Chronic Myelogenous Leukemia Bone Marrow Research Articles

KDM6A promotes imatinib resistance through YY1-mediated transcriptional upregulation of TRKA independently of its demethylase activity in chronic myelogenous leukemia

Rationale: Despite landmark therapy of chronic myelogenous leukemia (CML) with tyrosine kinase inhibitors (TKIs), drug resistance remains problematic. Cancer pathogenesis involves epigenetic dysregulation and in particular, histone lysine demethylases (KDMs) have been implicated in TKI resistance. We sought to identify KDMs with altered expression in CML and define their contribution to imatinib resistance.Methods: Bioinformatics screening compared KDM expression in CML versus normal bone marrow with shRNA knockdown and flow cytometry used to measure effects on imatinib-induced apoptosis in K562 cells. Transcriptomic analyses were performed against KDM6A CRISPR knockout/shRNA knockdown K562 cells along with gene rescue experiments using wildtype and mutant demethylase-dead KDM6A constructs. Co-immunoprecipitation, luciferase reporter and ChIP were employed to elucidate mechanisms of KDM6A-dependent resistance.Results: Amongst five KDMs upregulated in CML, only KDM6A depletion sensitized CML cells to imatinib-induced apoptosis. Re-introduction of demethylase-dead KDM6A as well as wild-type KDM6A restored imatinib resistance. RNA-seq identified NTRK1 gene downregulation after depletion of KDM6A. Moreover, NTRK1 expression positively correlated with KDM6A in a subset of clinical CML samples and KDM6A knockdown in fresh CML isolates decreased NTRK1 encoded protein (TRKA) expression. Mechanistically, KDM6A was recruited to the NTRK1 promoter by the transcription factor YY1 with subsequent TRKA upregulation activating down-stream survival pathways to invoke imatinib resistance.Conclusion: Contrary to its reported role as a tumor suppressor and independent of its demethylase function, KDM6A promotes imatinib-resistance in CML cells. The identification of the KDM6A/YY1/TRKA axis as a novel imatinib-resistance mechanism represents an unexplored avenue to overcome TKI resistance in CML.

Inhibition of interleukin-1 signaling enhances elimination of tyrosine kinase inhibitor–treated CML stem cells

AbstractTreatment of chronic myelogenous leukemia (CML) with BCR-ABL tyrosine kinase inhibitors (TKI) fails to eliminate leukemia stem cells (LSC). Patients remain at risk for relapse, and additional approaches to deplete CML LSC are needed to enhance the possibility of discontinuing TKI treatment. We have previously reported that expression of the pivotal proinflammatory cytokine interleukin-1 (IL-1) is increased in CML bone marrow. We show here that CML LSC demonstrated increased expression of the IL-1 receptors, IL-1 receptor accessory protein and IL-1 receptor type 1 (IL-1R1), and enhanced sensitivity to IL-1-induced NF-κB signaling compared with normal stem cells. Treatment with recombinant IL-1 receptor antagonist (IL-1RA) inhibited IL-1 signaling in CML LSC and inhibited growth of CML LSC. Importantly, the combination of IL-1RA with TKI resulted in significantly greater inhibition of CML LSC compared with TKI alone. Our studies also suggest that IL-1 signaling contributes to overexpression of inflammatory mediators in CML LSC, suggesting that blocking IL-1 signaling could modulate the inflammatory milieu. We conclude that IL-1 signaling contributes to maintenance of CML LSC following TKI treatment and that IL-1 blockade with IL-1RA enhances elimination of TKI-treated CML LSC. These results provide a strong rationale for further exploration of anti-IL-1 strategies to enhance LSC elimination in CML.

Role of Enhanced Microenvironmental Interleukin-1 (IL-1) Expression and Increased IL-1 Responsiveness in Persistence of Leukemia Stem Cells in TKI Treated CML Patients

BCR-ABL tyrosine kinase inhibitors (TKI), although highly effective in the treatment of chronic myelogenous leukemia (CML) patients, fail to eliminate leukemia stem cells (LSC), which remain a potential source of relapse. In previous studies we have shown that altered expression of inflammatory cytokines in the CML bone marrow (BM) microenvironment provides a selective growth advantage to CML compared with normal long term hematopoietic stem cells (LTHSC) (Cancer Cell 2012, 21:577). Our studies suggest an important role for the pivotal pro-inflammatory cytokine Interleukin-1α/β (IL-1α/β) in selectively promoting growth of CML LTHSC. Using a transgenic BCR-ABL mouse model of CML and human CML and normal CD34+CD38- cells, we showed that inhibition of IL-1 signaling using recombinant IL-1 receptor antagonist (IL-1RA) in combination with nilotinib (NIL) resulted in significantly greater inhibition of CML LSC, compared with NIL alone (Blood 2013, abstract 512). To further investigate the mechanisms underlying increased IL-1 sensitivity of CML stem cells, we evaluated expression of the IL-1 receptor components, IL-1 receptor-associated protein (IL-1RAP) and IL-1R1, on CML and normal stem cells using flow cytometry. Expression of both IL-1RAP and IL-1R1 were increased on primary CML CD34+CD38-CD90+ cells compared to their normal counterparts (n=5, p<0.05). Exposure to IL-1α (10ng/ml) resulted in increased expression of p-NF-kB (p65), p-p38 MAPK and p-JNK in CML compared to normal CD34+CD38-CD90+ cells as evaluated by flow cytometry, indicating enhanced sensitivity to IL-1 induced signaling (n=5, p<0.05). The expression of p-NF-kB(p65), p-p38 MAPK and p-JNK in CML CD34+CD38-CD90+ cells cultured in CML BM conditioned medium (CM) was reduced after treatment with NIL or IL-1RA, and further reduced by the combination of NIL and IL-1RA (n=4, p<0.05). Immunohistochemistry (IHC) analysis showed that nuclear NF-κB p65 protein was reduced in NIL and IL-1RA treated CML CD34+CD38-CD90+ cells compared with controls. Treatment with NIL and IL-1RA also significantly reduced expression of the NF-κB target genes NFκB1A, BCL2L1, BIRC3 and CD83 (n=6, p<0.001), and of the inflammatory cytokines IL6, CXCL1, CXCL2, CCL2, CCL3, CCL4 and TNF-α (n=6, p<0.05), as assessed by Q-RT-PCR. We evaluated IL-1 expression in BM samples from CML patients with undetectable minimal residual disease (UMRD) using Q-RT-PCR. Interestingly IL-1α, but not IL-1β, expression was increased in BM samples from CML patients with UMRD compared to normal BM samples (n=12, p<0.05). To evaluate the source of increased IL-1α expression we analyzed selected monocyte (CD45+CD14+), non-monocytic myeloid cell (CD45+CD14-CD33+), T cell (CD45+CD14-CD33-CD3+), B cell (CD45+CD14-CD33-CD19+), endothelial cell (CD45-GPA-CD31+) and mesenchymal cell (CD45-GPA-CD31-) populations from BM samples obtained from CML patients with UMRD and from normal healthy controls. These studies revealed significantly elevated IL-1α expression in BM CD14+ monocytic and CD31+ endothelial cells from CML patients with UMRD compared to normal controls (n=12, p<0.05). Our studies indicate that CML LSC demonstrate increased IL-1 receptor expression and IL-1 induced NF-kB, p38 MAPK and JNK signaling. We also observe enhanced IL-1α expression in BM endothelial and monocytic cells from CML patients achieving UMRD, indicating persistence of an inflammatory microenvironment that may contribute to persistence of residual LSC. Our studies provide a strong rationale for the application of anti-IL-1 directed strategies to inhibit inflammatory signaling and enhance LSC elimination in TKI treated CML patients. DisclosuresNo relevant conflicts of interest to declare.

