BGB324 Inhibits BCR-ABL TKI-Resistant Chronic Myeloid Leukemia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1569-1569
Author(s):  
Isabel Ben Batalla ◽  
Robert Erdmann ◽  
Heather Jørgensen ◽  
Rebecca Mitchell ◽  
Thomas Ernst ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Tyrosine Kinase ◽  
Cell Lines ◽  
Therapeutic Target ◽  
Research Funding ◽  
Combined Treatment ◽  
K562 Cells ◽  
Resistant Cell ◽  
Additive Effect ◽  
Significant Prolongation

Abstract Resistance and CML stem cell persistence preclude cure for the majority of patients treated with tyrosine kinase inhibitor (TKI) therapies. We demonstrated that the receptor tyrosine kinase (RTK) Axl of the Tyro-3, Axl, Mer (TAM) family is expressed by TKI-sensitive and -resistant CML cells (Erdmann R. et al. ASH 2013 and 2014). We have shown that blockade of the Gas6-Axl axis by the small molecule Axl inhibitor BGB324 (BerGenBio) represents a therapeutic target in AML. We are currently investigating BGB324 in a Phase 1b trial in refractory AML patients and in those non-eligible for intensive chemotherapy (BGBC003, NCT02488408). We hypothesised that Axl represents a tractable therapeutic target even in the most resistant forms of CML. Upon treatment with imatinib KCL-22 and K562 cells showed upregulation of Axl at the protein level indicating that Axl might be involved in resistance towards TKIs in CML. Consistently, Axl levels were higher in MNCs of TKI-resistant patients compared to -sensitive patients after 6 months of treatment (n=17/20, 1±0.4 vs. 0.16±0.03; *p<0.05). Upon combined treatment of KCL-22 and K562 cells with BGB324 and imatinib we detected an additive effect of growth inhibition (KCL-22 cells; n=3, viability 66.0±0.5% BGB324, 52.0±1.1% imatinib, 42.3±1.5% combo; combo vs. IM *p<0.01 and combo vs. BGB324 *(p<0.0001), and not shown). Analysis of intracellular signal transduction in these cell lines indicated that Axl induces phosphorylation of Stat5 by BCR-ABL independent pathways because we detected an additive effect of inhibition of Stat5 phosphorylation when combining imatinib and BGB324. We could not detect an additive inhibitory effect on phosphorylation of Erk and Akt. Consistently, combined BCR-ABL and Axl blockade by means of imatinib and shRNA respectively, demonstrated an additive effect in reducing cell viability in KCL-22 and K562 cells (KCL-22 cells; n=3, viability 84.5±0.8% shControl+imatinib, 74.5±2.6% shAxl, 50.4±0.9% shAxl+imatinib; shAxl+IM vs. IM *(p<0.0001) and vs. shAxl *(p<0.001) and not shown). We next investigated Axl activation in TKI insensitive BCR-ABL+ cell lines. In addition we tested a novel Ponatinib-resistant cell line KCL-22 PonR generated by subcloning parental KCL-22 in increasing concentrations of ponatinib. BCR-ABL is unmutated in these cells; oncoprotein kinase activity is switched off but cell death is not induced with 2mM ponatinib. We found that Axl phosphorylation was higher in the TKI-resistant cell lines BaF3/T315I, KCL-22 T315I and KCL-22 PonR when compared to the parental cell lines (n=3, 139±3.8% KCL-22 T315I, 214±1.3% KCL-22 PonR with respect to KCL-22 WT, *p<0.001 for both comparisons; 169±8.7% with respect to BaF3/p210, *p<0.005). Treatment with BGB324 inhibited cell proliferation with an IC50of 726, 3178 and 2720nM for BaF3/T315I, KCL-22 T315I and KCL-22 PonR, respectively. BGB324 could induce apoptosis and reduce proliferation in these cell lines. Furthermore, BGB324 blocked growth of colonies and induced apoptosis of T315I-mutated and pan-TKI-resistant (including ponatinib) primary CML MNCs. The finding that BGB324 inhibits TKI-resistant CML was further corroborated with KCL-22 T315I mutated and KCL-22 PonR xenograft models. In both models we observed a significant tumor growth reduction upon treatment with 25 mg/kg BGB324 twice daily compared to placebo leading to a 34% and 58% reduction in tumor volume, p=0.0044, p=0.0021 for KCL-22 T315I and KCL-22 PonR, respectively). Cell proliferation was quantified by pHH3 analysis indicating a significant reduction in KCL-22 T315I and KCL-22 PonR tumors (n=8, 242.8±10.9 vs. 182.2±8.1, *p<0.0001; n=9, 259.5±9.3 vs. 213.2±6.8; *p<0.0001, respectively). Furthermore, we observed a significant decrease of Axl, Erk and Stat5 phosphorylation after treatment with BGB324 for 8 days. We also investigated the therapeutic effect of BGB324 in a systemic model, by transplantation of KCL-22 PonR into sublethally irradiated NSG mice. In this model, treatment with 25 mg/kg BGB324 twice daily resulted in significant prolongation of overall survival (median OS 36 days (control) vs 43 days (BGB324), n=5 *p<0.05). In summary, our data highlight the advantage to be gained from inhibition of Axl even in the most resistant CML cells, and support the need for human clinical trials of the novel inhibitor BGB324 alone and in combination with TKIs. Disclosures Schafhausen: Novartis: Consultancy, Honoraria; ARIAD: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Hochhaus:Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding. Holyoake:Novartis: Research Funding; BMS: Research Funding. Loges:BerGenBio: Honoraria, Other: travel support, Research Funding.

