Exploration of the expression and significance of IL-6, STAT3 and PD-L1 in esophageal squamous cell carcinoma.

e16554 Background: Esophageal squamous cell carcinoma (ESCC) is one of the most common malignancies worldwide and has a very high morbidity and mortality rate. The IL-6/STAT3 axis can simultaneously promote the expansion of immunosuppressive cells.This study detected IL-6, STAT3 and PD-L1 in ESCC and analyzed the potential clinical application value. Methods: Between July 2018 and April 2019, 70 ESCC patients underwent radical thoracic surgery at Affiliated Hospital of North Sichuan Medical College. RT-PCR was used to detect PD-L1, IL-6, and STAT3 mRNA expression in cancer and adjacent normal tissues. Western blot detection of PD-L1, IL-6, and STAT3 was performed in 40 cancer and adjacent normal tissues. The correlation of PD-L1, IL-6 and STAT3 protein expression with tumor invasion depth, tumor size, lymph node metastasis,clinical stage and other clinicopathological characteristics as well as the correlation between the three proteins were analyzed statistically. Results: The mRNA levels of PD-L1, IL-6, and STAT3 in 70 ESCC patients were significantly different between cancerous and adjacent normal tissues (P < 0.001). In 40 ESCC patients, 28 ESCC tissues showed significantly higher PD-L1 expression than adjacent normal tissue (28/12, P < 0.001), 29 ESCC tissues showed significantly higher STAT3 expression (29/11,P = 0.009 ), and 27 ESCC tissues showed significantly higher IL-6 expression (27/13,P = 0.042). There was no correlation between PD-L1 expression and age, sex, tumor site or maximum tumor diameter, but PD-L1 expression showed a positive correlation with T stage (P = 0.009), lymph node metastasis (P = 0.044), and clinical stage (P = 0.033). There was no correlation between STAT3 expression and age, sex, tumor site, maximum tumor diameter, lymph node metastasis or clinical stage, but STAT3 expression showed a positive correlation with T stage (P = 0.025). IL-6 expression was not correlated with age, sex, maximum tumor diameter, lymph node metastasis or clinical stage, but IL-6 expression showed a positive correlation with T stage ( P = 0.003)and tumor site (P = 0.011). In addition, PD-L1 expression showed a positive correlation with STAT3 (P = 0.013) and IL-6 ( P = 0.008), and STAT3 showed a positive correlation with IL-6 ( P = 0.027). Conclusions: PD-L1, IL-6, and STAT3 are highly expressed in ESCC and their protein levels exhibit a positive correlation. The IL-6/STAT3 signaling pathway proteins may be a potential biomarker predicting the efficacy of immunotherapy by affecting the expression of PD-L1.