The leukemic cells of a patient with hairy cell leukemia were treated in vi
tro with 2'-deoxycoformycin (dCF), an inhibitor of adenosine deaminase, and
deoxyadenosine (dAdo). Following this treatment, viability of the hairy ce
lls progressively declined, and DNA fragmentation was observed. When the pa
tient was treated with 4 mg/m(2) dCF intravenously, hairy cells in his peri
pheral blood rapidly decreased, and a large number of TUNEL (terminal deoxy
nucleotidyl transferase-mediated dUTP- biotin nick end-labeling)-positive c
ells mere detected in a bone marrow biopsy specimen. These findings indicat
e that dCF induced apoptosis of hairy cells both in vivo and in vitro. Furt
hermore, bcl-2 mRNA was down-regulated by dCF and dAdo in the hairy cells i
n vitro. Our results suggest the importance of bcl-2 mRNA regulation in apo
ptotic cell death mediated by dCF in hairy cell leukemia.