Expression and clinical significance of interleukin-9 in renal tumors

Background To measure expression levels of interleukin-9 (IL-9) in renal tumors and to determine the clinical significance of those levels. Methods Using TCGA database analysis, we found that the expression of IL-9 in renal clear cell carcinoma was significantly down-regulated, and was significantly related to survival. We then verified this using experiments. We enrolled 66 patients who underwent surgical resection of renal tumors between January and December 2018 at the First Affiliated Hospital of Soochow University. Their tumor tissues were paired with adjacent normal tissues and IL-9 expression levels were measured using immunohistochemistry. We determined the correlation of IL-9 expression with clinicopathological features and progression-free survival (PFS). Results Expression of IL-9 in renal tumors was significantly lower than in adjacent normal tissues (P<0.0001). There was a significant negative correlation between IL-9 expression levels and R.E.N.A.L. scores (P=0.0277) as well as with differentiation (P=0.0041). However, no significant correlation was found between IL-9 levels and clinicopathological features, including gender (P=0.0716), age (P=0.2566), body mass index (BMI) (P=0.7941), tumor size (P=0.4193) or TNM staging (P=0.5402). PFS time in renal tumor patients with positive IL-9 expression was similar to that of patients with negative IL-9 expression. Conclusions IL-9 expression was higher in adjacent normal tissues than in renal tumors. Low expression of IL-9 was detected when R.E.N.A.L. score was high or cell differentiation was poor, suggesting that IL-9 may may play a protective role in renal tumor microenvironments.