Combination of Imatinib with CXCR4 Antagonist BKT140 Overcomes the Protective Effect of Stroma and Targets CML In Vitro and In Vivo

Functional role of CXCR4 in chronic myelogenous leukemia (CML) progression was evaluated. Elevated CXCR4 significantly increased the in vitro survival and proliferation in response to CXCL12. CXCR4 stimulation resulted in activation of extracellular signal-regulated kinase (Erk)-1/2, Akt, S6K, STAT3, and STAT5 prosurvival signaling pathways. In accordance, we found that in vitro treatment with CXCR4 antagonist BKT140 directly inhibited the cell growth and induced cell death of CML cells. Combination of BKT140 with suboptimal concentrations of imatinib significantly increased the anti-CML effect. BKT140 induced apoptotic cell death, decreasing the levels of HSP70 and HSP90 chaperones and antiapoptotic proteins BCL-2 and BCL-XL, subsequently promoting the release of mitochondrial factors cytochrome c and SMAC/Diablo. Bone marrow (BM) stromal cells (BMSC) markedly increased the proliferation of CML cells and protected them from imatinib-induced apoptosis. Furthermore, BMSCs elevated proto-oncogene BCL6 expression in the CML cells in response to imatinib treatment, suggesting the possible role of BCL6 in stroma-mediated TKI resistance. BKT140 reversed the protective effect of the stroma, effectively promoted apoptosis, and decreased BCL6 levels in CML cells cocultured with BMSCs. BKT140 administration in vivo effectively reduced the growth of subcutaneous K562-produced xenografts. Moreover, the combination of BKT140 with low-dose imatinib markedly inhibited tumor growth, achieving 95% suppression. Taken together, our data indicate the importance of CXCR4/CXCL12 axis in CML growth and CML-BM stroma interaction. CXCR4 inhibition with BKT140 antagonist efficiently cooperated with imatinib in vitro and in vivo. These results provide the rational basis for CXCR4-targeted therapy in combination with TKI to override drug resistance and suppress residual disease.

Photo-bio-synthesis of irregular shaped functionalized gold nanoparticles using edible mushroom Pleurotus florida and its anticancer evaluation

A green chemistry approach to the synthesis of gold nanoparticles using edible mushroom Pleurotus florida (Oyster mushroom) by photo-irradiation method has been attempted. The mixture containing the aqueous gold ions and the mushroom extract was exposed to sunlight; this resulted in the formation of biofunctionalized gold nanoparticles. These nanoparticles were characterized using various techniques like UV–visible spectroscopy; X-ray diffraction studies, Energy dispersive X-ray analysis, Field emission scanning electron microscopy, Atomic force microscopy, Transmission electron microscopy and Fourier transform infrared spectrometry. The obtained biofunctionalized gold nanoparticles showed effective anti-cancer property against four different cancer cell lines A-549 (Human lung carcinoma), K-562 (Human chronic myelogenous leukemia bone marrow), HeLa (Human cervix) and MDA-MB (Human adenocarcinoma mammary gland) and no lethal effect is observed in Vero (African green monkey kidney normal cell) cell lines.

Altered Microenvironmental Regulation of Leukemic and Normal Stem Cells in Chronic Myelogenous Leukemia

We characterized leukemia stem cells (LSC) in chronic phase chronic myelogenous leukemia (CML) using a transgenic mouse model. LSC were restricted to cells with long-term hematopoietic stem cell (LTHSC) phenotype. CML LTHSC demonstrated reduced homing and retention in the bone marrow (BM), related to decreased CXCL12 expression in CML BM, resulting from increased G-CSF production by leukemia cells. Altered cytokine expression in CML BM was associated with selective impairment of normal LTHSC growth and a growth advantage to CML LTHSC. Imatinib (IM) treatment partially corrected abnormalities in cytokine levels and LTHSC growth. These results were validated using human CML samples and provide improved understanding of microenvironmental regulation of normal and leukemic LTHSC and their response to IM in CML.

