IndraLab
Statements
trips
"Expression of CBLDeltaexon8 and CBLDeltaexon8+9 in FLT3-WT-Ba/F3 cells induced growth factor-independent proliferation associated with autophosphorylation of FLT3 and activated the downstream targets signal transducer and activator of transcription 5 (STAT5) and protein kinase B (AKT)."
sparser
"To demonstrate that this effect is through reduced FLT3 inhibition, we treated MOLM-14 cells with each TKI at concentrations greater than the IC 50 for inhibition of FLT3 autophosphorylation (10 nM and 100 nM) and assessed FLT3 autophosphorylation and downstream signaling in the presence or absence of human plasma ( xref )."
sparser
"To investigate whether its enzyme inhibitory properties translate into modulation of FLT3 signaling pathways in the cellular context, the effects of pacritinib on FLT3 auto-phosphorylation (pFLT3 Y591) and downstream STAT5 phosphorylation (pSTAT5 Y694), pERK1/2 (T202,Y204) and pAkt (T308) were investigated in two FLT3-ITD-harboring cell lines (MV4-11 and MOLM-13) and one FLT3-wt-bearing cell line (RS4;11)."
sparser
"Western blot analysis of cells expressing AC220-resistant FLT3-ITD-mutant isoforms revealed increased FLT3 autophosphorylation of D835 mutant iso-forms, but no discernable difference in phosphorylation of downstream targets, including the direct FLT3-ITD target STAT5A/B xref , and no difference in cellular proliferation ( xref )."
sparser
"FLT3/ITD mutation can lead to constitutive autophosphorylation of FLT3 and activation of its downstream effectors including RAS/RAF/MEK, MAPK/ERK, PI3K/AKT/mTOR and JAK/STAT5 signal pathways, while Quizartinib can inhibit these downstream pathways through specific FLT3 inhibition."
sparser
"The results of cell cycle analysis ( xref ) and Annexin V binding ( xref ; for Sample 1) confirm the synergistic cytotoxic effect of the combination. xref summarizes the induction of apoptosis for fixed concentrations of the 2 drugs for all 3 samples co-cultured with stroma and FL, and inhibition of FLT3 autophosphorylation and ERK phosphorylation is displayed in xref ."
sparser
"Whereas the PIA was designed to assess in vivo drug activity with regards to a specific target (e.g.: inhibition of FLT3 auto-phosphorylation by TKI), the modified PIA is similarly cell-based, but measures the clinically relevant biological end-points of cytotoxicity and proliferation inhibition."
sparser
"Normal functioning of FMS-like tyrosine kinase 3 (FLT3), a type
III receptor tyrosine kinase, is important for the development and
proliferation of hematopoietic stem cells. xref , xref The
binding of the FLT3 ligand to this transmembrane protein causes dimerization
and subsequent FLT3 autophosphorylation, which then triggers the activation
of several signaling cascades, including the RAS, SRC, and STAT5 pathways. xref − xref Constitutive activation of FLT3 leads to dysregulated cellular proliferation
of hematopoietic cells, and nearly one-third of AML patients have
mutations in the FLT3 gene. xref Two classes
of mutations are commonly found in FLT3: an internal tandem duplication
(ITD) located in the juxtamembrane domain, which is the most common,
and point mutations at or near residue Asp835. xref − xref Typically, an AML patient’s prognosis is worse
if he/she possesses the FLT3-ITD mutation compared to that for patients
having normal levels of wild-type FLT3 (wt-FLT3). xref , xref "
sparser
"During the last decade, several FLT3-inhibitors, ranging from relatively FLT3-selective to broad multikinase inhibitors, have been introduced and subsequently tested in clinical trials in patients with AML, either as single agents or in combination with chemotherapy. xref , xref , xref , xref So far, only a minority of patients, mainly those with FLT3-mutated leukemia, have shown some degree of clinical response although most often of limited duration. xref Notably, some FLT3-ITD patients do not respond to FLT3 inhibition treatment, despite almost complete inhibition of FLT3 autophosphorylation. xref "
sparser
"Hitherto, patients treated with FLT3 inhibitors have, with the possible exception of AC220, shown only modest and transient clinical response. xref Indeed, inhibition of FLT3 autophosphorylation does not always lead to cell death, and some leukemic cells may not be dependent on FLT3 signaling. xref In addition, monotherapy with TKIs is associated with the risk of developing resistance. xref , xref Thus, a TKI such as AKN-028, targeting other pathways apart from FLT3, may be potentially advantageous."
