FIP1L1-PDGFRα Imposes Eosinophil Lineage Commitment on Hematopoietic Stem/Progenitor Cells

Abstract

Although leukemogenic tyrosine kinases (LTKs) activate a common set of downstream molecules, the phenotypes of leukemia caused by LTKs are rather distinct. Here we report the molecular mechanism underlying the development of hypereosinophilic syndrome/chronic eosinophilic leukemia by FIP1L1-PDGFR␣. When introduced into c-Kit high Sca-1 ؉ Lineage ؊ cells, FIP1L1-PDGFR␣ conferred cytokine-independent growth on these cells and enhanced their self-renewal, whereas it did not immortalize common myeloid progenitors in in vitro replating assays and transplantation assays. Importantly, FIP1L1-PDGFR␣ but not TEL-PDGFR␤ enhanced the development of Gr-1 ؉ IL-5R␣ ؉ eosinophil progenitors from c-Kit high Sca-1 ؉ Lineage ؊ cells. FIP1L1-PDGFR␣ also promoted eosinophil development from common myeloid progenitors. Furthermore, when expressed in megakaryocyte/erythrocyte progenitors and common lymphoid progenitors, FIP1L1-PDGFR␣ not only inhibited differentiation toward erythroid cells, megakaryocytes, and B-lymphocytes but aberrantly developed eosinophil progenitors from megakaryocyte/erythrocyte progenitors and common lymphoid progenitors. As for the mechanism of FIP1L1-PDGFR␣-induced eosinophil development, FIP1L1-PDGFR␣ was found to more intensely activate MEK1/2 and p38 MAPK than TEL-PDGFR␤. In addition, a MEK1/2 inhibitor and a p38 MAPK inhibitor suppressed FIP1L1-PDGFR␣-promoted eosinophil development. Also, reverse transcription-PCR analysis revealed that FIP1L1-PDGFR␣ augmented the expression of C/EBP␣, GATA-1, and GATA-2, whereas it hardly affected PU.1 expression. In addition, short hairpin RNAs against C/EBP␣ and GATA-2 and GATA-3KRR, which can act as a dominant-negative form over all GATA members, inhibited FIP1L1-PDGFR␣-induced eosinophil development. Furthermore, FIP1L1-PDGFR␣ and its downstream Ras inhibited PU.1 activity in luciferase assays. Together, these results indicate that FIP1L1-PDGFR␣ enhances eosinophil development by modifying the expression and activity of lineage-specific transcription factors through Ras/MEK and p38 MAPK cascades.

World Health Organization Classification, Evaluation, and Genetics of the Myeloproliferative Neoplasm Variants

“…13,17 However, a subset of T cells normally expresses FGFR1, and constitutive activation of the receptor due to the rearrangement in a precursor cell may lead to autonomous expansion. 18 It might be argued that this group of neoplasms would be more appropriately classified according to their initial presentation-for example, CEL, CMML with eosinophilia or lymphoblastic lymphoma/leukemia with eosinophilia-but overall this subcategory exemplifies the WHO principles by combining morphologic and genetic features to define the disease and, in the cases with PDGFRA and PDGFRB abnormalities, even to identify the target for anti-tyrosine kinase inhibitor therapy.…”

Fractionation of Mature Eosinophils in GATA-Reporter Transgenic Mice

“…Eosinophils are easily detected by morphological examination of smear samples from bone marrow and peripheral blood; nevertheless it is not easy to estimate the extent of eosinophil infiltration in inflamed lungs (Foster et al 1996;Kopf et al 1996;Shen et al 2003;Ishizaki et al 2006). Preparation of mononuclear cell suspensions of the lung is an established technique (Stevens et al 2007) and several methods to analyze eosinophils in these parenchymal cell suspensions have been reported (Hansel et al 1991;Du et al 2002;Iwasaki et al 2005;Ishizaki et al 2006;Stevens et al 2007;Fukushima et al 2009;Mori et al 2009;Shen et al 2009). In previous approaches, eosinophils were fractionated according to specific gravity (Gärtner 1980) or their reactivity to specific antibodies against surface marker antigens with/without forward/side scatter gating (Hansel et al 1991;Du et al 2002;Ishizaki et al 2006;Rothenberg and Hogan 2006).…”

“…On the other hand, the balance between GATA2 and C/EBPα expression regulates the cell-fate decision of progenitor cells (Iwasaki et al 2006). RNA silencing and overexpression experiments demonstrate that GATA2 and C/EBPα , but not GATA1, drive eosinophil-specific gene expression (Fukushima et al 2009;Qiu et al 2009). These data suggest that GATA1 and GATA2 might regulate common but separate pathways of eosinophil development, and that expression of these genes might be used as a tool for isolating eosinophils.…”

“…CD16, Gr1,Mac1,etc) that are shared by other cells of hematopoietic origin and are normally present in inflammatory infiltrates, hampers the easy detection of eosinophils using flow cytometry (Hansel et al 1991;Gounni et al 2000;Stevens et al 2007;Fukushima et al 2009). To analyze the physiology and pathology of eosinophils, cytokine-induced differentiation systems of hematopoietic progenitor cells or cell lines are exploited (Clutterbuck and Sanderson 1988;Clutterbuck et al 1989;Caldenhoven et al 1998;Yamaguchi et al 1999;Querfurth et al 2000;Dyer et al 2008;Fukushima et al 2009;Qiu et al 2009). However, it is possible that cytokine-induced eosinophils are crucially different from eosinophils in vivo.…”

“…To date, specific types of monoclonal antibodies combined with strict forward/side scatter gating are used in flow cytometry-based methods to fractionate the cells (Hansel et al 1991;Du et al 2002;Iwasaki et al 2005;Ishizaki et al 2006;Munoz and Leff 2006;Stevens et al 2007;Fukushima et al 2009;Mori et al 2009;Shen et al 2009). However, expression of multiple cell surface markers (e.g.…”