Theophylline synergizes with chlorambucil in inducing apoptosis of B-chronic lymphocytic leukemia cells.
We tested the effects of theophylline, a phosphodiesterase inhibitor inducing intracellular accumulation of cyclic adenosine monophosphate (cAMP), on malignant B cells from 15 patients with B-chronic lymphocytic leukemia (B-CLL). We observed a large increase in apoptotic cell numbers (mean, 90% v 20% in medium alone) in the presence of theophylline (100 micrograms/mL) or chlorambucil (10 mumol/L) after 72 hours of incubation. Maximal apoptosis (90%) was reached after 36 hours when the two drugs were used together at fourfold lower concentrations, indicating a synergistic effect; no effect was observed with normal B cells, suggesting that the combination might have therapeutic interest. Chlorambucil induced intracellular Ca+2 influx, pointing to the involvement of two signaling pathways that might explain its synergy with theophylline through their effects on oncogenes. The expression of bcl-2 protein, a proto-oncogene inhibiting apoptosis, decreased after incubation with the drugs, while c-myc, recently described as having a potent role in apoptosis, was overexpressed. For p53 we observed an overexpression in the presence of chlorambucil or both theophylline-chlorambucil and a decrease after theophylline incubation. Chlorambucil- and theophylline-induced apoptosis was partially inhibited by interleukin-4 (IL-4), which also abrogated the effects on oncogene expression. These results provide insight into the mechanisms underlying B-CLL apoptosis and suggest that the theophylline-chlorambucil combination may be of therapeutic value in this setting.
Mentz
F
F
Department of Hematology, Unité Claude-Bernard C20, Pitie-Salpetriere Hospital, Paris, France.
Mossalayi
M D
MD
Ouaaz
F
F
Baudet
S
S
Issaly
F
F
Ktorza
S
S
Semichon
M
M
Binet
J L
JL
Merle-Beral
H
H
D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002699:Chlorambucil / Q000008:administration & dosage*; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D016259:Genes, myc; D016158:Genes, p53; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D015290:Second Messenger Systems; D013806:Theophylline / Q000008:administration & dosage*; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D002699:Chlorambucil; D013806:Theophylline; D000242:Cyclic AMP; D002118:Calcium