Heather G Jørgensen

University of Glasgow, Glasgow, Scotland, United Kingdom

Are you Heather G Jørgensen?

Claim your profile

Publications (47)266.83 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukaemia (CML) stem cell survival is not dependent on BCR-ABL protein kinase and treatment with ABL tyrosine kinase inhibitors (TKIs) cures only a minority of CML patients, thus highlighting the need for novel therapeutic targets. The JAK2/STAT5 pathway has recently been explored for providing putative survival signals to CML stem/progenitor cells (SPCs) with contradictory results. We investigated the role of this pathway using the JAK2 inhibitor, ruxolitinib. We demonstrated that the combination of ruxolitinib, at clinically achievable concentrations, with the specific and potent TKI nilotinib, reduced the activity of the JAK2/STAT5 pathway in vitro relative to either single agent alone. These effects correlated with increased apoptosis of CML SPCs in vitro and a reduction in primitive quiescent CML stem cells, including NOD.Cg-Prkdc(scid) IL2rg(tm1Wjl) /SzJ mice (NSG) repopulating cells, induced by combination treatment. A degree of toxicity towards normal SPCs was observed with the combination treatment, although this related to mature B cell engraftment in NSG mice with minimal effects on primitive CD34(+) cells. These results support the JAK2/STAT5 pathway as a relevant therapeutic target in CML SPCs and endorse the current use of nilotinib in combination with ruxolitinib in clinical trials to eradicate persistent disease in CML patients.
    Blood 06/2014; · 9.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The tyrosine kinase inhibitor (TKI) imatinib has transformed the treatment and outlook of chronic myeloid leukemia (CML); however, the development of drug resistance and the persistence of TKI-resistant stem cells remain obstacles to eradicating the disease. Inhibition of proteasome activity with bortezomib has been shown to effectively induce apoptosis in TKI-resistant cells. In this study, we show that exposure to the next generation proteasome inhibitor carfilzomib is associated with a decrease in ERK signaling and increased expression of Abelson interactor proteins 1 and 2 (ABI-1/2). We also investigate the effect of carfilzomib in models of imatinib-sensitive and -resistant CML and demonstrate a potent reduction in proliferation and induction of apoptosis in a variety of models of imatinib-resistant CML, including primitive CML stem cells. Carfilzomib acts synergistically with the TKIs imatinib and nilotinib, even in imatinib-resistant cell lines. In addition, we found that the presence of immunoproteasome subunits is associated with an increased sensitivity to carfilzomib. The present findings provide a rational basis to examine the potential of carfilzomib in combination with TKIs as a potential therapy for CML, particularly in imatinib-resistant disease.
    Oncogenesis. 01/2014; 3:e90.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukaemia (CML) is a hematological malignancy resulting from the transformation of a primitive hematopoietic progenitor by the fusion oncogene BCR-ABL, a constitutively active tyrosine kinase. In recent years major advances have been made in the treatment of CML with the development of tyrosine kinase inhibitors (TKIs), resulting in high rates of remission in CML chronic phase (CP) patients. However, relapse is driven by quiescent and self-renewing BCR-ABL+ CML stem cells (LSCs) that are resistant to TKIs. Consequently, identification of novel proteins or pathways which can be drug-targeted to eliminate the LSCs is a primary goal of current CML research. Through comparative analysis between CML and non-leukemic samples, we show that components of the repressive Polycomb group (PcG) complex PRC2 are significantly misregulated in CML samples. By performing genome-wide mRNA and epigenetic screens, we demonstrate that this has led to as many as 3-fold more gene repression events in CML cells being associated with gains in the histone modification H3K27me3. This misregulation results in different biological pathways being targeted by PRC2 than those found in non-leukemic samples. We demonstrate that the majority of this misregulation is present in the LSCs. EZH2 is a key component of the PRC2 complex, responsible for laying down the H3K27me3 mark. To determine the effect of inhibition of the complex on LSC survival we have utilised an inhibitor of EZH2, CPI-625. In the absence and presence of TKI, treatment of CP CML CD34+ cells (n=3) with CPI-625 resulted in decreased cell viability (p<0.001 and p<0.05, -/+ TKI respectively) and increased apoptosis (p<0.05 without TKI) in a dose dependent manner. Significantly, there was also a decrease in the number of cells in the undivided, quiescent ‘TKI resistant’ population relative to controls (p<0.01 and p<0.05 -/+ TKI respectively). This was accompanied by an increase in apoptosis (p<0.05 without TKI). Moreover, treatment with CPI-625 resulted in decreasing Colony Forming Cell (CFC) numbers, both in the absence (p<0.05) and presence (p<0.01) of TKI relative to controls. Similar results were seen with treatment of the more primitive CD34+38- cells. Importantly, these effects were not observed in non-leukemic cells. These results demonstrate that CPI-625 is capable of selective targeting of the LSC population. Our data strongly points to changes in H3K27me3 gene targets in CML as a feature related to misregulation of the PRC2 complex. We have demonstrated that targeting of this complex may have efficacy in the treatment of CML, including eradication of the drug resistant LSCs.