ATP Dependent Efflux Transporters ABCB1 and ABCG2 Are Unlikely to Impact the Efficacy, or Mediate Resistance to the Tyrosine Kinase Inhibitor, Ponatinib

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2745-2745 ◽  
Author(s):  
Deborah L. White ◽  
Liu Lu ◽  
Timothy P. Clackson ◽  
Verity A Saunders ◽  
Timothy P Hughes
Keyword(s):  
Tyrosine Kinase ◽  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Kinase Inhibitor ◽  
K562 Cells ◽  
Temperature Dependent ◽  
Advisory Committees ◽  
Significant Difference

Abstract Abstract 2745 Ponatinib is a potent pan-BCR-ABL tyrosine kinase inhibitor (TKI) currently in a pivotal phase 2 clinical trial. Ponatinib (PON) was specifically designed to target both native and all mutant forms of BCR-ABL, including T315I. The phase I study of oral ponatinib in patients with refractory CML/ALL or other hematologic malignancies recently reported that 66% and 53% of patients with CP-CML achieved MCyR and CCyR respectively (Cortes et al., ASH 2011 abstract #210). While extensive modelling experiments in BaF3 cells have been performed characterising in vitro response to ponatinib, little is known about the interactions of this drug and drug transporters that impact the response of other tyrosine kinase inhibitors (TKIs). To explore this we have examined both the degree of in vitro kinase inhibition mediated by ponatinib in BCR-ABL+ cell lines, and the intracellular uptake and retention (IUR) of ponatinib achieved. The IC50 was determined by assessing the reduction in %p-Crkl in response to increasing concentrations of ponatinib in vitro. The IUR assay was performed as previously using [14-C]-ponatinib. To determine the role of ABCB1 and ABCG2, both previously implicated in the transport of other TKIs, IC50 analysis was performed on K562 cells, and variants; ABCB1 overexpressing K562-DOX and ABCG2 overexpressing K562-ABCG2. As shown in Table 1, in contrast to the results previously observed with imatinib (IM), nilotinib (NIL) and dasatinib (DAS) there was no significant difference in the IC50ponatinib between these three cell lines, suggesting neither ABCB1 nor ABCG2 play a major role in ponatinib transport. Furthermore, the addition of either the ABCB1 and ABCG2 inhibitor pantoprazole, or the multidrug resistance (MDR) inhibitor cyclosporin did not result in a significant change in the IC50ponatinib in any of the cell lines tested. In contrast the addition of either pantoprazole or cyclosporin resulted in a significant reduction in IC50IM, IC50NIL. and IC50DAS of K562-DOX cells, supporting the notion that these TKIs interact with ABCB1.Table 1:The IC50 of ponatinib (compared to IM, NIL and DAS) in K562 cells and the over-expressing variants DOX and ABCG2 in the presence of the ABC inhibitors pantoprazole and cyclosporin. n=5. *p<0.05IC50% reduction in IC50+ pantoprazole+ cyclosporinPON (nM)IM (μM)NIL (nM)DAS (nM)PONIMNILDASPONIMNILDASK5627.793751111544*NA−107NA2DOX7.919*598*100*1018*63*1655*88*ABCG26.4730025*6NA To further examine the effect of ABC transporters on ponatinib efflux we have determined the IUR of [14-C]-ponatinib in K562, DOX and ABCG2 cell lines. We demonstrate no significant difference in the IUR between these cell lines at 37°C (n=6) (K562 vs DOX p=0.6; K562 vs ABCG2 p=0.37 and DOX vs ABCG2 p=0.667 at 2uM respectively). Temperature dependent IUR experiments reveal a significant reduction in the ponatinib IUR at 4°C compared to 37°C in K562 cells (n=6) (p=0.008), DOX cells (p=0.004) and ABCG2 cells (p=0.002) supporting the likely involvement of an ATP/temperature dependent, and yet to be determined, component of ponatinib influx. There was no significant difference in the IUR between these cell lines at 4°C (p=0.824, p=0.7 and p=0.803 respectively). Importantly, these data are consistent with the IC50ponatinib findings. If ATP dependent efflux pumps (ABCB1 and ABCG2) were actively transporting ponatinib, a significant decrease in IUR in DOX and ABCG2 at 37°C compared to K562 cells would be expected, but is not observed here. Analysis of ponatinib IUR in the prototypic ABCB1 over-expressing CEM-VBL100 cells, and their parental, ABCB1 null counterparts (CCRF-CEM) further confirmed these findings. The IUR in VBL100 cells was significantly higher than that observed in CEM's (p<0.001; n=5), providing further evidence that ponatinib was not being exported from the cell actively via ABCB1. These data suggest that the transport of ponatinib is, at least in part, temperature-dependent indicating a yet to be determined ATP transporter may be involved in the transport of ponatinib into leukaemic cells. Importantly, this data suggests that ponatinib is unlikely to be susceptible to resistance via the major ATP efflux transporters (ABCB1 or ABCG2) that have been previously demonstrated to significantly impact the transport of, and mediate resistance to other clinically available TKIs. Disclosures: White: BMS: Honoraria, Research Funding; Novartis Pharmaceuticals: Honoraria, Research Funding. Clackson:ARIAD: Employment. Hughes:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; ARIAD: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Efficacy of Ponatinib Against ABL Tyrosine Kinase Inhibitor Resistant Leukemia Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4413-4413
Author(s):  
Seiichi Okabe ◽  
Tetsuzo Tauchi ◽  
Kazuma Ohyashiki
Keyword(s):  
Cell Proliferation ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitor ◽  
Cell Line ◽  
Cell Lines ◽  
Kinase Inhibitor ◽  
Resistant Cell ◽  
Point Mutant ◽  
Abl Tyrosine Kinase ◽  
Abl Tyrosine Kinase Inhibitor

