Inhibition of Fatty Acid Metabolism Re-Sensitizes Resistant Leukemia Stem Cells to Venetoclax with Azacitidine

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.1272-1272
• Main Authors: Jones, Courtney L, Stevens, Brett M., Culp-Hill, Rachel, Dalessandro, Angelo, Krug, Anna, Goosman, Madeline, Pei, Shanshan, Pollyea, Daniel A, Jordan, Craig T
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-125773

The combination of venetoclax with hypomethylating agents has resulted in highly promising clinical outcomes for acute myeloid leukemia (AML) patients. However, a subset of patients are refractory or develop resistance to venetoclax based regimens, resulting in disease recurrence. The goal of this project was to determine a mechanism to re-sensitize resistant leukemia stem cells (LSCs) to venetoclax with azacitidine (ven/aza) treatment. LSCs are the population of leukemia cells that initiate disease and are not fully eradicated by conventional treatments resulting in disease recurrence. We have previously reported that ven/aza targets LSCs in de novo AML patients by perturbing amino acid uptake resulting in decreased oxidative phosphorylation (OXPHOS). To investigate how some AML patients, develop resistance to ven/aza, we first determined if ven/aza reduced amino acid uptake in primary human AML ven/aza resistant LSCs by stable isotope labeled metabolic flux and mass spectroscopy analysis. Amino acid uptake was significantly reduced in both ven/aza sensitive and resistant LSCs upon ven/aza treatment, indicating that ven/aza is still biologically active in resistant LSCs. Next, we performed gene expression analysis from LSCs isolated from AML patients who were treated with ven/aza, responded, and then either remained in remission or progressed on ven/aza therapy. Gene set enrichment analysis revealed that fatty acid transport was enriched in LSCs isolated from patients who eventually progressed on ven/aza therapy (FDR = 0.0088) (Figure A). We then determined differences in overall fatty acid levels by lipidomics mass spectroscopy analysis in ven/aza sensitive and resistant LSCs. We observed a significant increase in abundance of 20% (6/29) of fatty acids detected in resistant LSCs. To determine if targeting fatty acid transport could re-sensitize resistant LSCs to ven/aza we knocked down genes involved in fatty acid transport including CD36, CPT1A and CPT1C in 4 ven/aza resistant AML specimens and then measured viability and colony-forming potential upon ven/aza treatment (Figure B and C). Knockdown of CD36, CPT1A, or CPT1C in combination with ven/aza treatment significantly decreased both viability and colony forming ability in each of the AML specimens. In addition, knockdown of CPT1A or CPT1C in combination with ven/aza reduced OXPHOS, a known metabolic requirement of LSCs. To perturb fatty acid transport in a therapeutically relevant manner, we treated