CD34 and acute myeloid leukemia: To investigate if the observed synergy of biguanides with ABT-737 could also be observed with primary leukemic cells, we exposed 2 primary acute myelogenous leukemia samples to increasing concentrations of Metformin, ABT-737, or the combination of these two agents using a fixed dosing schedule for 24 h, and analyzed viable CD34(+) cells by flow cytometry.