Characteristics of etoposide-induced apoptotic cell death in the U-937 human lymphoma cell line.
Cell death induced by etoposide in the human lymphoma cell line U-937 GTB was characterized. Activity of caspases -3, -8 and -9 was measured by spectrophotometric detection of specific cleavage products, DNA fragmentation by TdT-mediated dUTP nick end-labelling (TUNEL), and apoptotic morphology by conventional staining and microscopy, as well as by a novel method-the microculture kinetics (MiCK) assay. Synthesis of protein and DNA during exposure was monitored by incorporation of radioactive leucine and thymidine, respectively. The effects of caspase inhibitors on total viability, as well as early and late morphological changes were studied. Etoposide rapidly induced apoptosis, dependent on caspase-3 and -8, but inhibition of these caspases did not prevent major cell death, but promoted a switch in late morphology. The novel MiCK assay added valuable information on early morphological events during cell death. Hence, this study provides support for caspase-8-mediated apoptosis in U-937 GTB when exposed to etoposide. General caspase inhibition switches cell death to one with a different morphology.
Martinsson
P
P
Department of Medical Sciences, Division of Clinical Pharmacology, University Hospital, Uppsala University, 751 85 Uppsala, Sweden. petra.martinsson@medsci.uu.se
Liminga
G
G
Nygren
P
P
Larsson
R
R
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D004273:DNA, Neoplasm / Q000096:biosynthesis*; D005047:Etoposide / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use; D006801:Humans; D020287:In Situ Nick-End Labeling; D007700:Kinetics; D008223:Lymphoma / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology*; D014176:Protein Biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects
D004273:DNA, Neoplasm; D005047:Etoposide; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases