In the absence of Epstein-Barr virus infection, phorbol ester modulates apoptosis in cycloheximide-treated Burkitt's lymphoma (BJA-B) cells.
We have shown previously that cycloheximide (CHX), a potent protein synthesis inhibitor, induces high levels of apoptosis in Epstein-Barr virus free (EBV(-)) Burkitt's lymphoma (BJA-B) cells, with comparably reduced levels of apoptosis in the EBV positive (EBV(+)) cells. Modulation of CHX-induced apoptosis in EBV(-) and (+) B cells is reported here using concurrent treatment with phorbol ester (phorbol 12, 13-dibutyrate, PdBu). Cells were collected at 0, 3, 6, 12, 24 and 48 hours after treatment with (i) 1 microgram/ml CHX, (ii) 0.1 microgram/ml PdBu (1 hour pretreatment before 0 h), or (iii) CHX + PdBu (CHX added at 0 h, 1 hour after PdBu). Control cultures were untreated. Apoptotic, necrotic or viable cells were quantified using histological, ultrastructural and biochemical parameters. Protein synthesis was assessed using 35S-methionine incorporation. Intracellular calcium concentrations were measured using flow cytometry. PdBu alone had little effect on cell death: High levels of CHX-induced apoptosis in EBV(-) cells were significantly reduced by concurrent addition of PdBu (P < 0.005). In contrast, low levels of CHX-induced apoptosis in EBV(+) cells were not significantly altered by PdBu treatment. In EBV(-) cells, a negative relationship was observed between levels of apoptosis and calcium concentrations, whereas in EBV(+) cells, there was negligible correlation between these parameters. Thus high levels of CHX-induced apoptosis in EBV(-) cells occur via a PKC-dependent pathway, whereas CHX treatment of EBV(+) cells induces comparatively low levels of apoptosis that occur via a PKC-independent mechanism. The results application in the therapeutic intervention for cancers developing in association with EBV infection.
Ishii
H
H
Department of Pathology, School of Medicine, Kitasato University, Sagamihara, Japan.
Tamauchi
H
H
Gobe
G C
GC
D017209:Apoptosis / Q000187:drug effects*; D002051:Burkitt Lymphoma / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D002118:Calcium / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000032:analysis; D004347:Drug Interactions; D004854:Herpesvirus 4, Human / Q000302:isolation & purification*; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D011500:Protein Synthesis Inhibitors; D015240:Phorbol 12,13-Dibutyrate; D003513:Cycloheximide; D002118:Calcium