Rationale for a Combination Therapy with the STAT5 Inhibitor AC-4-130 and the MCL1 Inhibitor S63845 in the Treatment of FLT3-Mutated or TET2-Mutated Acute Myeloid Leukemia.

Katja Seipel,Carolyn Graber,Ulrike Bacher,Thomas Pabst,Laura Flückiger

doi:10.3390/ijms22158092

Abstract

The FMS-like tyrosine kinase 3 (FLT3) gene is mutated in one-third of patients with de novo acute myeloid leukemia (AML). Mutated FLT3 variants are constitutively active kinases signaling via AKT kinase, MAP kinases, and STAT5. FLT3 inhibitors have been approved for the treatment of FLT3-mutated AML. However, treatment response to FLT3 inhibitors may be short-lived, and resistance may emerge. Compounds targeting STAT5 may enhance and prolong effects of FLT3 inhibitors in this subset of patients with FLT3-mutated AML. Here STAT5-inhibitor AC-4-130, FLT3 inhibitor midostaurin (PKC412), BMI-1 inhibitor PTC596, MEK-inhibitor trametinib, MCL1-inhibitor S63845, and BCL-2 inhibitor venetoclax were assessed as single agents and in combination for their ability to induce apoptosis and cell death in leukemic cells grown in the absence or presence of bone marrow stroma. Synergistic effects on cell viability were detected in both FLT3-mutated and FLT3-wild-type AML cells treated with AC-4-130 in combination with the MCL1 inhibitor S63845. AML patient samples with a strong response to AC-4-130 and S63845 combination treatment were characterized by mutated FLT3 or mutated TET2 genes. Susceptibility of AML cells to AC-4-130, PTC596, trametinib, PKC412, and venetoclax was altered in the presence of HS-5 stroma. Only the MCL1 inhibitor S63845 induced cell death with equal efficacy in the absence or presence of bone marrow stroma. The combination of the STAT5-inhibitor AC-4-130 and the MCL1 inhibitor S63845 may be an effective treatment targeting FLT3-mutated or TET2-mutated AML.

Highlights

FMS-like tyrosine kinase 3 (FLT3) is an inducible growth factor receptor signaling via PI3K-PDK1-AKT and via RAS-RAF-MEK-ERK leading to cell growth and proliferation [1,2]
To investigate the elevated susceptibility of FLT3 wild-type SKM-1 compared to FLT3-mutated MOLM-13 cells to AC-4-130, cell viability was determined in acute myeloid leukemia (AML) cells grown in the presence of bone marrow stroma cells secreting granulocyte and macrophage colony-stimulating factors (G-CSF, GM-CSF, M-CSF), and other cytokines thereby inducing STAT signaling
The elevated susceptibility of the SKM-1 cell line was unexpected, as there is no mutated FLT3 activating STAT5 signaling in these cells, and the presence of mutated tumor suppressor TP53 is often associated with chemoresistance

Summary

Introduction

FMS-like tyrosine kinase 3 (FLT3) is an inducible growth factor receptor signaling via PI3K-PDK1-AKT and via RAS-RAF-MEK-ERK leading to cell growth and proliferation [1,2]. Mutations of the FLT3 gene are detected in around a third of patients with de novo acute myeloid leukemia (AML). Mutated FLT3 variants are constitutively active kinases signaling via AKT and MAP kinases, and as a gain of function via STAT5 [3]. Treatment response to FLT3 inhibitors may be short-lived, and leukemia relapse is the major cause of treatment failure, as resistance may frequently emerge [4]. The stromal microenvironment provides an escape route from FLT3 inhibitors through the GAS6-AXL-STAT5 axis [5,6]

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Results

Conclusion