Halogenation of N⁶-benzyladenosine decreases its cytotoxicity in human leukemia cells.

Cytotoxicity of two halogen derivatives of N⁶-benzyladenosine (BAPR), N⁶-(3-iodobenzyl)-adenosine (I-BAPR) and 2-chloro-N⁶-(3-iodobenzyl)-adenosine (Cl-I-BAPR), was tested in human leukemia U937 cell line. Our results revealed that their cytotoxicity was surprisingly low. I-BAPR and also Cl-I-BAPR induced cell death with morphological and biochemical hallmarks of apoptosis, although the number of apoptotic cells was significantly lower than that found for BAPR. Our data strongly suggested that the decreased cytotoxic effect of halogenated derivatives of N⁶-benzyladenosine was related to their reduced intracellular phosphorylation by adenosine kinase.