Androgen and epidermal growth factor down-regulate cyclin-dependent kinase inhibitor p27Kip1 and costimulate proliferation of MDA PCa 2a and MDA PCa 2b prostate cancer cells.
Low levels of p27Kip1 in primary prostate cancer specimens have been shown to be associated with higher rates of disease recurrence and poor rates of disease-free survival in patients with localized disease. In this study, we provide the first direct evidence showing that dihydrotestosterone (DHT), a major proliferation regulator of prostate cancer, can down-regulate p27Kip1 and stimulate cyclin-dependent kinase-2 (CDK2) activity in established prostate cancer cell lines. We investigated the cooperative effects of DHT and epidermal growth factor (EGF) on the proliferation of androgen-responsive MDA PCa 2a and MDA PCa 2b prostate cancer cells. DHT and EGF each stimulated proliferation of these cells, but exposure of the cells to DHT and EGF together stimulated greater proliferation. Stimulation of cell proliferation by DHT and/or EGF was associated with increased CDK2 activity and a decreased level of p27Kip1. There seems to be a positive feedback stimulation loop between androgen-induced gene transcription and EGF-stimulated signal transduction, as one could stimulate the synthesis of the receptors for the other. Dual blockade of androgen receptor function with the antiandrogen hydroxyflutamide and EGF receptor superfamily-mediated signal transduction with the anti-EGF receptor monoclonal antibody C225 and the anti-HER2 receptor monoclonal antibody Herceptin significantly enhanced growth inhibition of the MDA PCa 2a cells. Our results demonstrate the importance of counteracting both androgen receptors and EGF receptors in the development of novel therapies for prostate cancer.
Ye
D
D
Department of Clinical Investigation, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Mendelsohn
J
J
Fan
Z
Z
D000726:Androgen Antagonists / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000096:biosynthesis; D005485:Flutamide / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008297:Male; D015741:Metribolone / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011944:Receptors, Androgen / Q000096:biosynthesis; D045165:Testosterone Congeners / Q000494:pharmacology; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D000726:Androgen Antagonists; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D011500:Protein Synthesis Inhibitors; D011944:Receptors, Androgen; D045165:Testosterone Congeners; D025521:Tumor Suppressor Proteins; D013196:Dihydrotestosterone; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015741:Metribolone; C014290:hydroxyflutamide; D004815:Epidermal Growth Factor; D005485:Flutamide; D003513:Cycloheximide; D066246:ErbB Receptors; D018844:Cyclin-Dependent Kinases; D000068878:Trastuzumab