Leukemia-Induced Alterations in Bone Marrow Cytokine and Chemokine Levels Contribute to Altered Stem Cell Lodgment and Impairment of Normal Stem Cell Growth in CML

Abstract 962Specialized bone marrow (BM) microenvironmental niches are essential for hematopoietic stem cell (HSC) lodgment and maintenance. However microenvironmental interactions of leukemia stem cells (LSC) are poorly understood. Although chronic myelogenous leukemia (CML) results from HSC transformation by the BCR-ABL gene, the role of the microenvironment in modulating leukemia development is not known. We employed the SCL-tTA-BCR/ABL mouse model of CML to investigate the LSC interactions with the BM microenvironment. In this model, targeted expression of the BCR-ABL gene in murine HSC via a tet-regulated SCL promoter results in development of a chronic phase CML-like disorder. We have reported that LSC capacity is restricted to BCR-ABL+ cells with long-term hematopoietic stem cell (LTHSC) phenotype(LSK Flt3-CD150+CD48-) (Blood 2010 116:1212A). LSC numbers are reduced in the BM but increased in the spleen of CML mice compared with LTHSC from control mice, suggesting that LSC have altered niche interactions. LSC also demonstrate altered trafficking with significant reduction in homing of IV injected LSC to BM, and markedly increased egress of intrafemorally injected LSC to the spleen, potentially related to reduced CXCL12 levels in the BM of CML mice. In addition, levels of several chemokines and cytokines, including MIP1α, MIP1β, MIP2, IL-1α, IL-1β, TNF-α, G-CSF and IL-6, were increased in CML BM, related to increased production by malignant hematopoietic cells. We investigated whether altered chemokine and cytokine expression was associated with altered capacity of the CML BM microenvironment to support LTHSC engraftment. LTHSC from control mice or LSC from CML mice were transplanted into irradiated CML or control recipients. There was reduced engraftment of both control LTHSC and CML LSC in the BM of CML compared to control recipients at 2 weeks after transplantation, associated with reduced homing to CML BM, potentially related to low BM CXCL12 levels. The numbers of control LTHSC in the BM of CML recipient mice remained low at 4 weeks post-transplantation, whereas the numbers of CML LSC increased to numbers similar to those seen in the BM of control recipients. Culture with CML BM supernatants (SN) resulted in impaired growth of control LTHSC compared to control BM SN. In contrast the growth of CML LSC was similar following culture with CML and control BM SN. Culture with individual factors at concentrations similar to those observed in CML BM (16ng/ml MIP1α, 8ng/ml MIP1β, 2.5ng/ml IL-1α, 3.5ng/ml IL-1β, 0.05ng/ml TNF-α) resulted in significantly reduced growth of normal LTHSC compared with CML LSC. These results indicate that diffusible factors produced by leukemic cells in the CML BM environment selectively inhibit normal LTHSC compared to CML LSC growth. Exposure of a murine stromal cell line to CML BM SN resulted in reduced CXCL12 mRNA levels compared to BM SN from control mice. The cytokine G-CSF, which was increased in CML BM SN, has been reported to reduce CXCL12 transcription. We observed significant reduction of CXCL12 mRNA levels in stromal cells cultured with G-CSF (0.2ng/ml), supporting a potential role for increased G-CSF production by leukemia cells in reduced CXCL12 production by CML BM stromal cells and reduced LSC retention in the BM. We evaluated whether defects in microenvironmental function in CML were affected by imatinib treatment. Treatment of CML mice with imatinib (200mg/kg/day, 2 weeks) led to reduction in MIP1α, MIP1β, IL-1β, and IL-6 levels in BM cells. Engraftment of normal LTHSC was significantly enhanced in BM of CML recipients pre-treated with imatinib. Results obtained with the mouse model were validated using specimens obtained from CML patients. CXCL12 mRNA levels were significantly reduced in human CML compared to normal MNCs, whereas expression of MIP1α, MIP-2, IL-1α and IL-1β were increased in CML MNCs, consistent with results obtained with the mouse model. Coculture with CML MNC conditioned medium (CM) resulted in selective impairment of growth of normal CD34+CD38- primitive progenitors compared to CM from normal MNC, but did not inhibit growth of CML progenitors. We conclude that leukemia-induced alterations in BM cytokine and chemokine levels contribute to altered LSC lodgment and to selective impairment of growth of normal LTHSC in the CML BM microenvironment, leading to a relative growth advantage for CML LSC over normal LTHSC and expansion of the leukemic clone. Disclosures:Holyoake:Novartis: Research Funding; Bristol Myers Squibb: Research Funding.

In vitro antiproliferativeactivity of Annona reticulata roots on human cancer cell lines.

Background:The phytochemical and pharmacological activities of Annona reticulata components suggest a wide range of clinical application in lieu of cancer chemotherapy.Materials and Methods:Ethanol and aqueous extracts of roots of Annona reticulata Linn were studied for their in vitro antiproliferative activity on A-549 (human lung carcinoma), K-562 (human chronic myelogenous leukemia bone marrow), HeLa (human cervix) and MDA-MB (human adenocarcinoma mammary gland) cancer cell lines by MTT [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] colorimetric assay.Results:The ethanol extract exhibited a prominent inhibitory effect against A-549, K-562, HeLa and MDA-MB human cancer cell lines at a concentration range between 10 and 40 μg/ml, whereas the aqueous extract showed a lower activity at the same concentration. Simultaneously, the effect of the ethanol extract toward the inhibition of Vero cell line proliferation was lower in comparison with the cancer cell lines.Conclusion:The significant antiproliferative activity of the ethanol extract of Annona reticulata roots against A-549, K-562, HeLa and MDA-MB human cancer cell lines may be attributed toward the collective presence of acetogenins, alkaloids and lower inhibitory effect on Vero cell line, which suggests Annona reticulata be used as a chemopreventive agent in cancer therapy.

