Blocking of Cytokine Survival Signals along with Intense Bcr-Abl Kinase Inhibition May Eradicate CML Progenitor Cells.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3250-3250
Author(s):  
Devendra K Hiwase ◽  
Deborah L White ◽  
Jason A Powell ◽  
Verity A Saunders ◽  
Stephanie Zrim ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Research Funding ◽  
Kinase Activity ◽  
Short Term ◽  
Kinase Inhibition ◽  
Gm Csf ◽  
Abl Kinase ◽  
Cd34 Cells ◽  
Short Term Culture

Abstract Abstract 3250 Poster Board III-1 Preclinical studies of imatinib set the paradigm of continuous Bcr-Abl kinase inhibition for optimal response in chronic myeloid leukemia (CML). However, the clinical success of once daily dasatinib, despite its short serum half life, implies that intermittent inhibition of Bcr-Abl kinase activity is sufficient for clinical response. In vitro studies also demonstrated that short-term intense (≥90%) Bcr-Abl kinase inhibition triggers cell death in BCR-ABL + cell lines, demonstrating their oncogene addiction. However, the effect of short-term intense kinase inhibition on CD34+ CML progenitors is not studied. Clinical, mathematical modelling and in vitro studies suggest that leukemic stem cells (LSC) are difficult to eradicate and hence the majority of CML patients may not be cured with tyrosine kinase inhibitors (TKI). Inadequate Bcr-Abl kinase inhibition has been postulated to cause refractoriness of LSC to TKI's. This may be due to increased expression of ABCB1 and ABCG2 efflux proteins, or the quiescent state of LSC. However, the phenomenon could be independent of Bcr-Abl kinase activity. In vivo leukemic progenitors live in a cytokine rich environment which may be providing a mechanism for Bcr-Abl independent resistance. We have assessed the impact of short-term intense Bcr-Abl kinase inhibition on CML cell lines and CML CD34+ primary cells in the presence and absence of cytokines. In CML cell lines, short-term (cells were cultured with dasatinib for 30 min and following thorough drug washout, cells were recultured in drug free media for 72 hr) intense Bcr-Abl kinase inhibition with 100 nM dasatinib triggers cell death. In CML-CD34+ cells 30 min of culture with 100 nM dasatinib (n=13) or 30 μM IM (n=7) reduced the level of p-Crkl (surrogate marker of Bcr-Abl kinase activity) by 97±3% and 96±4% respectively. In the presence of either a six growth factors cocktail (6-GF; n=10) or GM-CSF (n=11) or G-CSF (n=4) alone, despite 97% inhibition of p-Crkl, short-term culture with 100 nM dasatinib (D100ST) reduced colony forming cells (CFC) by only 24%, 32% or 5%, respectively. However without cytokines, D100ST reduced CML-CD34+ CFCs by 70%. Consistent with the results observed with dasatinib, short-term culture with 30 μM imatinib (IM) (n=3) also reduced 90% CFC in the absence of cytokines but by only 38% in the presence of 6-GF. These results suggest that in CML-CD34+ cells, GM-CSF, G-CSF or 6-GF mediate Bcr-Abl independent TKI resistance. It is possible that cytokines may be promoting cell survival via signalling pathways that are refractory to dasatinib. To examine this possibility, we assessed the effect of D100ST on p-STAT5 signalling in CML-CD34+ cells, in the presence and absence of GM-CSF, G-CSF or 6-GF. STAT5 was constitutively phosphorylated in CML-CD34+ cells, and in the absence of cytokines, D100ST reduced the p-STAT 5. STAT5 phosphorylation was not inhibited by D100ST when cells were cultured with 6-GFs or GM-CSF however, the combination of D100ST and a Janus kinase (Jak) inhibitor dramatically reduced p-STAT5. Similarly, in the presence of GM-CSF (32.35±5.16% vs. 68.33±14.90%) or G-CSF (58.13±13 vs. 94.68±21.12) combination of D100ST and JAK inhibitor significantly reduced CFC compared to D100ST only. Thus our data suggest that in contrast to CML cell lines, primary CML progenitors may not be completely dependent on the BCR-ABL oncogene and that activation of the cytokine mediated JAK-2/STAT-5 pathway may circumvent the need for BCR-ABL signalling for maintenance of survival. Thus a therapeutic strategy based on short-term intense kinase inhibition may have limited success unless critical redundant cytokine-induced survival pathways are also inhibited. We postulate that blockade of cytokine signalling along with short-term intense Bcr-Abl kinase inhibition with a potent second generation TKI may provide a novel strategy to eradicate primitive CML cells. Fig 1 In CML-CD34+ cells, Jak kinase inhibition abrogates the rescuing effect of cytokines on cell death induced by BCR-ABL blockade: In the absence of cytokines (No GF, n=11) short-term culture with 100 nM dasatinib (D100ST) reduced CFCs by 67% of control, however in the presence of 6-GFs (n=10), GM-CSF (n=10) or G-CSF (n=4) it could reduce CFCs by only 24%, 32% or 5% of control respectively (B) In the presence of GM-CSF (n= 4) or G-CSF (n= 4), combination of Jak inhibition and D100ST reduced CFC compared to dasatinib alone. Fig 1. In CML-CD34+ cells, Jak kinase inhibition abrogates the rescuing effect of cytokines on cell death induced by BCR-ABL blockade: In the absence of cytokines (No GF, n=11) short-term culture with 100 nM dasatinib (D100ST) reduced CFCs by 67% of control, however in the presence of 6-GFs (n=10), GM-CSF (n=10) or G-CSF (n=4) it could reduce CFCs by only 24%, 32% or 5% of control respectively (B) In the presence of GM-CSF (n= 4) or G-CSF (n= 4), combination of Jak inhibition and D100ST reduced CFC compared to dasatinib alone. Disclosures: White: Novartis and Britol-Myers Squibb: Research Funding. Hughes:BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Short –Term Intense Bcr-Abl Kinase Inhibition Is Adequate to Trigger Cell Death in CML Cell Lines but Not in CML-CD34+ Cells Unless They Are Growth Factor Deprived.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1086-1086
Author(s):  
Devendra K. Hi Wase ◽  
Deborah L. White ◽  
Verity A. Saunders ◽  
Junia V. Melo ◽  
Sharad Kumar ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Death ◽  
Growth Factors ◽  
Growth Factor ◽  
Cell Lines ◽  
Kinase Activity ◽  
Short Term ◽  
Kinase Inhibition ◽  
Abl Kinase ◽  
Cd34 Cells