Abstract Abstract 4413 Dasatinib (Sprycel®) and nilotinib (Tasigna®) have each shown superior efficacy as front line treatment for patients with chronic myeloid leukemia (CML)-chronic phase (CP) in comparison with imatinib. Dasatinib and nilotinib are also used for the treatment of CML patients resistant or intolerant to imatinib therapy. However, a substantial number of patients are acquired resistance to nilotinib or dasatinib, the management of CML following the development of ABL tyrosine kinase inhibitor (TKI) resistance remains a challenge. Ponatinib, also known as AP24534, is an oral, the multi-targeted TKI. Ponatinib is currently being investigated in a pivotal phase 2 clinical trial (PACE trial) in patients with resistant or intolerant CML and Philadelphia positive acute lymphoblastic leukemia (Ph+ ALL). However, the molecular and functional consequences of ponatinib against ABL TKI resistant cells are not fully known. In this study, we investigated the ponatinib efficacy by using the BCR-ABL positive cell line, K562 and ABL TKI resistant (K562 imatinib resistant (K562IR), K562 nilotinib resistant (K562NR), K562 dasatinib resistant (K562DR) cells and murine Ba/F3 cell line which was transfected BCR-ABL random mutation, and established the new imatinib and nilotinib resistant Ba/F3 BCR-ABL point mutant (E334V) cells. We first examined the cell proliferation by using resistant cell lines. The proliferation of K562IR and K562 NR and K562DR did not decrease after imatinib (10 μM) or nilotinib (2 μM) or dasatinib (1 μM) treatment compared with parental cell line, K562. The BCR-ABL kinase domain mutation was not found. Point mutant Ba/F3 cell (E334V) was also highly resistant to imatinib (IC50: 15μM) and nilotinib (IC50: 7.5μM). We next examined the intracellular signaling by using these cell lines. Phosphorylation of BCR-ABL and Crk-L was not decreased by ABL TKIs in K562IR, K562NR and Ba/F3 BCR-ABL point mutant cells (E334V). We found the one of src family kinase, Lyn was activated in K562IR and K562NR cells. Co-treatment src kinase inhibitor, PP2 and imatinib or nilotinib significantly reduced the cell proliferation of K562IR and K562NR cells. We also found the phosphorylation of Lyn was reduced and poly (ADP-ribose) polymerase (PARP) was activated. We next examined the efficacy of ponatinib against imatinib and nilotinib resistant cell lines. 72 hours treatment of ponatinib exhibits cell growth inhibition against K562 (IC50: 0.02nM), K562IR (IC50: 15nM), and K562NR (IC50: 3.5nM) cells. We also found the phosphorylation of BCR-ABL, Lyn and Crk-L was reduced and PARP was activated after ponatinib treatment. We next examined the imatinib and nilotinib resistant Ba/F3 cells with point mutant (E334V). We found the cell proliferation was significantly decreased after ponatinib treatment (IC50: 3nM). We also found the phosphorylation of BCR-ABL, Crk-L was reduced and PARP was activated after ponatinib treatment. We next investigated the ponatinib activity against dasatinib resistant cells. We found K562DR cells were highly resistant to ponatinib. IC50 was 400nM. These results suggest that the expression and protein activation signatures identified in this study provide insight into the mechanism of resistance to ABL TKIs. We also demonstrate ponatinib has anti-leukemia effect by reducing ABL and Lyn kinase activity and development of ponatinib resistance and suggests that this information may be of therapeutic relevance. Disclosures: No relevant conflicts of interest to declare.