    ASH 2013, New Orleans; 12/2013
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukaemia (CML) stem cells are not dependent on BCR-ABL kinase for their survival suggesting that kinase-independent mechanisms must contribute to their persistence. We observed that CML stem/progenitor cells (SPCs) produce tumour necrosis factor-alpha (TNF-α) in a kinase-independent fashion and at higher levels relative to their normal counterparts. We therefore investigated the role of TNF-α and found that it supports survival of CML SPCs by promoting NFκB/p65 pathway activity and expression of the interleukin-3 and granulocyte/macrophage-colony stimulating factor common β-chain receptor. Furthermore, we demonstrate that in CML SPCs inhibition of autocrine TNF-α signalling via a small molecule TNF-α inhibitor induces apoptosis. Moreover TNF-α inhibition combined with nilotinib induces significantly more apoptosis relative to either treatment alone and a reduction in the absolute number of primitive quiescent CML stem cells. These results highlight a novel survival mechanism of CML SPCs and suggest a new putative therapeutic target for their eradication.
    Blood 09/2013; · 9.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Imatinib mesylate (IM) induces clinical remission of chronic myeloid leukemia (CML). The Abelson helper integration site 1 (AHI-1) oncoprotein interacts with BCR-ABL and Janus kinase 2 (JAK2) to mediate IM response of primitive CML cells, but the effect of the interaction complex on the response to ABL and JAK2 inhibitors is unknown.Methods The AHI-1-BCR-ABL-JAK2 interaction complex was analyzed by mutational analysis and coimmunoprecipitation. Roles of the complex in regulation of response or resistance to ABL and JAK2 inhibitors were investigated in BCR-ABL + cells and primary CML stem/progenitor cells and in immunodeficient NSG mice. All statistical tests were two-sided.ResultsThe WD40-repeat domain of AHI-1 interacts with BCR-ABL, whereas the N-terminal region interacts with JAK2; loss of these interactions statistically significantly increased the IM sensitivity of CML cells. Disrupting this complex with a combination of IM and an orally bioavailable selective JAK2 inhibitor (TG101209 [TG]) statistically significantly induced death of AHI-1-overexpressing and IM-resistant cells in vitro and enhanced survival of leukemic mice, compared with single agents (combination vs TG alone: 63 vs 53 days, ratio = 0.84, 95% confidence interval [CI] = 0.6 to 1.1, P = .004; vs IM: 57 days, ratio = 0.9, 95% CI = 0.61 to 1.2, P = .003). Combination treatment also statistically significantly enhanced apoptosis of CD34+ leukemic stem/progenitor cells and eliminated their long-term leukemia-initiating activity in NSG mice. Importantly, this approach was effective against treatment-naive CML stem cells from patients who subsequently proved to be resistant to IM therapy.Conclusions Simultaneously targeting BCR-ABL and JAK2 activities in CML stem/progenitor cells may improve outcomes in patients destined to develop IM resistance.