Abstract After 5 years of imatinib treatment, only a minority of newly diagnosed chronic myeloid leukemia chronic phase (CML-CP) patients achieve complete molecular response. Imatinib has antiproliferative effects, but may not be able to eradicate CML-stem cells. Preclinical studies of imatinib suggested that sustained BCR-ABL kinase inhibition was required to block proliferation and induce apoptosis in CML cells. This formed the rationale for treatment regimens that maintain continuous kinase inhibition. Clinical studies with dasatinib suggested that daily dosing achieves equivalent response to twice daily even though ABL kinase inhibition only persists for 4–6 hours. We have demonstrated that 30 minutes of exposure to 100 nM dasatinib or 30 μ M imatinib (equipotent) inhibit p-Crkl (surrogate marker of Bcr-Abl kinase activity) by 80 to 90% in Bcr-Abl +ve cell lines and CML-CD34+ cells (n=8). We then sought to compare antiproliferative and pro-apoptotic effects of short term (ST; cells were cultured with dasatinib/imatinib for 30 minutes and after thorough wash, were recultured without dasatinib/imatinib for 72 hours) and continuous (CT, cells were cultured with drugs continuously) dasatinib or imatinib in BCRABL +ve cell lines (K562, Meg 01) and CD34+ cells of CML-CP patients. Although Bcr- Abl kinase reactivated within 30 minutes of drug removal, ST 100 nM dasatinib (D100ST) or 30μ M of imatinib (IM30ST) induced apoptosis (~80%) and blocked cell proliferation equivalent to continuous dasatinib (10 nM; D10CT) or imatinib (2μ M, IM2CT) in Bcr-Abl +ve cell lines. The kinetics of cell death and caspase-3 activation over 72 hours of culture were similar in D100ST and D10CT. In the presence of 6-growth factors (GFs; IL-3, IL- 6, G-CSF, SCF, TPO, Flt-3) D100ST and IM30ST reduced cell viability and CFU-GM colonies of CML-CD34+ cells by only 25 to 30% of no drug control. Moreover in the presence of GFs, 30 to 40% CD34+ve cells were viable and retained CFU-GM potential in spite of continuous dasatinib 100 nM (D100CT) or 30 μ M of imatinib (IM30CT). However, in the absence of GFs, D100ST and IM30ST reduced viability by 60 to 70%, and CFU-GM by 95% of control (with GFs, no TKI control; Fig 1). Figure 1: Survival of CFU-GM according to growth factor and dasatinib exposure: Figure 1:. Survival of CFU-GM according to growth factor and dasatinib exposure: Conclusion: Short term intense inhibition of BCR-ABL kinase activity triggers apoptosis in CML cell lines, which demonstrate their Bcr-Abl oncogene dependence. However, in spite of >80% kinase inhibition, D100ST and D100CT did not eliminate the majority of CML-CD34+ cells in the presence of GFs. In the absence of GFs, D100ST and IM30ST were able to inhibit cell proliferation, induce cell death and eliminate 95% of CFU-GM. This data suggests that oncogene dependence of CML CD34+ cells can be overcome by cytokines. Unlike CML cell lines where transient intense kinase inhibition leads to cell death, primary CML cells are only sensitive to this short term kinase inhibition in the absence of cytokines. Strategies that block cytokine pathways in combination with Bcr-Abl kinase inhibition may eliminate leukemic stem cells in-vivo even if only applied intermittently. CFU-GM colonies expressed as % of control. CML-CD34+ cells (n=3) were cultured with dasatinib in the presence (With GFs) or absence (No GFs) of 6-growth factors (GF) and CFU-GM colonies were plated on D3, using Methocult 4230 (Invitrogen) along with growth factors in all cases. Colonies were read after 14 days. In each patient values were normalised to cells cultured with GFs and no dasatinib. Short term (ST) and continuous (CT), Dasatinib 10 nM (D10), 100 nM (D100).

In Contrast to Imatinib, Dasatinib Intracellular Concentration In CML-CD34+ Progenitors Is Not Significantly Different Than That Observed In CD34- Mature Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1205-1205
Author(s):  
Devendra K Hiwase ◽  
Jane Engler ◽  
Verity Saunders ◽  
Deborah L. White ◽  
Timothy Hughes
Keyword(s):  
Mrna Expression ◽  
Research Funding ◽  
Kinase Activity ◽  
Intracellular Uptake ◽  
Leukemic Stem Cells ◽  
Kinase Inhibition ◽  
Abl Kinase ◽  
Psc 833 ◽  
Cd34 Cells ◽  
Expression And Activity

