Tetrandrine induces early G1 arrest in human colon carcinoma cells by down-regulating the activity and inducing the degradation of G1-S-specific cyclin-dependent kinases and by inducing p53 and p21Cip1.
Tetrandrine is an antitumor alkaloid isolated from the root of Stephania tetrandra. We find that micromolar concentrations of tetrandrine irreversibly inhibit the proliferation of human colon carcinoma cells in MTT and clonogenic assays by arresting cells in G(1). Tetrandrine induces G(1) arrest before the restriction point in nocodazole- and serum-starved synchronized HT29 cells, without affecting the G(1)-S transition in aphidicolin-synchronized cells. Tetrandrine-induced G(1) arrest is followed by apoptosis as shown by fluorescence-activated cell sorting, terminal deoxynucleotidyl transferase-mediated nick end labeling, and annexin V staining assays. Tetrandrine-induced early G(1) arrest is mediated by at least three different mechanisms. First, tetrandrine inhibits purified cyclin-dependent kinase 2 (CDK2)/cyclin E and CDK4 without affecting significantly CDK2/cyclin A, CDK1/cyclin B, and CDK6. Second, tetrandrine induces the proteasome-dependent degradation of CDK4, CDK6, cyclin D1, and E2F1. Third, tetrandrine increases the expression of p53 and p21(Cip1) in wild-type p53 HCT116 cells. Collectively, these results show that tetrandrine arrests cells in G(1) by convergent mechanisms, including down-regulation of E2F1 and up-regulation of p53/p21(Cip1).
Meng
Ling-Hua
LH
Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
Zhang
Hongliang
H
Hayward
Larry
L
Takemura
Haruyuki
H
Shao
Rong-Guang
RG
Pommier
Yves
Y
D000470:Alkaloids / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D044182:Benzylisoquinolines / Q000494:pharmacology*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000096:biosynthesis*; D048708:Cell Growth Processes / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015536:Down-Regulation; D016193:G1 Phase / Q000187:drug effects*; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D008958:Models, Molecular; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*
D000470:Alkaloids; D000972:Antineoplastic Agents, Phytogenic; D044182:Benzylisoquinolines; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C009438:tetrandrine; D016203:CDC2 Protein Kinase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases