Molecular and functional analysis of the stem cell compartment of chronic myelogenous leukemia reveals the presence of a CD34- cell population with intrinsic resistance to imatinib.
We show the molecular and functional characterization of a novel population of lineage-negative CD34-negative (Lin(-)CD34(-)) hematopoietic stem cells from chronic myelogenous leukemia (CML) patients at diagnosis. Molecular karyotyping and quantitative analysis of BCR-ABL transcript demonstrated that approximately one-third of CD34(-) cells are leukemic. CML Lin(-)CD34(-) cells showed kinetic quiescence and limited clonogenic capacity. However, stroma-dependent cultures induced CD34 expression on some cells and cell cycling, and increased clonogenic activity and expression of BCR-ABL transcript. Lin(-)CD34(-) cells showed hematopoietic cell engraftment rate in 2 immunodeficient mouse strains similar to Lin-CD34(+) cells, whereas endothelial cell engraftment was significantly higher. Gene expression profiling revealed the down-regulation of cell-cycle arrest genes and genes involved in antigen presentation and processing, while the expression of genes related to tumor progression, such as angiogenic factors, was strongly up-regulated compared with normal counterparts. Phenotypic analysis confirmed the significant down-regulation of HLA class I and II molecules in CML Lin(-)CD34(-) cells. Imatinib mesylate did not reduce fusion transcript levels, BCR-ABL kinase activity, and clonogenic efficiency of CML Lin(-)CD34(-) cells in vitro. Moreover, leukemic CD34(-) cells survived exposure to BCR-ABL inhibitors in vivo. Thus, we identified a novel CD34(-) leukemic stem cell subset in CML with peculiar molecular and functional characteristics.
Institute of Hematology and Medical Oncology L & A Seràgnoli, University of Bologna, Bologna, Italy. roberto.lemoli@unibo.it
Roberto M
RM
Lemoli
Valentina
V
Salvestrini
Elisa
E
Bianchi
Francesco
F
Bertolini
Miriam
M
Fogli
Marilina
M
Amabile
Agostino
A
Tafuri
Simona
S
Salati
Roberta
R
Zini
Nicoletta
N
Testoni
Cristina
C
Rabascio
Lara
L
Rossi
Ines
I
Martin-Padura
Fausto
F
Castagnetti
Paola
P
Marighetti
Giovanni
G
Martinelli
Michele
M
Baccarani
Sergio
S
Ferrari
Rossella
R
Manfredini
D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology; D001549:Benzamides; D001854:Bone Marrow Cells / Q000378:metabolism; D002478:Cells, Cultured; D016000:Cluster Analysis; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D020869:Gene Expression Profiling; D006801:Humans; D000068877:Imatinib Mesylate; D053631:Interleukin Receptor Common gamma Subunit / Q000172:deficiency / Q000235:genetics; D007621:Karyotyping; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016688:Mice, Inbred NOD; D018345:Mice, Knockout; D016513:Mice, SCID; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology / Q000637:transplantation; D020411:Oligonucleotide Array Sequence Analysis; D010879:Piperazines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014183:Transplantation, Heterologous; D001613:beta 2-Microglobulin / Q000172:deficiency / Q000235:genetics
D018952:Antigens, CD34; D000970:Antineoplastic Agents; D001549:Benzamides; C507942:Il2rg protein, mouse; D053631:Interleukin Receptor Common gamma Subunit; D010879:Piperazines; D011743:Pyrimidines; D001613:beta 2-Microglobulin; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl