Resistance to FLT3 inhibition in an in vitro model of primary AML cells with a stem cell phenotype in a defined microenvironment.
Relapse in acute myeloid leukaemia (AML) is mediated by survival of leukaemic stem cells following remission-induction chemotherapy. It would therefore be useful to identify therapeutic agents that target leukaemic stem cells. We devised a flow cytometric chemosensitivity assay allowing 48 h culture of leukaemic blasts in a defined microenvironment followed by enumeration of viable CD34+CD38-CD123+ leukaemic stem and progenitor cells (LSPC). The assay was used to investigate the LSPC response to cytosine arabinoside (Ara-C) and to the FLT3 inhibitor AG1296. There was a 3.6-fold increase in Ara-C-treated LSPC survival under defined 'niche-like' conditions compared to culture without microenvironmental support. Nine AML samples with internal tandem duplications of FLT3 (FLT3/ITDs) were treated with AG1296. Three samples were very sensitive (>50% kill) and 4 were moderately sensitive (10-50% kill) in bulk suspension culture without microenvironmental support. However, under defined 'niche-like' conditions, the survival of LSPC was enhanced rather than inhibited by AG1296 treatment. We conclude that an interaction between LSPC and a defined in vitro microenvironment models a chemoresistant niche. Our data point to a need to investigate more novel chemotherapeutic agents under these stringent conditions to identify agents that may be suitable to target minimal residual disease in AML.
Division of Haematology, University of Nottingham, Nottingham, UK.
U
U
Mony
M
M
Jawad
C
C
Seedhouse
N
N
Russell
M
M
Pallis
D051997:ADP-ribosyl Cyclase 1 / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D006801:Humans; D053650:Interleukin-3 Receptor alpha Subunit / Q000032:analysis; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000032:analysis; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D010641:Phenotype; D016185:Receptors, Interleukin-3 / Q000032:analysis; D020032:Tyrphostins / Q000494:pharmacology*; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors* / Q000235:genetics
D018952:Antigens, CD34; C115022:IL3RA protein, human; D053650:Interleukin-3 Receptor alpha Subunit; D008562:Membrane Glycoproteins; D016185:Receptors, Interleukin-3; D020032:Tyrphostins; D003561:Cytarabine; C106250:6,7-dimethoxy-3-phenylquinoxaline; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1