Geldanamycin, an inhibitor of the chaperone activity of HSP90, induces MAPK‐independent cell cycle arrest

• Published in: International journal of cancer Vol. 109; no. 5; pp. 643 - 652
• Main Authors: Bedin, Monique, Gaben, Anne‐Marie, Saucier, Cécile, Mester, Jan
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-05-2004; Wiley-Liss
• Subjects: ansamycin; Antibiotics, Antineoplastic - pharmacology; Antineoplastic agents; Benzoquinones; Biological and medical sciences; Blotting, Western; CDC2-CDC28 Kinases - drug effects; CDC2-CDC28 Kinases - metabolism; Cell Cycle - drug effects; Colonic Neoplasms - drug therapy; Colonic Neoplasms - metabolism; cyclin; Cyclin E - drug effects; Cyclin E - metabolism; Cyclin-Dependent Kinase 2; cyclin‐dependent kinase; Enzyme Inhibitors - pharmacology; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Neoplastic - drug effects; General aspects; Hsp90; HSP90 Heat-Shock Proteins - antagonists & inhibitors; Humans; Interphase - drug effects; Lactams, Macrocyclic; Male; Medical sciences; Mitogen-Activated Protein Kinase Kinases - metabolism; Molecular Chaperones - antagonists & inhibitors; Pharmacology. Drug treatments; Phosphorylation - drug effects; Plasmids - metabolism; Precipitin Tests; Promoter Regions, Genetic - drug effects; Prostatic Neoplasms - drug therapy; Prostatic Neoplasms - metabolism; Protein-Tyrosine Kinases - antagonists & inhibitors; Quinones - pharmacology; Retinoblastoma Protein - drug effects; Retinoblastoma Protein - metabolism; Transfection; Tumor Cells, Cultured; Antineoplastic agent; Prostate disease; Colon cancer; Cell cycle; Established cell line; Heat shock protein; Intestinal disease; Cyclin E; Male genital diseases; Heat shock protein 90; Human; Urinary system disease; Enzyme; Chaperone; Rodentia; Mitogen-activated protein kinase; Malignant tumor; In vitro; Biological activity; Colonic disease; Vertebrata; Antibiotic; Mammalia; Shutdown; Mouse; Animal; v; Digestive diseases; Fibroblast
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.20010

The effects of GA, an ansamycin antibiotic in development as a lead anticancer drug, were studied in mouse BP‐A31 fibroblasts and in human cancer‐derived cell lines. GA and related molecules act by inhibiting the chaperone function of the Hsp90 protein through competition for ATP binding. The antiproliferative effects of GA have been attributed to destabilization of the Raf‐1 protein, one of the targets of Hsp90, and to the resulting inhibition of MAPK. Addition of GA to BP‐A31 cells, synchronously progressing through the G1 phase, inhibited Rb hyperphosphorylation and G1/S transition irrespective of the time of addition. The G1 arrest was accompanied by a progressive decrease in Raf‐1 content, especially of the phosphorylated form; however, GA caused only partial inhibition of MAPK phosphorylation. We show that GA triggers a rapid and marked decrease in the kinase activity of the cyclin E/cdk2 complex coupled with a decline in both total and cdk2‐associated cyclin E. In transient transfection experiments, inhibition of cyclin E expression by GA was correlated with inhibition of the transcriptional activity of the cyclin E gene promoter. Inhibition of cdk4 activity by GA was observed 3 hr after addition of the drug to late G1 cells but not after a short (1 hr) exposure, as revealed by the phosphorylation of Rb on the Ser780 residue. In human cancer‐derived cell lines expressing or not a functional Rb protein, GA blocked proliferation and inhibited the transcriptional activity of the cyclin E gene promoter. In these cell lines, the antiproliferative effect of GA was not limited to the G1 phase, suggesting the existence of multiple cellular targets of the drug. © 2004 Wiley‐Liss, Inc.