FOXM1 contributes to treatment failure in acute myeloid leukemia
Irum Khan, … , Olga Frankfurt, Andrei L. Gartel
Irum Khan, … , Olga Frankfurt, Andrei L. Gartel
Published August 9, 2018
Citation Information: JCI Insight. 2018;3(15):e121583. https://doi.org/10.1172/jci.insight.121583.
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Categories: Research Article Hematology Oncology

FOXM1 contributes to treatment failure in acute myeloid leukemia

Abstract

Acute myeloid leukemia (AML) patients with NPM1 mutations demonstrate a superior response to standard chemotherapy treatment. Our previous work has shown that these favorable outcomes are linked to the cytoplasmic relocalization and inactivation of FOXM1 driven by mutated NPM1. Here, we went on to confirm the important role of FOXM1 in increased chemoresistance in AML. A multiinstitution retrospective study was conducted to link FOXM1 expression to clinical outcomes in AML. We establish nuclear FOXM1 as an independent clinical predictor of chemotherapeutic resistance in intermediate-risk AML in a multivariate analysis incorporating standard clinicopathologic risk factors. Using colony assays, we show a dramatic decrease in colony size and numbers in AML cell lines with knockdown of FOXM1, suggesting an important role for FOXM1 in the clonogenic activity of AML cells. In order to further prove a potential role for FOXM1 in AML chemoresistance, we induced an FLT3-ITD–driven myeloid neoplasm in a FOXM1-overexpressing transgenic mouse model and demonstrated significantly higher residual disease after standard chemotherapy. This suggests that constitutive overexpression of FOXM1 in this model induces chemoresistance. Finally, we performed proof-of-principle experiments using a currently approved proteasome inhibitor, ixazomib, to target FOXM1 and demonstrated a therapeutic response in AML patient samples and animal models of AML that correlates with the suppression of FOXM1 and its transcriptional targets. Addition of low doses of ixazomib increases sensitization of AML cells to chemotherapy backbone drugs cytarabine and the hypomethylator 5-azacitidine. Our results underscore the importance of FOXM1 in AML progression and treatment, and they suggest that targeting it may have therapeutic benefit in combination with standard AML therapies.

Authors

Irum Khan, Marianna Halasi, Anand Patel, Rachael Schultz, Nandini Kalakota, Yi-Hua Chen, Nathan Aardsma, Li Liu, John D. Crispino, Nadim Mahmud, Olga Frankfurt, Andrei L. Gartel

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Figure 6

Ixazomib shows antileukemic activity and inhibits FOXM1 in an orthotopic AML model with improved hematopoiesis.

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Ixazomib shows antileukemic activity and inhibits FOXM1 in an orthotopic...
(A) NSG mice were treated with 8 mg/kg ixazomib i.v. twice a week for 4 weeks. Ixazomib treatment resulted in substantial reduction of leukemic disease burden in the BM as assessed by CD45 expression. Representative flow plots are shown from each group. (B) Plot shows quantification of CD45 expression in vehicle- and ixazomib-treated animals. Data are expressed as the mean ± SEM (n = 8–10/group); P < 0.05 by unpaired 2-tailed t test. (C) Peripheral blood was analyzed to study the effects on normal blood production. Treated animals showed a higher hemoglobin count, suggesting improved hematopoiesis. (D) Following treatment, BM cells were collected for RNA extraction. FOXM1, Cdc25B, and Plk1 mRNA expression levels using quantitative PCR were quantified as percentage of mRNA expression levels in treated cells compared with control cells. Data are expressed as the mean ± SEM (n = 7/group); P < 0.05 by 1-way ANOVA followed by Tukey’s multiple comparison post test. (E) FOXM1 inhibition in the BM cells is shown by Western blotting. (F) Cytospins from the BM mononuclear cells were prepared, and representative images are shown (200× magnification). (G) Nuclear FOXM1 was quantified in ixazomib- and vehicle-treated animals. Animals treated with ixazomib had significant downregulation of nuclear FOXM1. Data are expressed as the mean ± SEM (n = 8/group); P = 0.058 by unpaired 1-tailed t test.