression of STING and PD-L1 in colorectal cancer and their correlation with clinical prognosis

PD-L1 might promote the occurrence of disease and STING might play an important role in anti-tumor immunity. PD-L1 was related with the prognosis of patients with colorectal cancer but the expression of STING was not obviously associated with the prognosis. Survival rates of patients with colorectal cancer were higher in patients with PD-L1 negative expression or STING positive expression. When PD-L1 expression was negative and STING expression was positive, the 5-year survival rate of patients with colorectal cancer was highest.

The colorectal tissue chip was taken as the research object. Immunohistochemical methods were used to detect expression of PD-L1 and STING of 87 cases of colorectal cancer tissue and corresponding adjacent tissue in the tissue chip. Chi-square test or Fisher's test were used to analyze the relationship of expression of PD-L1 and STING and with the clinical pathological features. Kaplan-Meier curves were used to analyze the relationship between expression of PD-L1 and STING and the prognosis of colorectal cancer.

To investigate the expression of PD-L1 and STING in colorectal cancer and analyze their correlation with disease prognosis.

The positive expression rate of PD-L1 in 87 cases of colorectal cancer tissue and corresponding adjacent tissue was 79.3% and 42.5% respectively, and the difference was significant (P < 0.05). The positive expression rate of PD-L1 in colorectal carcinoma tissues was not related with age, gender, tumor size, differentiation, TNM clinical stage, or depth of invasion (P > 0.05). The positive expression rate of STING in 87 cases colorectal cancer tissues and corresponding adjacent tissue was 9.2% and 40.2% respectively and the difference was significant (P < 0.05). The positive expression rate of STING in colorectal carcinoma tissue was correlated with gender, age, and differentiation (P < 0.05), but not associated with tumor size, depth of invasion, and TNM clinical stage (P > 0.05). The expression rate of PD-L1 was related to the prognosis of colorectal cancer (P=0.018). The expression rate of STING was not correlated with prognosis of colorectal cancer (P=0.784). In four independent groups (PD-L1+STING+ group, PD-L1-STING- group, PD-L1-STING+ group, PD-L1+STING- group), there were significant differences in 5-year survival (P=0.047 < 0.05), the 5-year survival rate of the PD-L1-STING+ group was significantly higher than that of the other three groups. In the STING positive group, the PD-L1+STING+ group had a worse prognosis than the PD-L1-STING+ group. In the STING negative group, the PD-L1-STING-group had a higher survival rate than the PD-L1+STING- group.