title: Triptolide abrogates growth of colon cancer and induces cell cycle arrest by inhibiting transcriptional activation of E2F.
abstract: Despite significant progress in diagnostics and therapeutics, over 50 thousand patients die from colorectal cancer annually. Hence, there is urgent need for new lines of treatment. Triptolide, a natural compound isolated from the Chinese herb Tripterygium wilfordii, is effective against multiple cancers. We have synthesized a water soluble analog of triptolide, named Minnelide, which is currently in phase I trial against pancreatic cancer. The aims of the current study were to evaluate whether triptolide/Minnelide is effective against colorectal cancer and to elucidate the mechanism by which triptolide induces cell death in colorectal cancer. Efficacy of Minnelide was evaluated in subcutaneous xenograft and liver metastasis model of colorectal cancer. For mechanistic studies, colon cancer cell lines HCT116 and HT29 were treated with triptolide and the effect on viability, caspase activation, annexin positivity, lactate dehydrogenase release, and cell cycle progression was evaluated. Effect of triptolide on E2F transcriptional activity, mRNA levels of E2F-dependent genes, E2F1- retinoblastoma protein (Rb) binding, and proteins levels of regulator of G1-S transition was also measured. DNA binding of E2F1 was evaluated by chromatin immunoprecipitation assay. Triptolide decreased colon cancer cell viability in a dose- and time-dependent fashion. Minnelide markedly inhibited the growth of colon cancer in the xenograft and liver metastasis model of colon cancer and more than doubles the median survival of animals with liver metastases from colon cancer. Mechanistically, we demonstrate that at low concentrations triptolide induces apoptotic cell death but at higher concentrations it induces cell cycle arrest. Our data suggest that triptolide is able to induce G1 cell cycle arrest by inhibiting transcriptional activation of E2F1. Our data also show that triptolide downregulates E2F activity by potentially modulating events downstream of DNA binding. Therefore, we conclude that Triptolide and Minnelide are effective against colon cancer in multiple pre-clinical models.
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Amanda
authors.initials: A
authors.lastname: Oliveira
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Georg
authors.initials: G
authors.lastname: Beyer
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Rohit
authors.initials: R
authors.lastname: Chugh
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Skube
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Kaustav
authors.initials: K
authors.lastname: Majumder
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Sulagna
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Veena
authors.initials: V
authors.lastname: Sangwan
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Lihua
authors.initials: L
authors.lastname: Li
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Rajinder
authors.initials: R
authors.lastname: Dawra
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Subbaya
authors.initials: S
authors.lastname: Subramanian
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Ashok
authors.initials: A
authors.lastname: Saluja
authors.affiliation: Division of Basic and Translational Research, Department of Surgery, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Vikas
authors.initials: V
authors.lastname: Dudeja
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D004224:Diterpenes / Q000494:pharmacology*; D050684:E2F Transcription Factors / Q000378:metabolism*; D004852:Epoxy Compounds / Q000494:pharmacology; D005260:Female; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D008819:Mice, Nude; D010755:Organophosphates / Q000494:pharmacology; D010616:Phenanthrenes / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D018906:Antineoplastic Agents, Alkylating; D004224:Diterpenes; D050684:E2F Transcription Factors; D004852:Epoxy Compounds; D010755:Organophosphates; D010616:Phenanthrenes; C001899:triptolide; C579022:14-O-phosphonooxymethyltriptolide disodium salt