2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im) directly targets mitochondrial glutathione to induce apoptosis in pancreatic cancer.
Surgical resection is the only curative strategy for pancreatic cancer (PC). Unfortunately, >80% of pancreatic cancer patients bear inoperable, locally advanced, chemoresistant tumors demonstrating the urgent need for development of novel therapeutic approaches to treat this disease. Here we report that the synthetic triterpenoid 2-cyano-3,12 dioxooleana-1,9 dien-28-imidazolide (CDDO-Im) antagonizes PC cell growth by inducing apoptosis at submicromolar concentrations. Notably, we demonstrate for the first time that the cytotoxicity of CDDO-Im is accompanied by the rapid and selective depletion of mitochondrial glutathione that results in accumulation of reactive oxygen species, oxidation of the cellular glutathione pool, loss of mitochondrial membrane potential, and phosphatidylserine externalization. The parent compound CDDO as well as the methyl ester of CDDO also depleted mitochondrial glutathione, demonstrating that this effect is mediated by the triterpenoid nucleus of these agents. Co-treatment with sulfhydryl nucleophiles completely prevented apoptosis and loss of viability induced by CDDO-Im, whereas alkylation of intracellular thiols by diethylmaleate or co-treatment with dithiothreitol decreased the accumulation of a biotinylated derivative of CDDO, TP-301, in PC cells, suggesting that intracellular reduced thiols are functional targets of the electrophilic triterpenoid nucleus of CDDO and its derivatives. In conclusion, our report is the first to identify mitochondrial glutathione as a target of CDDO and its derivatives and demonstrates that depletion of this antioxidant in the mitochondria is an effective strategy to induce cell death in PC cells. These results suggest that CDDO and its derivatives may offer a clinical benefit for the treatment of PC.
Samudio
Ismael
I
Section of Molecular Hematology and Therapy, Department of Blood and Marrow Transplantation, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Konopleva
Marina
M
Hail
Numsen
N
Shi
Yue-Xi
YX
McQueen
Teresa
T
Hsu
Timothy
T
Evans
Randall
R
Honda
Tadashi
T
Gribble
Gordon W
GW
Sporn
Michael
M
Gilbert
Hiram F
HF
Safe
Stephen
S
Andreeff
Michael
M
D000970:Antineoplastic Agents / Q000494:pharmacology; D000975:Antioxidants / Q000737:chemistry; D017209:Apoptosis; D001665:Binding Sites; D019921:Biotinylation; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D003593:Cytoplasm / Q000378:metabolism; D053938:DNA Fragmentation; D004789:Enzyme Activation; D005434:Flow Cytometry; D005978:Glutathione / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000494:pharmacology*; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D008956:Models, Chemical; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013997:Time Factors
C472829:1-(2-cyano-3,12-dioxooleana-1,9-dien-28-oyl) imidazole; D000970:Antineoplastic Agents; D000975:Antioxidants; D007093:Imidazoles; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D009828:Oleanolic Acid; D020169:Caspases; D005978:Glutathione