sparser
"The correlative assays from this trial revealed that if a patient had leukemic blasts that died when exposed to CEP-701 in vitro , and if that patient achieved a level of CEP-701 in plasma sufficient to significantly inhibit FLT3 autophosphorylation in sustained fashion, then a clinical response was observed."
sparser
"The results displayed that the FLT3 autophosphorylation in FLT3-ITD-dependent cell lines (MV4-11, MOLM-13, and MOLM-14) were significantly decreased and the phosphorylation of downstream signaling mediators including STAT5, AKT, and ERK were almost completely inhibited between 0.1 and 0.3 mM ( xref )."
sparser
"The PIA is a surrogate for measuring target inhibition by FLT3 inhibitors. xref In this study, the median result of this assay (the percentage of baseline FLT3 autophosphorylation) in all patients was 6% of pretreatment baseline activity (range, 0–32) (n = 25) on day 6 of induction, 2% (range, 0–24) (n = 15) on day 15 of consolidation, and 0% (range, 0–4) (n = 6) on day 15 of maintenance, demonstrating robust inhibition of FLT3 in vivo ( xref )."
sparser
"Each FLT3 activation loop mutant, including D835Y, D835A, D835E, D835H, D835N, D835V, D835del, and I836del, transformed Ba/F3 cells to factor-independent proliferation and had constitutive tyrosine kinase activation, as assessed by FLT3 autophosphorylation and activation of downstream effectors, including STAT5 and ERK."
sparser
"A single dose of LT-171-861 (10 mg/kg) was administered to subcutaneous MV4-11-xenograft mice, which showed sustained inhibition of p-FLT3, p-STAT5 and p-ERK1/2 (Figure xref B), indicating that LT-171-861 effectively inhibited autophosphorylation of FLT3 and its downstream effectors."
sparser
"In the original plasma inhibitory assay (PIA), FLT3/ITD-expressing cells are co-incubated with plasma samples from patients receiving a FLT3 TKI, and the extent of FLT3 inhibitory activity present in their plasma measured by Western blotting analysis of FLT3 auto-phosphorylation.( xref ) This is compared to total plasma drug levels to determine the relative efficacy of a drug in vivo compared to its activity in vitro and thus impute the effects of host factors on drug efficacy beyond simple metabolism."
sparser
"Expression of CBLDeltaexon8 and CBLDeltaexon8+9 in FLT3-WT-Ba/F3 cells induced growth factor-independent proliferation associated with autophosphorylation of FLT3 and activated the downstream targets signal transducer and activator of transcription 5 (STAT5) and protein kinase B (AKT)."
sparser
"There are more than 12 000 new cases in the United States every year. xref Up to 35% of AML patients harbor a mutation in the FMS-like tyrosine kinase 3 ( FLT3 ) gene, a member of the class III receptor tyrosine kinase family. xref Constitutively activated mutants of FLT3 have been shown to be transforming in cultured cell lines and leukemogenic in mice. xref Two major classes of activating mutations have been identified: internal-tandem duplications (ITDs) of 3 to 400 bp within the juxta-membrane domain or point mutations in the tyrosine kinase domain. xref These genetic alterations give rise to constitutive signaling of FLT3 and activation of downstream oncogenic pathways, leading to dysregulated cell cycle control and apoptosis. xref , xref Clinically, FLT3-ITD is a negative prognostic marker that is associated with increased relapse rate, increased blast count and poor overall survival. xref , xref , xref Overexpression of wild-type FLT3 in AML patients has been also shown to increase FLT3 auto-phosphorylation and was an unfavorable prognostic factor for overall survival. xref Therefore, aberrantly activated FLT3 kinase is a validated molecular target for the treatment of AML."
sparser
"The preferential cytotoxicity of PIM1 inhibition on FLT3-ITD cell lines and blasts has been previously reported.[ xref , xref ] In contrast to FLT3 inhibitors, AR00459339 has no effect on FLT3 autophosphorylation but does induce de-phosphorylation of the key downstream proteins, STAT5, AKT, and BAD."
