Finally, we found that N5-methylglutamine urine levels were not increased in mice with GS– p53-null/c-MYC liver tumors or in mice with GS+ pancreatic tumors (KrasLSL.G12D/+; Trp53R172H/+; Pdx1-Cre (KPC))11 compared to tumor-free mice (Fig. 6e and Extended Data Fig. 4l), strengthening the validity of this newly discovered GS-derived metabolite as a selective biomarker for β-catenin-mutant liver cancer. Here, TP53 is linked to liver cancer.