Homozygous JAK2 V617P Gain-of-Function Mutation Is Responsible for Constitutive JAK2/STAT5 Activation and Proliferation of HEL.92.1.7. Cell Line.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4377-4377
Author(s):  
Myka L. Estes ◽  
Yuki Ozawa ◽  
Ann H. Williams ◽  
Alan F. List ◽  
Lubomir Sokol
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Tyrosine Kinase ◽  
Cell Line ◽  
Cell Lines ◽  
K562 Cell ◽  
K562 Cells ◽  
Constitutive Activation ◽  
Jak2 Inhibitor ◽  
Hel Cells

Abstract HEL (Human erythroleukemia) is a growth factor independent erythroleukemic cell line established from the bone marrow of a patient with relapsed Hodgkin disease after autologous bone marrow transplantation (Martin P & Papayannopoulou T: Science1982;216:1233–1235). HEL cells display a block in differentiation at the level of common erythroid-megakaryocytic progenitor and have been commonly used as a model to study erythroid and megakaryocytic differentiation. Liu RY et al. (Blood1999;93:2369–2379) reported that constitutive activation of JAK2 tyrosine kinase in Dami/HEL cell line correlated with factor independent growth. Recently, several groups of investigators described a point mutation V617P in the autoinhibitory regulatory (JH2) domain of JAK2 tyrosine kinase in patients with myeloproliferative disorders (MPD). This acquired mutation results in constitutive activation of the JAK2/STAT5 pathway in hematopoietic cells. To date, the V617P mutation represents the most common causative genetic defect detected in patients with Philadelphia chromosome negative MPD. Interestingly, rare cases of patients with myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) were found to have the same mutation. We tested several hematopoietic cell lines including HL-60, HEL, KG-1, K-562, TF-1, U937 and UT-7 for the presence of V617P mutation using RFLP and automatic DNA sequencing. We found the homozygous mutation V617P only in HEL cells. This cell line has a very complex karyotype suggesting that a defect of multiple oncogenes or antioncogenes could be responsible for sustained cell proliferation. We employed the JAK2 inhibitor, AG490 at concentrations ranging from 0 to 100 mM and measured proliferation of HEL and control K562 cell lines using MTT assay. We observed dose-dependent inhibition of HEL cell proliferation with low micromolar concentrations of AG490 in contrast to K562 control cell line, harboring bcr-abl fusion tyrosine kinase. IC50 was 13 mM for HEL cells and 65 mM for control K562 cells, respectively. Low concentrations of AG490 significantly decreased phosphorylation of JAK2 and STAT5 in HEL cells but not in control K562 cell line, where bcr-abl activates separately JAK2 and STAT5 pathway. Exposure of HEL cells to AG490 [0–50mM] induced apoptosis as measured by annexin V labeling in a concentration dependent fashion. No significant increase in apoptosis was detected in K562 cells using similar concentrations of the JAK2 inhibitor. Overall, these results suggest that the mechanism of proliferation of the HEL cell line is driven by constitutive activation of JAK2 tyrosine kinase secondary to V617P gain-of-function mutation. Our data provides further evidence that the JAK2/STAT5 intracellular signaling pathway is preserved in this cell line. Thus, HEL cells can serve as a model to test novel JAK2 specific inhibitors in preclinical studies.

