Tristetraprolin regulates interleukin‐6, which is correlated with tumor progression in patients with head and neck squamous cell carcinoma

Abstract

BACKGROUND: Tumor‐derived cytokines play a significant role in the progression of head and neck squamous cell carcinoma (HNSCC). Targeting proteins, such as tristetraprolin (TTP), that regulate multiple inflammatory cytokines may inhibit the progression of HNSCC. However, TTP's role in cancer is poorly understood. The goal of the current study was to determine whether TTP regulates inflammatory cytokines in patients with HNSCC. METHODS: TTP messenger RNA (mRNA) and protein expression were determined by quantitative real‐time–polymerase chain reaction (Q‐RT‐PCR) and Western blot analysis, respectively. mRNA stability and cytokine secretion were evaluated by quantitative RT‐PCR and enzyme‐linked immunoadsorbent assay, respectively, after overexpression or knockdown of TTP in HNSCC. HNSCC tissue microarrays were immunostained for interleukin‐6 (IL‐6) and TTP. RESULTS: TTP expression in HNSCC cell lines was found to be inversely correlated with the secretion of IL‐6, vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE 2 ) . Knockdown of TTP increased mRNA stability and the secretion of cytokines. Conversely, overexpression of TTP in HNSCC cells led to decreased secretion of IL‐6, VEGF, and PGE 2 . Immunohistochemical staining of tissue microarrays for IL‐6 demonstrated that staining intensity is prognostic for poor disease‐specific survival ( P = .023), tumor recurrence and development of second primary tumors ( P = .014), and poor overall survival ( P = .019). CONCLUSIONS: The results of the current study demonstrated that down‐regulation of TTP in HNSCC enhances mRNA stability and promotes secretion of IL‐6, VEGF, and PGE 2 . Furthermore, high IL‐6 secretion in HNSCC tissue is a biomarker for poor prognosis. In as much as enhanced cytokine secretion is associated with poor prognosis, TTP may be a therapeutic target to reduce multiple cytokines concurrently in patients with HNSCC. Cancer 2011. © 2011 American Cancer Society. Tristetraprolin (TTP), a protein that decreases the stability of messenger RNA (mRNA) of cytokines and proinflammatory factors, is reduced in patients with head and neck squamous cell carcinoma with a corresponding increase in interleukin‐6 (IL‐6), vascular endothelial growth factor, and cyclooxygenase‐2 secretion. One of these tumor‐derived cytokines, IL‐6, is prognostic for poor disease‐specific survival, tumor recurrence, second primary lesions, and poor overall survival.