Calphostin C synergistically induces apoptosis with VP-16 in lymphoma cells which express abundant phosphorylated Bcl-2 protein.
A newly established human lymphoma cell line (OZ) has the t(14;18)(q32;q21) translocation and expresses large amounts of Bcl-2 compared to CCRF-CEM cells. VP-16 (40 micrograms/mL), a promising agent against lymphoma, caused DNA fragmentation (26.9% of total DNA) typical for apoptosis at 6 h in CCRF-CEM cells, but no significant changes in OZ cells until 24 h after the addition of VP-16. However, coincubation with calphostin C (0.2 microgram/mL), a protein kinase C (PKC) inhibitor, induced DNA fragmentation in VP-16-treated OZ cells (13.5% of total DNA) at 6 h after the treatment. Simultaneous immunoblot analysis revealed that this induction of apoptosis coincided with the downregulation of serine-phosphorylated Bcl-2 (13% of control cells). By contrast, apoptosis induced by VP-16 in CCRF-CEM cells was attenuated by the addition of 0.5 microM phorbol 12-myristate 13-acetate, a potent PKC stimulator. These observations suggest that Bcl-2 function is partly regulated by phosphorylation/ dephosphorylation mechanisms of the PKC system, and that phosphorylated Bcl-2 in lymphoma cells may play a role in the prevention of apoptosis.
Murata
M
M
First Department of Internal Medicine, Kagawa Medical University, Japan.
Nagai
M
M
Fujita
M
M
Ohmori
M
M
Takahara
J
J
D017209:Apoptosis / Q000187:drug effects*; D002883:Chromosomes, Human, Pair 14; D002887:Chromosomes, Human, Pair 18; D053938:DNA Fragmentation; D004357:Drug Synergism; D005047:Etoposide / Q000008:administration & dosage*; D006801:Humans; D008223:Lymphoma / Q000188:drug therapy / Q000473:pathology*; D009281:Naphthalenes / Q000008:administration & dosage*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014178:Translocation, Genetic; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D009281:Naphthalenes; D010750:Phosphoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D005047:Etoposide; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate