GLUL and hepatocellular carcinoma: 11 In fact, glutamine synthetase (GS; encoded by GLUL) immunohistochemistry is used as a biomarker for patients with CTNNB1-mutated HCC.15 However, targeting these downstream Wnt target genes has revealed novel negative feedback loops in the Wnt/β-catenin oncogenic circuit,16,17 necessitating the need to focus on targeting β-catenin directly for precision therapy.