KRN5500 induces apoptosis (PCD) of myeloid leukemia cell lines and patientblasts

The purpose of this study was to determine if KRN5500, a spicamycin derivat ive with a unique acyl tail, would induce programmed cell death (PCD) of my eloid leukemia cell lines and cryopreserved leukemic blasts from newly diag nosed children with acute leukemia (AL). Cells were incubated with varying concentrations (0-5 ng/ml) of KRN5500 and the percent PCD determined using a modified in situ end labeling (ISEL) technique with Klenow fragment. The percent PCD was calculated using the formula: Percent PCD (% PCD)= [number of apoptotic cells/(viable cells + apoptotic cells)] x 100. DMSO (0.30% w/v ) was added to the cells in culture as the positive control for PCD; the ne gative control was media or albumin. KRN5500 increased the amount of PCD si gnificantly in all five of the tested cell lines; U937 41 +/- 1.8%, KGla 40 +/- 0.3%, HEL 14 +/- 2.2.%, HL-60 41 +/- 0.9%, K562 36 +/- 2% (mean PCD +/ - SD). Patient blasts exposed to KRN5500 had an increase in PCD when expose d to 2 ng/ml of agent from 2 to 8 h; acute myeloid leukemia patients 7.5 +/ - 0.5% at 2 h to 43.5 +/- 1.6% at 8 h, and acute lymphocytic leukemia patie nts rose from 12.4 +/- 3.8% at 2 h to 29.9 +/- 11.6% after 8 h (mean +/- SE ). Overall the PCD for the patient samples was 3.7 versus 28 +/- 4% at 2 an d 8 h, respectively. PCD was proportional to the dose of KRN5500 and incuba tion time. Further pre-clinical and clinical studies are required. (C) 2000 Elsevier Science Ltd. All rights reserved.