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Identification of ABCG2 Inhibitors as a New Combination Therapy to Improve Outcome in AML
Author(s) -
Allcock Alice,
Fukuda Yu,
Lin Wenwei,
Chen Taosheng,
Schuetz John D.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1064.3
Subject(s) - lapatinib , mitoxantrone , abcg2 , pharmacology , myeloid leukemia , tyrosine kinase inhibitor , cancer research , medicine , atp binding cassette transporter , cancer , chemistry , chemotherapy , breast cancer , transporter , trastuzumab , biochemistry , gene
Acute myeloid leukemia (AML) arises secondary to lesions that disrupt normal myelopoiesis. Despite recent advances in chemotherapy, the 5‐year survival rate is poor (~50%) due to relapse and/or refractory disease. The primary treatment regimen for AML relies upon the antineoplastic, mitoxantrone. An ATP‐binding cassette (ABC) transporter, ABCG2, exports multiple cytotoxic chemotherapeutics, including mitoxantrone, from cancer cells producing strong resistance. In AML, ABCG2 is expressed at higher levels in samples from relapse patients, and high ABCG2 levels are associated with poor survival in multiple AML cohorts. Currently available ABCG2 inhibitors are not suitable due to neurotoxicity, low specificity, or possess a high IC 50 that is not clinically achievable. Therefore, we hypothesized that identification of chemotherapeutics that target pathways activated in AML, (e.g. Wnt or tyrosine kinase) but also inhibit ABCG2 function would have clinical impact when combined with a chemotherapy that includes mitoxantrone. To this end, we developed a high throughput screening assay that assessed ABCG2's ability to export a specific fluorescent substrate, pheophorbide a (PhA) from mouse embryonic fibroblasts (MEFs) which were engineered to express human ABCG2. We validated the assay using a previously reported ABCG2 inhibitor, lapatinib (tyrosine kinase inhibitor, TKI), as a control. Subsequently, using a single concentration of 10 μM, a library of ~12,000 bioactive compounds including FDA‐approved drugs was assessed for their ability to block the export of PhA. Compounds producing >80% inhibition, compared to lapatinib, were further subjected to a secondary dose responsive analysis. Chemotherapeutic agents displaying activity were further validated for their specificity and activity in wild‐type MEFs, MEFs lacking Abcg2(KO) or KO ‐MEFs harboring human ABCG2 . These compounds were evaluated for their ability to enhance the cytotoxicity of mitoxantrone in MEFs and AML cell lines. Several TKIs have been shown to inhibit ABCG2, but at high concentrations (>10 μM). We identified a TKI that inhibits ABCG2 with an IC 50 < 1 μM, but was previously unknown. We also identified a Wnt pathway antagonist that potently inhibits ABCG2. In summary, these potent ABCG2 inhibitors we identified have a selective advantage in killing AML cells because their dual actions will disrupt a vital pathway in AML, but also increase the cytotoxicity of mitoxantrone, an approach that is likely to reduce relapse and increase durable remissions. Support or Funding Information This work was supported by NIH and by the ALSAC.