Osteoclasts are multinucleated cells formed mainly on bone surfaces in response to cytokines by fusion of bone marrow-derived myeloid lineage precursors that circulate in the blood. Major advances in understanding of the molecular mechanisms regulating osteoclast formation and functions have been made in the past 20 years since the discovery that their formation requires nuclear factor-kappa B (NF-κB) signaling and that this is activated in response to the essential osteoclastogenic cytokine, receptor activator of NF-κB ligand (RANKL), which also controls osteoclast activation to resorb (degrade) bone. These studies have revealed that RANKL and some pro-inflammatory cytokines, including tumor necrosis factor, activate NF-κB and downstream signaling, including c-Fos and nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), and inhibition of repressors of NFATc1 signaling, to positively regulate osteoclast formation and functions. However, these cytokines also activate NF-κB signaling that can limit osteoclast formation through the NF-κB signaling proteins, TRAF3 and p100, and the suppressors of c-Fos/NFATc1 signaling, IRF8, and RBP-J. This paper reviews current understanding of how NF-κB signaling is involved in the positive and negative regulation of cytokine-mediated osteoclast formation and activation.
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Relationship Between Metabolic Syndrome and Bone Health – An Evaluation of Epidemiological Studies and Mechanisms Involved
Anaplastic thyroid cancer (ATC) is one of the most aggressive malignancies in humans, and its progression is poorly controlled by existing therapeutic methods. Curcumin has been shown to suppress inflammation and angiogenesis. In this study, we evaluated whether curcumin could augment docetaxel-induced apoptosis of ATC cells. We also analyzed changes in nuclear factor κB (NF-κB) and cyclooxygenase-2 (COX-2) expression levels to delineate possible mechanisms of their combined action.
ATC cells were cultured and treated with curcumin and docetaxel alone or in combination. The effects on cell viability were determined by MTS assay. Apoptosis was assessed by annexin V staining and confirmed by flow cytometric analysis. Caspase, COX-2, NF-κB levels were assayed by Western blotting.
Curcumin combined with docetaxel led to lower cell viability than treatment with docetaxel or curcumin alone. Annexin V staining followed by flow cytometric analysis demonstrated that curcumin treatment enhanced the docetaxel-induced apoptosis of ATC cells. Additionally, curcumin inhibited docetaxel-induced p65 activation and COX-2 expression.
We conclude that curcumin may enhance docetaxel's antitumor activity in ATC cells by interfering with NF-κB and COX-2. Our results suggest that curcumin may emerge as an attractive therapeutic candidate to enhance the antitumor activity of taxanes in ATC treatment.
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