Effect of neratinib (N) alone and in combination with trastuzumab (T) in HER2-positive breast cancer (BC) cell lines.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 632-632
Author(s):  
Alexandra Canonici ◽  
Kasper Pedersen ◽  
Naomi Walsh ◽  
John Crown ◽  
Norma O'Donovan
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitor ◽  
Cell Lines ◽  
Kinase Inhibitor ◽  
Combined Treatment ◽  
Clinical Problem ◽  
Resistant Cell ◽  
Her2 Positive ◽  
Her 2 ◽  
Resistant Cells

632 Background: HER-2, a member of the transmembrane receptor tyrosine kinase ErbB family, is over-expressed in approximately 25% of BC. HER-2 targeted therapies, in particular, T, a monoclonal antibody targeting HER-2, and lapatinib (L), a reversible HER-2 tyrosine kinase inhibitor, have been shown to significantly improve the prognosis for HER-2 positive BC patients. However, resistance to T and/or L is a significant clinical problem. The aim of this study is to assess the activity of N (HKI-272), an irreversible HER-2 tyrosine kinase inhibitor, in HER-2 overexpressing BC cell lines, including T and/or L resistant cells. Methods: Using proliferation assays, the effect of N was assessed alone and in combination with T in HER-2 positive BC cell lines, including T and/or L resistant cell lines. The effect of N on HER-2 and downstream signalling molecules, Erk and Akt, was determined by immunoblotting. Results: HER-2 positive BC cell lines, including T and/or L resistant cells, are sensitive to N alone with IC50 values (concentration which inhibits 50% of growth) ranging from 1 to 280 nM. The combination of N and T has additive effects in SkBR3 and BT474 which are sensitive to T and also in SKBR3-Lwhich are resistant to L. In the cell lines HCC1954, HCC1954-L, MDA-MB-453, JIMT1 and SKBR3-HL which are resistant to T, combined treatment with T and N showed no enhancement compared to N alone. Finally, N decreased phosphorylation of HER-2, Erk and Akt in all cell lines tested. Conclusions: Our results suggest that N should be studied in patients with HER-2 positive BC, including patients with T and/or L resistant BC. We also demonstrate that N in combination with T may be more effective than either agent alone in T sensitive cells.

K562-R As a Model to Study Jak2 in a Non Bcr-Abl Addicted Cell Line

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4412-4412
Author(s):  
Bastianella Perazzona ◽  
Yu-Hsi Lin ◽  
Ralph B. Arlinghaus
Keyword(s):  
Tyrosine Kinase ◽  
Cell Line ◽  
Cell Lines ◽  
K562 Cells ◽  
Resistant Cell ◽  
Resistant Cell Line ◽  
Janus Kinase ◽  
Cell Fractionation ◽  
Lyn Kinase

Abstract Abstract 4412 Chronic myeloid leukemia (CML) is a hematological disease caused by the fusion protein Bcr-Abl tyrosine kinase. Development of the tyrosine kinase inhibitor Imatinib Mesylate (IM) has significantly improved the long-term survival of early stage CML patients. However, occurrence of drug resistance, permanence of residual disease and recurrence of active leukemia if IM is discontinued, remain problems awaiting solution. Therefore, new therapeutic strategies aimed at targeting alternative signaling pathways or CML progenitor cells that survive IM treatment are needed. We have previously shown that Janus kinase 2 (Jak2) is activated in Bcr-Abl+ cells. We have demonstrated that reduction of Jak2 activity by the Jak2-specific inhibitor TG101209 (TG) or by genetic knock down (Jak2 shRNA and siRNA) in Bcr-Abl+ cell lines, IM-resistant cells and CML blast crisis cell lines resulted in reduced levels of phosphorylation of Tyr177 and of total Bcr-Abl protein. Jak2 inhibition results in diminished activation of the Ras, PI-3 kinase pathways and reduced levels of pTyrSTAT5 (Samanta et al., Leukemia 2011). During these studies we observed that K562 cells and IM-resistant cell line K562-R had different susceptibility to the effect of TG, with K562-R showing increase sensitivity to lower concentrations of TG resulting in faster destabilization of the Bcr-Abl protein. Based on these observations, we hypothesized that increased sensitivity of the K562-R cells was due to the different state of activation of Jak2. In addition, based on recent studies by (Dawson et al., Nat 2009) and by (Rinaldi et al., Blood 2010) we also hypothesized that different levels of Jak2 activation may influence the localization of Jak2 in the cell. We used cell fractionation and western blotting analysis to show that in K562-R cells, active Jak2 is mostly localized in the nucleus with a minor pool found in the cytoplasm. In K562 cells, active Jak2 is equally distributed in both cytoplasmic and nuclear compartment. In addition, immuno-fluorescence confocal analysis of total Jak2 distribution in K562 shows a very organized localization of Jak2 at one pole of the cells but this organization is lost in K562-R and total Jak2 appears uniformly distributed within the cell. K562-R cells were isolated as a Bcr-Abl independent IM resistant cell line that expressed high levels of activated Lyn kinase (Donato et al., Blood 2003). We used K562-R as a model to study the role of Jak2 in a non Bcr-Abl addicted cell line. Since we have previously published that Jak2 up-regulates Lyn kinase activity (Samanta et al., Oncogene 2009), we propose that the higher activation of Jak2 in K562-R is the main driver of oncogenicity and IM resistance and that this cell line may be used to model the role of Jak2 in a cell that is not Bcr-Abl “addicted.” Disclosures: No relevant conflicts of interest to declare.

