title: Knockdown of c-Fos suppresses the growth of human colon carcinoma cells in athymic mice.
abstract: Here we have investigated whether inhibition of c-Fos expression in RKO human colon carcinoma cells (HCCCs) would result in reduced TGFβ1 expression and suppression of tumor growth in athymic mice. We stably transfected RKO cells with c-Fos small interfering RNA (siRNA) or with the corresponding control siRNA. Using these stable cell lines, we demonstrated that siRNA-c-Fos significantly suppressed both AP-1 binding, promoter reporter activity at the proximal AP-1 site in the TGFβ1 promoter, and TGFβ1 production. Further, we established colon cancer xenografts with each of RKO-siRNA-EV, RKO-siRNA-Ctrl and RKO-siRNA-c-Fos cells. By 24 days, the tumor size of RKO-siRNA-c-Fos xenografts was 40% that of either RKO-EV or RKO-siRNA-Ctrl. Immunohistochemistry (IHC) of tumor xenografts demonstrated that siRNA-c-Fos significantly blocked c-Fos expression, and consequently expression of TGFβ1. However, expression of TGFβ2 and TGFβ3 were unaffected. Overall, our results demonstrate that blockade of TGFβ1 production by siRNA-c-Fos effectively suppressed tumor growth in vivo.
authors.affiliation: Department of Biochemistry and Molecular Biology, Penn State Hershey College of Medicine, Hershey, PA, USA.
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Pandey
authors.forename: Guangming
authors.initials: G
authors.lastname: Liu
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Cooper
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Mulder
mesh_terms: D000818:Animals; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control*; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D007124:Immunoenzyme Techniques; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012045:Regulatory Sequences, Nucleic Acid; D018808:Transcription Factor AP-1 / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; D053773:Transforming Growth Factor beta1; D008156:Luciferases