The stem cell factor–c-KIT pathway must be inhibited to enable apoptosis induced by BCR–ABL inhibitors in chronic myelogenous leukemia cells

Imatinib is an effective first-line therapy for chronic myelogenous leukemia (CML) that acts by targeting the tyrosine kinase activity of BCR-ABL. To overcome resistance, second-generation inhibitors of BCR-ABL have been developed. Among these, nilotinib is more potent against BCR-ABL than imatinib, and is effective against many imatinib-resistant BCR-ABL mutants. In this study, an in vitro flow cytometry assay to analyze imatinib- and nilotinib-induced apoptosis in CML cells has been developed. Both the drugs induced significant apoptosis in CD34+ cells from 36 CML bone marrow samples (P<10(-4)), whereas CD34+ cells from BCR-ABL negative samples were unaffected. When the experiments were carried out in the presence of a cocktail of cytokines, nilotinib- but not imatinib-induced apoptosis was inhibited. This differential inhibition was confirmed on K562 cells. A blocking anti-CD117 antibody alleviated the antiapoptotic effect of cytokines against nilotinib. Moreover, using short hairpin RNA against BCR-ABL, we showed that K562 cells were not dependent on BCR-ABL signaling as long as the stem cell factor (SCF) receptor pathway was activated. We conclude that the c-KIT pathway may substitute for BCR-ABL tyrosine kinase to activate survival signals, and that c-KIT must be inhibited besides Bcr-Abl to allow apoptosis of CML cells.

Leukemic Stem Cells and Progenitors Demonstrate Impaired Interaction with the Hematopoietic Microenvironment in Vivo in An Inducible Murine Model of Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is a stem cell malignancy induced by p210 BCR-ABL and characterized by myeloproliferation in BM and egression of leukemic stem cells and progenitors (LSC/P) to extramedullary sites. Persistence of BCR-ABL+ HSC in patients under Imatinib suggests inhibition of ABL-kinase alone is not sufficient to eliminate the LSC/P. One of the major hallmarks of CML induced by signaling downstream BCR-ABL is the loss of control of the hematopoietic microenvironment on LSC/P. Expression of p210 BCR-ABL has been associated with loss of adhesion to the bone marrow, impaired migration in response to CXCL12 and decreased retention in the BM. In order to study the putative LSC/P niches in steady-state chronic-phase leukemia, we have analyzed the ability of LSC/P to proliferate and get retained in the bone marrow (BM) in an inducible model of CML. Binary transgenic SCL-tTA/TRE-BCR-ABL mice (Koschmieder S et al., Blood 2005) express p210 BCR-ABL in LSC/P upon doxycycline withdrawal (CML mice). Induced myeloproliferation was associated with activation of the downstream signaling effectors CrkL and p38-MAPK and expansion of circulating (Table 1) and splenic LSC/P but not in BM, suggesting massive LSC/P egression from the marrow (Table 2). Proliferation analysis showed that myeloid expansion in the spleen was secondary to increased cycling of Lin−Sca1+c-Kit+ (LSK) cells (3.1-fold increase in S-phase cells, P<0.05), but not in Lin−/c-Kit+ (LK) population, compared with the control spleens. In agreement with the LSC/P BM content data, the frequency of BM-derived LSK and LK cells incorporating BrdU in CML and in control mice remained similar, suggesting a specific egression of LSC/P from the BM to extramedullary sites. To test whether this model truly represented a model of BM LSC/P egression, we compared the splenic and BM LSC/P compared with their controls regarding their adhesion molecule expression, interaction with the hematopoietic microenvironment (HM) and homing to the overall marrow cavity and endosteal space. Splenic, but not BM-derived, LSK and LSK CD34+ ST-HSCs had increased cell surface expression of CD44 compared to controls (1.35 fold, P=0.006 and 1.23 fold, P<0.05 respectively) and decreased expression of L-selectin (8.7 fold, P<0.05) while expression of CXCR4, α4β1 and α5β1 integrins remain similar in bone marrow and splenocytes from CML and control mice. CML BM progenitors also showed 18-fold reduced adhesion to fibronectin and 1.4-fold increased migration towards CXCL12 compared to control BM progenitors. Myeloproliferative disease was transplantable into non-transgenic littermates and homing of CML BM progenitors was increased (4.3 fold, P<0.005) in myeloablated littermate recipient BM. However, lineage-negative leukemic BM-derived cells which had increased homing in BM of recipient mice had an impaired ability to migrate to the BM endosteal space compared with their littermate controls (control: 31 ± 18% vs CML mice: 17.6 ± 17%), suggesting an specific impairment to lodge in specialized anatomically-defined hematopoietic “niches”. Altogether, this murine model may represent an adequate in vivo system to analyze the ability of p210 BCR-ABL-expressing LSC/P to interact with BM niches and study the control of the hematopoietic microenvironment on LSC/P survival, proliferation and retention.Table 1 Increase in circulating LSC/P in the CML mice after withdrawal of doxycyclinPeripheral BloodLSK (×103)Cells/mL Blood P<0.05LT-HSC(×103)Cells/mL Blood P<0.05CFU-GM+BFU-E/mL Blood P<0.05Control1.56 ± 0.250.459 ± 0.2960.86 ± 51.09CML mice3.56 ± 1.522.159 ± 2.03869.6 ± 628.4Table 2. Immunophenotypic analysis of BM and splenocytes in control and CML micePopulationBM (Cells ×104) (Control)BM (Cells x104) (CML)SP (Cells ×104) (Control)SP (Cells x104) (CML)C-Kit+Sca1+24.3 ± 9.921.3 ± 116.8 ± 4.530.1 ± 12.3 (P<0.05)Mac1+Gr1+1779 ± 3071583 ± 26578.4 ± 32608 ± 377 (P<0.05)CFU-C/105Cells342 ± 66334 ± 9963.3 ± 7.0979 ± 6.54 (P<0.05)

Activation of PP2A by FTY720 Inhibits Survival and Self-Renewal of the Ph(+) Chronic Myelogenous Leukemia (CML) CD34+/CD38− Stem Cell through the Simultaneous Suppression of BCR/ABL and BCR/ABL– independent Signals