scholarly journals Prolonged exposure to FLT3 inhibitors leads to resistance via activation of parallel signaling pathways

Blood ◽  
2006 ◽  
Vol 109 (4) ◽  
pp. 1643-1652 ◽  
Author(s):  
Obdulio Piloto ◽  
Melissa Wright ◽  
Patrick Brown ◽  
Kyu-Tae Kim ◽  
Mark Levis ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Signaling Pathways ◽  
Cell Lines ◽  
Kinase Inhibitors ◽  
Prolonged Exposure ◽  
Cellular Transformation ◽  
Mapk Signaling ◽  
Resistant Cell ◽  
Myelogenous Leukemia ◽  
Continuous Treatment

Abstract Continuous treatment of malignancies with tyrosine kinase inhibitors (TKIs) may select for resistant clones (ie, imatinib mesylate). To study resistance to TKIs targeting FLT3, a receptor tyrosine kinase that is frequently mutated in acute myelogenous leukemia (AML), we developed resistant human cell lines through prolonged coculture with FLT3 TKIs. FLT3 TKI-resistant cell lines and primary samples still exhibit inhibition of FLT3 phosphorylation on FLT3 TKI treatment. However, FLT3 TKI-resistant cell lines and primary samples often show continued activation of downstream PI3K/Akt and/or Ras/MEK/MAPK signaling pathways as well as continued expression of genes involved in FLT3-mediated cellular transformation. Inhibition of these signaling pathways restores partial sensitivity to FLT3 TKIs. Mutational screening of FLT3 TKI-resistant cell lines revealed activating N-Ras mutations in 2 cell lines that were not present in the parental FLT3 TKI-sensitive cell line. Taken together, these data indicate that FLT3 TKI-resistant cells most frequently become FLT3 independent because of activation of parallel signaling pathways that provide compensatory survival/proliferation signals when FLT3 is inhibited. Anti-FLT3 mAb treatment was still cytotoxic to FLT3 TKI-resistant clones. An approach combining FLT3 TKIs with anti-FLT3 antibodies and/or inhibitors of important pathways downstream of FLT3 may reduce the chances of developing resistance.

scholarly journals HSP90 Inhibitor, 17-DMAG, Alone and in Combination with Lapatinib Attenuates Acquired Lapatinib-Resistance in ER-positive, HER2-Overexpressing Breast Cancer Cell Line

Cancers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2630
Author(s):  
Hye Jin Lee ◽  
Seungho Shin ◽  
Jinho Kang ◽  
Ki-Cheol Han ◽  
Yeul Hong Kim ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Protein Expression ◽  
Cell Line ◽  
Cell Lines ◽  
Xenograft Model ◽  
Resistant Cell ◽  
Bt474 Cell ◽  
Hsp90 Inhibitors ◽  
Her2 Breast Cancer

Lapatinib, a Human Epidermal growth factor Receptor 2 (HER2)-targeting therapy in HER2-overexpressing breast cancer, has been widely used clinically, but the prognosis is still poor because most patients acquire resistance. Therefore, we investigated mechanisms related to lapatinib resistance to evaluate new therapeutic targets that may overcome resistance. Lapatinib-resistant cell lines were established using SKBR3 and BT474 cells. We evaluated cell viability and cell signal changes, gene expression and protein changes. In the xenograft mouse model, anti-tumor effects were evaluated using drugs. Analysis of the protein interaction network in two resistant cell lines with different lapatinib resistance mechanisms showed that HSP90 protein was commonly increased. When Heat Shock Protein 90 (HSP90) inhibitors were administered alone to both resistant cell lines, cell proliferation and protein expression were effectively inhibited. However, inhibition of cell proliferation and protein expression with a combination of lapatinib and HSP90 inhibitors showed a more synergistic effect in the LR-BT474 cell line than the LR-SKBR3 cell line, and the same result was exhibited with the xenograft model. These results suggest that HSP90 inhibitors in patients with lapatinib-resistant Estrogen Receptor (ER) (+) HER2 (+) breast cancer are promising therapeutics for future clinical trials.