Abstract Abstract 1205 Long term follow up of imatinib (IM) clinical studies and in vitro studies suggest that tyrosine kinase inhibitors (TKI) do not eradicate leukemic stem cells. Refractoriness of leukemic stem cells is postulated to be due to inadequate Bcr-Abl kinase inhibition which in turn could be due to low intracellular uptake and retention (IUR) of TKI. We have previously demonstrated that IM cellular uptake is predominantly mediated by the organic cation transporter protein (OCT-1) and patients with low OCT-1 activity have suboptimal response as compared to patients with high OCT-1 activity. More recently Engler et al (Leukemia 2010) demonstrated that IM IUR is significantly lower in CML-CD34+ cells compared to CD34- cells. This could be due to low expression and activity of the OCT-1 protein and/or high expression of ABCB1 and/or ABCG2 (Jiang et al Leukemia 2007). Although dasatinib is clinically available there are no published data assessing dasatinib IUR in CML-CD34+ progenitors. We and others have previously demonstrated that dasatinib cellular uptake is predominantly OCT-1 independent and dasatinib is a substrate of ABCB1 and ABCG2. We hypothesized that dasatinib IUR would be lower in CML-CD34+ cells compared to CD34- cells. In this study we compare dasatinib and IM IUR; and OCT-1 and ABCB1 mRNA expression in CML-CD34+ and CD34- cells of newly diagnosed CML-CP patients. CD34+ and CD34- cells were incubated with 14C-dasatinib (100 nM and 1 μM) or 14C-IM (2 μM) for 2h and IUR was assessed as described previously (Hiwase et al Clin Cancer Res. 2008). As shown previously, the OCT-1 expression and activity was lower in CML-CD34+ cells, and resulted in lower IM IUR in CML-CD34+ cells compared to CML-CD34- cells (15±5 vs. 27±5; p=0.04; Fig 1A and C). However at a therapeutically achievable concentration (100 nM dasatinib) and at higher concentration (1 μM dasatinib), there was no significant difference in dasatinib IUR in CML-CD34+ and CD34- cells (Fig 1B). Low OCT-1 expression and activity in CML-CD34+ cells did not influence the dasatinib IUR; further confirming that dasatinib cellular influx is predominantly OCT-1 independent. Despite higher ABCB1 mRNA expression in CML-CD34+ cells, the dasatinib IUR was not lower in CML-CD34+ cells compared to CD34- cells. High ABCB1 mRNA expression may not necessarily translate into high ABCB1 activity. To this end, we assessed the effect of PSC-833, an ABCB1 inhibitor, on dasatinib IUR and dasatinib mediated Bcr-Abl kinase inhibition in CML-CD34+ cells. The baseline p-Crkl, a surrogate marker of Bcr-Abl kinase activity, was significantly higher in CML-CD34+ compared to CML-CD34- cells (67±5% vs. 55±8%; p=0.002; n=9). PSC-833 neither increased dasatinib IUR, nor enhanced dasatinib mediated Bcr-Abl kinase inhibition in CML-CD34+ cells (% p-Crkl at 10 nM dasatinib: 20±6 vs. 27±10). Similarly, Ko143, an ABCG2 inhibitor, did not significantly change dasatinib IUR or Bcr-Abl kinase inhibition (% p-Crkl at 10 nM dasatinib: 21±3 vs. 27±10). In summary, although dasatinib is an ABCB1 and ABCG2 substrate, ABCB1 and ABCG2 inhibitors neither increase dasatinib IUR, nor enhance dasatinib mediated Bcr-Abl kinase inhibition in CML-CD34+ cells. This data suggest that dasatinib IUR in CML-CD34+ cells is not influenced by ABCB1 and ABCG2. Hatziieremia et al (Exp. Hematology, 2009) reported that ABCB1 activity is low in CML-CD34+ cells and suggested that it did not influence IM level in CML-CD34+ cells. We further demonstrated that 100 nM dasatinib inhibited ≥95% Bcr-Abl kinase activity in CML-CD34+ and CD34- cells. In summary our data demonstrates that in contrast to IM, the intracellular concentration of dasatinib is equivalent in mature and immature CML cell compartments which may contribute to better targeting of early CML progenitors with dasatinib. Fig. 1: In contrast to IM, dasatinib intracellular uptake and retention (IUR) is not significantly different in CML-CD34+and mature CD34-cells: (A) OCT-1 activity and IM IUR is significantly lower in CML-CD34+ than CD34- cells (p=0.04). (B) However, dasatinib IUR is not significantly different in CD34+ and CD34- cells (p=0.8) (C) OCT-1 mRNA expression is lower in CML-CD34+ cells than CD34- cells. While ABCB1 expression is significantly higher in CML-CD34+ compared to CD34- cells (p=0.007). Fig. 1:. In contrast to IM, dasatinib intracellular uptake and retention (IUR) is not significantly different in CML-CD34+ and mature CD34- cells: (A) OCT-1 activity and IM IUR is significantly lower in CML-CD34+ than CD34- cells (p=0.04). (B) However, dasatinib IUR is not significantly different in CD34+ and CD34- cells (p=0.8) (C) OCT-1 mRNA expression is lower in CML-CD34+ cells than CD34- cells. While ABCB1 expression is significantly higher in CML-CD34+ compared to CD34- cells (p=0.007). Disclosures: White: Novartis: Honoraria, Research Funding; BMS: Research Funding. Hughes:Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding.

scholarly journals Short-term intense Bcr–Abl kinase inhibition with nilotinib is adequate to trigger cell death in BCR-ABL+ cells

Leukemia ◽  
2009 ◽  
Vol 23 (6) ◽  
pp. 1205-1206 ◽  
Author(s):  
D K Hiwase ◽  
D L White ◽  
V A Saunders ◽  
S Kumar ◽  
J V Melo ◽  
...  
Keyword(s):  
Cell Death ◽  
Short Term ◽  
Kinase Inhibition ◽  
Abl Kinase ◽  
Trigger Cell Death

