Abstract 5093: Bcr-Abl leads to mast cell differentiation and promotes degranulation of cells derived from a chronic myeloid leukemia mouse model in a Gab2 dependent manner

Abstract ABL family kinases, ABL1 (ABL) and ABL2 (ARG), share functional domains such as SH2-, SH3- and kinase domains, and are highly homologous except their C-terminal domain. Fusions to TEL (ETV6), TEL-ABL and TEL-ARG, are constitutively-active kinases and have been reported in rare cases of human CML, AML or ALL. Although TEL-ABL is involved in leukemogenesis, the role of TEL-ARG has not been elucidated because this fusion protein has been always accompanied with other major translocations, such as PML-RARα. We have previously shown that although their kinase activities are comparable, TEL-ABL strongly transforms Ba/F3 cells, while TEL-ARG has a much lower transforming activity, and these differences are attributed to their distinct C-terminal domain (Okuda K and Hirai H, Open Journal of Blood Diseases 2013). At the last ASH annual meeting, we have shown that TEL-ABL induces myeloid leukemia in a short latency, whereas TEL-ARG induces lethal mastocytosis in a long latency in a mouse bone marrow (BM) transplantation model (Abstract number #2368, ASH 2014). Here we investigated the clonogenicity of mastocytosis and explored the detailed mechanism underlying the onset of mastocytosis induced by TEL-ARG. First, we performed a serial transplantation experiment to evaluate mastocytosis-initiating capacity of TEL-ARG-expressing cells. Hematopoietic stem/progenitor cells (HSPCs) from 5-FU-treated mice were retrovirally transduced with TEL-ARG and transplanted to the first recipient mice. BM cells from moribund mice due to mastocytosis were transplanted to the sublethally irradiated second recipients. On day 219 after transplantation, we detected mast cells circulating in the peripheral blood of these two recipients, and observed severe pancytopenia and body weight loss in one of them. In this mouse, mast cells engulfing blood cells were accumulated in the BM and spleen, and subcutaneous tissues were massively infiltrated by mast cells, all of which were characteristics of mastocytosis observed in the first recipients. These results indicate that TEL-ARG confers mastocytosis-initiating capacity on HSPCs. Next, we focused on the mechanisms why TEL-ARG induces mastocytosis, whereas TEL-ABL induces myeloid leukemia. HSPCs from 5-FU-treated mice were retrovirally transduced with TEL-ABL or TEL-ARG, and subjected to the in vitro mast cell differentiation assay in the presence of WEHI-conditioned medium, as a source of IL-3 (Figure). IL-3 enhanced differentiation and proliferation of empty-virus-transduced HSPCs toward mast cells in a dose-dependent manner. TEL-ARG induced mast cell differentiation in the absence of IL-3 to some extent, and IL-3 markedly increased mast cell number even at a lower concentration. TEL-ARG-expressing mast cells continue to proliferate for more than 4 months maintaining their phenotype as mast cells. In contrast, IL-3 did not enhance mast cell differentiation but support myeloid differentiation of TEL-ABL-expressing HSPCs. These data suggest that while TEL-ABL induces myeloid differentiation, TEL-ARG strongly promotes differentiation toward mast cells through sensitizing HSPCs to IL-3, an important factor for differentiation, survival and proliferation of mast cells. Furthermore, these results might account for differences in the phenotypes of diseases induced by TEL-ABL (myeloid leukemia) or TEL-ARG (mastocytosis). In conclusions, TEL-ABL strongly induces myeloid-skewed differentiation, whereas TEL-ARG promotes mast cell differentiation through increasing sensitivity to IL-3 and induces clonal mast cell disease. We are currently investigating the molecular mechanisms by which they activate distinct differentiation pathways toward myeloid cells or mast cells. We believe that further exploration of the underlying mechanisms will deepen our understanding of the molecular basis for ABL kinase-mediated leukemogenesis as well as mast cell disorders. Disclosures No relevant conflicts of interest to declare.

Download Full-text

Patients with Chronic Myeloid Leukemia Show Different Modulation of MYB-Dependent Oncogenic Pathway in the Course of Hematopoietic Differentiation upon Sensitivity to the TKI Treatment

Blood ◽

10.1182/blood.v126.23.1243.1243 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1243-1243

Author(s):

Klara Srutova ◽

Nikola Curik ◽

Koblihova Jitka ◽

Filipp Savvulidi ◽

Hana Klamova ◽

...

