Articular adipose tissue is a ubiquitous component of human joints, and adiponectin is a protein hormone secreted predominantly by differentiated adipocytes and involved in energy homeostasis. We investigated the signaling pathway involved in IL-6 production caused by adiponectin in both rheumatoid arthritis synovial fibroblasts and osteoarthritis synovial fibroblasts. Rheumatoid arthritis synovial fibroblasts and osteoarthritis synovial fibroblasts expressed the AdipoR1 and AdipoR2 isoforms of the adiponectin receptor. Adiponectin caused concentration- and time-dependent increases in IL-6 production. Adiponectin-mediated IL-6 production was attenuated by AdipoR1 and 5′-AMP-activated protein kinase (AMPK)α1 small interference RNA. Pretreatment with AMPK inhibitor (araA and compound C), p38 inhibitor (SB203580), NF-κB inhibitor, IκB protease inhibitor, and NF-κB inhibitor peptide also inhibited the potentiating action of adiponectin. Adiponectin increased the kinase activity and phosphorylation of AMPK and p38. Stimulation of synovial fibroblasts with adiponectin activated IκB kinase α/β (IKK α/β), IκBα phosphorylation, IκBα degradation, p65 phosphorylation at Ser (276), p65 and p50 translocation from the cytosol to the nucleus, and κB-luciferase activity. Adiponectin-mediated an increase of IKK α/β activity, κB-luciferase activity, and p65 and p50 binding to the NF-κB element and was inhibited by compound C, SB203580 and AdipoR1 small interference RNA. Our results suggest that adiponectin increased IL-6 production in synovial fibroblasts via the AdipoR1 receptor/AMPK/p38/IKKαβ and NF-κB signaling pathway.

Lung caner cells have a striking tendency to metastasize to bone. The chemokine stromal cell-derived factor-1 (SDF-1) is constitutively secreted by osteoblasts and bone marrow stromal cells and plays a key role for homing of hematopoietic cells to the bone marrow. Reverse transcriptase-polymerase chain reaction and flow cytometry studies demonstrated SDF-1 receptor (CXCR4) messenger RNA (mRNA) and surface expression of CXCR4 in lung cancer cell lines, especially higher in those with high invasiveness (A549) as compared with lower level in H928 cells and H1299 cells. SDF-1, osteoblast-conditioned medium (OBCM) and stromal cell-conditioned medium all induced the invasiveness of lung cancer cells. Matrix metalloproteinase (MMP)-9 small interfering RNA inhibited the SDF-1alpha- or OBCM-induced MMP-9 expression and thereby significantly inhibited the SDF-1alpha- or OBCM-induced cell invasion. Furthermore, mitogen-activated protein kinase kinase inhibitor PD98059 suppressed SDF-1alpha-induced MMP-9 mRNA expression. Transient transfection with dominant-negative extracellular signal-regulated kinase (ERK) mutant also showed that the ERK-signaling pathway was involved in SDF-1alpha-induced MMP-9 expression. Moreover, nuclear factor-kappaB (NF-kappaB) decoy oligodeoxynucleotide suppressed the MMP-9 promoter activity enhanced by SDF-1alpha. Both mitogen-activated protein kinase kinase inhibitor and ERK mutant also antagonized SDF-1alpha-induced NF-kappaB-driven luciferase promoter activity. Taken together, our results indicated that bone marrow-derived-SDF-1alpha enhances the invasiveness of lung cancer cells by increasing MMP-9 expression through the CXCR4/ERK/NF-kappaB signal transduction pathway.

CCL5 (previously called RANTES) is in the CC-chemokine family and plays a crucial role in the migration and metastasis of human cancer cells. On the other hand, the effect of CCL5 is mediated via CCR receptor. RT-PCR and flow cytometry studies demonstrated CCR5 but not CCR1 and CCR3 mRNA in oral cancer cell lines, especially higher in those with high invasiveness (SCC4) as compared with lower levels in HSC3 cells and SCC9 cells. Stimulation of oral cancer cells with CCL5 directly increased the migration and metalloproteinase-9 (MMP-9) production. MMP-9 small interfering RNA inhibited the CCL5-induced MMP-9 expression and thereby significantly inhibited the CCL5-induced cell migration. Activations of phospholipase C (PLC), protein kinase Cdelta (PKCdelta), and NF-kappaB pathways after CCL5 treatment was demonstrated, and CCL5-induced expression of MMP-9 and migration activity was inhibited by the specific inhibitor of PLC, PKCdelta, and NF-kappaB cascades. In addition, migration-prone sublines demonstrate that cells with increasing migration ability had more expression of MMP-9, CCL5, and CCR5. Taken together, these results indicate that CCL5/CCR5 axis enhanced migration of oral cancer cells through the increase of MMP-9 production.

Tumor malignancy is associated with several features such as proliferation ability and frequency of metastasis. Connective tissue growth factor (CTGF), a secreted protein that binds to integrins, modulates the invasive behavior of certain human cancer cells. However, the effect of CTGF on migration activity in human chondrosarcoma cells is mostly unknown. Here we found that CTGF increased the migration and expression of matrix metalloproteinase (MMP)-13 in human chondrosarcoma cells (JJ012 cells). RGD peptide, alphavbeta3 monoclonal antibody (mAb) and MAPK kinase (MEK) inhibitors (PD98059 and U0126) but not RAD peptide inhibited the CTGF-induced increase of the migration and MMP-13 up-regulation of chondrosarcoma cells. CTGF stimulation increased the phosphorylation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). In addition, treatment of JJ012 cells with NF-kappaB inhibitor (PDTC) or IkappaB protease inhibitor (TPCK) inhibited CTGF-induced cell migration and MMP-13 up-regulation. Stimulation of JJ012 cells with CTGF also induced IkappaB kinase alpha/beta (IKK alpha/beta) phosphorylation, IkappaBalpha phosphorylation, p65 Ser(536) phosphorylation, and kappaB-luciferase activity. The CTGF-mediated increases in kappaB-luciferase activities were inhibited by RGD, PD98059, U0126 or FAK, and ERK2 mutant. Taken together, our results indicated that CTGF enhances the migration of chondrosarcoma cells by increasing MMP-13 expression through the alphavbeta3 integrin, FAK, ERK, and NF-kappaB signal transduction pathway.

Prostate cancer is the most commonly diagnosed malignancy in men and shows a predilection for metastasis to the bone. D-pinitol, a 3-methoxy analogue of d-chiro-inositol, was identified as an active principle in soy foods and legumes, and it has been proven to induce tumor apoptosis and metastasis of cancer cells. In this study, we investigated the anti-metastasis effects of D-pinitol in human prostate cancer cells. We found that D-pinitol reduced the migration and the invasion of prostate cancer cells (PC3 and DU145) at noncytotoxic concentrations. Integrins are the major adhesive molecules in mammalian cells and have been associated with the metastasis of cancer cells. Treatment of prostate cancer cells with D-pinitol reduced mRNA and cell surface expression of αvβ3 integrin. In addition, D-pinitol exerted its inhibitory effects by reducing focal adhesion kinase (FAK) phosphorylation, c-Src kinase activity and NF-κB activation. Thus, D-pinitol may be a novel anti-metastasis agent for the treatment of prostate cancer metastasis.