RESUMO
In tumor necrosis factor (TNF) signaling, phosphorylation and activation of receptor interacting protein kinase 1 (RIPK1) by upstream kinases is an essential checkpoint in the suppression of TNF-induced cell death. Thus, discovery of pharmacological agents targeting RIPK1 may provide new strategies for improving the therapeutic efficacy of TNF. In this study, we found that 3-O-acetylrubianol C (3AR-C), an arborinane triterpenoid isolated from Rubia philippinesis, promoted TNF-induced apoptotic and necroptotic cell death. To identify the molecular mechanism, we found that in mouse embryonic fibroblasts, 3AR-C drastically upregulated RIPK1 kinase activity by selectively inhibiting IKKß. Notably, 3AR-C did not interfere with IKKα or affect the formation of the TNF receptor1 (TNFR1) complex-I. Moreover, in human cancer cells, 3AR-C was only sufficient to sensitize TNF-induced cell death when c-FLIPL expression was downregulated to facilitate the formation of TNFR1 complex-II and necrosome. Taken together, our study identified a novel arborinane triterpenoid 3AR-C as a potent activator of TNF-induced cell death via inhibition of IKKß phosphorylation and promotion of the cytotoxic potential of RIPK1, thus providing a rationale for further development of 3AR-C as a selective IKKß inhibitor to overcome TNF resistance in cancer therpay.
Assuntos
Apoptose/fisiologia , Quinase I-kappa B/metabolismo , Receptor de Morte Celular Programada 1/metabolismo , Animais , Apoptose/genética , Linhagem Celular Tumoral , Sobrevivência Celular/genética , Sobrevivência Celular/fisiologia , Humanos , Quinase I-kappa B/genética , Espectroscopia de Ressonância Magnética , Camundongos , Receptor de Morte Celular Programada 1/genética , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Complement 3a (C3a) and complement 5a (C5a), small cleavage fragments generated by complement activation, has been previously shown to be obviously up-regulated in highly metastatic hepatocellular carcinoma (HCC) cells. However, their functional roles in HCC cells remains unclear. Here, we investigated the biological function of G protein-coupled receptor C3aR/C5aR using small interference RNA in HCC cells. Our data showed that C3aR and C5aR knockdown significantly inhibited the proliferation, migration and invasion of HCC cells using CCK-8, colony formation and transwell assays. Flow cytometry assay showed C3aR and C5aR knockdown induced cell cycle G0/G1 phase arrest and apoptosis in HCC cells. Moreover, we found down-regulation of C3aR/C5aR obviously down-regulated the expression of PCNA, Ki-67 and suppressed the epithelial-mesenchymal transition (EMT) markers (E-cadherin, N-cadherin and vimentin) in HCC cells. Collectively, our data demonstrated that targeting C3aR/C5aR may hold promise for the treatment of HCC.