The Protein Tyrosine Phosphatase STS-1 Interacts with Bcr-Abl and Impairs the Response of Philadelphia-Positive Acute Lymphoblastic Leukemia (ALL) to Tyrosine Kinase Inhibitors

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3236-3236
Author(s):  
Marcus Liebermann ◽  
Daniela Hoeller ◽  
Susanne Badura ◽  
Tamara Tesanovic ◽  
Hubert Serve ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
B Cell ◽  
Cell Line ◽  
Cell Lines ◽  
Research Funding ◽  
Kinase Activity ◽  
Kinase Inhibitors ◽  
Signalling Pathways ◽  
Abl Kinase ◽  
Clinical Resistance

Abstract Abstract 3236 Bcr-Abl is a leukemogenic fusion gene that by itself is sufficient for cellular transformation (Daley et al.) and is the hallmark of chronic myeloid leukemia and Philadelphia chromosome positive (Ph+) ALL. The Bcr-Abl fusion protein is a constitutively active tyrosine kinase (TK) which disrupts multiple cellular signalling pathways controlling apoptosis, cell cycle, proliferation and DNA repair. In Ph+ ALL, a subtype of ALL with a particularly poor prognosis, targeted inhibition of Bcr-Abl activity by Abl kinase inhibitors such as imatinib has improved treatment outcome but has not abrogated the frequent development of clinical resistance. In addition to mutations in the Bcr-Abl tyrosine kinase domain (TKD), it has become apparent that other resistance mechanisms contribute to disease progression. The activity of proteins involved in the above-mentioned signalling pathways and possibly resistance to TK inhibitors (TKI) is controlled at least partially by posttranslational modifications such as phosphorylation, which is regulated by the balance between kinases and protein tyrosine phosphatases (PTP). We previously showed that PTP1B is a negative regulator of Bcr-Abl-mediated transformation and modulates sensitivity to the TKI imatinib (Koyama et al). We hypothesized that other phosphatases for which Bcr-Abl is a substrate may also contribute to resistance, one candidate being Suppressor of T-cell receptor Signalling 1 (STS-1), which negatively regulates the endocytosis of receptor TK involved in a variety of hematologic malignancies. It was the aim of this study to determine whether: i) Bcr-Abl is a substrate of STS-1 ii) STS-1 is able to dephosphorylate Bcr-Abl iii) expression of STS-1 reduces the proliferation of Bcr-Abl expressing cells by inhibiting Bcr-Abl kinase activity iv) the level of STS-1 expression modulates the sensitivity of Bcr-Abl positive cells to TKI In order to answer these questions, we used 293T cells, a human primary embryonal kidney cell line, and the IL3-dependent murine pro B cell line Ba/F3. Both cell lines were modified with constructs encoding both forms of Bcr-Abl (p185/p210) and Sts-1. For experiments with endogenous Bcr-Abl (p185) and Sts-1 we used Sup B15 cells, a human B cell precursor leukemia, and its TKI-resistant subline (Sup B15 RT), which was generated in our lab and is highly resistant not only to imatinib but also to 2nd generation TKIs (Nilotinib & Dasatinib), with no evidence of TKD mutations or transcriptional up-regulation of Bcr-Abl. In all above described cell lines the interaction between Bcr-Abl and Sts-1 could be shown in an overexpressed system (293T & Ba/F3) and on an endogenous level (Sup B15 & Sup B15 RT) by using co-IPs followed by SDS-PAGE and Western blotting. The functional relevance was examined by testing the ability of Sts-1 to dephosphorylate Bcr-Abl. Complete dephosphorylation of Bcr-Abl was shown for p185bcr-abl and p210bcr-abl in 293T cells. To verify that the functional activity was also present in hematopoietic cells, we analyzed the ability of Sts-1 to dephosphorylate Bcr-Abl in Ba/F3 and Sup B15 cells. Dephosphorylation was observed in both cell lines but was less pronounced than in 293T cells. We therefore more closely examined the most important tyrosine (Tyr) residues of Bcr-Abl and identified Tyr245 and Tyr412 as the major targets of Sts-1. Phosphorylation of Tyr245 and Tyr412 was decreased by ∼60% in Ba/F3 cells and ∼39% in Sup B15 cells. These two residues are known to be important for regulating cell proliferation, survival and cell motility. In a competitive proliferation assay in the absence of IL3, the proliferation rate of BA/F3 cells infected with Bcr-Abl and Sts – 1 was reduced compared to a Bcr-Abl infected control population. When treated with imatinib the Sts-1 expressing cells showed an approximately 5-fold reduced proliferation rate compared to cells lacking Sts-1, or to imatinib-resistant cells harbouring the Bcr-Abl “gatekeeper mutation” T315I. The expression level of Sts-1 was found to be approximately 3-fold lower in the Sup B15 RT compared to the WT cell line. Regulation appeared to occur at the transcriptional level as shown by quantitive RT-PCR. These results show that Bcr-Abl is a substrate of Sts-1, that this phosphatase modulates Bcr-Abl kinase activity and may abrogate the response to TKI. This suggests that phosphatases may contribute to the development of clinical resistance of Ph+ leukemias to TKIs. Disclosures: Ottmann: Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding.

