Combinations of HDAC inhibitor and PPAR agonist induce ferroptosis of leukemic stem cell-like cells in acute myeloid leukemia

Purpose: Leukemia stem cells (LSCs) are responsible for leukemia initiation, relapse, and therapeutic resistance. Therefore, the development of novel therapeutic approaches targeting LSCs is urgently needed for patients with AML. Methods: The LSCs-like cell lines (KG-1α and Kasumi-1), CD34+ primary AML cells purified from AML patients (n=23) treated with CS055 and/or chiglitazar and were analyzed for viability, death, and colony formation assay. We performed RNA-seq, Glutamate-Release, Intracellular-GSH, Lipid-ROS, transmission-electron-microscopy, Western-Blotting assay, and confirmed ferroptosis in LSCs-like cells. The luciferase-reporter, co-immunoprecipitation, HDAC3-shRNA/HDAC3/deacetylase-deficient LSCs-like cell lines, His-pull-down, and chromatin-immunoprecipitation assays performed to clarify the molecular mechanism of CS055/chiglitazar in LSCs-like cells. We also established CDX and PDX mouse models to evaluate the therapeutic efficacy of CS055/chiglitazar against-AML in vivo. Results: We report that the histone deacetylase inhibitor CS055, in combination with peroxisome proliferator-activated receptor (PPAR) pan-agonist (chiglitazar), synergistically targets leukemia stem-like cells from leukemia cell lines and patient samples, while sparing normal hematopoietic progenitor cells. Mechanistically, chiglitazar enhances the inhibitory effect of CS055 on HDAC3 and induces ferroptosis in LSCs-like cells by down-regulating the expression of ferroptosis suppressor SLC7A11. In fact, the inhibition of HDAC3 increases H3K27AC levels in the promoter region of activating transcription factor 3 (ATF3), a transcriptional repressor of the SLC7A11 gene, and upregulates the expression of ATF3. In contrast, ATF4, a SLC7A11 activator, is suppressed by HDAC3 inhibition. Conclusions: Our findings suggest that treatment with CS055 combined with chiglitazar, will target LSCs by inducing ferroptosis and may confer an effective approach for the treatment of AML.