CML is a clonal disorder of the pluripotent hematopoietic stem cell characterized by the sustained kinase activity of the BCR/ABL oncoprotein. We reported that the BCR/ABL-dependent and SET-mediated inhibition of protein phosphatase PP2A tumor suppressor activity is essential for the leukemogenic potential of CD34+ CML bone marrow progenitors, as molecular and pharmacologic restoration of PP2A inhibits the activity of BCR/ABL and that of several important regulators of cell survival/proliferation, thus resulting in marked apoptosis, impaired clonogenic potential and in vivo leukemogenesis of imatinib/dasatinib-sensitive and -resistant Ph(+), but not normal, CD34+ blasts and/or BCR/ABL+ mouse marrow progenitors. Here we show that SET-dependent suppression of PP2A activity is a common feature of Ph(+) progenitors (CMP and GMP) and imatinib/ dasatinib-insensitive CD34+/CD38- BCR/ABL+ (n=3) stem cells but not of the equivalent cell fractions from healthy individuals (n=3). To determine the biological importance and therapeutic implications of impaired PP2A activity in Ph(+) stem cells, we evaluated by clonogenic, CFC/replating, LTC-IC and CFSE-mediated cell division-tracking assays, the effects of FTY720 (2.5 mM), a PP2A activator currently in phase III trials for MS patients, and lentiviral-mediated ectopic PP2Ac expression on survival and self-renewal of BCR/ ABL+ stem/progenitor cells isolated from bone marrow of CML blast crisis patients (ntot=8; Ph1≥90%) and/or SCL-tTA-BCR/ABL transgenic animals (ntot=10). FTY720 treatment (2.5–5mM) severely suppressed the clonogenic potential of CD34+/CD38− and CD34+/CD38+/CD45RA−/+ CML stem/progenitor cells. Accordingly, self-renewal and long-term repopulating potential of CML leukemic stem cells was markedly impaired by pharmacologic PP2A reactivation. In fact, the CFC output of LTC-IC cultures (6 weeks) deriving from FTY720-treated (2.5 mM; 72h) Ph(+) CD34+ cells was more than 95% inhibited if compared to that of LTC-IC cultures from untreated CML cells. By contrast, imatinib (5 mM) and dasatinib (200 nM) treatment led to a 3.5 and 5-fold increase in CFC output, respectively. Consistent with the ability of FTY720 to impair self-renewal of CML stem cells, a 50–90% reduction of the CFSEMAX/quiescent cell population was observed in CFSE-stained CD34+ CML cells treated for 6–9 days with FTY720. Notably, FTY720 did not exert any significant effect on CFSE-stained CD34+ cells from healthy individuals whereas, as expected, imatinib (5 mM) and dasatinib (200 nM) treatment led to a 22% and 27% increase in CFSEMAX CML cells, respectively. Interestingly, only FTY720 triggered apoptosis of CFSEMAX CML cells (41% Annexin V+ cells) although BCR/ABL activity (phospho-ABL intracellular flow-cytometry staining) in CFSEMAX cells was efficiently inhibited by FTY720, Imatinib and dasatinib, suggesting that BCR/ABL-independent PP2A-regulated signals control the survival and self-renewal of CML stem cells. Indeed, lentiviral-driven PP2Ac-overexpression as well as treatment with FTY720, but not imatinib, significantly decreased (40–90% reduction) CFC/serial replating efficiency, colony size and percentage of CFSEMAX fraction (66–96% reduction) of Lin−/ Sca+/Kit+ (LSK) cells isolated from bone marrow and spleen of leukemic SCL-tTA-BCR/ ABL mice. Mechanistically, the detrimental effect of PP2A activation on survival and self-renewal of CML stem cells might depend on the ability of PP2A to inactivate b-catenin that, reportedly, is a PP2A target essential for the self-renewal of the CML blast crisis GMP progenitors. In fact, immunoblotting, direct immunofluorescence and LET/TCF luciferase assays showed that ectopic PP2Ac expression and/or FTY720, but not imatinib, treatment leads to inactivation/degradation of nuclear b-catenin in BCR/ABL+ primary mouse LSK and/or 32D-BCR/ABL cells. Altogether our data not only highlight the importance of PP2A inactivation for survival and self-renewal of CML stem cells but also suggest the existence of BCR/ABL-independent, PP2A-sensitive and b-catenin-mediated signals that may account for resistance of CML quiescent stem cells to tyrosine kinase inhibitor monotherapy. Thus, FTY720 treatment has the potential to eradicate CML by efficiently targeting both stem and progenitor Ph(+) cells regardless of their degree of sensitivity to imatinib and dasatinib.

Efficient Duplex Real-Time Quantitative RT-PCR of BCR-ABL and ABL Gene Transcripts for Monitoring of Minimal Residual Disease