The Oncogenic Role of Tumor Suppressor Protein p27 in Ph+ Chronic Myeloid Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3276-3276 ◽  
Author(s):  
Anupriya Agarwal ◽  
Ryan Mackenzie ◽  
Dorian LaTocha ◽  
Kavin Vasudevan ◽  
Eduardo Firpo ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Tumor Suppressor ◽  
Cell Lines ◽  
Research Funding ◽  
Bone Marrow Cells ◽  
Chronic Phase ◽  
Abl Kinase ◽  
Blastic Phase ◽  
Cd34 Cells ◽  
Marrow Cells

Abstract Abstract 3276 Poster Board III-1 Background: Several studies have indicated that BCR-ABL causes cell cycle defects by interfering with the cell cycle regulatory functions of p27, a Cyclin dependent kinase (Cdk) inhibitor and tumor suppressor. Studies in BCR-ABL positive cell lines have shown that BCR-ABL promotes proteasomal degradation of p27 in a pathway that involves the SCFSKP2 ubiquitin ligase, while cytoplasmic mislocalization has been described in primary CML cells. It has been suggested that the principal effect of this cytoplasmic mislocalization is to remove p27 from the nucleus, thereby relieving Cdks from p27 inhibition. However, recent studies have shown that a p27 mutant (p27CK-), that cannot bind to Cdks or Cyclins, actively contributes to oncogenesis. This raises the question as to whether cytoplasmic mislocalization of p27 in CML cells may in fact promote leukemogenesis rather than merely compromise Cdk inhibition. We therefore hypothesized that the net contribution of p27 in CML is to promote leukemogenesis due to the oncogenic activity of cytoplasmic p27. Experimental approach and results: We determined p27 localization in BCR-ABL positive cell lines and CD34+ progenitor cells from newly diagnosed chronic phase CML patients (N=7) and from CML patients in blast crisis (N=2) by immunoblotting of nuclear and cytoplasmic cellular fractions. We found that p27 is predominantly cytoplasmic in most CML cell lines and in CD34+ cells from 8/9 (89%) patient samples, including patients in blastic phase. Cytoplasmic localization of p27 in CD34+ cells from CML patients was also confirmed by immunofluorescence analysis. Further, we observed that inhibition of BCR-ABL kinase by imatinib, an Abl kinase inhibitor increased nuclear p27 in all cell lines tested and in 4/9 patient samples (3/7 chronic phase and 1/2 blastic phase samples). However, we did not observe a substantial change in the cytoplasmic p27 levels. Similar results were obtained in Ba/F3 and 32D murine hematopoietic cell lines expressing BCR-ABL when compared with the respective parental cells. Further, SKP2 was up-regulated in CD34+ cell from CML patients as compared to the normal patients consistent withSKP2 mediated down-regulation of nuclear p27. These data suggest that nuclear but not cytoplasmic p27 levels are predominantly regulated by BCR-ABL kinase activity. To test whether p27 is crucial for BCR-ABL-driven leukemia, we compared leukemogenesis between recipients of BCR-ABL transduced p27+/+ and p27-/- bone marrow. Mice transplanted with BCR-ABL infected p27-/- marrow had significantly longer median survival (70 days, range 48-150 days) compared to recipients of p27+/+ marrow (37 days, range 14-56 days) (p=0.0123). To exclude that this difference was related to the differences in homing and engraftment capabilities of p27+/+ and p27-/- bone marrow cells, we compared short term homing and long term engraftment of p27+/+ and p27-/- bone marrow cells transplanted into wild-type recipients and found no differences. These data suggest that the net contribution of p27 to BCR-ABL-mediated leukemogenesis is positive. Further, to investigate the contribution of nuclear p27 to leukemogenesis, we utilized marrow from p27S10A mice in the murine CML model. In p27S10A mice, p27 is nuclear to to abrogation of the phosphorylation site implicated in nuclear export. We injected BCR-ABL transduced bone marrow cells of p27S10A and p27+/+ mice into wild-type recipients and compared the disease progression. We observed that mice transplanted with BCR-ABL infected p27S10A marrow had significantly longer median survival (28 days, range 23-79 days) compared to the recipients of p27+/+ marrow (23 days, range 21-38 days) (p=0.0139). This data is consistent with nuclear tumor suppressor function of p27. Combined with the data above, this suggests that cytoplasmic p27 promotes BCR-ABL mediated leukemogenesis. Conclusions: Our data suggest that though nuclear p27 functions as a tumor suppressor, the net contribution of p27 in CML might be oncogenic due to an oncogenic role of the increased cytoplasmic p27. Restoring nuclear p27 or reducing cytoplasmic p27 may be therapeutically useful in malignancies with low nuclear and high cytoplasmic p27 expression. Disclosures: Druker: OHSU patent #843 - Mutate ABL Kinase Domains: Patents & Royalties; MolecularMD: Equity Ownership; Roche: Consultancy; Cylene Pharmaceuticals: Consultancy; Calistoga Pharmaceuticals: Consultancy; Avalon Pharmaceuticals: Consultancy; Ambit Biosciences: Consultancy; Millipore via Dana-Farber Cancer Institute: Patents & Royalties; Novartis, ARIAD, Bristol-Myers Squibb: Research Funding. Deininger:Genzyme: Research Funding; BMS: Consultancy; Novartis: Consultancy, Honoraria; Ariad : Research Funding.

