ABSTRACT
PURPOSE: Toll-like receptor 4 (TLR4) was found to be aberrantly expressed in bladder cancer, inducing some genes expression and facilitating tumor progression. Recent data suggest that tumor associated Interleukin-6 (IL-6) correlates with tumor size and grade in bladder cancer. However, the molecule mechanisms of the induction of IL-6 response in bladder cancer cells are not well elucidated. In this study, we manage to find out whether TLR4 signaling is involved in the production of IL-6 by human bladder cancer cells, and the detailed molecule mechanisms by which IL-6 is up-regulated. METHODS: We selected human bladder cancer T24 cell line in the present study, and examined its expression of TLR4 and CD14 by using flow cytometry. TLR4 signaling was activated by lipopolysaccharide (LPS) and IL-6 secretion in culture supernatants was tested by using ELISA kit. The expression of p38, ERK, JNK and Akt were determined by western-blot analysis using specific antibodies. RESULTS: Our study demonstrated that CD14 and TLR4 were constitutively expressed in T24 cells and activation of TLR4 signaling by LPS resulted in phosphorylation of MAPK and PI3K pathways and up-regulation of IL-6 in dose- and time-dependent manner. Pretreatment of cells with SB203580 (inhibitor of p38) and PD98059 (inhibitor of ERK) attenuated LPS-induced IL-6 expression, whereas LY294002 (inhibitor of PI3K) markedly amplified the LPS-stimulated synthesis of IL-6. CONCLUSIONS: Our results demonstrate that activation of TLR4 signaling in bladder cancer cells induces tumor-associated IL-6 expression via activation of p38 and ERK, whereas activation of PI3K/Akt exerts an opposing action.
Subject(s)
Extracellular Signal-Regulated MAP Kinases/metabolism , Interleukin-6/genetics , Phosphatidylinositol 3-Kinases/metabolism , Toll-Like Receptor 4/genetics , Urinary Bladder Neoplasms/genetics , p38 Mitogen-Activated Protein Kinases/metabolism , Cell Line, Tumor , Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors , Gene Expression Regulation, Neoplastic/drug effects , Gene Expression Regulation, Neoplastic/immunology , Humans , Lipopolysaccharide Receptors/genetics , Lipopolysaccharides/pharmacology , Toll-Like Receptor 4/metabolism , Urinary Bladder Neoplasms/enzymology , Urinary Bladder Neoplasms/immunology , p38 Mitogen-Activated Protein Kinases/antagonists & inhibitorsABSTRACT
TLR4 (Toll-like receptor 4) and B7-H1, which were known to be restricted to immune cells in the past, were found to be aberrantly expressed in a majority of tumor cells, facilitating tumor evasion from immune surveillance. Our study demonstrated that activation of TLR4 signaling in bladder cancer cells up-regulated B7-H1 expression. Furthermore, this regulation was significantly attenuated by ERK or JNK inhibitor. Our results elucidated the molecule mechanism of regulation of B7-H1 expression through TLR4 signaling and may suggest new strategies of down-regulating the cancer-associated B7-H1 expression for bladder cancer treatment.
