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.
Mony
U
U
Division of Haematology, University of Nottingham, Nottingham, UK.
Jawad
M
M
Seedhouse
C
C
Russell
N
N
Pallis
M
M
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