Publication Date:
2009-11-20
Description:
Abstract 2759 Poster Board II-735 A subpopulation of cells with characteristics of cancer stem cells can be identified by the side population (SP) phenotype that is based on the efflux of the fluorescent dye Hoechst 33342 and detected by flow cytometric analysis. We previously reported the identification of SP cells in 4 human myeloma cell lines (HMCL) and 18 of 21 bone marrow samples from patients with myeloma in which the percentage of SP cells ranged from 0 to 4.9% (median=0.3; mean=0.8; SD=1.2). We now report the mechanism underlying the Hoechst 33342 efflux in SP cells, which may be a contributor to the drug resistance in myeloma cancer stem cells (MCSC). SP and main population (MP) subsets of HMCL (KMS-11 and RPMI-8226), based on Hoechst-33342 staining, were analyzed or sorted by BD FACSAria™ II using a blue and red dual-wavelength analysis after UV excitation. In this study, we examined the activities of three main drug transporter classes associated to SP phenotype – ABCB1 (MDR1), ABCG2 (BCRP1) and ABCC (MRP). Inhibition of the SP phenotype using PSC833, Ko143, and sulfinpyrazone (ABCB1, ABCG2, and ABCC inhibitors respectively) were first tested. Only the Ko143 and sulfinpyrazone were able to inhibit the entire SP phenotype in HMCL. Next, the activity of each transporter in unfractionated, sorted-SP and sorted-MP cells was examined. Relative cellular accumulation of fluorescent substrate for each transporter, namely rhodamine123 1 μg/mL, mitoxantrone 20 μM, and fluo-3 am 1 μg/mL, was determined. Experiments were conducted in the presence or absence of specific inhibitors. There were significant increases of mitoxantrone (P=0.0033** and P=0.0262*) and fluo-3 am (P=0.0006*** and P=0.0152*) in unfractionated RPMI-8226 and KMS-11 in the presence of Ko143 and sulfinpyrazone respectively. In the presence of sulfinpyrazone, benzbromarone, or dipyridamole (ABCC inhibitors), there was a significant increase of fluo-3 am in both SP and MP cells (P
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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