p53-Independent induction of Fas and apoptosis in leukemic cells by an adenosine derivative, Cl-IB-MECA

Abstract

A 3 adenosine receptor (A 3 AR) agonists have been reported to influence cell death and survival. The effects of an A 3 AR agonist, 1- [2-chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-1-deoxy-N-methyl-β-D-ribofuranonamide (Cl-IB-MECA), on apoptosis in two human leukemia cell lines, HL-60 and MOLT-4, were investigated. Cl-IB-MECA (≥30 μM) increased the apoptotic fractions, as determined using fluorescence-activated cell sorting (FACS) analysis, and activated caspase 3 and poly-ADP-ribose-polymerase. Known messengers coupled to A 3 AR (phospholipase C and intracellular calcium) did not seem to play a role in the induction of apoptosis. Neither dantrolene nor BAPTA-AM affected the Cl-IB-MECA-induced apoptosis. Cl-IB-MECA failed to activate phospholipase C in HL-60 cells, while UTP activated it through endogenous P2Y 2 receptors. Induction of apoptosis during a 48 hr exposure to Cl-IB-MECA was not prevented by the A 3 AR antagonists [5-propyl-2-ethyl-4-propyl-3-(ethylsulfanylcarbonyl)-6-phenylpyridine-5-carboxylate] (MRS 1220) or N- [9-chloro-2-(2-furanyl) [l,2,4]triazolo [l,5-c]quinazolin-5-yl]benzeneacetamide (MRS 1523). Furthermore, higher concentrations of MRS 1220, which would also antagonize A 1 and A 2A receptors, were ineffective in preventing the apoptosis. Although Cl-IB-MECA has been shown in other systems to cause apoptosis through an A 3 ARmediated mechanism, in these cells it appeared to be an adenosine receptor-independent effect, which required prolonged incubation. In both HL-60 and MOLT-4 cells, Cl-IB-MECA induced the expression of Fas, a death receptor. This induction of Fas was not dependent upon p53, because p53 is not expressed in an active form in either HL-60 or MOLT-4 cells. Cl-IB-MECAinduced apoptosis in HL-60 cells was augmented by an agonistic Fas antibody, CH-11, and this increase was suppressed by the antagonistic anti-Fas antibody ZB-4. Therefore, Cl-IB-MECA induced apoptosis via a novel, p53-independent up-regulation of Fas. Published by Elsevier Science Inc.

Induction of Apoptosis by the Adenosine Derivative IB-MECA in Parental or Multidrug-Resistant HL-60 Leukemia Cells: Possible Relationship to the Effects on Inhibitor of Apoptosis Protein Levels

“…Previous studies have demonstrated that activation of A 3 AR by the compound can exert signifi cant inhibitory effects on the in vitro and in vivo growth of different tumor cell types [11,19,20] . In addition, the presence of functional A 3 AR in HL-60 cells has been reported [15][16][17] , and, in the present study, comparable amounts of A 3 AR mRNA were found in HL-60 and HL-60R cells.…”

“…The occurrence of A 3 AR in HL-60 cells has previously been reported [15][16][17] . We compared the expression of A 3 AR mRNA in HL-60 and HL-60R cells by RT-PCR.…”

A3 Adenosine Receptor Activation in Melanoma Cells

“…Earlier studies demonstrated that A3AR agonists such as IB-MECA or Cl-IB-MECA, at micromolar concentrations, induced apoptosis in different cell types. In some of the studies, the activity was found to be A3AR-mediated, whereas in others, A3AR antagonists did not counteract the effect, demonstrating that the apoptosis was not A3AR-mediated (27,28). In distinction from these studies, in the present work, IB-MECA was used at nanomolar concentrations, and its activity was counteracted by the antagonist MRS 1523, demonstrating that the response was A3AR-dependent.…”

A3Adenosine Receptors in Human Astrocytoma Cells: Agonist-Mediated Desensitization, Internalization, and Down-Regulation

“…We now speculate that desensitization/down-regulation of the A 3 AR under such agonist exposure conditions is indeed at the basis of cytoprotection. This implies a causative role for this receptor subtype in induction of cell death, as nevertheless suggested by data obtained in different experimental models (Shneyvais et al, 1998;Appel et al, 2001;Kim et al, 2002).…”