    CancerSpectrum Knowledge Environment 02/2013; · 14.07 Impact Factor
  • Source
    Blood Cells Molecules and Diseases 03/2012; 48(3):199-201. · 2.26 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: MECOM oncogene expression correlates with chronic myeloid leukaemia (CML) progression. Here we show that the knockdown of MECOM (E) and MECOM (ME) isoforms reduces cell division at low cell density, inhibits colony-forming cells by 34% and moderately reduces BCR-ABL1 mRNA and protein expression but not tyrosine kinase catalytic activity in K562 cells. We also show that both E and ME are expressed in CD34(+) selected cells of both CML chronic phase (CML-CP), and non-CML (normal) origin. Furthermore, MECOM mRNA and protein expression were repressed by imatinib mesylate treatment of CML-CP CD34(+) cells, K562 and KY01 cell lines whereas imatinib had no effect in non-CML BCR-ABL1 -ve CD34(+) cells. Together these results suggest that BCR-ABL1 tyrosine kinase catalytic activity regulates MECOM gene expression in CML-CP progenitor cells and that the BCR-ABL1 oncoprotein partially mediates its biological activity through MECOM. MECOM gene expression in CML-CP progenitor cells would provide an in vivo selective advantage, contributing to CML pathogenesis.
    British Journal of Haematology 02/2012; 157(4):446-56. · 4.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Omacetaxine is a natural product extract originating from Chinese medicine and finding therapeutic use as a potent myelosuppressive agent in leukemia. When planning in vitro cell biology experiments to assess omacetaxine activity against primary leukemic stem cells, it became apparent that the literature rarely describes the in vitro stability of the molecule, although accessible chromatographic methods have been published. Clearly whole organisms vs their component cells will differ in the way in which they handle xenobiotics, with the latter more dependent on physiochemical parameters such as pH and temperature in the absence of active metabolism or excretion. This could impact on the cells' experience of drug in culture. We therefore report here on examination of a modified, high-performance liquid chromatography (HPLC) method with assessment of degradant production from a 72 h solution stability study, clearly demonstrating that omacetaxine is highly stable in representative cell culture conditions (37 °C, neutral pH) and persists for many days in marked contrast to its short-half life in vivo.
    Biomedical Chromatography 08/2011; 26(5):545-7. · 1.95 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The LC-ESI-MS was developed and validated for the analysis of imatinib in plasma and bone marrow samples using deuterated imatinib (D(8)-IM) as an internal standard. The biological samples were extracted using Strata-X-C SPE cartridges and separated on C(8) column (50 x 3 mm, 3 μm), and methanol: 0.1% formic acid (70:30) was delivered at the rate of 0.7 ml/min as a mobile phase. Imatinib was quantified in samples by monitoring the ions m/z 494.3 for imatinib and 502.3 for D(8)-imatinib on mass spectrometer. The method was linear in the concentration range of 1-1500 ng/250 μl in spiked human plasma samples and limit of quantification was 5 ng/mL. Inter-day and intra-day variations in spiked human plasma spiked with 50, 250 and 500 ng /mL were less than 3.16%. The repeatability and reproducibility and other parameters of the methods were also validated. The method was employed for the analysis of the imatinib in human plasma and bone marrow samples. The drug levels in bone marrow and plasma samples were correlated to the degree of cytogenetic response. No significant difference of imatinib level between blood and bone marrow in IM-treated patients dosed to steady state was observed.
