Ral GTPases as novel regulators of acinar cell plasticity in the pancreas – implications for cancer development and treatment

• Applicant: Dr. Andrea Oeckinghaus
• Subject Area: Cell Biology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502983674

Pancreatic cancer represents one of the deadliest cancers with a 5-year survival rate of 10 %. The initial step in pancreatic ductal adenocarcinoma (PDAC) development is the transdifferentiation of acinar to ductal cells (acinar-to-ductal metaplasia, ADM), which then further progress to form neoplasias and finally invasive carcinoma. We found that loss of RALGAP complexes, negative regulators of signaling by the small RAL GTPases RALA and RALB, sensitizes acinar cells to ADM and drastically increases their susceptibility to oncogenic transformation through oncogenic KRASG12D and PDAC development. RALGAP deficiency also prevents regeneration of the acinar cell compartment after acute pancreatitis, where ADM is normally transient, suggesting deregulation of RALGAP/RAL activity as a risk factor for cancer development. RAL GTPase activity is frequently upregulated in PDAC samples and cell lines. However, no in vivo studies have addressed the role of RAL GTPases in PDAC and RAL GTPase function has until now not been connected to acinar plasticity. The aim of this proposal is to provide a comprehensive analysis of RAL GTPase function(s) in the ADM process. We wish to fully characterize the phenotype of RALGAPβ loss, where RAL GTPases are hyperactive, in respect to ADM and its impact on the inflammatory response upon acute and chronic pancreatitis and we will elucidate when and how RAL GTPase activity is regulated during inflammatory processes in the pancreas. Furthermore, we will investigate the effects of genetic ablation of RALA and/or RALB on ADM and tumor development during acute and chronic inflammation in respective in vivo models. Here, we will be able to characterize, for which phase during acinar plasticity RAL GTPases are critical and whether RAL isoform-specific dependencies exist. As pancreatic cancer remains difficult to treat, there is great research interest in identifying new treatment options. We will test if RAL inhibition using the small molecule BQU57 can prevent or revert ADM and thus serve as an early intervention strategy. Finally, we wish to unravel the signaling pathways and cellular processes that are driven by RAL to control acinar plasticity. We have established 3D organoid and cell culture systems that allow analysis of ADM in ex vivo settings, which we will combine with RNA sequencing and phosphoproteomics approaches to identify critical mediators and processes downstream of RAL GTPases. Our findings will improve our understanding of the regeneration processes after pancreatitis and the initiating events in PDAC development, which we hope will promote the discovery of markers for early detection as well as strategies for early intervention.

• DFG Programme: Research Grants