RACK1 attenuates pancreatic tumorigenesis by suppressing acinar-to-ductal metaplasia through inflammatory signaling modulation.

PURPOSE: Pancreatic ductal adenocarcinoma (PDA) remains one of the most lethal malignancies with limited early diagnostic and therapeutic options. Although receptor for activated C kinase 1 (RACK1) is an evolutionarily conserved scaffold protein, its functional role and mechanistic involvement in PDA pathogenesis remain elusive. METHODS: Using multimodal approaches including: (1) genetically engineered mouse models of pancreatitis and carcinogenesis, (2) patient-derived PDA tissues with matched normal specimens, (3) primary acinar cell 3D cultures, and (4) orthogonal gain/loss-of-function assays in PDA cell lines, we systematically investigated RACK1's spatiotemporal expression patterns and functional impacts. Mechanistic dissection was performed through gene expression profiling and pathway enrichment analyses with functional validation. RESULTS: RACK1 exhibited progressive silencing across pancreatic lesion progression: acinar cells (normal) > ADM > pancreatic intraepithelial neoplasia (PanIN) > PDA. This acinar-specific protein was undetectable in ductal/islet lineages and was further suppressed under inflammatory challenge. Functionally, RACK1 depletion accelerated ADM initiation and enhanced PDA cell motility and metastatic dissemination in vivo, whereas its overexpression exerted tumor-suppressive effects. Mechanistically, caerulein/TGF-α stimulation and Kras(G12D) activation converged to inhibit RACK1 while activating MAP2K3-SRC-RELA(p65) signaling nodes, establishing a pro-inflammatory feedforward loop. CONCLUSIONS: RACK1 serves as a gatekeeper restraining inflammation-driven ADM transformation, with its downregulation constituting an early molecular event in PDA pathogenesis. The RACK1-MAP2K3 axis orchestrates malignant transition through simultaneous NF-κB activation (inflammatory priming) and MAPK hyperactivation (proliferative drive). Our findings nominate RACK1 as both a stratification biomarker for high-risk pancreatic lesions and a druggable node for intercepting preneoplastic progression.