Keyword(s):

Cell Differentiation ◽

Chronic Myeloid Leukemia ◽

Mouse Model ◽

Myeloid Leukemia ◽

Research Funding ◽

De Novo ◽

Qrt Pcr ◽

Healthy Donors ◽

Tki Resistance ◽

Tki Treatment

Abstract Introduction: Inhibition of the BCR-ABL protein activity by tyrosine kinase inhibitors (TKIs) plays crucial role in leukemic transformation from the chronic phase (CP) of the chronic myeloid leukemia (CML) into fatal blast crisis (BC). However 20 - 30 % of CML patients develop resistance to the TKIs. Beside mutations in BCR-ABL kinase domain, BCR-ABL independent mechanisms of acquired TKIs resistance including microRNAs (miR) may be also involved. A significant reduction of miR-150 levels associates with CML progression. MiR-150 is an inhibitor of the Myeloblastoma oncogene c-MYB, which is required for BCR-ABL-dependent leukemogenesis in a mouse model of CML-BC. Recently MYB was found to positively regulating another miR, miR-155, that inhibits tumor suppressor and pro-differentiation factor PU.1 in AML/MPS mouse model. PU.1 is a major regulator of myelopoiesis whose levels require precise guidance. We recently reported increased levels of miR-155 in CML-BC. Objectives: We hypothesize that BCR-ABL activity together with low levels of miR-150 activates putative oncogenic signaling pathway MYB/miR-155/PU.1 in CML leading to a progressive blockade of cell differentiation and possibly also of resistance to TKIs. Material and Method: Bone marrow (BM) cells of CML-CP patients at the time of diagnosis (n=10), and of treated patients either sensitive (n=8) or resistant (n=11) to TKIs, were FACS sorted for CD34 and CD38 into subpopulations representing the stages of cell differentiation. CD34+ and CD34- leukocytes from peripheral blood of healthy donors (n=10) were isolated by MACS and used as control. Levels of miR-150, BCR-ABL, MYB, miR-155 and PU.1 were determined by qRT-PCR. Expression of surface differentiation markers on BM cells was determined using flow cytometry at the time of diagnosis (n=10) and upon TKIs resistance (n=5). The effect of miR-150 overexpression and BCR-ABL inhibition was studied in CML-BC cell line K562 using nucleofection of the synthetic miR-150 and siRNA BCR-ABL (and by cell cultivation with TKI imatinib). mRNA and protein expression of BCR-ABL, MYB and miR-150 levels were determined by qRT-PCR and immunoblotting. Results: In the groups of healthy donors and de novo diagnosed CML patients we observed significant positive or negative correlations of expression levels between studied molecules among the sorted cell subpopulations, which outlined the activity of the putative pathway BCR-ABL/miR-150/MYB/miR-155/PU.1 in CML-CP. Interestingly, in the group of patients resistant to TKI, we found that correlation between MYB and miR-155 was not observed suggesting this pathway is deregulated upon TKI resistance. Conversely, we found gain of negative correlation between expression of MYB and PU.1 in the group of patients responding to TKI suggesting that MYB and PU.1 oppose each other upon normal cell differentiation. We also observed significant differences of the surface marker phenotype profiles between BM cells of de novo diagnosed CML patients and patients resistant to TKIs treatment. While relatively differentiated (granulocyte) CD34- CD38- CD11b+ CD14- population presents about 7 % of BM cells for the group of patients at diagnosis, it comprises only 0.3 % of BM cells for resistant group (P= 0.0027) indicating that TKI resistance associates with significant blockade of myeloid differentiation. We next utilized K562 cells showing that levels of miR-150 significantly increased after BCR-ABL inhibition by imatinib (P=0.0017) and also upon BCR-ABL knockdown with siRNA (P=0.002). This suggests that miR-150 is regulated by BCR-ABL. Similarly, MYB mRNA and protein levels were markedly decreased upon miR-150 overexpression and this was enhanced by inhibition of BCR-ABL activity with imatinib. Conclusions: Dysregulation of BCR-ABL/miR-150/MYB/miR-155/PU.1 pathway was observed in CML stages and stage-specific cell populations in relation to TKI-sensitivity and disease progression. Our model consists of the BCR-ABL upregulating MYB both through miR-150 inhibition and by other downstream mechanisms by additive effect, thus the cooperation of miR-150 and imatinib through inhibiting MYB may represent an important barrier to CML progression. Even more our results show that regulation of miR-155 and PU.1 may play role in resistance to TKI treatment. Supported by GAUK 178215 and by project 00023736 from the Czech Ministry of Health Disclosures Klamova: Bristol Myers-Squibb: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Machova Polakova:Bristol Myers-Squibb: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding.

