Celastrol, a novel triterpene, potentiates TNF-induced apoptosis and suppresses invasion of tumor cells by inhibiting NF-κB–regulated gene products and TAK1-mediated NF-κB activation

Abstract

Celastrol, a quinone methide triterpene derived from the medicinal plant Tripterygium wilfordii, has been used to treat chronic inflammatory and autoimmune diseases, but its mechanism is not well understood. Therefore, we investigated the effects of celastrol on cellular responses activated by TNF, a potent proinflammatory cytokine. Celastrol potentiated the apoptosis induced by TNF and chemotherapeutic agents and inhibited invasion, both regulated by NF-B activation. We found that TNF induced the expression of gene products involved in antiapoptosis (IAP1, IAP2, Bcl-2, Bcl-X L , c-FLIP, and survivin), proliferation (cyclin D1 and COX-2), invasion (MMP-9), and angiogenesis (VEGF) and that celastrol treatment suppressed their expression. Because these gene products are regulated by NF-B, we postulated that celastrol mediates its effects by modulating the NF-B pathway. We found that celastrol suppressed both inducible and constitutive NF-B activation. Celastrol was found to inhibit the TNF-induced activation of I B␣ kinase, I B␣ phosphorylation, I B␣ degradation, p65 nuclear trans- IntroductionModern targeted therapies for most chronic illnesses, including cancer, have been mostly unsuccessful because of their ineffectiveness, lack of safety, and cost. Although monotherapy was advocated at one time, recent experience indicates that agents that target multiple pathways have more potential in cancer treatment. This understanding has led to combination therapy. Although traditional therapies have been around for thousands of years, their active components and their mechanisms of action remain undefined. Identification of an active chemical entity and its molecular targets can lead to rediscovery of the clinical potential of such therapies, as in the case of paclitaxel, derived from Taxus (yew) species during a random screening of US Department of Agriculture collection of plants. 1 Celastrol, also known as tripterine, is one such compound that was originally identified from traditional Chinese medicine ("God of Thunder Vine") almost 3 decades ago and used for the treatment of cancer and other inflammatory diseases. 2 Celastrol, a triterpenoid from the Celastracae family and extracted from the plant Tripterygium wilfordii, 3 has attracted interest, especially for its potential anti-inflammatory effects. 4 The in vivo anti-inflammatory effects of this triterpene have been demonstrated in animal models of collagen-induced arthritis, 5 Alzheimer disease, 6 asthma, 7 systemic lupus erythematosus, 8,9 and rheumatoid arthritis. 10 Celastrol is also known to inhibit the proliferation of a variety of tumor cells, including those from leukemia, 11 gliomas, 12 and prostate cancer. 13 The ability of celastrol to modulate the expression of proinflammatory cytokines, 3,14,15 6 inducible nitric oxide (NO) synthase (iNOS), 16 adhesion molecules in endothelial cells, 17 proteasome activity, 13 topoisomerase II, 11 potassium channels, 18 and heat shock response 19 has been reported. However, the molecular mechanism underlying the ...

Targeting Nuclear Factor-κB Activation Pathway by Thymoquinone: Role in Suppression of Antiapoptotic Gene Products and Enhancement of Apoptosis

“…To measure apoptosis, we used the Live/Dead cell viability assay (Molecular Probes), which determines intracellular esterase activity and plasma membrane integrity (73). Calcein-AM, a nonfluorescent polyanionic dye, is retained by live cells, in which it produces intense green fluorescence through enzymatic (esterase) conversion.…”

Pinitol targets nuclear factor-κB activation pathway leading to inhibition of gene products associated with proliferation, apoptosis, invasion, and angiogenesis

“…To determine the effect of pinitol on TNF-induced IKK activation, we analyzed IKK by a method described elsewhere (22). Briefly, the IKK complex from whole-cell extracts was precipitated with antibodies against IKKa and IKKh then treated with protein A/G-agarose beads (Pierce).…”

“…The effect of pinitol on TNF-induced NF-nB-dependent reporter gene transcription in A293 cells was measured as described elsewhere (22).…”

Targeted inhibition of tumor proliferation, survival, and metastasis by pentacyclic triterpenoids: Potential role in prevention and therapy of cancer

“…Celastrol has attracted great interest recently, especially for its potential anti-inflammatory and anti-cancer activities. The in vivo anti-inflammatory effects of this triterpene have been demonstrated in animal models of collagen-induced arthritis, rheumatoid arthritis, Alzheimer's disease, asthma, and systemic lupus erythematosus [83][84][85]. This triterpene has also been found to suppress tumor initiation, promotion and metastasis in various cancer models through modulation of multiple pro-inflammatory cytokines, chemokines, enzymes and transcription factors [4,[86][87][88][89][90][91].…”