Inhibiting tumor cell-intrinsic UBA6 by inosine augments tumor immunogenicity

Metabolic alteration influences cancer immunity. However, the role and mechanism of metabolic adaption on immune checkpoint blockade (ICB) responses remains ill-defined. Here, metabolomic profiling in mouse tumor models and cancer patients treated with ICB was performed. We found that metabolite inosine was associated with ICB sensitivity in mice and humans, and overcame ICB resistance in several mouse tumor models. Notably, inosine sensitized tumor cells to T cell-mediated cytotoxicity by amplifying tumor-intrinsic immunogenicity. Chemical proteomics further identified that inosine directly bound and inhibited ubiquitin-activating enzyme UBA6. Tumor intrinsic UBA6 loss augmented tumor immunogenicity and substituted the synergistic effect of inosine in combination with ICB. Clinically, tumor UBA6 expression negatively correlated with ICB response in cancer patients. Thus, we reveal an unappreciated function of inosine on tumor-intrinsic immunogenicity and UBA6 as a candidate target for immunotherapy. Comparative gene expression profiling analysis of RNA-seq data for wildtype and UBA6 knockout 4T1 breast cancer cells.