Osteoblast‐Derived TGF‐β1 Stimulates IL‐8 Release Through AP‐1 and NF‐κB in Human Cancer Cells |
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| Authors: | Yi‐Chin Fong Ming‐Chei Maa Fuu‐Jen Tsai Wen‐Chi Chen Jaung‐Geng Lin Long‐Bin Jeng Rong‐Sen Yang Wen‐Mei Fu Chih‐Hsin Tang PhD |
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| Affiliation: | 1. Graduate Institute of Chinese Medical Science, China Medical University, Taichung, Taiwan;2. Department of Orthopaedics, China Medical University Hospital, Taichung, Taiwan;3. School of Chinese Medicine, China Medical University, Taichung, Taiwan;4. Institute of Medical Science, China Medical University, Taichung, Taiwan;5. Department of Pediatrics and Medical Genetics, China Medical University Hospital, Taichung, Taiwan;6. Graduate Institute of Integrated Medicine, China Medical University, Taichung, Taiwan;7. Graduate Institute of Acupuncture Science, China Medical University, Taichung, Taiwan;8. Department of Surgery, China Medical University Hospital, Taichung, Taiwan;9. Department of Orthopaedics, College of Medicine, National Taiwan University, Taipei, Taiwan;10. Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan;11. Department of Pharmacology, China Medical University, Taichung, Taiwan |
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| Abstract: | Introduction: The bone marrow microenvironment is further enriched by growth factors released during osteoclastic bone resorption. It has been reported that the chemokine interleukin (IL)‐8 is a potent and direct activator of osteoclastic differentiation and bone resorption. However, the effect of bone‐derived growth factors on the IL‐8 production in human cancer cells and the promotion of osteoclastogenesis are largely unknown. The aim of this study was to investigate whether osteoblast‐derived TGF‐β1 is associated with osteolytic bone diseases. Materials and Methods: IL‐8 mRNA levels were measured using RT‐PCR analysis. MAPK phosphorylation was examined using the Western blot method. siRNA was used to inhibit the expression of TGF‐β1, BMP‐2, and IGF‐1. DNA affinity protein‐binding assay and chromatin immunoprecipitation assays were used to study in vitro and in vivo binding of c‐fos, c‐jun, p65, and p50 to the IL‐8 promoter. A transient transfection protocol was used to examine IL‐8, NF‐κB, and activator protein (AP)‐1 activity. Results: Osteoblast conditioned medium (OBCM) induced activation of IL‐8, AP‐1, and NF‐κB promoter in human cancer cells. Osteoblasts were transfected with TGF‐β1, BMP‐2, or IGF‐1 small interfering RNA, and the medium was collected after 48 h. TGF‐β1 but not BMP‐2 or IGF‐1 siRNA inhibited OBCM‐induced IL‐8 release in human cancer cells. In addition, TGF‐β1 also directly induced IL‐8 release in human cancer cells. Activation of AP‐1 and NF‐κB DNA‐protein binding and MAPKs after TGF‐β1 treatment was shown, and TGF‐β1–induced IL‐8 promoter activity was inhibited by the specific inhibitors of MAPK cascades. Conclusions: In this study, we provide evidence to show that the osteoblasts release growth factors, including TGF‐β1, BMP‐2, and IGF‐1. TGF‐β1 is the major contributor to the activation of extracellular signal‐related kinase (ERK), p38, and c‐Jun N‐terminal kinase (JNK), leading to the activation of AP‐1 and NF‐κB on the IL‐8 promoter and initiation of IL‐8 mRNA and protein release, thereby promoting osteoclastogenesis. |
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| Keywords: | osteoblasts interleukin‐8 TGF‐β 1 NF‐κ B activator protein 1 |
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