BCL-ABL fusion gene can be found in 100% chronic myelogenous leukemia (CML) and about 25% adult acute lympholid leukemia where its expression level is a crucial parameter for monitoring of minimal residual disease (MRD). Depending on the breakpoint in BCR, exon 2 of ABL (a2) joins with exons 1 (e1), 13 (b2), or 14 (b3), or rarely to exon 19 (e19) of BCR resulting in chimeric proteins of p190, p210 and p230, respectively. The c-ABL gene is one of the best controls for MRD detection by real-time quantitative RT-PCR (RQ-RT-PCR). In most studies published before, PCR probes were labeled by single fluorescence such as FAM, and BCR-ABL and ABL transcripts were detected in separate PCR reactions.Purpose: To design and evaluate a duplex, real-time quantitative RT-PCR (RQ-RT-PCR) system labeled with double fluorescence Taqman probes to simultaneously measure both BCR-ABL and ABL transcripts.Methods:Positive controls are plasmids containing full-length target sequence of BCR-ABLP210 and ABL. 70 cases of CML bone marrow samples collected in Nanfang Hospital from Jane 2005 to July 2008 were examined. Patients were untreated ones and those treated with STI571 or allo-hematological stem cell transplantation. RQ-RT-PCR value=copies of BCR-ABL/copies of ABL. The results are compared with fluorescence chromosomal in situ hybridization (FISH) for BCR-ABL.Probes and primers recommended by Europe Anti-Cancer group in 2003 were used as gold standard control; probe and primers for bcr-ablP210 gene are ENF541, ENP501 and ENR561, respectively; probe and primers for abl gene are ENPr1043, ENF1003 and ENR1063, respectively. Both Taqman probes are FAM labed.For duplex RQ-RT-PCR, HEX labeled probe is used for the ABL gene, along with corresponding primers, ENP541 labeled with FAM fluorescence and ENF501 and ENR561 were also used for BCR-ABLP210.The experiments were carried out in the same tube on a Biorad Opticon2 RQ-PCR unit. The end concentration is 0.3μmoL/L for primers and 0. 2 μmoL/L for probe. The PCR reaction was carried out in 25μL. PCR condition is at 50°C×2min+95°C×10min, then followed 95°C×15s+60°C×1min for 50cycle.Result: Testing using serial dilutions of plasmid positive control suggested that HEX-FAM duplex is readily amplified with the FAM Taqman probes of BCR-ABLP210, and the HEX-ABL results is same with those with FAM-ABL (recommeded by Europe Anti-Cancer group). Coefficiency of variation among different experiments is less than 5%. The 70 CML cases can be divide into 3 groups based on FISH value: ≥10% (n=32), 0.5% 10% (n=27) and negative (n=11). The corresponding RQ-PCR ratio of BCR-ABL/ABL are 0.590±0.264, 0.044±0.041 and (9.46±6.99)×10|4, respectively, P<0.01 between each group.Conclusion: We have established an efficient duplex RQ-RT-PCR method with FAM and HEX Taqman probes. This approach enables acquisition of more information from each test and hence reduces the amount of sample needed for each test. We believe this method will be useful to MRD monitoring in CML and BCL-ABL + B-ALL.

The Induction of Dendritic Cells with IFN-alpha and GM-CSF from Bone Marrow Mononuclear Cells from Patients with Chronic Myeloid Leukemia.

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease arising from the clonal expansion of a stem cell with the typical Philadelphia (Ph) chromosome cytogenetic abnormality. IFN-a has been proven to be effective for patients in the chronic phase of myelogenous leukemia (CML), yet the mechanisms of the antitumor action of these cytokines are still a matter of debate. Dendritc cells (DCs) are potent antigen-presenting cells that prime effective T-cell response aginst tumour antigens. Recent studies have shown that IFN-a can exert a variety of effects on dendritic cells (DCs), which may play an important role in the induction of an antitumor immunity. Human DCs can be generated in vitro from peripheral blood(PB) monocytes or from CD34+ haematopoietic precursor cells in culture medium containing human granulocyte macrophage-colony stimulating factor (GM-CSF), IL-4 and some other cytokines. Previous studies have shown a new effective protocol for the generation of human DCs from unseparated BM aspirate cells with excellent functional capacity of antigen uptake and of stimulating naive and memory T cell responses superior to that of DCs from peripheral blood(PB) monocytes. We, therefore, explored whether treatment with IFN-a may influence the CML bone marrow mononuclear cells(BMMNCs) derived DCs in vitro. Treatment BMMNCs of 12 patients with CML in chronic phase with IFN-a+rhGM-CSF(IFN-a-DC) generated DCs with more mature phenotype properties expressing higher of CD80,CD86,HLA-DR,CD83 compared to the CML- BMMNCs treated with rhGM-CSF+IL-4(IL-4-DC). And in parallel with phenotypes, IFN-a-DC also showed more effective than IL-4-DC in eliciting an allogeneic mixed lymphocyte reaction by MTT assay. FISH confirmed the DCs of both groups were leukemic origin. These findings demonstrate that IFN-a promotes the differentiation/maturation of DCs derived from BMMNCs of patients with CML in vitro, these studies also broaden the clinical scope of IFN-a as a promising agent in the immunotherapy of CML.

Chronic myelogenous leukemia: molecular and cellular aspects.

Chronic myelogenous leukemia (CML) originates in a pluripotent hematopoietic stem cell of the bone marrow and is characterized by greatly increased numbers of granulocytes in the blood. Myeloid and other hematopoietic cell lineages are involved in the process of clonal proliferation and differentiation. After a period of 4-6 years the disease progresses to acute-stage leukemia. On the cellular level, CML is associated with a specific chromosome abnormality, the t(9; 22) reciprocal translocation that forms the Philadelphia (Ph) chromosome. The Ph chromosome is the result of a molecular rearrangement between the c-ABL proto-oncogene on chromosome 9 and the BCR (breakpoint cluster region) gene on chromosome 22. Most of ABL is linked with a truncated BCR. The BCR/ABL fusion gene codes for an 8-kb mRNA and a novel 210-kDa protein which has higher and aberrant tyrosine kinase activity than the normal c-ABL-coded counterpart. Phosphorylation of a number of substrates such as GAP, GRB-2, SHC, FES, CRKL, and paxillin is considered a decisive step in transformation. An etiological connection between BCR/ABL and leukemia is indicated by the observation that transgenic mice bearing a BCR/ABL DNA construct develop leukemia of B, T, and myeloid cell origin. CML cells proliferate and expand in an almost unlimited manner. Adhesion defects in bone marrow stromal cells have been proposed to explain the increased number of leukemic cells in the peripheral blood. However, findings of our laboratory have shown that the BCR/ABL chimeric protein that is expressed in transfected cells may, under certain conditions, also increase the adhesion to fibronectin via enhanced expression of integrin. Our previous immunocytological studies on the expression of beta1 and beta2 integrins have found no qualitative differences between normal and CML hematopoietic cells in vitro. Even long-term-cultured CML bone marrow or blood cells continuously express those adhesion molecules that are characteristic of the cytological type. Recent experiments indicate that certain early CML progenitors may adhere to the stromal layer in vitro similarly to their normal counterparts. They cannot be completely removed by long-term culture on allogeneic stromal cells. At present, the only curative therapy is transplantation of allogeneic hematopoietic stem cells. Based on the molecular and cellular state of knowledge of CML, new therapies are being developed. BCR/ABL antisense oligonucleotides, inhibitors of tyrosine kinase, peptide-specific adoptive immunotherapy or peptide vaccination, and restoration of hematopoiesis by autologous stem cell transplantation following CML cell purging are examples of important approaches to improving CML treatment.

