Lymphotoxin alpha eradicates acute myeloid leukemia and simultaneously promotes healthy hematopoiesis in mice

Acute myeloid leukemia (AML) is characterized by frequent relapse, which is driven by resistant leukemic stem or progenitor cells (LSCs). Here, we reported on a tumor-suppressive mechanism that can be harnessed to simultaneously clear LSCs and promote healthy hematopoiesis. Genetic deletion of the tumor necrosis factor (TNF) superfamily member lymphotoxin alpha (Lta) blocked cell death and accelerated leukemogenesis in murine AML models. Accordingly, exposure of leukemic cells to exogenous recombinant lymphotoxin alpha (LTa3) induced myeloid differentiation and, in part, cell death in AML progenitors. In syngeneic and patient-derived xenograft mouse models, exposure to recombinant LTa3 resulted in deep and durable remissions. LTa3 repressed leukemia by depleting tumor necrosis factor receptor (TNFR)-associated factor 2 (TRAF2) through activation of TNF receptors TNFR1 and TNFR2. In contrast with conventional therapies, LTa3 exerted only minimal toxicity on the healthy hematopoiesis but instead promoted hematopoietic progenitors. Leveraging this endogenous tumor-suppressive mechanism may decouple treatment efficacy on malignant cells from undesired bone marrow suppression. Overall design: Cell lines or bone marrow from AML patients and healthy CD34+ HSPCs were treated with rhLTa3 and TNF for 24 hours and total RNA from primary cells was isolated using miRNeasy Mini Kit (Qiagen). Total RNA from AML cell lines (OCI-AML3 and MOLM-13) were isolated using peq gold total RNA kit (VWR). mRNA library was made with poly A enrichment using akit developed by Novogene (Novogene GmbH) and 150bp paired end sequencing was performed on Illumina Sequencing platform NovaSeq 6000. Raw sequencing data from cell lines and the count tables from primary samples were deposited in NCBI's Gene Expression Omnibus (S.V. to include). NGS reads were mapped using STAR and differential gene expression was calculated with DESeq2. The reference genome for mapping was hg38, default parameters have been used for all individual steps. To count the gene expression the program “featureCounts” was used.