    Pakistan journal of pharmaceutical sciences 07/2011; 24(3):285-91. · 0.95 Impact Factor
  • Source
    E K Allan, T L Holyoake, A R Craig, H G Jørgensen
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukaemia (CML) is maintained by a rare population of tyrosine kinase inhibitor (TKI)-insensitive malignant stem cells. Our long-term aim is to find a BcrAbl-independent drug that can be combined with a TKI to improve overall disease response in chronic-phase CML. Omacetaxine mepesuccinate, a first in class cetaxine, has been evaluated by clinical trials in TKI-insensitive/resistant CML. Omacetaxine inhibits synthesis of anti-apoptotic proteins of the Bcl-2 family, including (myeloid cell leukaemia) Mcl-1, leading to cell death. Omacetaxine effectively induced apoptosis in primary CML stem cells (CD34(+)38(lo)) by downregulation of Mcl-1 protein. In contrast to our previous findings with TKIs, omacetaxine did not accumulate undivided cells in vitro. Furthermore, the functionality of surviving stem cells following omacetaxine exposure was significantly reduced in a dose-dependant manner, as determined by colony forming cell and the more stringent long-term culture initiating cell colony assays. This stem cell-directed activity was not limited to CML stem cells as both normal and non-CML CD34(+) cells were sensitive to inhibition. Thus, although omacetaxine is not leukaemia stem cell specific, its ability to induce apoptosis of leukaemic stem cells distinguishes it from TKIs and creates the potential for a curative strategy for persistent disease.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 04/2011; 25(6):985-94. · 10.16 Impact Factor
  • Experimental Hematology. 01/2011; 39(8):S18-S18.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic Myeloid Leukemia (CML) stem/progenitor cells, which over-express Bcr-Abl, respond to imatinib by a reversible block in proliferation without significant apoptosis. As a result, patients are unlikely to be cured owing to the persistence of leukemic quiescent stem cells (QSC) capable of initiating relapse. Previously, we have reported that intracellular levels of imatinib in primary primitive CML cells (CD34+38(lo/⁻)), are significantly lower than in CML progenitor cells (total CD34+) and leukemic cell lines. The aim of this study was to determine if potentially sub-therapeutic intracellular drug concentrations in persistent leukemic QSC may be overcome by targeted drug delivery using synthetic Low Density Lipoprotein (sLDL) particles. As a first step towards this goal, however, the extent of uptake of sLDL by leukemic cell lines and CML patient stem/progenitor cells was investigated. Results with non-drug loaded particles have shown an increased and preferential uptake of sLDL by Bcr-Abl positive cell lines in comparison to Bcr-Abl negative. Furthermore, CML CD34+ and primitive CD34+38(lo/⁻) cells accumulated significantly higher levels of sLDL when compared with non-CML CD34+ cells. Thus, drug-loading the sLDL nanoparticles could potentially enhance intracellular drug concentrations in primitive CML cells and thus aid their eradication.
    Journal of Controlled Release 12/2010; 148(3):380-7. · 7.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Imatinib mesylate (IM) induces clinical remissions in chronic-phase chronic myeloid leukemia (CML) patients but IM resistance remains a problem. We recently identified several features of CML CD34(+) stem/progenitor cells expected to confer resistance to BCR-ABL-targeted therapeutics. From a study of 25 initially chronic-phase patients, we now demonstrate that some, but not all, of these parameters correlate with subsequent clinical response to IM therapy. CD34(+) cells from the 14 IM nonresponders demonstrated greater resistance to IM than the 11 IM responders in colony-forming cell assays in vitro (P < .001) and direct sequencing of cloned transcripts from CD34(+) cells further revealed a higher incidence of BCR-ABL kinase domain mutations in the IM nonresponders (10%-40% vs 0%-20% in IM responders, P < .003). In contrast, CD34(+) cells from IM nonresponders and IM responders were not distinguished by differences in BCR-ABL or transporter gene expression. Interestingly, one BCR-ABL mutation (V304D), predicted to destabilize the interaction between p210(BCR-ABL) and IM, was detectable in 14 of 20 patients. T315I mutant CD34(+) cells found before IM treatment in 2 of 20 patients examined were preferentially amplified after IM treatment. Thus, 2 properties of pretreatment CML stem/progenitor cells correlate with subsequent response to IM therapy. Prospective assessment of these properties may allow improved patient management.