sparser
"All samples included in this analysis were positive for FLT3 or FLT3-ITD expression and FLT3 autophosphorylation, and responded to AC220 as monitored by reduced pY589/Y591-FLT3, pY694-Stat5, or pT202/Y204-Erk ( xref , xref , Online Supplementary Figures S10 and S11 , and data not shown )."
sparser
"In all, 18% of MLL-rearranged ALL cases harbor FLT3-activating mutations that lead to high expression levels. xref In vitro studies have demonstrated that a novel enzyme inhibitor of FLT3, Hydrate ® (CEP-701, lestaurtinib; Cephalon Inc.), suppresses FLT3-driven leukemic cell survival. xref Lestaurtinib is an orally available inhibitor that selectively inhibits FLT3 autophosphorylation, thereby killing leukemic cells."
sparser
"In support, western blotting of FLT-3 autophosphorylation of these mutants, F691L and D835F/Y, from the untreated total cell extracts showed reduced autophosphorylation of FLT3 in comparison with FLT3-ITD ( xref ), thus supporting the notion that these mutations confer resistance by destabilizing the active state rather than direct steric hindrance to the drug."
sparser
"The emergence of targeted therapies has transformed the treatment paradigm for both newly diagnosed AML and relapsed or refractory (R/R) AML. xref Gilteritinib is an oral, highly specific type I FLT3 inhibitor with demonstrated activity against FLT3 -ITD and FLT3 tyrosine kinase domain ( FLT3 -TKD) mutations. xref Findings from a phase 1/2 study showed that ≥80-mg/day doses of single-agent gilteritinib resulted in potent inhibition of FLT3 receptor autophosphorylation and an overall response rate of 52% in patients with FLT3 -mutated ( FLT3 mut+ ) R/R AML. xref The phase 3 Study of ASP2215 Versus Salvage Chemotherapy in Patients With Relapsed or Refractory Acute Myeloid Leukemia (AML) With FMS-like Tyrosine Kinase ( FLT3 ) Mutation (ADMIRAL) trial demonstrated the superiority of gilteritinib to salvage chemotherapy (SC) in patients with R/R FLT3 mut+ AML xref and led to approval of gilteritinib for this population. xref "
sparser
"We also found that A674563 was most potent against auto-phosphorylation of FLT3-ITD (EC 50 : 0.085 μM) and FLT3-D835Y (EC 50 : 0.045 μM), but was least potent against auto-phosphorylation of FLT3-ITD-D835Y (EC 50 : 1.26 μM), FLT3-ITD-F691L (EC 50 : 0.4 μM) and FLT3 wt (EC 50 : 0.87 μM); this is consistent with the demonstrated anti-proliferative activity of A674563 (Figure xref and xref )."
sparser
"Several small molecule inhibitors of tyrosine kinases were studied in early phase clinical studies. ( xref ) One of the most studied early agents in development is lestaurtinib (CEP701) with a phase 1/2 trial of lestaurtinib in relapsed or refractory AML patients with FLT3 mutations in 2003.[ xref ] Correlative assays in this and a subsequent phase 2 study demonstrated that clinical response was more likely in patients who had in vitro leukemic blast sensitivity to CEP-701, and if, in vivo, CEP-701 in plasma level was sufficient to significantly inhibit FLT3 autophosphorylation in a sustained fashion."
sparser
"In the FLT3-ITD+ patient primary cells, 500 nM concentration of compound 165 could completely block FLT3-ITD Y589/591 auto-phosphorylation. ( xref ) In addition, in the purified CD34+ bone marrow cells, upon FLT3 ligand stimulation, compound 165 could also effectively inhibit the FLT3 wt Y589/591’s auto-phosphorylation. ( xref , xref ) Flow cytometry analysis demonstrated that at 30 nM, compound 165 strongly arrests cell cycle progression in the G0/G1 phase. ( xref ) At 24 h, 30 nM compound 165 significantly induced apoptosis in MOLM13 cells, as evidenced by an increase in PARP and Caspase-3 cleavage. ( xref ) This strong apoptotic induction was also observed in MOLM14 and MV4-11 cells."