Type: Oral
Session: 617. Acute Myeloid Leukemias: Biomarkers, Molecular Markers and Minimal Residual Disease in Diagnosis and Prognosis: Immunologic and Metabolic Biomarkers of Disease Control
Hematology Disease Topics & Pathways:
Research, Clinical Practice (Health Services and Quality), Diseases, Therapies
Two established AML models were used to assess BCL-2 expression profile in HPCs. Isolated LSK cells were co-cultured with mouse AML (HOXA9/Meis1 or MN1 overexpressing cells). RT-qPCR analysis identified BCL-2 upregulation in LSKs co-cultured with both AML cell types. To understand the significance of this in vivo, MN1 cells were engrafted into C57BL/6 mice and LSKs were FACS purified. Analysis confirmed increased BCL-2 gene and protein expression by RT-qPCR and flow cytometry when compared to control LSKs. Next, to recapitulate the clinical cytopenias, MN1 engrafted mice or control mice were treated with venetoclax for 7 days by oral gavage. Flow cytometry analysis of bloods and bone marrow in venetoclax-treated AML mice determined neutrophil depletion and reduced numbers of HPCs, namely LSK, MPP, HSC and GMP, compared to untreated AML mice. To determine the mechanism of BCL-2 upregulation in LSKs we explored various signalling pathways using targeted inhibitors on LSKs cultured with MN1 conditioned media. Using this method, we established that interleukin 3 (IL-3) activates BCL-2 transcription in LSKs leading to a dependency on pro-survival BCL-2 protein. Furthermore, treatment of LSKs, cultured in MN1 conditioned media with IL-3 neutralising antibody MP2-8F8 reduced BCL-2 gene and protein expression in LSKs. Finally, MN1 engrafted mice were treated with venetoclax and IL-3 neutralising antibody in combination which restored neutrophil levels to numbers observed in untreated AML mice.
Here, we demonstrate that BCL-2 is overexpressed in non-malignant HPCs during AML progression using two AML models. In addition, using our syngeneic mouse model we show that venetoclax induces HPC depletion. In vitro studies confirm that IL-3 mediates BCL-2 upregulation in HPCs - this sensitises HPCs to venetoclax and causes cytopenias. We also demonstrate that neutrophils can be recovered using IL-3 neutralisation in combination with venetoclax in AML engrafted mice. Taken together, these findings provide biologic insight for IL-3 inhibition alongside venetoclax to reduce the incidence of cytopenias observed in elderly AML patients.
References
1. DiNardo CD, Pratz K, Pullarkat V, Jonas BA, Arellano M, Becker PS, et al. Venetoclax combined with decitabine or azacitidine in treatment-naive, elderly patients with acute myeloid leukemia. Blood. 2019;133(1):7-17.
2. Wei AH, Montesinos P, Ivanov V, DiNardo CD, Novak J, Laribi K, et al. Venetoclax plus LDAC for newly diagnosed AML ineligible for intensive chemotherapy: a phase 3 randomized placebo-controlled trial. Blood. 2020;135(24):2137-45.
3. DiNardo CD, Jonas BA, Pullarkat V, Thirman MJ, Garcia JS, Wei AH, et al. Azacitidine and Venetoclax in Previously Untreated Acute Myeloid Leukemia. N Engl J Med. 2020;383(7):617-29.
Disclosures: No relevant conflicts of interest to declare.