    Blood 09/2010; 116(12):2112-21. · 9.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukemia (CML) is treated effectively with tyrosine kinase inhibitors (TKIs); however, 2 key problems remain-the insensitivity of CML stem and progenitor cells to TKIs and the emergence of TKI-resistant BCR-ABL mutations. BCR-ABL activity is associated with increased proteasome activity and proteasome inhibitors (PIs) are cytotoxic against CML cell lines. We demonstrate that bortezomib is antiproliferative and induces apoptosis in chronic phase (CP) CD34+ CML cells at clinically achievable concentrations. We also show that bortezomib targets primitive CML cells, with effects on CD34+38(-), long-term culture-initiating (LTC-IC) and nonobese diabetic/severe combined immunodeficient (NOD/SCID) repopulating cells. Bortezomib is not selective for CML cells and induces apoptosis in normal CD34+38(-) cells. The effects against CML cells are seen when bortezomib is used alone and in combination with dasatinib. Bortezomib causes proteasome but not BCR-ABL inhibition and is also effective in inhibiting proteasome activity and inducing apoptosis in cell lines expressing BCR-ABL mutations, including T315I. By targeting both TKI-insensitive stem and progenitor cells and TKI-resistant BCR-ABL mutations, we believe that bortezomib offers a potential therapeutic option in CML. Because of known toxicities, including myelosuppression, the likely initial clinical application of bortezomib in CML would be in resistant and advanced disease.
    Blood 03/2010; 115(11):2241-50. · 9.78 Impact Factor
  • Blood 01/2010; 116(21):1393-1394. · 9.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder maintained by cancer stem cells. To target this population, we investigated the mechanism of action of BMS-214662, developed as a farnesyl transferase inhibitor (FTI) and unique in inducing apoptosis in these cells. By contrast, a related congener and equally effective FTI, BMS-225975 does not induce apoptosis, indicating a novel mechanism of action. BMS-214662 significantly and selectively induced apoptosis in primitive CD34(+)38(-) CML compared with normal cells. Apoptosis proceeded via the intrinsic pathway: Bax conformational changes, loss of mitochondrial membrane potential, generation of reactive oxygen species, release of cytochrome c, and caspase-9/3 activation were noted. Up-regulation of protein kinase Cbeta (PKCbeta), down-regulation of E2F1, and phosphorylation of cyclin A-associated cyclin-dependent kinase 2 preceded these changes. Cotreatment of CML CD34(+) and CD34(+)38(-) cells with PKC modulators, bryostatin-1, or hispidin markedly decreased these early events and the subsequent apoptosis. None of these events was elicited by BMS-214662 in normal CD34(+) cells or by BMS-225975 in CML CD34(+) cells. These data suggest that BMS-214662 selectively elicits a latent apoptotic pathway in CML stem cells that is initiated by up-regulation of PKCbeta and mediated by Bax activation, providing a molecular framework for development of novel therapeutics.
