Introduction

Intraductal papillary mucinous neoplasm (IPMN) is a significant precancerous lesions of pancreatic cancer, with GNAS mutations frequently observed. We previously demonstrated that GNAS mutations suppress the invasive potential of IPMN-derived cancer cells by inhibition the Notch signaling pathway in a PKA-dependent manner. However, the influence of GNAS mutations on coexisting pancreatic cancers remains unclear. MicroRNAs (miRNAs) are known to regulate gene expression post transcriptionally and can be transferred via extracellular vesicles (EVs) under tumor microenvironmental conditions. In this study, we investigated the paracrine effects of EVs derived from GNAS-mutant IPMN cells and the roles of miRNA cargo in the development and progression of IPMN-associated pancreatic cancers.

Aims & Methods

This study aimed to evaluate the tumor suppressive effects of EVs derived from GNAS-mutant IPMN cells on pancreatic cancer and to identify EV-encapsulated miRNAs that regulate tumor progression. EV-containing supernatants were collected from human pancreatic cancer cells harboring GNAS R201H mutation (established from IPMN-derived invasive cancer) and from a genome-edited GNAS wild-type subline. miRNA profiles in EVs were assessed using GeneChip miRNA microarray. Gene expression was analyzed by qPCR, and protein expression were evaluated via Western blotting.

Results

When EV-containing supernatants from mutant or wild-type GNAS cells were added to pancreatic cancer cells (e.g., Panc-1), those from GNAS-mutant cells significantly suppressed cancer cell invasion and migration. Microarray analysis revealed that miR-602 was more than two-fold upregulated in EVs from mutant cells compared to wild-type cells. Treatment with a PKA inhibitor decreased miR-602 expression in GNAS-mutant cells, whereas PKA activator increased its expression in wild-type cells, indicating that GNAS mutation upregulates miR-602 expression in a PKA signaling. Overexpression of miR-602 in pancreatic cancer cells suppressed their invasive and migratory capabilities. Target gene analysis identified RAC2 and PAK4 –downstream effectors of KRAS pathway– as direct targets of miR-602. These genes are also implicated in PI3K phosphorylation. miR-602 overexpression suppressed PI3K phosphorylation and upregulated E-cadherin expression. These findings suggest that miR-602 act as a tumor suppressor by targeting RAC2/PAK4 and attenuating epithelial-mesenchymal transition (EMT) via PI3K signaling suppression.

Conclusion

IPMNs harboring GNAS mutation upregulate miR-602 expression in EVs in a PKA-dependent manner. These EVs exert paracrine tumor-suppressive effect by downregulating RAC2/PAK4 expression and inhibiting PI3K phosphorylation in neighboring pancreatic cancer cells, thereby attenuating malignant progression. Understanding this regulatory mechanism may contribute to improved risk stratification and surveillance strategy for IPMN-related pancreatic carcinogenesis.