Mutant KRAS Mediates circARFGEF2 Biogenesis to Promote Lymphatic Metastasis of Pancreatic Ductal Adenocarcinoma

Circular RNAs (circRNA) contribute to cancer stemness, proliferation, and metastasis. The biogenesis of circRNAs can be impacted by the genetic landscape of tumors. Herein, we identified a novel circRNA, circARFGEF2 (hsa_circ_0060665), which was upregulated in KRAS(G12D) pancreatic ductal adenocarcinoma (PDAC) and positively associated with KRAS(G12D) PDAC lymph node (LN) metastasis. CircARFGEF2 overexpression significantly facilitated KRAS(G12D) PDAC LN metastasis in vitro and in vivo. Mechanistically, circARFGEF2 biogenesis in KRAS(G12D) PDAC was significantly activated by the alternative splicing factor QKI-5, which recruited U2AF35 to facilitate spliceosome assembly. QKI-5 bound the QKI binding motifs and neighboring reverse complement sequence in intron 3 and 6 of ARFGEF2 pre-mRNA to facilitate circARFGEF2 biogenesis. CircARFGEF2 sponged miR-1205 and promoted the activation of JAK2, which phosphorylated STAT3 to trigger KRAS(G12D) PDAC lymphangiogenesis and LN metastasis. Importantly, circARFGEF2 silencing significantly inhibited LN metastasis in the Kras(G12D/+)Trp53(R172H/+)Pdx-1-Cre (KPC) mouse PDAC model. These findings provide insight into the mechanism and metastasis-promoting function of mutant KRAS-mediated circRNA biogenesis. SIGNIFICANCE: Increased splicing-mediated biogenesis of circARFGEF2 in KRAS-mutant pancreatic ductal adenocarcinoma activates JAK2–STAT3 signaling and triggers lymph node metastasis, suggesting circARFGEF2 could be a therapeutic target to inhibit pancreatic cancer progression.