C6-NBD-SM fluorescence of leukemic blasts following 18-hour culture.
(A) Blasts from pgp−ve patient LC incubated overnight with C6-NBD-SM demonstrate intense fluorescence on the subset of cells defined by region 5 (R5). Backgating of the (B) R4 and (C) R5 subsets demonstrated that R5 C6-NBD-SM high cells were the smaller cells with higher side scatter, typical flow cytometric features of apoptosis.35 The figure is a representative plot of a consistent finding. (D) Histogram of the same sample incubated without (filled plot) and with (unfilled plot) 1 μmol/L PSC-833, which demonstrates an increase in C6-NBD-SM high cells. (E, F) C6-NBD-SM–loaded blasts from pgp+ve patients (E) GO and (F) RF demonstrate a fluorescence shift in the entire population as well as in the fluorescence-high subset when untreated samples (filled plots) are compared to samples treated with PSC-833 (unfilled plot, thick line). (F) The lowering effect of UIC2 (unfilled plot, dotted line) on C6-NBD-SM fluorescence is also shown.