AT9283, a Small Molecule Multi-Targeted Kinase Inhibitor Induces Antimyeloma Activity Via Potent Aurora Kinase and STAT3 Inhibition.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3833-3833
Author(s):  
Loredana Santo ◽  
Teru Hideshima ◽  
Erik A. Nelson ◽  
Diana Cirstea ◽  
Madhavi Bandi ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Cell Lines ◽  
Small Molecule ◽  
Research Funding ◽  
Kinase Activity ◽  
Histone H3 ◽  
Aurora Kinase ◽  
Aurora B ◽  
Kinase Inhibition ◽  
M Phase

Abstract Abstract 3833 Poster Board III-769 Aurora kinases, a family of mitotic regulators, whose expression has been recently linked to genetic instability and cellular proliferation in several cancers including multiple myeloma (MM), are being studied as novel mitotic therapeutic targets. Aurora A plays a crucial role in centrosome separation and spindle assembly and is required for mitosis and bipolar mitotic spindle formation. Aurora B, a member of the chromosomal passenger complex, is required for chromosome segregation, spindle assembly checkpoint and cytokinesis. Both aurora kinase A and B are significantly overexpressed in MM cells prompting the investigation of aurora kinase inhibitors as a therapeutic strategy in MM. Here, we investigated the preclinical activity of a small molecule multi-targeted inhibitor, AT9283, with potent in vitro kinase activity against aurora A and B kinases (3 nM), JAK2 and 3 (at 1.2 and 1.1 nM, respectively) and Abl T315I (at 4 nM). Growth inhibitory effects of AT9283 on MM cell lines and patient derived cells was observed with IC50 values of 0.25μM -0.5 μM at 48 hours using a [3H]-thymidine incorporation assay. Cell cycle analysis following AT9283 treatment resulted in increased G2/M phase and polyploidy consistent with failed cytokinesis (associated with aurora kinase B inhibition) confirmed by immunofluorescence assay. This was followed by induction of apoptosis assessed by Annexin V+PI+ staining peaking at 48 - 72 hours with associated caspase-8/-9 cleavage. The cellular inhibition of aurora kinase activity by AT9283 was confirmed by evaluating the phosphorylation of histone H3 at serine-10, a direct downstream substrate of aurora B kinase. Pretreatment of MM.1S cells with nocodazole, known to induce maximal phosphorylation of histone H3 by causing an M-phase block, resulted in decreased levels of phosphorylated histone H3 after AT9283 treatment suggesting the role of aurora B kinase inhibition by AT9283. Importantly, in addition to aurora kinase inhibition, we observed that AT9283 also inhibited signal transducer and activator of transcription (STAT3) tyrosine phosphorylation in MM cells within 30 minutes of treatment. Janus Kinase (JAK)2/STAT3 pathway is one of the major signaling cascades activated by gp130 family member cytokines that promotes MM cell survival. The effect of AT9283 on pSTAT3 inhibition was further investigated by using U3A cells stably expressing a luciferase reporter gene under the control of a STAT-dependent promoter. AT9283 inhibited STAT3-dependent luciferase activity with an EC50 of approximately 0.125 μM suggesting that STAT3 was functionally inhibited by AT9283. Since MM cell lines with the constitutive STAT3 tyrosine phosphorylation were more sensitive to AT9283, ongoing studies are aimed at understanding whether AT9283-induced effects on the JAK/STAT pathway enhances the efficacy of the aurora kinase inhibition in the context of MM. Finally, in vivo data using a xenograft mouse model of human MM show that mice treated with AT9283 demonstrated slower tumor growth compared to the control group without adverse effects. Our results show pleiotropic effects of AT9283 in MM and warrant further study to determine its suitability for clinical evaluation in MM. Disclosures: Squires: Astex Therapeutics, Ldt: Employment. Yule:Astex Therapeutics Ldt: Employment. Anderson:Novartis, Millennium, Celgene: Consultancy, Honoraria, Research Funding. Raje:Celgene, Norvartis, Astrazeneca: Research Funding.

Proton Pump Inhibitors Augment Nilotinib and Dasatinib Mediated Bcr-Abl Kinase Inhibition

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3991-3991 ◽  
Author(s):  
Devendra K Hiwase ◽  
Laura Eadie ◽  
Verity Saunders ◽  
Timothy Hughes ◽  
Deborah L. White
Keyword(s):  
Proton Pump Inhibitors ◽  
Proton Pump ◽  
Research Funding ◽  
Kinase Activity ◽  
Surrogate Marker ◽  
K562 Cells ◽  
P Value ◽  
Intracellular Uptake ◽  
Kinase Inhibition ◽  
Abl Kinase

