GSE113158
Elucidating the role of glycogen debranching enzyme AGL in bladder carcinogenesis by generation and characterization of knockout mice
Amylo-alpha-1-6-glucosidase-4-alpha-glucanotransferase (AGL) is an enzyme primarily responsible for glycogen debranching. Inactivating germline mutations lead to glycogen storage disease III (GSDIII). AGL was found to be a tumor suppressor in xenograft models of bladder cancer (BC) and low levels of expression in BC were associated with poor patient prognosis. However, the impact of AGL levels in normal tissues on susceptibility to carcinogenesis is unknown. We address this gap by developing a full body/germline AGL knock-out (AGL-FBKO) that recapitulates biochemical and histological features of GSDIII. AGL-FBKO mice exposed to N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN) had higher BC incidence at several time points following exposure, compared to wild type littermates (AGL-FBWT). To determine if this increased BC prevalence was due to decreased expression of AGL in the urothelium, we derived a urothelium specific conditional AGL knock-out (AGL-cKO) mouse driven by a Uroplakin II-Cre/loxP system. BBN experiments with these mice revealed AGL-cKO had higher BC incidence than mice without AGL knock-out (AGL-cWT). RNA-sequencing revealed that tumors from AGL-FBKO had 19 differentially expressed genes compared to AGL-FBWT mice. An “AGL Loss” gene signature was developed and found to successfully stratify normal and tumor samples in two BC patient datasets. These results support the role of AGL as a tumor suppressor. Our work suggests that evaluating AGL expression levels, or AGL KO gene signature scores, in normal urothelium may serve as a predictor for increased risk of BC development in individuals with carcinogenic exposures, such as smoking. Overall design: RNA-seq of BBN induced tumors in AGL-FBWT and AGL-FBKO mice