Potentiation of TNF-mediated cell killing by VP-16: relationship to DNA single-strand break formation.
Interaction between tumor necrosis factor (TNF) and the DNA topoisomerase II inhibitor, etoposide VP-16, in cell killing has been studied. To accurately investigate the nature of DNA damage during the cell killing process, experiments were assessed using the highly TNF-sensitive WEHI164.13 murine fibrosarcoma clone and DNA filter elution methodology. Concomitant treatment of cells with combination of TNF/VP-16 resulted in marked enhancement of cell lysis. Using the alkaline elution technique, we show that TNF fails to induce DNA single-strand breaks as compared to those generated by VP-16. In addition, the potentiating effect of VP-16 on TNF-mediated WEHI164.13 cell killing was not associated with an increase in its intrinsic activity with respect to DNA single-strand break formation. While the 2 phospholipase A2 inhibitors, quinacrine and dexamethasone, were efficient in inhibiting TNF-mediated cell lysis, only quinacrine was efficient in selectively abrogating the TNF/VP-16 cell killing pathway. The inhibitory effect of quinacrine on VP-16/TNF-mediated cell lysis was accompanied by a marked decrease in VP-16-mediated DNA single-strand break generation. Taken together, our findings suggest that TNF and TNF/VP-16 treatments may involve different events during cell killing and support the hypothesis that 2 signals are required for optimal induction of cell lysis by the combination of VP-16/TNF: one signal provided by VP-16 resulting in topoisomerase II inhibition and subsequent DNA single-strand break generation, and a second signal involving TNF.
Branellec
D
D
Laboratoire d'Immunologie UA1156, Institut Gustave-Roussy, Villejuif, France.
Markovits
J
J
Chouaib
S
S
D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects*; D004277:DNA, Single-Stranded / Q000187:drug effects*; D003907:Dexamethasone / Q000494:pharmacology; D004357:Drug Synergism; D005047:Etoposide / Q000494:pharmacology*; D005354:Fibrosarcoma; D051379:Mice; D011796:Quinacrine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004273:DNA, Neoplasm; D004277:DNA, Single-Stranded; D014409:Tumor Necrosis Factor-alpha; D005047:Etoposide; D003907:Dexamethasone; D011796:Quinacrine