GADD45a Controls Self-Renewal in Acute Myeloid Leukemia Stem Cells

Acute myeloid leukemia (AML) is a heterogenous malignancy, where the persistence of chemo-resistant leukemia stem cells (LSCs) contributes to disease relapse. We have previously demonstrated the clinical significance of WNT/β-catenin signaling in driving AML LSCs (Science, 327:1650-1653, 2010; Cancer Cell, 38:1-16, 2020). In this study, we uncover that GADD45a (growth arrest and DNA-damage inducible protein) is an essential regulator of β-catenin signaling pathway and its loss promotes LSC function and leukemia progression.

Transgenic knockout of Gadd45a led to a progressive increase in aberrant self-renewal and leukemogenesis in vivo. Gadd45a^-/- leukemic cells developed a more aggressive leukemia with a shorter latency than Gadd45a^+/+ cells in mice, indicating the involvement of Gadd45a loss in AML initiation and progression. Subsequent serial transplantation experiments showed that Gadd45a deletion enhanced LSC self-renewal in vivo. In agreement with our findings in murine LSCs, deletion of GADD45a by CRISPR/Cas9 in AML patient-derived xenograft (PDX) cells revealed increased engraftment and tumor burden in NSG mice. Consistent with our phenotypic observations, knockout of GADD45a increased βcatenin activity and key WNT/self-renewal target genes in human AML cells. In addition, our cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) data showed that GADD45a deletion in patient-derived LSCs was associated with cell metabolism, reactive oxygen species and tumor progression, as well as poor patient outcomes in AML. Further studies are being conducted to evaluate transcriptional mechanisms discovered by our single-cell sequencing.

Taken together, this study is the first to demonstrate that GADD45a loss promotes LSC potential and consequently enhances tumor growth in murine and PDX models of AML, thus showcasing GADD45a as a promising therapeutic target in AML.

References:

Wang Y, Krivtsov AV, Sinha AU, et al. The Wnt/beta-catenin pathway is required for the development of leukemia stem cells in AML. Science. 2010;327:1650-1653.

Salik B, Yi H, Hassan N, et al. Targeting RSPO-LGR4 signaling for leukemia stem cell eradication in acute myeloid leukemia. Cancer Cell. 2020; 38:1-16.