VEGF-C maturation mediated by CircFOCAD-orchestrated CCBE1 and ADAM10 expression in nuclear-cytoplasmic synergy drives lymphatic metastasis

Lymphangiogenesis is essential for tumor lymphatic metastasis, yet the molecular mechanisms governing the activation of its key cytokine, VEGF-C, remain unclear. Herein, we identified a circRNA, circFOCAD, through VEGF-C maturation-associated multiple transcription sequencing. CircFOCAD is overexpressed in lymph node (LN)-metastatic bladder cancer (BCa) and is associated with poor prognosis. In footpad popliteal LN metastasis and orthotopic BCa models, circFOCAD enhances VEGF-C-dependent lymphangiogenesis and LN metastasis in BCa. Mechanistically, circFOCAD potentiates pro-VEGF-C cleavage by facilitating the expression of CCBE1 and its newly identified partner, the metalloprotease ADAM10. Specifically, circFOCAD promotes ADAM10 promoter H3K9 acetylation by recruiting YBX1. ADAM10 requires CCBE1 as a scaffold, binding at residue R301/R302, to interact with N-terminal propeptide of pro-VEGF-C at residue E58, provoking VEGF-C maturation and sustaining lymphangiogenesis in BCa. Clinically, neutralizing antibodies against CCBE1 and ADAM10 diminished the LN metastatic of BCa in a patient-derived xenograft (PDX) model. Our findings indicate that circFOCAD acts as an initiator of VEGF-C maturation and may represent a promising therapeutic target in LN metastatic BCa.