Mutant GNAS drives a pyloric metaplasia with tumor suppressive glycans in intraductal papillary mucinous neoplasia

ABSTRACT BACKGROUND & AIMS Intraductal Papillary Mucinous Neoplasms (IPMNs) are cystic lesions and bona fide precursors for pancreatic ductal adenocarcinoma (PDAC). Recent studies have shown that pancreatic precancer is characterized by a transcriptomic program similar to gastric metaplasia. The aims of this study were to assay IPMN for pyloric markers, to identify molecular drivers, and to determine a functional role for this program in the pancreas. METHODS Pyloric marker expression was evaluated by RNA-seq and multiplex immunostaining in patient samples. Cell lines and organoids expressing Kras G12D +/- GNAS R201C underwent RNA sequencing. A PyScenic-based regulon analysis was performed to identify molecular drivers, and candidates were evaluated by RNA-seq, immunostaining, and small interfering RNA knockdown. Glycosylation profiling was performed to identify GNAS R201C -driven changes. Glycan abundance was evaluated in patient samples. RESULTS Pyloric markers were identified in human IPMN. GNAS R201C drove expression of this program as well as an indolent phenotype characterized by distinct glycosyltransferase changes. Glycan profiling identified an increase in LacdiNAcs and loss of pro-tumorigenic Lewis antigens. Knockdown of transcription factors Spdef or Creb3l1 or chitinase treatment reduced LacdiNAc deposition and reversed the indolent phenotype. LacdiNAc and 3’-sulfoLe A/C abundance discriminated low from high grade patient IPMN. CONCLUSION GNAS R201C drives an indolent phenotype in IPMN by amplifying a differentiated, pyloric phenotype through SPDEF/CREB3L1 which is characterized by distinct glycans. Acting as a glycan rheostat, mutant GNAS elevates LacdiNAcs at the expense of pro-tumorigenic acidic Lewis epitopes, inhibiting cancer cell invasion and disease progression. LacdiNAc and 3’-Sulfo-Le A/C are mutually exclusive and may serve as markers of disease progression.