Peripheral benzodiazepine receptor (PBR) ligand cytotoxicity unrelated to PBR expression.
Some synthetic ligands of the peripheral-type benzodiazepine receptor (PBR), an 18 kDa protein of the outer mitochondrial membrane, are cytotoxic for several tumor cell lines and arise as promising chemotherapeutic candidates. However, conflicting results were reported regarding the actual effect of these drugs on cellular survival ranging from protection to toxicity. Moreover, the concentrations needed to observe such a toxicity were usually high, far above the affinity range for their receptor, hence questioning its specificity. In the present study, we have shown that micromolar concentrations of FGIN-1-27 and Ro 5-4864, two chemically unrelated PBR ligands are toxic for both PBR-expressing SK-N-BE neuroblastoma cells and PBR-deficient Jurkat lymphoma cells. We have thereby demonstrated that the cytotoxicity of these drugs is unrelated to their PBR-binding activity. Moreover, Ro 5-4864-induced cell death differed strikingly between both cell types, being apoptotic in Jurkat cells while necrotic in SK-N-BE cells. Again, this did not seem to be related to PBR expression since Ro 5-4864-induced death of PBR-transfected Jurkat cells remained apoptotic. Taken together, our results show that PBR is unlikely to mediate all the effects of these PBR ligands. They however confirm that some of these ligands are very effective cytotoxic drugs towards various cancer cells, even for reputed chemoresistant tumors such as neuroblastoma, and, surprisingly, also for PBR-lacking tumor cells.
Hans
Gregory
G
Centre of Cellular and Molecular Neurobiology, Université de Liège, 17 Place Delcour, 4020 Liège 2, Belgium. G.hans@teledisnet.be
Wislet-Gendebien
Sabine
S
Lallemend
François
F
Robe
Pierre
P
Rogister
Bernard
B
Belachew
Shibeshih
S
Nguyen
Laurent
L
Malgrange
Brigitte
B
Moonen
Gustave
G
Rigo
Jean-Michel
JM
D017209:Apoptosis / Q000187:drug effects; D001570:Benzodiazepinones / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D007210:Indoleacetic Acids / Q000494:pharmacology*; D019169:Jurkat Cells; D008024:Ligands; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D009336:Necrosis; D009447:Neuroblastoma / Q000473:pathology; D009842:Oligopeptides / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000502:physiology*
D001570:Benzodiazepinones; D007210:Indoleacetic Acids; D008024:Ligands; D009842:Oligopeptides; D011963:Receptors, GABA-A; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; C081306:N,N-di-n-hexyl-2-(4-fluorophenyl)indole-3-acetamide; C028513:4'-chlorodiazepam