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.