Involvement of Fas-Mediated Apoptosis in the Inhibitory Effects of Interferon-α in Chronic Myelogenous Leukemia

AbstractInterferon-α (IFN-α) is an established treatment for chronic myelogenous leukemia (CML) in chronic phase, but the mechanism of its antileukemic activity is not clear. One possible mechanism of action might include the induction of apoptosis, and especially Fas-mediated cell killing may play an important role in the elimination of malignant cells. We investigated Fas receptor (Fas-R) expression and the consequences of Fas-R triggering in CML patients. Using two-color flow cytometry, we found a significantly higher number of Fas-R–expressing CD34+ cells in the bone marrow (BM) of CML patients compared with normal subjects. We have previously shown that IFN-γ induces Fas-R expression on CD34+ cells; in this study, we investigated whether IFN-α induces Fas-R expression on CML progenitor cells. Dose-dependent induction of Fas-R expression was observed after IFN-α stimulation of CD34+ cells from CML BM. In methylcellulose culture, IFN-α alone at a therapeutic concentration showed only marginal antiproliferative effects on both normal and CML BM progenitors. In contrast, a Fas-R agonist, the anti-CD95 monoclonal antibody CH11, inhibited colony formation from normal progenitors, and the inhibition was even stronger on CML progenitors. When CML BM cells were cultured in the presence of IFN-α, Fas-R–mediated inhibition of colony growth was potentiated in a dose-dependent fashion, consistent with IFN-α induction of Fas-R expression. This functional effect did not require the presence of accessory cells, since similar results were obtained with purified CD34+ cells. In suspension cultures, we demonstrated that suppression of CML hematopoiesis by IFN-α and Fas-R agonist was exerted through Fas-R–mediated induction of apoptosis. Our findings suggest that the Fas-R/Fas-ligand system might be involved in the immunologic regulation of CML progenitor growth and that its effect can be amplified by IFN-α.

The 30/35 kDa chymotryptic fragment of fibronectin enhances retroviral-mediated gene transfer in purified chronic myelogenous leukemia bone marrow progenitors.

We have previously shown by reverse transcriptase-PCR (rtPCR) that CML CD34+ HLA-DR- cells are enriched for BCR/ABL(-) hematopoietic progenitor cells (HPC) while leukemic HPC reside predominately within CML CD34+ HLA-DR+ cells. We investigated whether the 30/35 kDa fragment of fibronectin (FN) could be used to enhance retroviral-mediated gene transfer (RMGT) in chronic phase CML marrow HPC. CML CD34+ HLA-DR- and CD34+ HLA-DR+ cells were transduced with vector supernate containing the neomycin resistance gene on plates coated with either FN or bovine serum albumin (BSA) as control, then assayed for transduced HPC in progenitor cell assays in the presence or absence of G418. Transduction efficiency of CML CD34+ HLA-DR- cells over BSA ranged from 0.09 to 7.2% (mean 3.3 +/- 1.5%), while that over FN plates ranged from 3.8 to 23% (mean 11.0 +/- 4.5%) (n = 4). Transduction efficiencies of CML CD34+ HLA-DR+ cells ranged from 0.4 to 9.8% (mean 3.7 +/- 1.7%) and 6.0 to 26% (mean 17.3 +/- 4.5%) (n = 5) over BSA and FN, respectively. rtPCR analysis for BCR/ABL mRNA of individual G418-resistant HPC generated from CD34+ HLA-DR- cells revealed that normal BCR/ABL(-) HPC were successfully transduced under these experimental conditions. These results demonstrate the feasibility of transducing normal CML primitive HPC, and illustrate the potential clinical use of FN in the setting of gene therapy for CML, as well as other diseases.

806 Priming for killing: Can the association GM-CSF-cytarabine have any role in the treatment of chronic myelogenous leukemia (CML)?

Except for bone marrow (BM) transplant, current therapies fail to cure CML because Ph’c1one cannot be eradicated. In vitro, exposing blastcrisis CML blasts to CM-CSF results in a three fold increment of cells in S phase and cell killing is 34% higher when GM-CSF+cytabarine are added simultaneously. This in vitro experience deals with the likelihood of priming CML BM cultures with GM-CSF followed by exposure to Cytarabine to evaluate Ph’c1one depletion. The BMs of 12 CML pts (3 newly diagnosed, 6 chronic phase, 3 hematological/cytogenetic complete remission) were cultured during the 24 hrs as follows: 1. controls; 2: GM-CSF (Leukomax, Schering Plough) 0.2 μg/ml; 3. Cytarabine (Ara-C, Rontag) 0.1 μg/ml 6 hrs before harvesting; 4. GM-CSF + cytarabine (as in 2 and 3). Colchicine 0.1 μg/ml was added 1 hr before harvesting. Mitotic index (MI) was expressed as X ± SE for all cultures (Table 1). Table 1: Mitotic index mean values according to cultures: Culture MI (X ± SE) 1. Controls 4.50 ± 120* *P 2. GM-CSF 6.75 ± 1.80*≈ 3. Cytarabine 3.00 ± 0.78 4. GM-CSF + Cytabarine 3.50 ± 0.77 *p According to these data, MI in CML BMs exposed to GM-CSF Is higher than MI of controls (*P

Abnormal Function of the Bone Marrow Microenvironment in Chronic Myelogenous Leukemia: Role of Malignant Stromal Macrophages