    Blood 10/2009; 114(19):4186-96. · 9.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Imatinib mesylate and nilotinib are highly effective at eradicating the majority of chronic myeloid leukemia (CML) cells; however, neither agent induces apoptosis of primitive CML CD34(+) cells. One possible explanation is that CD34(+) cells do not accumulate sufficient intracellular drug levels because of either inadequate active uptake or increased efflux. To determine the interaction of nilotinib with major clinically implicated drug transporters, we analyzed their interactions with MDR1 (ABCB1), MRP1 (ABCC1), ABCG2 (BCRP) and human organic cation transporter (hOCT)1 in CML cell lines and primitive (CD34(+)) primary CML cells. Nilotinib is neither dependent on active import by hOCT1, nor effluxed through the ATP-binding cassette transporters analyzed. Indeed, we found nilotinib to be an inhibitor of hOCT1, MDR1 and ABCG2. The efflux transporters MDR1, MRP1 and ABCG2 are expressed on CML CD34(+) cells at 13.5, 108 and 291% of control, respectively, although hOCT1 expression was absent; however, inhibition of efflux transporter activity did not potentiate the effect of nilotinib on apoptosis, Bcr-Abl inhibition or CML CD34(+) cell proliferation. Therefore, we have found no evidence for either active uptake of nilotinib through hOCT1 or efflux through MDR1, MRP1 or ABCG2, and it is therefore unlikely that these transporters will have any effect on the clinical response to this drug.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 09/2009; 23(11):1999-2006. · 10.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the interaction of imatinib mesylate (IM) with the clinically relevant adenosine triphosphate-binding cassette efflux transporter MDR1 (ABCB1) in cells from patients with chronic myeloid leukemia (CML) and to explore whether inhibition of this transporter would improve IM's efficacy in the elimination of CML CD34(+) cells by increasing cell-associated drug accumulation. Cells from newly diagnosed chronic-phase CML patients were harvested by leukapheresis and enriched to >95% CD34(+). Expression of the transporter gene MDR1 was performed by quantitative reverse transcription polymerase chain reaction. Interaction of IM with MDR1 was analyzed by substrate (rhodamine 123) displacement assay. Cell-associated levels of IM in CML CD34(+) cells were measured by high-pressure liquid chromatography. Intracellular phospho-CrkL levels, apoptosis in total CML CD34(+) cells and high-resolution tracking of cell division were assayed by flow cytometry. Measurements of cell-associated IM uptake showed significantly lower drug levels in CD34(+) cells, particularly the CD38(-) subpopulation, as compared to IM-sensitive K562 cells. MDR1 was expressed at low level and dye efflux studies demonstrated very little MDR1 activity in CML CD34(+) cells. Furthermore, combination treatment of primitive CML cells with IM and the MDR1 inhibitor PSC833 did not result in elevated cell-associated IM levels. Although we observed slightly enhanced cytostasis with IM when combined with PSC833, this was independent of BCR-ABL inhibition because no associated decrease in phospho-CrkL was observed. Our findings demonstrate that inhibition of MDR1 neither enhances the effect of IM against BCR-ABL activity, nor significantly potentiates IM's efficiency in eliminating primitive CML cells.
    Experimental hematology 04/2009; 37(6):692-700. · 3.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The recent success in treating chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKI), such as imatinib mesylate (IM), has created a demand for reproducible methods to accurately assess inhibition of BCR-ABL activity within CML cells, including rare stem and progenitor cells, either in vitro or in vivo. The purpose of this study was to develop an enzyme-linked immunosorbent (ELISA) method to measure total tyrosine phosphorylation (P-Tyr) in small samples of cells that express BCR-ABL and to compare to more established methods. The assay was first validated in BCR-ABL wild-type and mutant vs BCR-ABL-negative cell lines. P-Tyr levels were then measured by ELISA in primary CD34(+) CML cells treated with IM. In vitro exposure to TKI resulted in decreases in the level of P-Tyr, in both BCR-ABL-positive cell lines and primary CD34(+) CML samples, which were comparable to the reduction in P-Tyr by flow cytometry and phosphorylation of CrkL by either Western blot or flow cytometry. We have developed an accurate ELISA method to measure BCR-ABL activity within Ph(+) cells, which is comparable to other in vitro BCR-ABL assessment techniques in terms of sensitivity and could be adapted for high throughput.
    Experimental hematology 02/2009; 37(3):395-401. · 3.11 Impact Factor
  • Source
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 02/2009; 23(5):1006-8. · 10.16 Impact Factor

Publication Stats

2k Citations
266.83 Total Impact Points

Institutions

  • 2001–2014
    • University of Glasgow
      • • Institute of Cancer Sciences
      • • School of Medicine
      Glasgow, Scotland, United Kingdom
  • 2012
    • Dow University of Health Sciences
      Kurrachee, Sindh, Pakistan
  • 2003–2011
    • University of Strathclyde
      • • Strathclyde Institute of Pharmacy and Biomedical Sciences
      • • Department of Bioscience
      Glasgow, SCT, United Kingdom