The mitochondrial effects of small organic ligands of BCL-2: sensitization of BCL-2-overexpressing cells to apoptosis by a pyrimidine-2,4,6-trione derivative.
We have investigated the mitochondrial effects of BH3I-2', Chelerythrine, and HA14-1, small organic molecules that share the ability to bind the BH3 domain of BCL-2. All compounds displayed a biphasic effect on mitochondrial respiration with uncoupling at low concentrations and respiratory inhibition at higher concentrations, the relative uncoupling potency being BH3I-2' (half-maximal uncoupling at about 80 nm) > Chelerythrine (half-maximal uncoupling at about 2 microm) > HA14-1 (half-maximal uncoupling at about 20 microm). At concentrations lower than required for uncoupling all compounds sensitized the permeability transition pore (PTP) to opening both in isolated mitochondria and intact cells. To assess whether the effects on BCL-2 binding, PTP induction and respiration could be due to different structural determinants we have tested a set of HA14-1 analogs from the Hoffmann-La Roche chemical library. We have identified 5-(6-chloro-2,4-dioxo-1,3,4,10-tetrahydro-2H-9-oxa-1,3-diaza-anthracen-10-yl)-pyrimidine-2,4,6-trione (EM20-25) as a molecule devoid of effects on respiration that is able to induce PTP opening, to disrupt the BCL-2/BAX interactions in situ and to activate caspase-9 in BCL-2-overexpressing cells. EM20-25 neutralized the antiapoptotic activity of overexpressed BCL-2 toward staurosporine and sensitized BCL-2-expressing cells from leukemic patients to the killing effects of staurosporine, chlorambucil, and fludarabine. These results provide a proof of principle that the potentially toxic effects of BCL-2 ligands on mitochondrial respiration are not essential for their antiapoptotic activity and represent an important step forward in the development of tumor-selective drugs acting on BCL-2.
Department of Biomedical Sciences and Consiglio Nazionale delle Ricerche Institute of Neurosciences, University of Padova, Viale Giuseppe Colombo 3, I-35121 Padua, Italy.
Eva
E
Milanesi
Paola
P
Costantini
Alberto
A
Gambalunga
Raffaele
R
Colonna
Valeria
V
Petronilli
Anna
A
Cabrelle
Gianpietro
G
Semenzato
Andrea M
AM
Cesura
Emmanuel
E
Pinard
Paolo
P
Bernardi
D000470:Alkaloids; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001463:Barbiturates / Q000737:chemistry / Q000494:pharmacology*; D053119:Benzophenanthridines; D001578:Benzopyrans / Q000737:chemistry / Q000494:pharmacology*; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D002699:Chlorambucil / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D010617:Phenanthridines / Q000737:chemistry; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000378:metabolism; D011743:Pyrimidines / Q000737:chemistry; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D019311:Staurosporine / Q000494:pharmacology; D013997:Time Factors; D014740:Vidarabine / Q000031:analogs & derivatives / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
C510606:5-(6-chloro-2,4-dioxo-1,3,4,10-tetrahydro-2H-9-oxa-1,3-diazaanthracen-10-yl)pyrimidine-2,4,6-trione; D000470:Alkaloids; D000970:Antineoplastic Agents; D001463:Barbiturates; D053119:Benzophenanthridines; D001578:Benzopyrans; D008024:Ligands; D010617:Phenanthridines; D019253:Proto-Oncogene Proteins c-bcl-2; D011743:Pyrimidines; D034741:RNA, Small Interfering; D051028:bcl-2-Associated X Protein; D002699:Chlorambucil; C016299:chelerythrine; C506433:CASP9 protein, human; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases; D014740:Vidarabine; D019311:Staurosporine; C030986:pyrimidine; C024352:fludarabine