Polyamines increase in human peripheral blood and bone marrow mononuclear cells following administration of...

Eight patients who had refractory leukemia and 1 patient with refractory multiple myeloma were treated with the polyamine biosynthesis inhibitors methylgloxal bis(guanylhydrazone) (MGBG) and difluoromethylornithine (DFMO). After the first dose of MGBG there was an increase in polyamine content in the mononuclear cells of both the peripheral blood and the bone marrow despite the administration of DFMO in all patients with leukemia. Putrescine levels increased in the mononuclear cells of all patients, cellular spermidine levels increased in 4 and cellular spermine levels increased in 5 patients. The cellular polyamine levels remained elevated above the pretreatment levels for up to 1 week in some patients. Subsequent treatment with MGBG, administered after 1-2 weeks of DFMO treatment, also promoted increases in mononuclear cell polyamine concentrations. Since enhanced tumor cell uptake of MGBG after DFMO priming is hypothesized to be dependent on a decrease in cellular polyamine levels, the increase in cellular polyamines after MGBG has important implications for the scheduling of this drug combination. From these observations, withholding MGBG until DFMO treatment has produced a decrease in tumor cell polyamine concentrations would be the schedule most likely to enhance the uptake of MGBG.