Functional lymphatic imaging from vascular endothelial growth factor (VEGF)-C overexpressing B16F10 melanoma

Objectives For many cancers, the lymphatic system provides the major pathway for the initial cancer cell dissemination. Vascular endothelial growth factor (VEGF)-C is known to induce tumor lymphangiogenesis and enhance lymph node metastasis of melanoma. However, relatively little is known about lymphatic function in the process of tumor progression and metastasis, due mainly to the lack of lymphatic imaging approaches. Herein, we used a functional lymphatic imaging technique and longitudinally imaged transient changes of lymphatic function and architecture in mice bearing VEGF-C overexpressing B16F10 (VEGF-C-B16F10) or mock-transduced B16F10 (mock-B16F10) melanoma tumors.

Methods C57BL6 mice were injected with 10ul of indocyanine green (ICG) in the base of the tail and were dynamically imaged for baseline information before implantation of VEGF-C-B16F10 or mock-B16F10 in the hindlimb every three to four days for up to 27 days after inoculation.

Results Our dynamic near-infrared (NIR) fluorescence imaging data show that ICG-laden lymph accumulates into a VEGF-C-B16F10 tumor at 3 days post implantation; thereafter lymphatic leakage is visualized only in peritumoral lymphatic vessels. Our longitudinal imaging data also show dilated and tortuous lymphatic vessels and transient changes of propulsive lymphatic function in the process of VEGF-C-B16F10 growth. However, mock-B16F10 tumors do not show lymphatic vessel leakage in early tumor progression.

Conclusions NIR fluorescence imaging can be used to non-invasively and quantitatively detect functional lymphatic changes associated with cancer, which may enable accurate nodal staging of cancer patients and provide new approaches to diagnose and treat cancer metastasis