Background and Aims: Acute myeloid leukaemia (AML) is a heterogenous and aggressive blood cancer with no effective therapy against leukemic stem cells (LSCs) resulting in poor prognosis and high mortality. We have demonstrated the clinical significance of aberrant β-catenin activation in AML and low levels of reactive oxygen species (ROS) as a key feature of LSCs. This study extends our recent findings of a new β-catenin pathway (Salik et al., 2020) and explore therapeutic targets for pathway inhibition and the resultant oxidative stress. The research aims to investigate a stress sensor, GADD45A (growth arrest and DNA-damage inducible protein), as a potential key regulator of β-catenin pathway, and a resistance mechanism of cell death in human AML.
Methods and Results: Tumour burden was assessed using Gadd45a knockout transgenic mice and bioluminescence imaging of AML patient-derived xenograft (PDX) mice, where GADD45A were deleted by the CRISPR/Cas9 system. Our studies discovered that GADD45a has a crucial role in AML LSCs. Gadd45a deletion led to a progressive increase in aberrant self-renewal and leukaemogenesis in vivo. Deletion of GADD45a in human AML cells also showed increased engraftment and tumour burden in PDX mice, with increased β-catenin activity and criticalself-renewal target genes. To understand transcriptional regulatory mechanisms of GADD45a, we performed single-cell multi-omics in human PDX cells derived from relapsed AML and identified key GADD45a targets, such as ferritin heavy chain-1 and peroxiredoxin-1, which were validated and demonstrated to play a crucial role in iron detoxification conferring ferroptosis resistance to iron-dependent cell death.
Discussion and Conclusions: This innovative study was the first to demonstrate the role of GADD45a loss in promoting ferroptosis resistance in human LSCs and consequently enhancing leukaemogenesis in both murine and patient-derived xenograft models of AML, thus showcasing GADD45a as a promising therapeutic target for LSC eradication. Low GADD45α may also serve as a potential biomarker to identify drug-resistant patient cohorts for LSC-targeted therapies and ferroptosis sensitivity in poor prognosis AML.