Prognostic significance of interleukin-17 in solid tumors: a meta-analysis

Background: The prognostic significance of intratumoral and peripheral interleukin-17 (IL-17) in tumors has been studied worldwide during these years, providing un-uniformed conclusions. Methods: We conducted a meta-analysis of published literatures that evaluated the correlation between IL-17 and clinical staging, overall survival (OS) and/or disease free survival (DFS). Results: A total of 28 studies enrolling 2902 patients were included. For the overall population, a high expression of IL-17 was found significantly correlated with worse DFS (HR = 1.59, 95% CI: 1.24-2.03) in patients with solid tumors. For gastrointestinal tumors, patients with IL-17 high seemed to have worse OS (HR = 1.85, 95% CI: 1.24-2.75) and DFS (HR = 2.41, 95% CI: 1.98-2.92). Sub-group meta-analysis revealed that IL-17 indicated late clinical staging in non-small cell lung cancer (NSCLC) patients (HR = 2.33, 95% CI: 1.25-4.32), on the other hand, early clinical staging in patients with esophageal squamous carcinoma (HR = 0.63, 95% CI: 0.42-0.94). Negative impacts of IL-17 on OS were shown in patients with hepatocellular carcinoma (HCC) (HR = 1.87, 95% CI: 1.23-2.84) or NSCLC (HR = 1.55, 95% CI: 1.02-2.35). However, positive impacts on OS were provided in patients with esophageal squamous carcinoma (HR = 0.65, 95% CI: 0.50-0.84). Besides, a high expression of IL-17 predicted better DFS in ovarian cancer patients (HR = 0.33, 95% CI: 0.11-1.00). Conclusions: Our meta-analysis revealed that IL-17 might correlate with poor OS and DFS in gastrointestinal tumors. Specifically, IL-17 was a detrimental factor for HCC and NSCLC patients, whereas a beneficial factor for patients with esophageal squamous carcinoma and ovarian cancer.