2-Chlorodeoxyadenosine Chemotherapy Triggers Programmed Cell Death in Normal and Malignant Lymphocytes

Abstract

2-Chloro-2′-deoxyadenosine (CdA) is a congener of deoxyadenosine that is resistant to adenosine deaminase. Rationale for the development of CdA as an immunosuppressive and antineoplastic agent derives from the lymphocytotoxicity of elevated plasma deoxyadenosine in congenital deficiency of adenosine deaminase¹. Recent clinical trials have documented promising efficacy of CdA in the treatment of chronic B-cell and T-cell lymphoid malignancies, notably chronic lymphocytic leukemia (CLL) and hairy cell leukemia^2,3. Among nucleoside antimetabolites, CdA is uniquely toxic to non-dividing lymphocytes, as well as to most proliferating T-lymphoblasts⁴. Surprisingly, mature blood monocytes are also lysed by CdA at the nanomolar concentrations readily achieved by continuous infusion in vivo⁵. In both non-dividing lymphocytes and monocytes, CdA causes the prompt accumulation of DNA strand breaks, with subsequent NAD depletion, inhibition of RNA synthesis, and eventual cell lysis^5,6.