Citations

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, arising from both B and T cell lineages (B-ALL and T-ALL). Current therapy exploits ALL cells’ low expression of asparagine synthetase (ASNS) by using L-asparaginase, a bacterial enzyme that depletes circulating asparagine. However, resistance can emerge through induction of ASNS, mediated in part by the amino acid stress sensor GCN2. In this study, we addressed the efficacy of L-asparaginase in combination with genetic or pharmacological inhibition of GCN2 and the ASNS inhibitor ASX-173. Using a Kras G12D -driven mouse model of T-ALL, we found that GCN2 is dispensable for leukemogenesis. However, genetic inactivation or pharmacologic inhibition of GCN2 sensitized ALL cells to asparagine depletion, correlating with impaired ASNS induction. While GCN2 targeting enhanced sensitivity to asparagine depletion, a subset of Gcn2 –/– T-ALL cells retained high ASNS expression and remained resistant to L-asparaginase. Likewise, some human T-ALL cells with elevated ASNS levels were refractory to GCN2 inhibition even under asparagine-depleted conditions. When combined with L-asparaginase, ASX-173 effectively eliminated ASNS hi leukemic cells in vitro and in vivo. These findings suggest that direct targeting of ASNS provides therapeutic benefit in leukemias that express high levels of ASNS and are resistant to GCN2 inhibition under asparagine-depleted conditions.

Abstract Mesenchymal stem/progenitor cells (MSPCs) have immunomodulatory activity. We previously observed that osteoprogenitors and CD8+T cells are increased in the bone marrow (BM) of mice lacking the transcription factor Nmp4. Transcriptome analysis of MSPCs from Nmp4−/− and wild type (WT) mice revealed significant changes in genes related to innate immune responses, including reduced expression of Tlr3 and Mda5 in the null MSPCs. Loss of Nmp4 increased mRNA translation, ribosomal biogenesis, and Gadd34 expression in MSPCs; collectively, these processes likely promote the unfolded protein response (UPR), expanding the processing capacity of the endoplasmic reticulum. Therefore, we hypothesized that disabling Nmp4 would improve innate immune cell function. To test this, Nmp4−/− mice (C57BL6) were infected intranasally with influenza A/PR8 (H1N1; 150pfu). Despite having similar virus load in the lung, H1N1-infected Nmp4−/− mice lost less body weight than WT mice post infection and had improved survival. Infected Nmp4−/− mice had fewer infiltrating neutrophils (PMNs; CD11b+/Ly6G+) and monocytes (CD11b+/SiglecFNeg/Ly6GNeg/Ly6C+) in bronchoalveolar lavage (BAL) but more BAL macrophages (CD11c+/SiglecF+); CD4+ and CD8+ T cells were not different between genotypes. Ex vivo, Nmp4-deficiency did not alter the differentiation of BM marrow-derived macrophages; however, Chil3/Ym1 and Alox15 mRNA expression was reduced in Nmp4−/− macrophages polarized with IL-4/IL-13, suggesting cell-autonomous regulation of M2 macrophage activation by Nmp4. Our data point to Nmp4 as a novel regulator of innate immunity and influenza response in mice.