Capsaicin Is a Novel Blocker of Constitutive and Interleukin-6^Inducible STAT3 Activation ManishaBhutani, 1 AshutoshK.Pathak, 1 Asha S. Nair, 1 Ajaikumar B. Kunnumakkara, 1 Sushovan Guha, 2 Gautam Sethi, 1 andBharatB.Aggarwal 1 Abstract Purpose: 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 mul- tiple myeloma cells. Experimental Design: 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 cellswasinvestigated. 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 ofJanus-activated kinase1 and c-Src, implicated in STAT3 activation, was also inhibited by the vanilloid, with no effect on extracellular signal-regulated kinase1/2 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, capsaicininduced 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 ofVelcade 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. Conclusion: 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 andothercancers. Capsaicin (trans -8-methyl-N-vanillyl-6-nonenamide) is a prin- cipal pungent ingredient of hot red and chili peppers that belong to the plant genus Capsicum (Solanaceae). In addition to alleviating neuropathic pain and itching in humans (1–4), capsaicin has exhibited anticancer effects in animal models, suppressing carcinogenesis of the skin (5), colon (6), lung (7), tongue (8), and prostate (9, 10). The mechanism by which this vanilloid mediates its anticarcinogenic effects is not understood but has been shown to alter the metabolism of carcinogens such as aflatoxin B1 (11) and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (12, 13). In culture, capsaicin has been found to selectively suppress the growth of various human tumor cells (14, 15), including leukemic (16–18), gastric (19), hepatic (20), glioma (21), and prostate cells (9). How capsaicin mediates its anticancer effects is not fully understood, but the roles of NADH oxidase activity (14), proteasome (9), cyclooxygenases (22), c-Jun NH 2 -terminal kinase (23), nuclear factor-nB (24), peroxisome proliferator-activated receptor g (25, 26), perox- ynitrite (21), and mitochondrial respiration (27) have been implicated. Its immunosuppressive effects have been linked to its ability to suppress nuclear factor-nB activation (28). Members of the signal transducer and activator of transcrip- tion (STAT) family of transcription factors regulate the expression of gene products involved in cell survival, prolifera- tion, chemoresistance, and angiogenesis (29, 30). The activa- tion of STATs involves the phosphorylation of a critical tyrosine residue by Janus-activated kinases (JAK), or the Src family kinases, leading to dimerization of STAT monomers, nuclear Cancer Therapy: Preclinical Authors’Affiliations: 1 Cytokine Research Laboratory, Department of ExperimentalTherapeutics and 2 Department of Gastrointestinal Medicine and Nutrition, The University of Texas M. D. Anderson CancerCenter, Houston, Texas Received10/24/06;revised2/2/07;accepted2/27/07. Grant support: ClaytonFoundationforResearchandNIHgrantP01CA91844on lung chemoprevention (B.B. Aggarwal). This work was also supported by the National Institutes of Health core grant 5P30 CA016672-32 for flow cytometric analysis. Thecostsofpublicationofthisarticleweredefrayedinpartbythepaymentofpage charges.This article must therefore be hereby marked advertisement in accordance with18 U.S.C. Section1734 solely toindicate this fact. Note: B.B.AggarwalistheRansomHorne,Jr.ProfessorofCancerResearch. Requests for reprints: Bharat B. Aggarwal, Department of Experimental Therapeutics,The University ofTexas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 143, Houston,TX 77030. Phone: 713-792-3503; Fax:713-794-1613;E-mail:aggarwal@mdanderson.org. F 2007AmericanAssociationforCancerResearch. doi:10.1158/1078-0432.CCR-06-2575 www.aacrjournals.org Clin Cancer Res 2007;13(10) May15, 2007 3024 Downloaded from http://aacrjournals.org/clincancerres/article-pdf/13/10/3024/1968382/3024.pdf by guest on 19 June 2022