title: Two pathways of apoptosis induced with all-trans retinoic acid and etoposide in the myeloid cell line P39.
abstract: P39/Tsugane is a myelomonocytoid cell line derived from a patient with myelodysplastic syndrome (MDS). The cells readily undergo apoptosis in response to various agents, and the cell line has been suggested as a useful model to study apoptosis in MDS. The aims of the present study were to assess differentiation and apoptosis induced with all-trans retinoic acid (ATRA) and etoposide, to characterize the mode of apoptosis in these two model systems, and to assess the influence of granulocyte colony-stimulating factor (G-CSF), which in combination with erythropoietin has been shown to inhibit apoptosis in MDS. ATRA induced differentiation and apoptosis in a concentration- and time-dependent manner. Differentiated cells were partially rescued (by 50%) from apoptosis with G-CSF. Etoposide induced apoptosis in a concentration- and time-dependent manner, but no signs of preceding maturation or G-CSF rescue were detected. ATRA- and etoposide-induced apoptosis were both mediated through the caspase pathway and were partially blocked with the general caspase inhibitor zVAD-fmk. Simultaneous treatment with G-CSF and zVAD-fmk additively blocked ATRA-induced apoptosis. However, the two pathways differed in terms of substrate cleavage during apoptosis. ATRA-induced apoptosis caused actin cleavage, which was not affected by G-CSF, and Bcl-2 downregulation. Etoposide induced a caspase-dependent cleavage of Bcl-2, while actin remained intact. The Fas system did not seem to play a major role in any of these apoptotic pathways. Our results may provide new tools to study the mechanisms of apoptosis in MDS.
authors.affiliation: Department of Hematology, Huddinge University Hospital, Stockholm, Sweden. Zuzana.Hassan@kfcmail.hs.sll.se
authors.forename: Z
authors.initials: Z
authors.lastname: Hassan
authors.forename: B
authors.initials: B
authors.lastname: Fadeel
authors.forename: B
authors.initials: B
authors.lastname: Zhivotovsky
authors.forename: E
authors.initials: E
authors.lastname: Hellström-Lindberg
mesh_terms: D000199:Actins / Q000378:metabolism; D000208:Acute Disease; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001752:Blast Crisis / Q000209:etiology / Q000473:pathology; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004921:Erythropoietin / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology*; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007951:Leukemia, Myeloid / Q000209:etiology / Q000473:pathology*; D009190:Myelodysplastic Syndromes / Q000150:complications / Q000473:pathology*; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D019014:fas Receptor / Q000276:immunology
chemical_list: D000199:Actins; D000590:Amino Acid Chloromethyl Ketones; D000911:Antibodies, Monoclonal; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D004921:Erythropoietin; D016179:Granulocyte Colony-Stimulating Factor; D014212:Tretinoin; D005047:Etoposide; D020169:Caspases