Abstract Abstract 3991 Proton pump inhibitors (PPIs) are widely used for the treatment of gastro-oesophageal reflux and peptic ulcer disease. PPIs may not only alter absorption and metabolism of tyrosine kinase inhibitors (TKIs) but could also alter intracellular uptake and retention (IUR) into leukemic cells by interacting with ABCB1 and ABCG2 pump. There is limited literature assessing the interaction of PPI with TKI's at the cellular level. Here we compare the interaction of PPI with dasatinib, imatinib and nilotinib. Mononuclear cells (MNC) of CML-CP patients, K562 and K562-Dox (ABCB1 overexpressing), K562-ABCG2 cells were cultured with 14C-labelled dasatinib, imatinib and nilotinib with or without PPI for 2h and IUR were assessed. The effect of combining PPI with TKI's on Bcr-Abl kinase activity was assessed by measuring p-Crkl (surrogate marker of Bcr-Abl kinase activity). High concentrations of pantoprazole (1 and 2 mM) significantly increased dasatinib IUR in K562-Dox cells (p=0.004 and p=0.0006 respectively) but not in K562 cells (p=0.7 and p=0.1). Similarly, 1 mM (p=0.01) and 2 mM (p=0.007) esomeprazole significantly increased dasatinib IUR in K562-Dox cells but not in K562 cells. These data suggest that high concentration of PPI inhibit ABCB1 mediated dasatinib efflux. This was further supported by significant reduction in IC50dasatinib in K562-Dox cells by 1 mM pantoprazole (112±37 nM to 28±6; p=0.02; n=4). Similarly, 1 mM esomeprazole reduced IC50dasatinib (112±37 nM to 12±3 nM; n=2). This demonstrates that PPI mediated increase in IUR translates to increased kinase inhibition and lower IC50dasatinib. At lower concentrations (100 to 400 μM), neither pantoprazole nor esomeprazole significantly changed the dasatinib IUR or the IC50dasatinib in K562-Dox cells. In K562-ABCG2 cell line 100, 200, 400, 500, 1000 μM pantoprazole reduced IC50dasatinib from 27 nM to 15, 7, 11, 9.5 and 6.5 nM respectively. Similarly, 100, 200, 400, 500 and 1000 μM esomeprazole reduced IC50dasatinib from 21 nM to 15, 11, 8.5, 4.5 and 3.5 nM respectively. These data suggest that PPI enhances dasatinib mediated Bcr-Abl kinase inhibition in ABCG2-overexpressing cells. Although PPI did not change dasatinib IUR significantly in primary CML-MNC (n=10, Table I), it reduced IC50dasatinib (n=4, Table II). Similarly, pantoprazole and esomeprazole (5 to 400 μM) significantly increased nilotinib IUR (n=10, Table I) and significantly reduced IC50nilotinib in CML-MNC (n=3, Table II). Pantoprazole also increased the nilotinib IUR in K562 and K562-Dox cells, and reduced the IC50nilotinib in K562 (500 vs. 250 nM) and K562-Dox (600 vs. 230 nM) cells. Similarly esomeprazole reduced the IC50nilotinib in K562 (500 vs. 250 nM) and K562-Dox (600 vs. 150 nM) cells. The effect of PPI on IC50nilotinib was dose dependent. Pantoprazole and esomeprazole reduced imatinib IUR in K562, K562-Dox and CML-MNC. Pantoprazole increased IC50imatinib in K562 (3.8 to 4 μM) and K562-Dox (6.5 to 8 μM) cells. Similarly, 200 μM of pantoprazole and esomeprazole significantly reduced IM IUR in CML-MNC. However, the effect of pantoprazole on IC50imatinib in CML-MNC was variable and modest (Table II). Our data provide evidence that PPI might interfere with TKI activity. PPI's can enhance the dasatinib and nilotinib mediated Bcr-Abl kinase inhibition in primary CML cells. Table I: Effect of PPI on dasatinib, imatinib and nilotinib intracellular uptake and retention (IUR) in CML-MNC (n=10) TKI at 1μM TKI at 2μM Pantoprazole 0 μM 100μM 200μM 400μM 0uM 100μM 200μM 400μM Imatinib 13.3 10.9 9.9 8.8 23.7 20.4 18.9 16.3 p-value 0.06 0.01 0.004 0.2 0.09 0.01 Nilotinib 13.0 16.4 16.6 17.4 30.5 56.9 66.2 74.7 p-value 0.04 0.02 0.03 0.004 0.001 <0.001 Dasatinib 10.3 11.1 9.4 7.9 18.9 18.3 17.7 18.9 p-value 0.6 0.1 0.08 0.4 0.4 0.2 Table II: Effect of PPI on IC50 of nilotinib, dasatinib and imatinib in CML-MNC Nilotinib Nilotinib + 200 μM pantoprazole (% change) Nilotinib + 200 μM esomeprazole (% change) CML1 62.5 nM 30 nM (−52) 55 nM (−12) CML2 80 nM 32 nM (−60) 17 nM (−78) CML3 75 nM 68 nM (−9.4) 27 nM (−64) Dasatinib Dasatinib + 200 μM pantoprazole (% change) Dasatinib + 200 μM esomeprazole (% change) CML1 1.8 nM 0.7 nM (−61) 1.2 nM (−33) CML2 3 nM 2.6 nM (−13) – CML3 7 nM 2.5 nM (−64) – CML4 2.25 nM 1.7 nM (−25) 1.5 nM (−33) Imatinib Imatinib + 200 μM pantoprazole (% change) Imatinib + 200 μM esomeprazole (% change) CML1 1.05 μM 0.325 μM (−69) 0.8 μM (−23) CML2 1.8 μM 1.35 μM (−25) CML3 0.83 μM 1.15 μM (+38) 0.65 μM (−21) Disclosures: Hughes: Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding. White:Novartis: Honoraria, Research Funding; BMS: Research Funding.

scholarly journals Induction of programmed cell death in human hematopoietic cell lines by fibronectin via its interaction with very late antigen 5.

1994 ◽  
Vol 179 (6) ◽  
pp. 1757-1766 ◽  
Author(s):  
H Sugahara ◽  
Y Kanakura ◽  
T Furitsu ◽  
K Ishihara ◽  
K Oritani ◽  
...  
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Cell Lines ◽  
Growth Suppression ◽  
Hematopoietic Cell ◽  
Leukemia Cell Line ◽  
Gm Csf ◽  
Late Antigen ◽  
Antigen 5 ◽  
Hematopoietic Cell Lines

