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FLT3 tyrosine kinase inhibitors synergize with BCL-2 inhibition to eliminate FLT3/ITD acute leukemia cells through BIM activation.

ABSTRACT: Tyrosine kinase inhibitors (TKIs) targeting FLT3 have shown activity but when used alone have achieved limited success in clinical trials, suggesting the need for combination with other drugs. We investigated the combination of FLT3 TKIs (Gilteritinib or Sorafenib), with Venetoclax, a BCL-2 selective inhibitor (BCL-2i), on FLT3/ITD leukemia cells. The combination of a FLT3 TKI and a BCL-2i synergistically reduced cell proliferation and enhanced apoptosis/cell death in FLT3/ITD cell lines and primary AML samples. Venetoclax also re-sensitized FLT3 TKI-resistant cells to Gilteritinib or Sorafenib treatment, mediated through MAPK pathway inhibition. Gilteritinib treatment alone dissociated BIM from MCL-1 but increased the binding of BIM to BCL-2. Venetoclax treatment enhanced the binding of BIM to MCL-1 but dissociated BIM from BCL-2. Treatment with the drugs together resulted in dissociation of BIM from both BCL-2 and MCL-1, with an increased binding of BIM to the cell death mediator BAX, leading to increased apoptosis. These findings suggest that Venetoclax mitigates the unintended pro-survival effects of FLT3 TKI mainly through the dissociation of BIM and BCL-2 and also decreased BIM expression. This study provides evidence that the addition of BCL-2i enhances the effect of FLT3 TKI therapy in FLT3/ITD AML treatment.

SUBMITTER: Zhu R

PROVIDER: S-EPMC8141515 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Pim kinases modulate resistance to FLT3 tyrosine kinase inhibitors in FLT3-ITD acute myeloid leukemia.

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Mutations of FLT3/ITD confer resistance to multiple tyrosine kinase inhibitors.

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| S-EPMC4333682 | biostudies-literature

Role of CYP3A4 in bone marrow microenvironment-mediated protection of FLT3/ITD AML from tyrosine kinase inhibitors.

Project description:An intriguing aspect of the clinical activity of FMS-like tyrosine kinase 3 inhibitors (FLT3 TKIs) is their apparent higher activity against peripheral blasts from FLT3/internal tandem duplication (ITD) acute myeloid leukemia than marrow disease in the same patients. Accordingly, studies showed that the bone marrow microenvironment plays a role in FLT3 TKI resistance, although the underlying mechanisms are unclear. We recently identified a previously undescribed mechanism by which the bone marrow microenvironment can contribute to drug resistance: expression of cytochrome P450 enzymes (CYPs). In fact, bone marrow stromal cells (BMSCs) expressed most CYPs, including CYP3A4. Because hepatic CYP3A4 plays a role in the inactivation of several FLT3 TKIs, we explored the potential role of CYP3A4 in bone marrow microenvironment-mediated FLT3 TKI resistance. We found that CYP3A4 plays a major role in BMSC-mediated inhibition in the activity of 3 different FLT3 TKIs (sorafenib, quizartinib, and gilteritinib) against FLT3/ITD acute myeloid leukemia (AML). Furthermore, clarithromycin, a clinically active CYP3A4 inhibitor, significantly reversed the protective effects of BMSCs. We show, for the first time, that bone marrow stromal CYP3A4 contributes to FLT3 TKI resistance in the bone marrow. These results suggest that combining FLT3 TKIs with CYP3A4 inhibitors could be a promising strategy toward improving the activity of FLT3 TKIs.

| S-EPMC6436013 | biostudies-literature

Emergence of polyclonal FLT3 tyrosine kinase domain mutations during sequential therapy with sorafenib and sunitinib in FLT3-ITD-positive acute myeloid leukemia.

Project description:To evaluate the clinical activity of sequential therapy with sorafenib and sunitinib in FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD)-positive acute myelogenous leukemia (AML) and monitor the emergence of secondary FLT3 tyrosine kinase domain (TKD) mutations during treatment.Six children with relapsed/refractory AML were treated with sorafenib in combination with clofarabine and cytarabine, followed by single-agent sorafenib if not a candidate for transplantation. Sunitinib was initiated after sorafenib relapse. Bone marrow samples were obtained for assessment of FLT3 TKD mutations by deep amplicon sequencing. The phase of secondary mutations with ITD alleles was assessed by cloning and sequencing of FLT3 exons 14 through 20. Identified mutations were modeled in Ba/F3 cells, and the effect of kinase inhibitors on FLT3 signaling and cell viability was assessed.Four patients achieved complete remission, but 3 receiving maintenance therapy with sorafenib relapsed after 14 to 37 weeks. Sunitinib reduced circulating blasts in two patients and marrow blasts in one. Two patients did not respond to sorafenib combination therapy or sunitinib. FLT3 mutations at residues D835 and F691 were observed in sorafenib resistance samples on both ITD-positive and -negative alleles. Deep sequencing revealed low-level mutations and their evolution during sorafenib treatment. Sunitinib suppressed leukemic clones with D835H and F691L mutations, but not D835Y. Cells expressing sorafenib-resistant FLT3 mutations were sensitive to sunitinib in vitro.Sunitinib has activity in patients that are resistant to sorafenib and harbor secondary FLT3 TKD mutations. The use of sensitive methods to monitor FLT3 mutations during therapy may allow individualized treatment with the currently available kinase inhibitors.

| S-EPMC3878304 | biostudies-literature

Partnering with PARP inhibitors in acute myeloid leukemia with FLT3-ITD.

