title: Inhibition of Wnt signaling by cucurbitacin B in breast cancer cells: reduction of Wnt-associated proteins and reduced translocation of galectin-3-mediated β-catenin to the nucleus.
abstract: The cucurbitacins are tetracyclic triterpenes found in plants of the family Cucurbitaceae. Cucurbitacins have been shown to have anti-cancer and anti-inflamatory activities. We investigated the anti-cancer activity of cucurbitacin B extracted from Thai medicinal plant Trichosanthes cucumerina Linn. Cell viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results indicated that cucurbitacin B from T. cucumerina Linn. has a cytotoxic effect on breast cancer cell lines SKBR-3 and MCF-7 with an IC50 of 4.60 and 88.75 µg/ml, respectively. Growth inhibition was attributed to G2/M phase arrest and apoptosis. Cyclin D1, c-Myc, and β-catenin expression levels were reduced. Western blot analysis showed increased PARP cleavage and decreased Wnt-associated signaling molecules β-catenin, galectin-3, cyclin D1 and c-Myc, and corresponding changes in phosphorylated GSK-3β levels. Cucurbitacin B treatment inhibited translocation to the nucleus of β-catenin and galectin-3. The depletion of β-catenin and galectin-3 in the nucleus was confirmed by cellular protein fractionation. T-cell factor (TCF)/lymphoid enhancer factor (LEF)-dependent transcriptional activity was disrupted in cucurbitacin B treated cells as tested by a TCF reporter assay. The relative luciferase activity was reduced when we treated cells with cucurbitacin B compound for 24 h. Our data suggest that cucurbitacin B may in part induce apoptosis and exert growth inhibitory effect via interruption the Wnt signaling.
authors.affiliation: Mahidol University, Bangkok, Thailand.
authors.forename: Sumana
authors.initials: S
authors.lastname: Dakeng
authors.forename: Suwit
authors.initials: S
authors.lastname: Duangmano
authors.forename: Weena
authors.initials: W
authors.lastname: Jiratchariyakul
authors.forename: Yaowalak
authors.initials: Y
authors.lastname: U-Pratya
authors.forename: Oliver
authors.initials: O
authors.lastname: Bögler
authors.forename: Pimpicha
authors.initials: P
authors.lastname: Patmasiriwat
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019938:Cyclin D1 / Q000378:metabolism; D005260:Female; D037502:Galectin 3 / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000096:biosynthesis / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D010936:Plant Extracts / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D021381:Protein Transport; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D051820:TCF Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism; D029778:Trichosanthes; D014315:Triterpenes / Q000494:pharmacology*; D051153:Wnt Proteins / Q000378:metabolism*; D060449:Wnt Signaling Pathway / Q000187:drug effects*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: C530104:CCND1 protein, human; D037502:Galectin 3; C489427:MYC protein, human; D010936:Plant Extracts; D016271:Proto-Oncogene Proteins c-myc; D051820:TCF Transcription Factors; D014315:Triterpenes; D051153:Wnt Proteins; D051176:beta Catenin; C041246:cucurbitacin B; D019938:Cyclin D1; D011065:Poly(ADP-ribose) Polymerases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3