Download Full-text

Role of eIF3a in 4-amino-2-trifluoromethyl-phenyl retinate-induced cell differentiation in human chronic myeloid leukemia K562 cells

Gene ◽

10.1016/j.gene.2018.10.035 ◽

2019 ◽

Vol 683 ◽

pp. 195-209 ◽

Cited By ~ 4

Author(s):

Ge Li ◽

Ke Wang ◽

Yue Li ◽

Jinging Ruan ◽

Cong Wang ◽

...

Keyword(s):

Cell Differentiation ◽

Chronic Myeloid Leukemia ◽

Myeloid Leukemia ◽

K562 Cells

Download Full-text

Artesunate suppresses tumor growth and induces apoptosis through the modulation of multiple oncogenic cascades in a chronic myeloid leukemia xenograft mouse model

Oncotarget ◽

10.18632/oncotarget.3004 ◽

2015 ◽

Vol 6 (6) ◽

pp. 4020-4035 ◽

Cited By ~ 24

Author(s):

Chulwon Kim ◽

Jong Hyun Lee ◽

Sung-Hoon Kim ◽

Gautam Sethi ◽

Kwang Seok Ahn

Keyword(s):

Chronic Myeloid Leukemia ◽

Mouse Model ◽

Tumor Growth ◽

Myeloid Leukemia ◽

Xenograft Mouse Model

Download Full-text

Kit ligand/mast cell growth factor-independent differentiation of mast cells in myelodysplasia and chronic myeloid leukemic blast crisis

Blood ◽

10.1182/blood.v84.12.4322.bloodjournal84124322 ◽

1994 ◽

Vol 84 (12) ◽

pp. 4322-4332 ◽

Cited By ~ 29

Author(s):

P Valent ◽

E Spanblochl ◽

HC Bankl ◽

WR Sperr ◽

C Marosi ◽

...

Keyword(s):

Mast Cell ◽

Growth Factor ◽

Mast Cells ◽

Chronic Myeloid Leukemia ◽

Myeloid Leukemia ◽

Blast Crisis ◽

Cell Lineage ◽

Kit Ligand ◽

Mast Cell Growth Factor

Autonomous, factor-independent growth and differentiation of malignant cells in preleukemic and leukemic disease states is a well-recognized phenomenon and is often associated with a poor prognosis. Mast cells are distinct hematopoietic cells and express a unique profile of antigens. Growth and differentiation of normal mast cells is dependent on mast cell growth factor (MGF), the ligand of the c-kit protooncogene product. In this study, we screened for mast cell-lineage involvement in 52 patients suffering from myeloid leukemias, myelodysplastic syndromes (MDS), systemic mastocytosis, or other diseases by probing for mast cell-related molecules (c-kit, tryptase, histamine, and MGF) and by analyzing kit ligand/MGF-independent growth of mast cells in long-term suspension culture. Of the 52 patients tested, 2 patients with refractory anemia with excess of blast cells in transformation and 1 patient suffering from chronic myeloid leukemia blast crisis (CML-BC) were diagnosed as mastocytic disease. These patients were characterized by complex chromosomal abnormalities, splenomegaly, high percentages of circulating metachromatic cells (5% to 25%), high levels of cellular tryptase (> 10 ng/10(5) peripheral blood mononuclear cells/mL) and a tryptase/histamine (ng:ng) ratio greater than 1. The metachromatic cells expressed the mast-cell-related surface antigen c-kit, but not basophil-related antigens (CD11b, CDw17). Furthermore, in these 3 patients, spontaneous, MGF-independent growth of mast cells along with spontaneous synthesis of tryptase was demonstrable in long-term culture. No autocrine production, paracrine production, or overproduction of MGF was found. The spontaneous growth of mast cells could neither be abbrogated by addition of monoclonal antibodies (MoAbs) to c-kit nor by MoAbs against MGF (< 5% inhibition), whereas factor (MGF)-dependent differentiation of mast cells in these patients could be abbrogated by MoAbs to c-kit or MoAbs to MGF (> 70% inhibition, P < .001). In addition, serum MGF levels in these patients were within the normal range and MGF could not be detected in cell-free culture supernatants. All 3 patients showed rapid progression of disease and had a survival time of less than 1 year. In conclusion, we describe a unique form of transformation in MDS and CML-BC characterized by mast cell lineage involvement and factor-independent differentiation of mast cells. This form of leukemic transformation has to be delineated from chronic myeloid leukemia with basophilia or basophil crisis, from primary mast cell leukemia, and from monocytic leukemias and myelodysplastic disorders associated with basophilia.

