ONCOGENIC GNAS DRIVES A GASTRIC PYLORUS-TYPE PROGRAM IN INTRAEPITHELIAL PAPILLARY MUCINOUS NEOPLASIA OF THE PANCREAS

BACKGROUND & AIMS: Intraductal Papillary Mucinous Neoplasms (IPMNs) are cystic lesions of the pancreas driven by oncogenic KRAS +/- GNAS which can serve as precursors for pancreatic ductal adenocarcinoma (PDAC). Recently, we showed that acinar to ductal metaplasia (ADM), an injury repair program associated with pancreatic tumorigenesis, is characterized by a pylorus-type transcriptomic program similar to gastric spasmolytic polypeptide expressing metaplasia (SPEM), suggesting common mechanisms of reprogramming between the stomach and pancreas. The aims of this study were to assay IPMN for SPEM markers and to identify molecular drivers of this program.

METHODS: Published RNA-seq studies of IPMN were assessed for SPEM markers, which were validated by immunostaining (mxIHC) in 41 patient samples. Kras^G12D +/- GNAS^R201C expression was manipulated in murine PDAC cell lines by siRNA and underwent RNA-sequencing to identify distinct and overlapping transcriptomic programs driven by each oncogene. Results were compared computationally to SPEM and validated in vivo, in a mouse model of IPMN. PyScenic-based regulon analysis was performed to identify drivers of SPEM in the pancreas. Expression of candidate drivers was evaluated in patient samples by RNA-seq and immunostaining and a role for SPDEF was investigated.

RESULTS: SPEM markers were identified in human IPMN at the transcript and protein level. GNAS^R201C was sufficient to drive expression of these markers in murine cell lines and siRNA targeting of GNAS^R201C or Kras^G12D demonstrates that GNAS^R201C amplifies a mucinous, SPEM-like phenotype. Kras^G12D/Gnas^R201C driven IPMN are dominated by mucus-producing cells. Regulon analysis identified a role for transcription factors SPDEF, CREB3L1, and CREB3L4, which are expressed in patient samples. siRNA-targeting of SPDEF inhibited GNAS^R201C-driven expression of SPEM markers.

CONCLUSIONS: De novo expression of a pylorus-type/SPEM phenotype has been identified in pancreatitis, oncogenic Kras^G12D-driven pancreatic neoplasia, and in Kras^G12D;GNAS^R201C-driven IPMN, suggesting common mechanisms of reprogramming between these lesions and the stomach. IPMN-specific GNAS^R201C amplifies a mucinous phenotype through expression of transcription factor SPDEF.