Project description:Germinal centre (GC) B cells proliferate at some of the highest rates of any mammalian cell. Yet the metabolic processes which enable this are poorly understood. We performed integrated metabolomic and transcriptomic profiling of GC B cells, and found that asparagine metabolism is highly upregulated. Asparagine is conditionally essential to B cells, and its synthetic enzyme, asparagine synthetase (ASNS) is markedly upregulated following their activation, through the integrated stress response sensor general control non-derepressible 2 (GCN2). When Asns is deleted, B cell survival in low asparagine conditions is severely impaired. Using stable isotope tracing, we found that metabolic adaptation to the absence of asparagine requires ASNS, and that the synthesis of nucleotides is particularly sensitive to asparagine deprivation. Conditional deletion of Asns in B cells selectively impairs GC formation, associated with a reduction in RNA synthesis rates. Finally, removal of environmental asparagine by asparaginase was found to also severely compromise the GC reaction.
Project description:Single - cell profiling of patient tumours and of mouse models is revealing that many cancers are constituted of communities of genetically and phenotypically distinct clonal lineages 1 - 12. A functional model of breast cancer heterogeneity revealed that clonal sub - populations proficient at generating circulating tumour cells were not equally capable of forming metastases at secondary sites 13. A combination of differential expression and focused in vitro and in vivo RNAi screens revealed candidate drivers of metastasis discriminating these clones, which were then evaluated in gene expression datasets from breast cancer patients. Among these, Asparagine Synthetase (Asns) expression in a patient's primary tumour was most strongly correlated with later metastatic relapse. Silencing of Asns reduced both metastatic potential in vivo and invasive potential in vitro. Conversely, increasing the availability of extracellular asparagine increased the invasive potential of mouse and human breast cancer cells, and enforced Asns expression promoted metastasis. Decreasing asparagine availability in mice by treatment with L-asparaginase or even by dietary restriction strongly reduced metastasis from orthotopic tumours. Asparagine availability varies betwe en tissues, potentially explaining selective effects on particular steps of tumor progression. Asparagine limitation reduced the production of proteins that promote the epithelial to mesenchymal transition, providing one potential mechanism for how the availability of a single amino acid could regulate metastatic progression.
Project description:Asparagine deprivation by L-Asparaginase is a successful therapeutic strategy in Acute Lymphoblastic Leukemia, with resistance occurring due to upregulation of ASNS. L-Asparaginase efficacy in solid tumors is hampered by dose-related toxicities. Large scale loss of function genetic screens identified ASNS, the only human enzyme synthetizing asparagine, as a cancer dependency in several solid malignancies, including melanoma. We here evaluate the therapeutic potential of targeting ASNS in melanoma cells in-vitro and in-vivo. Using ex-vivo quantitative proteome and transcriptome profiling, we observed that concomitant ASNS deletion and asparagine deprivation elicit a compensatory mechanism allowing tumor growth. Genome wide CRISPR screens upon manipulation of aminoacid levels identifies MAPK and GCN2 as critical nodes mediating the observed resistance mechanism. Importantly MEK and GCN2 inhibitor synergize with L-Asparaginase suggesting novel potential therapeutic strategy in melanoma.
Project description:Tumor cells often employ many ways to restrain type I interferon (IFN-I) signaling to evade immune surveillance. However, whether cellular amino acid metabolism regulate this process remains unclear and its effects on antitumor immunity are relatively unexplored. Here, our study reports that asparagine generated by asparagine synthetase (ASNS) inhibits IFN-I signaling and promotes immune escape in bladder cancer. We further show that depletion of ASNS strongly limits in vivo tumor growth in a CD8+ T cell-dependent manner, thus boosting the immunotherapy efficacy. Moreover, clinically approved ASNase synergizes with anti-PD-1 therapy in suppressing tumor growth in mouse models of bladder cancer. Mechanistically, asparagine intensifies the interaction of E3 ligase CBL and RIG-I, promoting K48-linked polyubiquitination and degradation of RIG-I, thus suppressing RIG-I mediated IFN signaling and anti-tumor immune response. Clinically, ASNS is overexpressed in muscle-invasive bladder cancer and correlated with poor response of immunotherapy. Together, our findings uncover asparagine as a natural metabolite to modulate RIG-I-mediated IFN-I signaling, providing the basis for developing the combinatorial use of ASNase and anti-PD-1 for bladder cancer.
2025-03-19 | GSE270353 | GEO
Project description:Effects of Asparagine Deprivation on CD8+ T Cell Activation
