Cancer-Associated Fibroblast-Derived circKLHL24 Drives Perineural Invasion in Pancreatic Cancer via Dual Regulation of the Sec31A-CXCL12 Axis
Background: Cancer-associated fibroblasts (CAFs) are key drivers of neural invasion in pancreatic cancer, yet their regulatory mechanisms remain elusive.This study explores the role of circular RNAs (circRNAs) in CAFs and their involvement in regulating neural invasion in pancreatic cancer. Methods: CAF-derived circRNAs were identified through circRNA high-throughput sequencing and quantitative real-time PCR (qRT-PCR). The impact of CAF-derived circKLHL24 on perineural invasion (PNI) in tumor cells was evaluated both in vitro and in vivo. RNA sequencing, RNA pulldown, RNA immunoprecipitation, and luciferase reporter assays were conducted to identify downstream targets and elucidate the underlying mechanism of circKLHL24 in PNI. Results: CircKLHL24 (hsa_circ_0001369), a CAF-specific circRNA, is associated with PNI and poor survival in advanced PDAC. Silencing or overexpressing circKLHL24 in CAFs altered the ability of CAFs to induce tumor cell invasion and nerve infiltration via chemokine (C-X-C Motif) ligand 12 (CXCL12). Mechanistically, first, circKLHL24 binds to the membrane protein Sec31A, inhibiting its ubiquitination and degradation, thereby enhancing CXCL12 secretion. Second, circKLHL24 acts as a sponge for miR-615-5p, relieving its suppression of CXCL12 mRNA and amplifying CXCL12 expression.Moreover, high circKLHL24 levels were positively correlated with elevated serum CXCL12 levels in PDAC and poor patient survival. Targeting circKLHL24 or neutralizing CXCL12 suppresses PDAC invasion and neuronal recruitment in nude mouse and KPC models. Conclusions: The circKLHL24/Sec31A/miR-615-5p/CXCL12 axis is critical for CAF-induced PNI in PDAC. Therefore, circKLHL24 could serve as a potential therapeutic target for PDAC. Overall design: To investigate the functional role of circKLHL24 in CAFs, RNA-seq were performed  to compare gene expression profiles following circKLHL24 knockdown in CAFs