Session: 604. Molecular Pharmacology and Drug Resistance in Myeloid Diseases: Poster III
Hematology Disease Topics & Pathways:
AML, apoptosis, Diseases, Therapies, Combinations, Biological Processes, Technology and Procedures, gene editing, Myeloid Malignancies, Clinically relevant, flow cytometry, pathways
To determine if targeting Mcl-1 enhances the activity of TKIs in FLT3 mutated AML, we treated MV4-11 and Molm13 cells with Mcl-1 inhibitor AMG176 and TKI gilteritinib (GIL) and observed synergism, as defined by combination index < 1 in both cells. Mechanistic studies demonstrated that GIL markedly decreased Mcl-1 and antagonized AMG176-induced Mcl-1 induction. GIL and its combination with AMG176 also decreased Bcl-xL. Although Bcl-2 protein levels were largely not changed in MV4-11 cells, we found both single treatment and the combination greatly decreased Bcl-2 associated athanogene (BAG) proteins BAG1, BAG3, and BAG4 at the RNA level, which needs to be confirmed at the protein level. The BAG proteins are a family of chaperone regulators and BAG1 was reported to bind and enhance the activity of multiple proteins known to support cells survival, including Bcl-2 (Takayama S et al., Cell 1995). Interestingly, GIL treatment greatly diminished the levels of beta-catenin and its target protein c-Myc, consistent with our previous report that FLT3 regulates beta-catenin signaling (Xiang et al., CCR, 2018). We have generated Mcl-1 overexpressing (OE) and VEN-resistance (VEN-R) MV4-11 and Molm13 cells. The Mcl-1 OE cells are highly resistant to VEN and the VEN-R cells expressed high levels of Mcl-1. Combined inhibition of AMG176 and GIL synergistically induced cell death in Mcl-1 OE and VEN-R resistant cells. Although the expression is low in AML cells we tested, BCL2A1 is also known as a resistant factor to VEN. We generated BCL2A1 OE MV4-11 and Molm13 cells and demonstrated that combined inhibition of FLT3 and Mcl-1 was highly effective in these cells as well. Western blot analysis revealed that GIL effectively decreased Mcl-1 in Mcl-1 OE and VEN-R and BCL2A1 in BCL2A1 OE MV4-11 cells.
Next, we treated FLT3 mutated AML patient samples harboring both, ITD and D835 mutations, from 2 patients who had both failed VEN-based therapy and from 1 patient with ITD mutation, with AMG176 and GIL under MSC co-culture conditions. Synergy was observed in all samples in AML blasts and AML stem/progenitor cells.
Collectively, our data demonstrate that targeting Mcl-1 enhances the activity of GIL in FLT3 mutated AML, including those resistant to/relapsed from VEN-based therapy, findings that may warrant clinical evaluation.
Disclosures: Carter: Syndax: Research Funding; Ascentage: Research Funding; AstraZeneca: Research Funding; Amgen: Research Funding. Hughes: Amgen: Current Employment. Chen: Amgen: Current Employment. Morrow: Amgen: Current Employment. Andreeff: Amgen: Research Funding; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy.
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