Download Full-text

C/EBPβ is a critical mediator of IFN-α–induced exhaustion of chronic myeloid leukemia stem cells

Blood Advances ◽

10.1182/bloodadvances.2018020503 ◽

2019 ◽

Vol 3 (3) ◽

pp. 476-488 ◽

Cited By ~ 3

Author(s):

Asumi Yokota ◽

Hideyo Hirai ◽

Ryuichi Sato ◽

Hiroko Adachi ◽

Fumiko Sato ◽

...

Keyword(s):

Stem Cells ◽

Chronic Myeloid Leukemia ◽

Myeloid Leukemia ◽

Chronic Phase ◽

Interferon Α ◽

Dependent Manner ◽

Distal Enhancer ◽

Induced Differentiation ◽

Ifn Γ

Abstract Even in the era of ABL tyrosine kinase inhibitors, eradication of chronic myeloid leukemia (CML) stem cells is necessary for complete cure of the disease. Interferon-α (IFN-α) has long been used for the treatment of chronic-phase CML, but its mechanisms of action against CML stem cells remain unclear. We found that IFN-α upregulated CCAAT/enhancer binding protein β (C/EBPβ) in BCR-ABL–expressing mouse cells by activating STAT1 and STAT5, which were recruited to a newly identified 3′ distal enhancer of Cebpb that contains tandemly aligned IFN-γ–activated site elements. Suppression or deletion of the IFN-γ–activated site elements abrogated IFN-α–dependent upregulation of C/EBPβ. IFN-α induced differentiation and exhaustion of CML stem cells, both in vitro and in vivo, in a C/EBPβ-dependent manner. In addition, IFN-α upregulated C/EBPβ and induced exhaustion of lineage− CD34+ cells from CML patients. Collectively, these results clearly indicate that C/EBPβ is a critical mediator of IFN-α–induced differentiation and exhaustion of CML stem cells.

Download Full-text

Specific MiRNA Silencing by Lentivirus Mediated Antagomir Expression in Chronic Myeloid Leukemia (CML) Cells.

Blood ◽

10.1182/blood.v110.11.1017.1017 ◽

2007 ◽

Vol 110 (11) ◽

pp. 1017-1017

Author(s):

Michaela Scherr ◽

Letizia Venturini ◽

Karin Battmer ◽

Michael Schaller-Schoenitz ◽

Daniel Schaefer ◽

...

Keyword(s):

