Tumor cell Jagged-1 promotes regional lymphatic metastasis and predicts recurrence in node-positive breast cancer

Background Lymph node metastasis marks a clinically and biologically important transition in breast cancer, reflecting more aggressive disease and increased risk of recurrence. Expression of the Notch ligand JAG1 is linked to poor breast cancer outcomes, but its role in lymphatic dissemination is unclear.Methods Tumor microarray analysis with multiplex staining was performed on synchronous breast and lymph node metastases from node-positive patients to quantify JAG1 expression and correlate findings with clinical outcomes. Orthotopic implantation of human and murine breast cancer cells was used to assess the impact of JAG1 expression on lymphovascular invasion and lymph node metastasis in vivo. The contribution of VEGFR3 signaling to JAG1-mediated lymphatic dissemination was evaluated using a soluble VEGFR3 antagonist. The cell-specific response of lymphatic endothelial cells to JAG1 was assessed by transendothelial migration assays, barrier examination, and sequencing.Results Mammary tumor cells expressing JAG1 demonstrated increased lymphovascular and lymph node metastasis in mouse models. Inhibition with a soluble VEGFR3 antagonist attenuated JAG1-dependent lymph node metastasis. Exposure to JAG1 disrupted lymphatic endothelial barrier integrity, promoted tumor cell migration across cultured endothelium, and induced pro-inflammatory and pro-adhesion changes in lymphatic endothelial cells. Tumor microarray analyses revealed enrichment of JAG1 in metastatic tumor cells within lymph nodes relative to matched primary tumors. High JAG1 expression in lymph node metastases was significantly associated with increased risk of recurrence.Conclusions These findings support a role for tumor cell JAG1 promoting lymphatic dissemination and lymph node metastasis in breast cancer through effects on lymphatic endothelial signaling and barrier function. Enrichment of JAG1 in lymph node metastases and its association with recurrence further support its potential utility as a prognostic biomarker and therapeutic target in node-positive breast cancer.