Endosomal trafficking bypassed by RAB5B-CD109 interplay promotes axonogenesis in KRAS-mutant pancreatic cancer

Perineural invasion (PNI) represents a unique biological feature causing the poor prognosis of pancreatic ductal adenocarcinoma (PDAC), especially with KRAS mutation. Extracellular vesicle (EVs)-packaged circRNAs function as essential mediator for tumor microenviroment communication to trigger PDAC cells invading into the surrounding regions and lead to distant metastasis. However, the regulatory mechanism of exosomal circRNA in PNI of KRAS-mutated PDAC has not been elucidated. Herein, we identified an KRASG12D-mutation responsive exosomal circRNA-circPNIT, which was positively correlated with PNI of PDAC. Functionally, KRASG12D PDAC-derived EV-packaged circPNIT promotes axonogenesis and PNI both in vitro and in vivo. Mechanistically, circPNIT-mediated Rab5B-CD109 interplay bypassed traditional endosomal trafficking to anchor Rab5B in the lipid rafts of multivescular body and fostered the secretion of circPNIT as a cargo of CD109+EVs. Subsequently, CD109+EVs achieved the targeted delivery of circPNIT to neurons by recognizing their surface receptor TRPV1 and facilitated DSCAML1 transcription-induced axonogenesis, which in turn enhanced the PNI by activating GFRα1/RET pathway. Importantly, we established an engineered si-cirPNIT-loaded CD109+EVs to dramatically inhibit PNI of PDAC in a KRASG12D/+ Trp53R172H/+ Pdx-1-Cre mice model. Collectively, Our findings highlight the mechanism underlying EV-packaed circRNA mediating PNI of KRAS mutated-PDAC dependent of a Rab5B endosomal bypass, supporting circPINT as an effective target for the treatment of neuro-metastatic PDAC