3-Deazaadenosine (DZA), one of the potent inhibitors of S-adenosylhomocysteine hydrolase, is known to possess several biological properties including an induction of apoptosis. To evaluate a possibility that DZA may be utilized for the treatment of human leukemia, we studied molecular events of cell death induced by DZA in human leukemia HL-60 and U-937 cells. DZA induced a specific cleavage of poly ADP-ribose polymerase (PARP) and an activation of the cysteine protease caspase-3/CPP32 which is known to cleave PARP. DZA-mediated nuclear DNA-fragmentation was completely blocked in the presence of a universal inhibitor of caspases (z-VAD-fmk) or the specific inhibitor of caspase-3 (z-DEVD-fmk) unlike of cycloheximide (CHX). DNA fragmentation was preceded by the lowering of c-myc mRNA in the DZA treated cells. In addition, DZA-induced apoptosis was blocked by pretreatment with adenosine transporter inhibitors such as nitrobenzylthioinosine (NBTI) and dipyridamole (DPD). Taken together, these results demonstrate that DZA-induced apoptosis initiated through an active transport of DZA into human leukemia cells, is dependent on the caspase-3-like activity without de novo synthesis of proteins and possibly involves c-myc down-regulation.
Adenosine/metabolism ; *Apoptosis ; Biological Transport, Active ; Carrier Proteins/metabolism ; Caspases/*metabolism ; Down-Regulation ; Enzyme Activation ; Genes, myc ; HL-60 Cells ; Human ; Leukemia, Promyelocytic, Acute/*drug therapy ; Thioinosine/*analogs & derivatives/pharmacology ; Transcription Factors/genetics ; Tubercidin/*pharmacology ; U937 Cells

delta12-Prostaglandin (PG) J2 is known to elicit an anti-neoplastic effects via apoptosis induction. Previous study showed delta12-PGJ2-induced apoptosis utilized caspase cascade through cytochrome c-dependent pathways in HeLa cells. In this study, the cellular mechanism of delta12-PGJ2- induced apoptosis in HeLa cells, specifically, the role of two mitochondrial factors; bcl-2 and apoptosis-inducing factor (AIF) was investigated. Bcl-2 attenuated delta12-PGJ2-induced caspase activation, loss of mitochondrial transmembrane potential (delta psi m), nuclear fragmentation, DNA laddering, and growth curve inhibition for approximately 24 h, but not for longer time. AIF was not released from mitochondria, even if the delta psi m was dissipated. One of the earliest events observed in delta12-PGJ2-induced apoptotic events was dissipation of delta psi m, the process known to be inhibited by bcl-2. Pre-treatment of z-VAD- fmk, the pan-caspase inhibitor, resulted in the attenuation of delta psi m depolarization in delta12-PGJ2- induced apoptosis. Up-regulation of Sox-4 protein by delta12-PGJ2 was observed in HeLa and bcl-2 overexpressing HeLa B4 cell lines. Bcl-2 overexpression did not attenuate the expression of Sox-4 and its expression coincided with other apoptotic events. These results suggest that delta12-PGJ2 induced Sox-4 expression may activate another upstream caspases excluding the caspase 9-caspase 3 cascade of mitochondrial pathway. These and previous findings together suggest that delta12-PGJ2-induced apoptosis in HeLa cells is caspase-dependent, AIF-independent events which may be affected by Sox-4 protein expression up-regulated by delta12-PGJ2.
Amino Acid Chloromethyl Ketones/pharmacology ; Antineoplastic Agents/*pharmacology ; Apoptosis/drug effects/*physiology ; Caspases/physiology ; Cytochromes c/physiology ; Female ; Flavoproteins/metabolism/*physiology ; Hela Cells ; High Mobility Group Proteins/*physiology ; Humans ; Membrane Proteins/metabolism/*physiology ; Mitochondria/metabolism/physiology ; Prostaglandin D2/*pharmacology ; Protein Transport/physiology ; Proto-Oncogene Proteins c-bcl-2/biosynthesis/*physiology ; Research Support, Non-U.S. Gov't ; Trans-Activation (Genetics) ; Trans-Activators/*physiology