title: In the erythroleukemic cell line HEL Prostate-apoptosis-response-gene-4 (par-4) fails to down-regulate Bcl-2 and to promote apoptosis.
abstract: In a variety of malignant cells Prostate-apoptosis-response-gene-4 (Par-4) exhibits a pro-apoptotic influence sensitizing these cells to apoptosis-inducing agents by downregulating expression of Bcl-2. Considering the crucial role of Bcl-2 in the development of chemoresistance of acute myeloid leukemia (AML) cells, we here assessed the potential of Par-4 to down-regulate Bcl-2 and to induce apoptosis in the erythroleukemic cell line HEL. Testing a potential pro-apoptotic role of Par-4 upon incubation with various conventional chemotherapeutic drugs, novel agents such as the signal transduction inhibitor STI 571 and the histone deacetylase (HDAC)- inhibitor trichostatin A (TSA), as well as with the experimental substances Fas and TRAIL, we provide evidence that in the erythroleukemic cell line HEL expression of Par-4 is not sufficient to sensitize to any of these pro-apoptotic stimuli. We further demonstrate that--in contrast to previous reports in non-AML cells--Par-4 expression in HEL cells leads to an upregulation of Bcl-2. Moreover, Par-4-positive HEL cells exhibit a decreased level of the proapoptotic protein Bax as compared to Par-4- negative cells. In addition, Par-4 increases the expression of Daxx--whose downregulation is associated with augmented chemosensitivity--as well as expression of the procaspases-8, -9 and -10, whereas the levels of the procaspases-3 and -7 remain unaltered. In conclusion we here demonstrate that in the erythroleukemic cell line HEL--in contrast to other cell types Par-4 fails to promote apoptosis and outline the underlying molecular mechanisms.
authors.affiliation: Department of Internal Medicine III, Hematology and Oncology, Johann Wolfgang Goethe-University Hospital, 60590 Frankfurt am Main, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Boehrer
authors.forename: Angela
authors.initials: A
authors.lastname: Brieger
authors.forename: Simone
authors.initials: S
authors.lastname: Schaaf
authors.forename: Natasa
authors.initials: N
authors.lastname: Kukoc-Zivojnov
authors.forename: Daniel
authors.initials: D
authors.lastname: Nowak
authors.forename: Martin
authors.initials: M
authors.lastname: Ruthardt
authors.forename: Dieter
authors.initials: D
authors.lastname: Hoelzer
authors.forename: Paris S
authors.initials: PS
authors.lastname: Mitrou
authors.forename: Eckhart
authors.initials: E
authors.lastname: Weidmann
authors.forename: Kai Uwe
authors.initials: KU
authors.lastname: Chow
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001549:Benzamides; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D053455:Caspase 10; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D056970:Co-Repressor Proteins; D004792:Enzyme Precursors / Q000096:biosynthesis / Q000235:genetics; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D019254:Genes, bcl-2; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D000068877:Imatinib Mesylate; D047908:Intracellular Signaling Peptides and Proteins; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000819:agonists; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D010879:Piperazines / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D011743:Pyrimidines / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000819:agonists; D051028:bcl-2-Associated X Protein; D019014:fas Receptor / Q000187:drug effects
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C494826:BAX protein, human; D001549:Benzamides; D002352:Carrier Proteins; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D004792:Enzyme Precursors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011743:Pyrimidines; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; C101296:prostate apoptosis response-4 protein; C012589:trichostatin A; D000068877:Imatinib Mesylate; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053455:Caspase 10; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; C506438:CASP10 protein, human