Stem cells of GATA1-related leukemia undergo pernicious changes after 5-fluorouracil treatment.
OBJECTIVE
Transcription factor GATA1 plays a critical role in erythropoiesis through the integrated regulation of cell proliferation, differentiation, and apoptosis. In Gata1.05 gene knockdown mice, Gata1 expression deteriorates to 5% of wild-type allelic expression, a level insufficient for supporting normal erythropoiesis and one that leads to accumulation of erythroid progenitors that are readily transformed into erythroblastic leukemia. Serial engraftment of leukemic cells into primary or subsequent nude mice reconstituted complete leukemic phenotype in recipient. To delineate characteristics of leukemic stem cells (LSCs), we analyzed LSCs of Gata1.05 leukemia, which have a potential to reestablish leukemia in mice.


METHODS
Leukemic cells isolated from the first recipient mice of Gata1.05 leukemia cells were divided into two fractions using Hoechst dye. Fractionated cells were transplanted into second recipient, or analyzed gene expression profiles and cell-cycle status. Consequences of 5-fluorouracil (5-FU) treatment on leukemic cells in vivo were studied.


RESULTS
LSCs were enriched in the Hoechst dye-excluded side population (SP), and leukemic cells in the SP population (LSP cells) were morphologically and immunophenotypically indistinguishable from other leukemic cells. However, expression of hematopoietic stem cell (HSC)-related genes was upregulated in the LSP cells. In cell-cycle analyses, LSP cells were quiescent like HSCs, but reentry into the cell cycle was stimulated by 5-FU treatment. Nonetheless, 5-FU treatment established a point of newly adjusted equilibrium in the LSP cells and the cells never recovered to their previous quiescent state.


CONCLUSIONS
Based on this observation, distinct self-renewal regulatory mechanisms in LSCs may be considered as one of the causes of worsening of the features of leukemia after injury and relapse.
Abe
Kanako
K
Graduate School of Comprehensive Human Sciences and Center for Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba, Japan.
Shimizu
Ritsuko
R
Pan
Xiaoqing
X
Hamada
Hiromi
H
Yoshikawa
Hiroyuki
H
Yamamoto
Masayuki
M
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology*; D050982:GATA1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D007938:Leukemia / Q000188:drug therapy*; D051379:Mice; D018345:Mice, Knockout; D008819:Mice, Nude; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000187:drug effects*; D015854:Up-Regulation
D050982:GATA1 Transcription Factor; C494689:Gata1 protein, mouse; D005472:Fluorouracil