Extracellular matrix (ECM) molecules such as fibronectin (FN), collagens, and laminin have important roles in hematopoiesis. However, little is known about the precise mechanisms by which ECM molecules regulate proliferation of human hematopoietic progenitor cells. In this study, we have investigated the effects of ECM molecules, particularly of FN, on the proliferation of a myeloid leukemia cell line, M07E, which proliferates in response to either human granulocyte/macrophage colony-stimulating factor (GM-CSF) or stem cell factor (SCF). The [3H]thymidine incorporation and cell enumeration assays showed that FN strikingly inhibited GM-CSF- or SCF-induced proliferation of M07E cells in a dose-dependent manner, whereas little or no inhibition was induced by collagen types I and IV. The growth suppression of M07E cells was not due to the inhibitory effect of FN on ligand binding or very early events in the signal transduction pathways from the GM-CSF or SCF receptors. DNA content analysis using flow cytometry after staining with propidium iodide revealed that the treatment of M07E cells with FN did not block the entry of the cells into the cell cycle after stimulation with GM-CSF or SCF, whereas the treatment resulted in the appearance of subdiploid peak. Furthermore, FN was found to induce oligonucleosomal DNA fragmentation and chromatin condensation in the cells even in the presence of GM-CSF or SCF, suggesting the involvement of programmed cell death (apoptosis) in the FN-induced growth suppression. The growth suppression or apoptosis induced by FN was rescued by the addition of either anti-FN antibody, anti-very late antigen 5 monoclonal antibody (anti-VLA5 mAb), or GRGDSP peptide, but not by that of anti-VLA4 mAb or GRGESP peptide, suggesting that the FN effects on M07E cells were mediated through VLA5. In addition, the FN-induced apoptosis was detectable in VLA5-positive human hematopoietic cell lines other than M07E cells, but not in any of the VLA5-negative cell lines. These results suggest that FN is capable of inducing apoptosis via its interaction with VLA5, and also raise the possibility that the FN-VLA5 interaction may contribute, at least in part, to negative regulation of hematopoiesis.

The Dual SRC/ABL Kinase Inhibitor BMS-354825 Potently Inhibits the Growth of Myeloid Leukemic Cells Characterized by FLT3-ITD Expression, GM-CSF Dependency, or G-CSF Responsiveness Via an ABL-Independent Mechanism.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4480-4480
Author(s):  
Jukka Kanerva ◽  
Ogonna Nwawka ◽  
Kevin Hwang ◽  
Francis Y. Lee ◽  
Seth J. Corey
Keyword(s):  
Growth Inhibition ◽  
Cell Lines ◽  
Western Blotting ◽  
Mtt Assay ◽  
Tyrosine Kinases ◽  
Kinase Inhibitor ◽  
Src Kinase ◽  
Myeloid Cell ◽  
Gm Csf ◽  
Abl Kinase

Abstract BMS-354825 is a dual SRC and ABL inhibitor, which has been shown effective in imatinib-resistant BCR-ABL+ cells, and it is in phase I trials for patients with imatinib-resistant leukemia. We conducted a study to evaluate growth inhibition and inhibition of Src v. Abl protein tyrosine kinases in human myeloid cell lines: MV4-11 expressing an internal tandem duplication of Flt3 (Flt3-ITD), the murine pro-B cell line Ba/F3 that expresses the Flt3-ITD, the GM-CSF dependent Mo7e, and the G-CSF-responsive BaF3-GR (Ba/F3 cells expressing the human G-CSF receptor). We compared BMS-354825 with PP1, a SRC kinase inhibitor with in vitro IC50 at sub-micromolar concentrations. We sought to correlate growth inhibition with SRC or ABL inhibition. In these myeloid cell lines, LYN is the predominant SRC kinase. Methods: Growth inhibition was assessed by Trypan blue exclusion and MTT assay using drug concentrations 0.1 uM – 10 uM. Drugs were added daily to the cell suspension during the 3-day experiment. After a 60 min incubation at concentrations 0.1 nM – 1 uM, SRC or ABL kinase inhibition was analyzed by blotting with a polyclonal phospho-SRC (Tyr416) antibody or a polyclonal phospho-ABL (Tyr245) antibody. Results: In MV4-11 cells BMS-354825 and PP1 caused similar growth inhibition IC50 at 5 uM. By western blotting, inhibition of phospho-Src 416 occurred at 1 nM concentrations of both compounds. Protein expression of ABL was not detected in MV4-11 cells. In Ba/F3-ITD cells, the IC50 for BMS-354825 was 1–10 uM (grown in IL-3) and 0.01 uM (without IL-3). The IC50 for PP1 was 1–10 uM (grown in IL-3) and 0.1 uM (without IL-3). Inhibition of phospho-SRC occurred at 10 nM. In Mo7e cells, grown in the presence of GM-CSF, the IC50 was 5 uM for BMS-354825 v. 10 uM for PP1 by MTT assay. By western blotting, inhibition of phospho-SRC 416 occurred at 1 nM for both BMS-354825 and PP1. To determine specific contribution of LYN to Mo7e growth, we treated Mo7e cells with LYN siRNA. With 70% knock-down of LYN, there was 50% growth inhibition. ABL was present in Mo7e cells, but no phosphoAbl was demonstrated (K562 cells served as positive control). In BaF3-GR cells grown in G-CSF, the IC50 was 5 uM for BMS-354825 vs. 10 uM for PP1 by MTT assay. In western blotting, inhibition of phospho-Src 416 was detected at 10 nM BMS-354825. ABL was present in Ba/F3GR cells, but no phospho-ABL was demonstrated (K562 cells served as positive control). Conclusions: BMS-354825 is more potent than PP1 in causing growth inhibition and SRC kinase inhibition in Mo7e and Ba/F3GR cells that serve as models for acute myeloid leukemia. It is unlikely that ABL is the drug target, because MV4-11 cells do not express ABL and phospho-ABL was not found in Mo7e or Ba/F3 cells. These results suggest that inhibition of SRC tyrosine kinases contributes predominantly to growth inhibition caused by the dual SRC/ABL kinase inhibitor BMS-354825 in myeloid cell lines expressing Flt3-ITD and cytokine-driven proliferation and survival via the IL-3/GM-CSF Receptor or G-CSF Receptor.

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