Asparagine regulates RIG-I stability to suppress anti-tumor immunity in bladder cancer

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. Overall design: In order to screen downstream genes regulated by Asns gene, transcriptome analysis was performed in MBT2 cells transfected with shAsns and compaired vector.