title: Thymoquinone inhibits proliferation, induces apoptosis and chemosensitizes human multiple myeloma cells through suppression of signal transducer and activator of transcription 3 activation pathway.
abstract: OBJECTIVE
  Constitutive activation of the signal transducer and activator of transcription 3 (STAT3) pathway is frequently encountered in several human cancers including multiple myeloma (MM). Thus, agents that suppress STAT3 phosphorylation have a potential for treatment of MM. In the present report, we investigated whether thymoquinone (TQ), the main component isolated from the medicinal plant Nigella sativa, modulated the STAT3 signalling pathway in MM cells.
  
  
  METHODS
  The effect of TQ on both constitutive and IL-6-induced STAT3 activation, associated protein kinases, STAT3-regulated gene products involved in proliferation, survival and angiogenesis, cellular proliferation and apoptosis in MM cells, was investigated.
  
  
  RESULTS
  We found that TQ inhibited both constitutive and IL-6-inducible STAT3 phosphorylation which correlated with the inhibition of c-Src and JAK2 activation. Vanadate reversed the TQ-induced down-regulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase. Indeed, we found that TQ can induce the expression of Src homology-2 phosphatase 2 that correlated with suppression of STAT3 activation. TQ also down-regulated the expression of STAT3-regulated gene products, such as cyclin D1, Bcl-2, Bcl-xL, survivin, Mcl-1 and vascular endothelial growth factor. Finally, TQ induced the accumulation of cells in sub-G1 phase, inhibited proliferation and induced apoptosis, as indicated by poly ADP ribose polymerase cleavage. TQ also significantly potentiated the apoptotic effects of thalidomide and bortezomib in MM cells.
  
  
  CONCLUSIONS
  Our study has identified STAT3 signalling as a target of TQ and has thus raised its potential application in the prevention and treatment of MM and other cancers.
authors.affiliation: Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Peramaiyan
authors.initials: P
authors.lastname: Rajendran
authors.forename: Gautam
authors.initials: G
authors.lastname: Sethi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D016227:Benzoquinones / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D000072181:Inositol Polyphosphate 5-Phosphatases; D015850:Interleukin-6 / Q000494:pharmacology; D053614:Janus Kinase 2 / Q000378:metabolism; D009101:Multiple Myeloma / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011719:Pyrazines / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013792:Thalidomide / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D016227:Benzoquinones; D001897:Boronic Acids; D015850:Interleukin-6; D011719:Pyrazines; D050796:STAT3 Transcription Factor; D014638:Vanadates; D013792:Thalidomide; D000069286:Bortezomib; D053614:Janus Kinase 2; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; C003466:thymoquinone