Cell Proliferation ◽

Chronic Myeloid Leukemia ◽

Myeloid Leukemia ◽

Mrna Translation ◽

K562 Cells ◽

Mature Mirnas ◽

Dependent Manner ◽

Aberrant Expression ◽

Over Expression ◽

Micro Rnas

Abstract Micro RNAs (miRNA) are small non-coding RNAs that regulate gene expression by specific hybridization to complementary sequences in the 3′ untranslated region of corresponding mRNAs. Concomitant recruitment of specific multi-protein complexes results either in inhibition of mRNA translation or mRNA degradation. miRNAs are processed in a regulated multi-step process from primary transcripts into mature miRNAs by cellular components which are also at least partially involved in the process of RNA interference (RNAi). Aberrant expression of specific miRNAs has recently been described in human lymphoma and leukemia. In particular, BCR-ABL and c-MYC dependent over-expression of the polycistronic and oncogenic miR-17-92 cluster (encoding miR-17, miR-18a, miR-19a, miR-20a, miR-19b, and miR-92) has been described in chronic myeloid leukemia (CML) cell lines, primary CD34+ cells from CML patients (Venturini et al. 2007), and in lung cancer. In BCR-ABL positive K562 cells, miR-17-92 encoded miRNAs repress luciferase activity in miRNA-specific reporter assays. In addition, lentivirus-mediated over-expression of miR-17-92 increases both cell proliferation and sensitivity to imatinib induced cell death. To analyse the function of individual miRNAs of the miR-17-92 polycistron, we generated lentivirus-based strategies to induce stable miRNA-specific loss- and gain-of function phenotypes for miR-18a, miR-19b, and miR-20a, respectively. Over-expression of miRNAs embedded within miR-30-derived sequences from an internal SFFV-LTR promoter allows isolation of K562 cells with increased miRNA expression. In contrast, expression of complementary oligonucleotides (antagomirs) from a H1 promoter located in the lentiviral 3′LTR can induce stable hypomorphic miRNA-phenotypes. In lentivirally transduced K562 cells, individual silencing of miR-18a, miR-19b, and miR-20a by the corresponding antagomirs (ant-miR-18a, ant-miR-19b, ant-miR-20a) specifically relieves miRNA-mediated reporter gene repression. Correspondingly, inhibition of miRNA-function correlates to reduced ‘miRNA’-amplification by miRNA-specific quantitative RT-PCR. Furthermore, protein expression of E2F-1, a known miR-20 target, is enhanced by lentivirally expressed anti-miR-20 in a dose-dependent manner, whereas over-expression of miR-20a reduces E2F-1 levels. Finally, combined over-expression of specific miRNAs and antagomirs reveals specific induction of cell proliferation by miR-18a but strong inhibition by miR-20a in K562 cells, respectively. In contrast, anti-miR-18a, but not anti-miR-19b, anti-miR-20a, or control antagomirs inhibits proliferation of K562 cells. These data demonstrate individual and complementary functions of miR-17-92 encoded miRNAs in CML and identify potential targets for specific therapeutic intervention on the miRNA level.

Download Full-text

Quantitative Phosphoproteomics Identified a New Syk-Lyn-Axl Signalling Pathway Involved In Resistance to Nilotinib In Chronic Myeloid Leukemia Cells.

Blood ◽

10.1182/blood.v116.21.3376.3376 ◽

2010 ◽

Vol 116 (21) ◽

pp. 3376-3376

Author(s):

Romain Gioia ◽

Cedric Leroy ◽

Claire Drullion ◽

Valérie Lagarde ◽

Serge Roche ◽

...

Keyword(s):

Chronic Myeloid Leukemia ◽

Tyrosine Kinase ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Critical Role ◽

Dependent Manner ◽

Stable Isotope Labelling ◽

Resistant Cells

Abstract Abstract 3376 Nilotinib has been developed to overcome resistance to imatinib, the first line treatment of chronic myeloid leukemia (CML). To anticipate resistance to nilotinib, we generate nilotinib resistant CML cell lines in vitro to characterize mechanisms and signaling pathways that may contribute to resistance. Among the different mechanisms of resistance identified, the overexpression of the Src-kinase Lyn was involved in resistance both in vitro, in a K562 cell line (K562-rn), and in vivo, in nilotinib-resistant CML patients. To characterize how Lyn mediates resistance, we performed a phosphoproteomic study using SILAC (Stable Isotope Labelling with Amino acid in Cell culture). Quantification and identification of phosphotyrosine proteins in the nilotinib resistant cells point out two tyrosine kinases, the spleen tyrosine kinase Syk and the UFO receptor Axl. The two tyrosine kinase Syk and Axl interact with Lyn as seen by coimmunopreciptation. Syk is phosphorylated on tyrosine 323 and 525/526 in Lyn dependent manner in nilotinib resistant cells. The inhibition of Syk tyrosine kinase by R406 or BAY31-6606 restores sensitivity to nilotinib in K562-rn cells. In parallel, the inhibition of Syk expression by ShRNA in K562-rn cells abolishes Lyn and Axl phosphorylation and then interaction between Lyn and Axl leading to a full restoration of nilotinib efficacy. In the opposite, the coexpression of Lyn and Syk in nilotinib sensitive K562 cells induced resistance to nilotinib whereas a Syk kinase dead mutant did not. These results highlight for the first time the critical role of Syk in resistance to tyrosine kinase inhibitors in CML disease emphasizing the therapeutic targeting of this tyrosine kinase. Moreover, Axl, which is already a target in solid tumor, will be also an interesting pathway to target in CML. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

ENOX2 NADH Oxidase: A BCR-ABL1-dependent cell surface and secreted redox protein in chronic myeloid leukemia (CML)

10.1101/2021.01.23.427819 ◽

2021 ◽

Author(s):

Seda Baykal-Köse ◽

Maud Voldoire ◽

Christophe Desterke ◽

Nathalie Sorel ◽

Emilie Cayssials ◽

...

