Similarity of apoptosis induction by 2-chlorodeoxyadenosine and cisplatin in human mononuclear blood cells

The purine analogue 2-chlorodeoxyadenosine (CdA) is unique compared with traditional antimetabolite drugs, as it has shown equal activity in dividing and resting lymphocytes. Poly(ADP-ribose)polymerase (PARP) activation and consecutive NAD+ consumption have been associated with the induction of apoptosis in resting cells. The potential of CdA to induce the p53-dependent DNA damage response was assessed in resting and phytohaemagglutinine (PHA)-activated peripheral blood mononuclear cells (PBMCs) and compared with cisplatin (DDP), a cell cycle-dependent and DNA-damaging agent that is mainly used in the treatment of solid tumours. Both drugs induced transactivation of the p53 target genes waf1 and mdm2, NAD+ consumption and apoptotic death. The expression pattern of p53 and waf1 suggests a partly p53-independent induction of waf1. The expression of c-myc and PARP, which both have a dual role in proliferation and apoptosis, was selectively induced by CdA. Cell cycle stimulation increased the cytotoxic activity of both drugs. These data show that DDP is also a potent inducer of apoptosis in resting and proliferating peripheral blood mononuclear cells. Activation of the p53-dependent DNA damage response seems to be an important component of the toxic effect of CdA.