Inhibition of caspase activity delays apoptosis in a transfected NS/0 myeloma cell line.
The productivity of NS/0 myeloma batch cultures is often compromised by the premature induction of apoptosis, now established to be the predominant method of cell death during culture decline. Caspase proteases have recently been shown to play a major role in the transmission of signals for apoptotic cell death. Using a specific inhibitor that targets a range of caspases (Z-VAD-fmk) we assessed whether inhibition of caspase activity could prolong the viability of NS&vbar;h=0 cells under conditions that cause apoptotic cell death in batch cultures. Z-VAD-fmk was found to significantly reduce apoptotic cell death (by approximately 50%) induced by cytotoxins and to preserve membrane integrity to a similar extent. In conditions of low serum, Z-VAD-fmk reduced certain features of apoptosis (e.g., DNA fragmentation), but only marginally improved viability. In medium-depleted batch cultures, Z-VAD-fmk afforded a delay of between 24 and 48 h in both the induction of apoptosis and loss of viability. Despite an apparent increase in viability in Z-VAD-fmk-treated NS&vbar;h=0 cultures, no improvement in productivity could be demonstrated, suggesting that at least some normal pathways for protein production are shut down upstream of caspase activation. An examination of mitochondrial membrane potential (Deltapsim) in Z-VAD-fmk-treated and untreated NS&vbar;h=0 cells revealed only a small initial difference (5%) in the levels of Deltapsim depolarization. Similar levels of mitochondrial dysfunction, despite caspase inactivity, may therefore be responsible for the comparable productivity in untreated and Z-VAD-fmk-treated cultures. Thus, this study suggests that, while a delay in cell death due to caspase inhibition may reduce problems associated with cellular disintegration, it does not permit productivity improvements in this type of culture.
McKenna
S L
SL
Tumour Biology Laboratory, Department of Biochemistry, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland. s.mckenna@ucc.ie
Cotter
T G
TG
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D018929:Cell Culture Techniques / Q000379:methods; D002462:Cell Membrane / Q000187:drug effects; D016895:Culture Media, Serum-Free; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014162:Transfection; D014407:Tumor Cells, Cultured
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D016895:Culture Media, Serum-Free; D015853:Cysteine Proteinase Inhibitors; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases