title: Capsaicin is a novel blocker of constitutive and interleukin-6-inducible STAT3 activation.
abstract: OBJECTIVE
  Capsaicin, a constituent of green and red peppers, has been linked with suppression of tumorigenesis through a mechanism that is not well understood. Because the transcription factor signal transducer and activator of transcription 3 (STAT3) has been closely linked with tumorigenesis, we investigated the effect of this vanilloid on the STAT3 pathway in human multiple myeloma cells.
  
  
  METHODS
  The effect of capsaicin on both constitutive and interleukin-6-induced STAT3 activation, associated protein kinases, and STAT3-regulated gene products involved in proliferation, survival and angiogenesis, cellular proliferation, and apoptosis in multiple myeloma cells was investigated.
  
  
  RESULTS
  We found that capsaicin inhibited constitutive activation of STAT3 in multiple myeloma cells in a dose- and time-dependent manner, with minimum effect on STAT5. Capsaicin also inhibited the interleukin-6-induced STAT3 activation. The activation of Janus-activated kinase 1 and c-Src, implicated in STAT3 activation, was also inhibited by the vanilloid, with no effect on extracellular signal-regulated kinase 1/2 activation. Pervanadate reversed the capsaicin-induced down-regulation of STAT3, suggesting the involvement of a protein tyrosine phosphatase. Capsaicin down-regulated the expression of the STAT3-regulated gene products, such as cyclin D1, Bcl-2, Bcl-xL, survivin, and vascular endothelial growth factor. Finally, capsaicin induced the accumulation of cells in G(1) phase, inhibited proliferation, and induced apoptosis, as indicated by caspase activation. Capsaicin also significantly potentiated the apoptotic effects of Velcade and thalidomide in multiple myeloma cells. When administered i.p., capsaicin inhibited the growth of human multiple myeloma xenograft tumors in male athymic nu/nu mice.
  
  
  CONCLUSIONS
  Overall, these results suggest that capsaicin is a novel blocker of the STAT3 activation pathway, with a potential role in the prevention and treatment of multiple myeloma and other cancers.
authors.affiliation: Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Manisha
authors.initials: M
authors.lastname: Bhutani
authors.forename: Ashutosh K
authors.initials: AK
authors.lastname: Pathak
authors.forename: Asha S
authors.initials: AS
authors.lastname: Nair
authors.forename: Ajaikumar B
authors.initials: AB
authors.lastname: Kunnumakkara
authors.forename: Sushovan
authors.initials: S
authors.lastname: Guha
authors.forename: Gautam
authors.initials: G
authors.lastname: Sethi
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D002211:Capsaicin / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000037:antagonists & inhibitors; D004247:DNA / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D015850:Interleukin-6 / Q000494:pharmacology; D053613:Janus Kinase 1 / Q000037:antagonists & inhibitors; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors; D009101:Multiple Myeloma / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors; D011719:Pyrazines / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000077022:Survivin; D013792:Thalidomide / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors; D051020:bcl-X Protein / Q000037:antagonists & inhibitors
chemical_list: D000970:Antineoplastic Agents; C107489:BIRC5 protein, human; D001897:Boronic Acids; D061945:Caspase Inhibitors; D051034:Inhibitor of Apoptosis Proteins; D015850:Interleukin-6; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011719:Pyrazines; D050796:STAT3 Transcription Factor; D000077022:Survivin; D042461:Vascular Endothelial Growth Factor A; D051020:bcl-X Protein; D019938:Cyclin D1; D013792:Thalidomide; D000069286:Bortezomib; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases; D053613:Janus Kinase 1; D048049:Extracellular Signal-Regulated MAP Kinases; D017027:Protein Tyrosine Phosphatases; D053148:Caspase 3; D002211:Capsaicin