The bone marrow microenvironment supports and regulates the proliferation and differentiation of hematopoietic cells. Dysregulated hematopoiesis in chronic myelogenous leukemia (CML) is caused, at least in part, by abnormalities in CML hematopoietic progenitors leading to altered interactions with the marrow microenvironment. The role of the microenvironment itself in CML has not been well characterized. We examined the capacity of CML stroma to support the growth of long-term culture-initiating cells (LTC-IC) obtained from normal and CML marrow. The growth of normal LTC-IC on CML stroma was significantly reduced compared with normal stroma. This did not appear to be related to abnormal production of soluble factors by CML stroma because normal LTC-IC grew equally well in Transwells above CML stroma as in Transwells above normal stroma. In addition, CML and normal stromal supernatants contained similar quantities of both growth-stimulatory (granulocyte colony-stimulating factor (CSF), interleukin-6, stem cell factor, granulocyte-macrophage CSF, and interleukin-1 beta) and growth-inhibitory cytokines (transforming growth factor-beta, macrophage inflammatory protein-1 alpha, and tumor necrosis factor-alpha). The relative proportion of different cell types in CML and normal stroma was similar. However, polymerase chain reaction and fluorescence in situ hybridization studies showed the presence of bcr-abl-positivo cells in CML stroma, which were CD14+ stromal macrophages. To assess the effect of these malignant macrophages on stromal function, CML and normal stromal cells were separated by fluorescence-activated cell sorting into stromal mesenchymal cell (CD14-) and macrophage (CD14+) populations. CML and normal CD14- cells supported the growth of normal LTC-IC equally well. However, the addition of CML macrophages to normal or CML CD14- mesenchymal cells resulted in impaired progenitor support. This finding indicates that the abnormal function of CML bone marrow stroma is related to the presence of malignant macrophages. In contrast to normal LTC-IC, the growth of CML LTC-IC on allogeneic CML stromal layers was not impaired and was significantly better than that of normal LTC-IC cocultured with the same CML stromal layers. These studies demonstrate that, in addition to abnormalities in CML progenitors themselves, abnormalities in the CML marrow microenvironment related to the presence of malignant stromal macrophages may contribute to the selective expansion of leukemic progenitors and suppression of normal hematopoiesis in CML.

Interferon-alpha restores normal adhesion of chronic myelogenous leukemia hematopoietic progenitors to bone marrow stroma by correcting impaired beta 1 integrin receptor function.

Treatment of chronic myelogenous leukemia (CML) with interferon-alpha frequently results in normalization of peripheral blood counts and, in up to 20% of patients, reestablishment of normal hematopoiesis. We hypothesize that interferon-alpha may restore normal adhesive interactions between CML progenitors and the bone marrow microenvironment and restore normal growth regulatory effects resulting from these progenitor-stroma interactions. We demonstrate that treatment with interferon-alpha induces a significant, dose-dependent increase in the adhesion of primitive long-term culture initiating cells and committed colony-forming cells (CFC) from CML bone marrow to normal stroma. Adhesion of CFC seen after interferon-alpha treatment could be inhibited by blocking antibodies directed at the alpha 4, alpha 5, and beta 1 integrins and vascular cell adhesion molecule, but not CD44 or intracellular adhesion molecule, suggesting that interferon-alpha induces normalization of progenitor-stroma interactions in CML. Because FACS analysis showed that the level of alpha 4, alpha 5, and beta 1 integrin expression after interferon-alpha treatment is unchanged, this suggests that interferon-alpha may restore normal beta 1 integrin function. Normalization of interactions between CML progenitors and the bone marrow microenvironment may then result in the restoration of normal regulation of CML progenitor proliferation, and explain, at least in part, the therapeutic efficacy of interferon-alpha in CML.

Subcellular localization of Bcr, Abl, and Bcr-Abl proteins in normal and leukemic cells and correlation of expression with myeloid differentiation.

We used specific antisera and immunohistochemical methods to investigate the subcellular localization and expression of Bcr, Abl, and Bcr-Abl proteins in leukemic cell lines and in fresh human leukemic and normal samples at various stages of myeloid differentiation. Earlier studies of the subcellular localization of transfected murine type IV c-Abl protein in fibroblasts have shown that this molecule resides largely in the nucleus, whereas transforming deletion variants are localized exclusively in the cytoplasm. Here, we demonstrate that the murine type IV c-Abl protein is also found in the nucleus when overexpressed in a mouse hematopoietic cell line. However, in both normal and leukemic human hematopoietic cells, c-Abl is discerned predominantly in the cytoplasm, with nuclear staining present, albeit at a lower level. In contrast, normal endogenous Bcr protein, as well as the aberrant p210BCR-ABL and p190BCR-ABL proteins consistently localize to the cytoplasm in both cell lines and fresh cells. The results with p210BCR-ABL were confirmed in a unique Ph1-positive chronic myelogenous leukemia (CML) cell line, KBM5, which lacks the normal chromosome 9 and hence the normal c-Abl product. Because the p210BCR-ABL protein appears cytoplasmic in both chronic phase and blast crisis CML cells, as does the p190BCR-ABL in Ph1-positive acute leukemia, a change in subcellular location of Bcr-Abl proteins between cytoplasm and nucleus cannot explain the different spectrum of leukemias associated with p210 and p190, nor the transition from the chronic to the acute leukemia phenotype seen in CML. Further analysis of fresh CML and normal hematopoietic bone marrow cells reveals that p210BCR-ABL, as well as the normal Bcr and Abl proteins, are expressed primarily in the early stages of myeloid maturation, and that levels of expression are reduced significantly as the cells mature to polymorphonuclear leukocytes. Similarly, a decrease in Bcr and Abl levels occurs in HL-60 cells induced by DMSO to undergo granulocytic differentiation. The action of p210BCR-ABL and its normal counterparts may, therefore, take place during the earlier stages of myeloid development.