PMC:3940921 / 7278-9390 JSONTXT

{"project":"2_test","denotations":[{"id":"24590311-17591945-79065516","span":{"begin":2110,"end":2112},"obj":"17591945"}],"text":"Antiproliferative and apoptotic effects of carfilzomib in models of imatinib-sensitive and -resistant CML\nCML cell lines were treated either continuously or pulsed for 1 h with increasing concentrations of carfilzomib (1–1000 nM) for up to 72 h. A time- and dose-dependent decrease in viability was observed in all cell lines with an IC50 of \u003c15 nM at 24 h cultured continuously in the presence of carfilzomib (Figure 2a). To mimic the in vivo pharmacokinetics of carfilzomib, cell lines were pulsed for 1 h with the same concentrations of carfilzomib, followed by growth in drug-free medium for up to 72 h. This treatment also induced a time- and dose-dependent decrease in viability, although higher concentrations were required to achieve IC50 (20–79 nM, 24 h) (Figure 2b). Under both conditions, imatinib-resistant cell lines displayed equal or greater sensitivity to carfilzomib as their imatinib-sensitive counterparts.\nCD34+38− cells were enriched from three CML patient samples and normal bone marrow (NBM). As numbers of this enriched cell population are small, cells were exposed to a median dose of 50 nM carfilzomib for 1 h before being transferred to drug-free medium. After 24 h, the viability of CML CD34+38− cells was reduced by 39±1 % compared with 19±2 % in NBM (P=0.02; Figure 2c). To assess the effect of carfilzomib on longer-term stem cell proliferation, CD34+ cells were enriched from CML (n=3) and NBM samples (n=2), pulsed for 1 h with 50 nM carfilzomib and transferred to LTC-IC assays. Colony formation was reduced by 58±11% in CML stem cells compared with 44±7% in normal stem cells (P=0.04; Figure 2d).\nThe effect of 1-h exposure to carfilzomib on the induction of apoptosis in CML cell lines and primary samples was investigated. Pulse treatment with carfilzomib at IC50 doses induced an increase in caspase-3 activity along with an associated increase in the number of sub G0/G1 events, indicative of apoptosis (Supplementary Figure 2). Further analysis demonstrated induction of apoptosis through both the caspase-8 and -9 pathways, consistent with previous reports (Figure 2e).25"}