CELL-CYCLE KINETIC-STUDIES IN 68 PATIENTS WITH MYELODYSPLASTIC SYNDROMES FOLLOWING INTRAVENOUS IODODEOXYURIDINE AND OR BROMODEOXYURIDINE/

Sixty-eight patients with myelodysplastic syndromes (MDS) received seq uential infusions of iodo- and/or bromodeoxyuridine for tell kinetic a nalysis. Bone marrow biopsy sections were treated by appropriate antib odies and a labeling index (LI), duration of S-phase (Ts), and total c ell cycle time (Tc) of myeloid cells were determined. The mean LI was 28.4%, Ts was 11.8 hours and Tc was 40.7 hours. The %LI decreased as t he disease evolved from refractory anemia toward transformation to acu te leukemia (p = 0.04). Double-labeling of biopsy sections for apoptos is and proliferation showed that 30-90% of S-phase cells in MDS patien ts were simultaneously apoptotic or ''antonymous.'' We conclude that M DS are highly proliferative disorders in which the ineffective hematop oiesis is probably the result of excessive apoptosis rather than slow proliferation.