PKC412 Effectively Inhibits Constitutively Activated FGFR3 Mutants in Murine Leukemia Models and t(4;14) Myeloma Cell Lines.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2448-2448
Author(s):  
Jing Chen ◽  
Benjamin H. Lee ◽  
Ifor R. Williams ◽  
Jeffery L. Kutok ◽  
Nicole Duclos ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Tyrosine Kinase ◽  
Cell Lines ◽  
Small Molecule ◽  
Kinase Activity ◽  
Cell Lymphoma ◽  
Ectopic Expression ◽  
B Cell Lymphoma ◽  
Tyrosine Kinase Activity ◽  
Significant Prolongation

Abstract Reccurent translocation t(4;14) associated ectopic expression of FGFR3, sometimes containing the activation mutation K650E (TDII), has been identified in 25% of human multiple myeloma (MM) patients and cell lines. However, current empirically-derived cytotoxic chemotherapy does not effectively treat this disease. One potential therapeutic strategy of treating MM is to inhibit the tyrosine kinase activity of FGFR3. In this report, we evaluated the efficacy of PKC412 (N-benzoyl-staurosporine), a small molecule tyrosine kinase inhibitor, for the treatment of FGFR3 mutants induced diseases. PKC412 effectively inhibits the tyrosine kinase activity and activation of downstream effector pathways of FGFR3 TDII or the constitutively activated TEL-FGFR3 fusion that was reported in a subtype of human peripheral T-cell lymphoma (PTCL), as well as proliferation of hematopoietic Ba/F3 cells transformed by the FGFR3 mutants. Furthermore, PKC412 drastically inhibits proliferation of four different multiple myeloma-derived primary cell lines that are associated with t(4;14) and expression of dysregulated FGFR3. Moreover, oral-gavage treatment with PKC412 resulted in statistically significant prolongation of survival in the murine bone marrow transplant (BMT) models of FGFR3 TDII-induced pre-B cell lymphoma or TEL-FGFR3 fusion-induced myeloproliferative disease, which suggests suitable pharmacokinetic and toxicity profiles of PKC412 for clinical use. Together, our data establish the small molecule inhibitor PKC412 as a molecularly targeted therapy for multiple myeloma and other human malignancies expressing activated FGFR3.

The Tyrosine Kinase src Is Highly Activated in AML and Plays a Crucial Role in Leukemic Cell Proliferation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4402-4402
Author(s):  
Gunter Schuch ◽  
Ellen Schafer ◽  
Katharina Eggert ◽  
Sonja Loges ◽  
Manfred Jucker ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Tyrosine Kinase ◽  
Western Blot ◽  
Cell Lines ◽  
Crucial Role ◽  
Leukemic Cell ◽  
Clinical Samples ◽  
Dependent Manner ◽  
Coding Region ◽  
Rt Pcr

Abstract The tyrosine kinase pp60src is involved in several signal transduction pathways such as signalling of hematopoetic growth factors and cytokines. The viral form v-src was the first oncogene described and mutations of regulatory tyrosine residues in cellular src (c-src) have been linked to malignant transformation. However, no mutations in the gene of c-src have been described in leukemia so far, although some data of src mutations in solid tumors have been reported. The current study was undertaken to examine the role of src in acute myeloid leukemia (AML). Blood and bone marrow specimen of patients with newly diagnosed or recurrent AML treated at our institution were sampled. AML cell lines or CD34 positive cells of healthy donors served as positive and negative controls, respectively. RNA was isolated, and RT-PCR was performed using 4 different primer pairs spanning the coding region of c-src. Protein expression and phosphorylation was studied after protein extraction and Western blot analyses using src and phospho-src specific antibodies. The effect of src inhibitors PP1 and PP2 on leukemic cell proliferation was studied in human and murine cell lines. Mutational analyses of the coding region were performed using SSCP/heteroduplex and bi-directionally sequencing. In all 60 patients analyzed expression of c-src mRNA was detected by RT-PCR. Western blot analyses confirmed strong expression of src on the protein level and revealed a robust activation of the protein as determined by tyrosine phosphorylation. Inhibition of src phosphorylation by src-specific inhibitors PP1 and PP2 was detected by Western blot using an antibody specific for phospho-src. Incubation of leukemic cells with PP1 and PP2 caused significant inhibition of proliferation in a dose dependent manner. Mutational analyses as performed by SSCP/heteroduplex and bi-directionally sequencing revealed wildtype sequence in all cell lines and 60 clinical samples. In summary, pp60src is highly expressed and activated in cell lines and clinical samples of human AML. Moreover, phosphorylation of src is essential for leukemic cell proliferation. Mutations in the coding sequence of c-src causing constitutive activation could be excluded by mutational analyses of primary AML samples. These data suggest that pp60src plays a crucial role in AML and src inhibition by targeted therapy might offer a useful new approach in the treatment of AML.

