Abstract A43: Direct visualization of changes of lymphatic function and drainage pathways in lymph node metastasis of B16F10 melanoma using near-infrared fluorescence imaging

Abstract

Abstract The lymphatic system provides an initial route for cancer cell dissemination in many cancers including melanoma. However, it is largely unknown how the lymphatic system changes during tumor progression, due in part to the lack of imaging techniques available. In this study, we non-invasively imaged changes of lymphatic function and drainage patterns using dynamic near-infrared fluorescence (NIRF) imaging. Dynamic NIRF imaging following intradermal injection of indocyanine green (ICG) was conducted in C57BL/6 mice prior to inoculation of B16F10 murine melanoma cells to the dorsal foot for baseline data and until 21 days post-implant (p.i.). A series of acquired fluorescent images were quantified to measure lymphatic contractile function. Computed tomography (CT) was also performed to measure the volume of tumor-draining lymph nodes (LNs). In addition, intravital color images using a stereomicroscope were acquired after a skin incision. Then, the PLNs and inguinal LNs (ILNs) were harvested for ex vivo NIRF and intravital color imaging. We observed significant reduction of lymphatic contractility from 7 days p.i. until 21 days p.i.. Altered lymphatic drainage patterns were detected at 21 days p.i., due to lymphatic obstruction of normal lymphatic drainages caused by extensive tumor invasion of draining LNs. Magnified fluorescent images of tumor-draining lymphatic vessels showed numerous fluorescent lymphatic vessels at day 21 p.i. as compared to well-defined fluorescent vessels from a baseline image. Our CT data showed enlarged tumor-draining PLNs at 21 days p.i. and intravital images confirmed the PLN harbored melanoma cells. Overlay of white light and fluorescent images of dissected LNs showed strong ICG fluorescence in the ILN and to less extent in the PLN on the tumor bearing side, indicating significantly reduced lymph flow to the PLN due to blockage of normal lymph flow by tumor in the PLN. Since lymphatic function and architecture were progressively altered during tumor growth and metastasis, non-invasive NIRF imaging may provide a new method to stage disease. In addition, this novel technique can be used as a diagnostic method to non-invasively assess lymphatic response as mechanism of therapeutic action. Citation Format: Sunkuk Kwon, Germaine Agollah, Grace Wu, Sevick Sevick-Muraca. Direct visualization of changes of lymphatic function and drainage pathways in lymph node metastasis of B16F10 melanoma using near-infrared fluorescence imaging. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A43.