ABSTRACT
Interleukin (IL)-15 is a proinflammatory cytokine, as it induces the production of inflammatory cytokines [IL-6, tumor necrosis factor alpha (TNFalpha), IL-17, etc.]. A correlation between high intratumoral IL-15 concentrations and poor clinical outcome in lung and head and neck cancer patients has been recently reported. The purpose of this study was to investigate the role of the soluble alpha chain of IL-15 receptor (sIL-15Ralpha), a natural regulator of IL-15, in head and neck cancer. Fifty-three newly diagnosed untreated head and neck cancer patients were included in this study. Quantification of sIL-15Ralpha was performed with a newly developed RIA. Increased serum sIL-15Ralpha concentrations were found in head and neck cancer patients and were closely correlated with poor clinical outcome both in terms of locoregional control and survival even on multivariate analysis. sIL-15Ralpha was mainly produced by tumor cells via proteolytic cleavage of IL-15Ralpha mediated by ADAM-17. A correlation was observed between ADAM-17 expression in tumor cells and serum sIL-15Ralpha concentrations. Surprisingly, sIL-15Ralpha did not act in vitro as an IL-15 antagonist but rather as an enhancer of IL-15-induced proinflammatory cytokines (IL-6, TNFalpha, and IL-17) that may promote tumor progression. This new tumor evasion mechanism based on amplification of the intratumoral inflammatory reaction is probably not restricted to head and neck cancer, as other tumors have been shown to release sIL-15Ralpha. Overall, these results support for the first time an original protumor role of sIL-15Ralpha in cancer.
Subject(s)
Gene Expression Regulation, Neoplastic , Head and Neck Neoplasms/pathology , Interleukin-15 Receptor alpha Subunit/physiology , ADAM Proteins/biosynthesis , ADAM17 Protein , Cross-Linking Reagents/pharmacology , Disease Progression , Humans , Inflammation , Interleukin-15/metabolism , Interleukin-15 Receptor alpha Subunit/blood , Interleukin-15 Receptor alpha Subunit/chemistry , Models, Biological , Multivariate Analysis , Prognosis , Protein Isoforms , RadioimmunoassayABSTRACT
PURPOSE: CD4(+) T cells play a central role in initiating and maintaining anticancer immune responses. However, regulatory CD4(+)CD25(+) T cells which express Foxp3 have also been shown to inhibit antitumor effector T cells. In view of these heterogeneous CD4(+) T-cell populations, this study was designed to determine the prognostic value of various tumor-infiltrating CD4(+) T-cell populations in head and neck squamous cell carcinoma. EXPERIMENTAL DESIGN: Eighty-four newly diagnosed untreated patients with histologically proven primary head and neck squamous cell carcinoma were included in this study. Double or triple immunofluorescence staining was done to assess and quantify the activated CD4(+)CD69(+) T cells, regulatory CD4(+)Foxp3(+) T cells, and mixed CD4(+)CD25(+) T cells comprising both activated and regulatory T cells. RESULTS: On univariate analysis, high levels of tumor-infiltrating CD4(+)CD69(+) T cells were correlated with both better locoregional control (P = 0.01) and longer survival (P = 0.01). Infiltration by regulatory Foxp3(+)CD4(+) T cells was positively associated with a better locoregional control of the tumor. Multivariate analysis showed that the only significant prognostic factors related to locoregional control were T stage (P = 0.02) and CD4(+)Foxp3(+) T-cell infiltration of the tumor (P = 0.02). In the Cox multivariate analysis, only two variables influenced overall survival probability: T stage (P = 0.036) and CD4(+)CD69(+) T-cell infiltration (P = 0.017). CONCLUSION: This study shows that tumor-infiltrating activated CD4(+)CD69(+) T cells are associated with a good prognosis in head and neck squamous cell carcinoma. In addition, regulatory Foxp3(+)CD4(+) T cells are positively correlated with locoregional control may be through down-regulation of harmful inflammatory reaction, which could favor tumor progression.