Jak2: A Potential Therapeutic Target for Chronic Myelogenous Leukemia (CML).

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2121-2121
Author(s):  
Ajoy K. Samanta ◽  
Hui Lin ◽  
Tong Sun ◽  
Hagop Kantarjian ◽  
Ralph B. Arlinghaus
Keyword(s):  
Tyrosine Kinase ◽  
Cell Lines ◽  
Therapeutic Target ◽  
Philadelphia Chromosome ◽  
Chronic Phase ◽  
Myelogenous Leukemia ◽  
Leukemia Cells ◽  
Imatinib Treatment ◽  
Potential Therapeutic Target ◽  
Imatinib Resistant

Abstract In most CML patients Bcr-Abl, a constitutively active tyrosine kinase derived from the Philadelphia chromosome, is highly expressed and is the causative factor in most CML patients. Imatinib mesylate, an inhibitor of the Bcr-Abl kinase, is a very effective drug for treatment of CML. However in some CML patients, drug resistance develops and the patients relapse. Thus, alternative drug targets need to be identified. We have shown that Bcr-Abl activates its downstream target, the Jak2 tyrosine kinase, leading to the enhancement of c-Myc expression (Xie et al. Oncogene21: 7137, 2002; Samanta et al. Cancer Res.66: 6468, 2006). Our recent studies showed that Bcr-Abl activated the transcriptional factor NF-kB through Jak2, which in turn activated c-Myc transcription. Jak2 also activated Akt, which increased c-Myc protein levels by inhibiting GSK3. Addition of AG490, an inhibitor of the Jak2 kinase, prevented enhanced expression of c-Myc and caused induction of apoptosis in BCR-ABL+ leukemia cells. Immunoprecipitation experiments showed that Bcr-Abl is associated with a cluster of signaling proteins including Jak2, Gab2, Akt and GSK3b. Treatment of CML cell lines and mouse BCR-ABL+ 32D cells (myeloid lineage) with the either Jak2 siRNA or the Jak2 kinase inhibitor AG490 caused inhibition of pTyr Gab2 formation, pSer Akt formation and the activation of NFkB. Of interest, treatment of BCR-ABL+ 32 D cells with IL-3 reversed the apoptotic effects of imatinib by activation of Jak2 even though Bcr-Abl was inhibited. Importantly, mouse BaF3 hematopoietic cells expressing the T315I and E255K imatinib-resistant mutants of BCR-ABL underwent apoptosis upon exposure to either the Jak2 inhibitor AG490 or siRNA for Jak2, yet were resistant to imatinib. Cells from a number of CML patients (including six chronic phase, one accelerated phase, and two blast crisis patients who failed imatinib treatment) were induced to enter apoptosis upon treatment with AG490, whereas normal samples were not affected by AG490. Further analysis of imatinib resistant Bcr-Abl cell lines showed that transfection of the cells with Jak2 specific siRNA or by treating the cells with AG490 reduced levels of pLyn, pAkt, c-Myc and pGSK3 level compared to untreated cells. Transfection of Lyn specific siRNA into K562 and 32Dp210 cells resulted in down-regulation of pGab2, pAkt, pGsk3 and c-Myc, but did not alter pJak2 levels; this result indicates that pLyn is downstream of Jak2 but upstream of Gab2, pAkt, pGSK3 in BCR-ABL+ leukemia cells. We hypothesize that Jak2 activation of Lyn tyrosine kinase in BCR-ABL+ leukemia cells leads to tyrosine phosphorylation of the YxxM motif of Gab2, which activates the PI-3 kinase-Akt pathway. In conclusion, since inactivation of Jak2 inhibits many of the critical oncogenic targets of Bcr-Abl (resulting in apoptosis induction), we propose that Jak2 is a potential therapeutic target for CML, in both imatinib sensitive and imatinib resistant patients.

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