Inhibition of heat shock protein 90 function by 17-allylamino-17-demethoxy-geldanamycin in Hodgkin's lymphoma cells down-regulates Akt kinase, dephosphorylates extracellular signal-regulated kinase, and induces cell cycle arrest and cell death.
OBJECTIVE
Heat shock protein 90 (HSP90) is a chaperone for several client proteins involved in transcriptional regulation, signal transduction, and cell cycle control. HSP90 is abundantly expressed by a variety of tumor types and has been recently targeted for cancer therapy. The objective of this study was to determine the role of HSP90 in promoting growth and survival of Hodgkin's lymphoma and to determine the molecular consequences of inhibiting HSP90 function by the small-molecule 17-allylamino-17-demethoxy-geldanamycin (17-AAG) in Hodgkin's lymphoma.


METHODS
HSP90 expression in Hodgkin's lymphoma cell lines was determined by Western blot and in primary lymph node sections from patients with Hodgkin's lymphoma by immunohistochemistry. Cell viability was determined by the 3-(4,5-dimethyl-thiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Apoptosis and cell cycle fractions were determined by flow cytometry. Expression of intracellular proteins was determined by Western blot.


RESULTS
HSP90 is overexpressed in primary and cultured Hodgkin's lymphoma cells. Inhibition of HSP90 function by 17-AAG showed a time- and dose-dependent growth inhibition of Hodgkin's lymphoma cell lines. 17-AAG induced cell cycle arrest and apoptosis, which were associated with a decrease in cyclin-dependent kinase (CDK) 4, CDK 6, and polo-like kinase 1 (PLK1), and induced apoptosis by caspase-dependent and caspase-independent mechanisms. Furthermore, 17-AAG depleted cellular contents of Akt, decreased extracellular signal-regulated kinase (ERK) phosphorylation, and reduced cellular FLICE-like inhibitory protein levels (FLIP), and thus enhanced the cytotoxic effect of doxorubicin and agonistic anti-tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor antibodies.


CONCLUSIONS
Inhibition of HSP90 function induces cell death and enhances the activity of chemotherapy and anti-tumor necrosis factor-related apoptosis-inducing ligand death receptor antibodies, suggesting that targeting HSP90 function might be of therapeutic value in Hodgkin's lymphoma.
Georgakis
Georgios V
GV
Department of Lymphoma and Myeloma, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Li
Yang
Y
Rassidakis
Georgios Z
GZ
Martinez-Valdez
Hector
H
Medeiros
L Jeffrey
LJ
Younes
Anas
A
D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D016227:Benzoquinones; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005434:Flow Cytometry; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006689:Hodgkin Disease / Q000188:drug therapy* / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic; D008198:Lymph Nodes / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000097869:Polo-Like Kinase 1
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D016227:Benzoquinones; D020169:Caspases; D018797:Cell Cycle Proteins; D018844:Cyclin-Dependent Kinases; D004317:Doxorubicin; D048049:Extracellular Signal-Regulated MAP Kinases; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D008562:Membrane Glycoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017828:Rifabutin; D053221:TNF-Related Apoptosis-Inducing Ligand; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000097869:Polo-Like Kinase 1; C505653:TNFSF10 protein, human; C434062:TNIP2 protein, human; C112765:tanespimycin