title: Silibinin modulates TNF-α and IFN-γ mediated signaling to regulate COX2 and iNOS expression in tumorigenic mouse lung epithelial LM2 cells.
abstract: Silibinin inhibits mouse lung tumorigenesis in part by targeting tumor microenvironment. Tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) can be pro- or anti-tumorigenic, but in lung cancer cell lines they induce pro-inflammatory enzymes cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS). Accordingly, here we examined mechanism of silibinin action on TNF-α + IFN-γ (hereafter referred as cytokine mixture) elicited signaling in tumor-derived mouse lung epithelial LM2 cells. Both signal transducers and activators of the transcription (STAT)3 (tyr705 and ser727) and STAT1 (tyr701) were activated within 15 min of cytokine mixture exposure, while STAT1 (ser727) activated after 3 h. Cytokine mixture also activated Erk1/2 and caused an increase in both COX2 and iNOS levels. Pretreatment of cells with a MEK, NF-κB, and/or epidermal growth factor receptor (EGFR) inhibitor inhibited cytokine mixture-induced activation of Erk1/2, NF-κB, or EGFR, respectively, and strongly decreased phosphorylation of STAT3 and STAT1 and expression of COX2 and iNOS. Also, janus family kinases (JAK)1 and JAK2 inhibitors specifically decreased cytokine-induced iNOS expression, suggesting possible roles of JAK1, JAK2, Erk1/2, NF-κB, and EGFR in cytokine mixture-caused induction of COX2 and iNOS expression via STAT3/STAT1 activation in LM2 cells. Importantly, silibinin pretreatment inhibited cytokine mixture-induced phosphorylation of STAT3, STAT1, and Erk1/2, NF-κB-DNA binding, and expression of COX2, iNOS, matrix metalloproteinases (MMP)2, and MMP9, which was mediated through impairment of STAT3 and STAT1 nuclear localization. Silibinin also inhibited cytokine mixture-induced migration of LM2 cells. Together, we showed that STAT3 and STAT1 could be valuable chemopreventive and therapeutic targets within the lung tumor microenvironment in addition to being targets within tumor itself, and that silibinin inhibits their activation as a plausible mechanism of its efficacy against lung cancer.
authors: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Denver, Aurora, Colorado 80045, USA.
authors: Alpna
authors: A
authors: Tyagi
authors: Chapla
authors: C
authors: Agarwal
authors: Lori D
authors: LD
authors: Dwyer-Nield
authors: Rana P
authors: RP
authors: Singh
authors: Alvin M
authors: AM
authors: Malkinson
authors: Rajesh
authors: R
authors: Agarwal
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000473:pathology; D007371:Interferon-gamma / Q000378:metabolism* / Q000494:pharmacology; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D016328:NF-kappa B; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D012838:Silymarin; C494080:Stat1 protein, mouse; C494087:Stat3 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D000077385:Silybin; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D048052:Mitogen-Activated Protein Kinase 3; D020930:MAP Kinase Kinase Kinases; D020778:Matrix Metalloproteinase 2; C522362:Mmp2 protein, mouse; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse