Page 196 - Haematologica March 2020

H. Kuusanmäki et al.
whereas in FAB M4/5 subtypes the differentiation block- ade is “leaky”. In addition to immature blasts in FAB M4/5 samples, leukemic cells often show myelomonocytic or monocytic differentiation, respectively. To achieve opti- mal response in patients, the drugs should target the less
differentiated leukemic blasts.9 However, due to cellular heterogeneity, blast-specific drug responses are challeng- ing to measure with conventional cell viability assays such as CellTiter-Glo (CTG) or tetrazolium reduction assays (MTT/MTS).10 Although enrichment of blasts is possible,
ABC
DE
F
H
G
Figure 2. Comparison of flow cytometry (FC) and CellTiter-Glo (CTG) based drug screening approaches. (A) Spearman’s correlation between CTG and FC-based cell viability assays with CD45+ leukocytes as the FC readout, or (B) blasts in samples with clinical blast count >50%, or (C) blasts in samples with clinical blast count <50% as the FC readout. (D) Representative FC scatter plots of drug effects on different cell populations in acute myeloid leukemia (AML) sample 18 with low blast count (20%). Absolute cell counts inside the gates were calculated after 72h drug treatment and normalized to the cell counts in the DMSO-treated wells (represent- ed as percentages). (E) Venetoclax dose response curves of different cell populations present in acute monocytic leukemia (FAB M5) sample 18 assessed by FC and overall BM sensitivity with the CTG-based cell viability assay. (F) Representative FC scatter plots of drug effects on patient sample 5806 with FAB M5. (G) Dose response curves of different cell populations after MEK inhibitor trametinib treatment calculated with FC or overall sensitivity calculated with CTG. (H) Comparison of the drug sensitivity score (DSS) values for idarubicin, cytarabine and idarubicin+cytarabine combination in blasts between induction treatment resistant and sen- sitive patient samples using FC. (I) DSS measured with CTG from the same cohort. P-values calculated with Mann-Whitney U test.
710
haematologica | 2020; 105(3)
I