Keyword(s):

Chronic Myeloid Leukemia ◽

Mrna Expression ◽

Cell Lines ◽

Myeloid Leukemia ◽

Myeloproliferative Neoplasm ◽

Chronic Phase ◽

Dependent Manner ◽

Western Blots ◽

Hematopoietic Stem ◽

Redox Protein

AbstractChronic myeloid leukemia (CML) is a myeloproliferative neoplasm caused by the acquisition of BCR-ABL1 fusion in a hematopoietic stem cell. We identified the ENOX2 gene as up-regulated in BCR-ABL1-expressing UT-7 cell lines through a transcriptome assay. The oncofoetal ENOX2 protein (Ecto-Nicotinamide Adenine Dinucleotide Oxidase Disulfide Thiol Exchanger 2) is expressed on the external plasma membrane surface of cancer cells and can be released in cancer patients’ serum. Considering these data, we studied ENOX2 expression in CML cell lines and patients using quantitative RT-PCR, western-blots, the ELISA method, and transcriptomic dataset reanalysis. We confirmed increased ENOX2 mRNA expression in the BCR-ABL1-expressing UT-7 cell line. Comparable results were obtained in CML patients at diagnosis. Western-blot analyses on UT-7 and TET-inducible Ba/F3 cell lines established the up-regulation of ENOX2 protein. BCR-ABL1 has been found to induce ENOX2 overexpression in a kinase-dependent manner. In a series of 41 patients with CML, ELISA assays showed a highly significant increase of ENOX2 protein levels in the plasma of patients with CML (p < 0.0001) as compared to controls (n=28). Transcriptomic dataset (GSE4170) reanalyzes have shown specific ENOX2 mRNA overexpression in the chronic phase of the disease. Bioinformatic analyses identified several genes whose mRNA expression was positively correlated to ENOX2. Some of them encode proteins involved in cellular functions compatible with the growth deregulation observed in CML. All in all, our results demonstrate for the first time the upregulation of a secreted Redox protein in a BCR-ABL1-dependent manner in CML. Our data suggest that ENOX2 (through its transcriptional program) plays a significant role in the BCR-ABL1 leukemogenesis. Further studies are required to clarify the relationship between BCR-ABL1 and ENOX2.

Download Full-text

Enhanced sensitivity to inhibition of SHP2, STAT5, and Gab2 expression in chronic myeloid leukemia (CML)

Blood ◽

10.1182/blood-2005-08-3087 ◽

2006 ◽

Vol 107 (8) ◽

pp. 3279-3287 ◽

Cited By ~ 77

Author(s):

Michaela Scherr ◽

Anuhar Chaturvedi ◽

Karin Battmer ◽

Iris Dallmann ◽

Beate Schultheis ◽

...

Keyword(s):

Chronic Myeloid Leukemia ◽

Colony Formation ◽

Myeloid Leukemia ◽

Lentiviral Vector ◽

Therapeutic Potential ◽

Dependent Manner ◽

Abl Tyrosine Kinase ◽

Enhanced Sensitivity ◽

First Line Therapy ◽

Cd34 Cells

Abstract Although targeting the BCR-ABL tyrosine kinase activity by imatinib mesylate has rapidly become first-line therapy in chronic myeloid leukemia (CML), drug resistance suggests that combination therapy directed to a complementing target may significantly improve treatment results. To identify such potential targets, we used lentivirus-mediated RNA interference (RNAi) as a tool for functional genomics in cell lines as well as primary normal and CML CD34+ cells. In a conditional cell culture model, we demonstrate that RNAi-mediated reduction of SHP2, STAT5, and Gab2 protein expression inhibits BCR-ABL-dependent but not cytokine-dependent proliferation in a dose-dependent manner. Similarly, colony formation of purified primary CML but not of normal CD34+ colony-forming cells is specifically reduced by inhibition of SHP2, STAT5, and Gab2 expression, respectively. In addition, coexpression of both anti-BCR-ABL and anti-SHP2 shRNAs from a single lentiviral vector induces stronger inhibition of colony formation as compared to either shRNA alone. The data indicate that BCR-ABL expression may affect the function of normal signaling molecules. Targeting these molecules may harbor significant therapeutic potential for the treatment of patients with CML.

Download Full-text