Project description:Internal tandem duplications within the juxtamembrane domain of fms-like tyrosine kinase 3 (FLT3-ITD) occur in acute myeloid leukemia (AML) cells of 20-25% of patients and are associated with poor treatment outcomes. FLT3 inhibitors have been developed, but have had limited clinical efficacy due to development of resistance, highlighting the need for better understanding of the function of FLT3-ITD and how to target it more effectively using novel combination strategies. Poly (ADP-ribose) polymerase (PARP) inhibitors have shown efficacy in cancers with impaired homologous recombination (HR) due to BRCA mutations, but PARP inhibitor efficacy has not been fully explored in BRCA-proficient cancers, including AML. Recent research has connected inhibition of FLT3-ITD signaling to downregulation of numerous DNA repair proteins, including those involved in HR, and the novel combination with PARP inhibitors induces synthetic lethality in AML. Additionally, PARP inhibitor therapy may also target the highly error-prone alternative non-homologous end-joining (ALT NHEJ) DNA repair pathway in which PARP participates, thereby decreasing genomic instability and development of therapy resistance. Therefore, PARP inhibitors may be attractive therapeutic agents in combination with FLT3 inhibitors in FLT3-ITD AML.

| S-EPMC6528833 | biostudies-literature

Selective Akt inhibitors synergize with tyrosine kinase inhibitors and effectively override stroma-associated cytoprotection of mutant FLT3-positive AML cells.

Project description:ObjectivesTyrosine kinase inhibitor (TKI)-treated acute myeloid leukemia (AML) patients commonly show rapid and significant peripheral blood blast cell reduction, however a marginal decrease in bone marrow blasts. This suggests a protective environment and highlights the demand for a better understanding of stromal:leukemia cell communication. As a strategy to improve clinical efficacy, we searched for novel agents capable of potentiating the stroma-diminished effects of TKI treatment of mutant FLT3-expressing cells.MethodsWe designed a combinatorial high throughput drug screen using well-characterized kinase inhibitor-focused libraries to identify novel kinase inhibitors capable of overriding stromal-mediated resistance to TKIs, such as PKC412 and AC220. Standard liquid culture proliferation assays, cell cycle and apoptosis analysis, and immunoblotting were carried out with cell lines or primary AML to validate putative candidates from the screen and characterize the mechanism(s) underlying observed synergy.Results and conclusionsOur study led to the observation of synergy between selective Akt inhibitors and FLT3 inhibitors against mutant FLT3-positive AML in either the absence or presence of stroma. Our findings are consistent with evidence that Akt activation is characteristic of mutant FLT3-transformed cells, as well as observed residual Akt activity following FLT3 inhibitor treatment. In conclusion, our study highlights the potential importance of Akt as a signaling factor in leukemia survival, and supports the use of the co-culture chemical screen to identify agents able to potentiate TKI anti-leukemia activity in a cytoprotective microenvironment.

| S-EPMC3578845 | biostudies-literature

Glutaminolysis is a metabolic dependency in FLT3 ITD Acute Myeloid Leukemia unmasked by FLT3 Tyrosine Kinase Inhibition

Project description:FLT3ITD are common mutations in Acute Myeloid Leukemia (AML) and carry a particularly bad prognosis. Although new generation FLT3 tyrosine kinase inhibitors (TKI) have shown promising results, the outcome of FLT3-mutated AML patients remains poor and demands the identification of novel, specific and validated therapeutic targets for this highly aggressive AML subtype. Utilizing an unbiased genome-wide CRISPR/Cas9 screen, we identify GLS, the first enzyme in glutamine metabolism, as synthetically lethal with FLT3 TKI treatment. Using complementary metabolomic and gene-expression analysis, we demonstrate that glutamine metabolism, through its ability to support both mitochondrial function and cellular redox metabolism, becomes a metabolic dependency of FLT3ITD AML, specifically unmasked by FLT3-TKI treatment. We extend these findings to AML subtypes driven by other tyrosine kinase activating mutations, and validate the role of GLS as a clinically actionable therapeutic target in both primary AML and in vivo models. Our work highlights the role of metabolic adaptations as a resistance mechanism to several TKI inhibitors, and suggests glutaminolysis as a therapeutically targetable vulnerability when combined with specific TKI in FLT3ITD and other TK activating mutation driven leukemias.

2018-03-07 | GSE105161 | GEO

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