Lymphatic collection and cell isolation from mouse models for multiomic profiling.

Premetastatic cancer cells often spread from the primary lesion through the lymphatic vasculature and, clinically, the presence or absence of lymph node metastases impacts treatment decisions. However, little is known about cancer progression via the lymphatic system or of the effect that the lymphatic environment has on cancer progression. This is due, in part, to the technical challenge of studying lymphatic vessels and collecting lymph fluid. Here we provide a step-by-step procedure to collect both lymph and tumor-draining lymph in mouse models of cancer metastasis. This protocol has been adapted from established methods of lymph collection and was developed specifically for the collection of lymph from tumors. The approach involves the use of mice bearing melanoma or breast cancer orthotopic tumors. After euthanasia, the cisterna chyli and the tumor are exposed and viewed using a stereo microscope. Then, a glass cannula connected to a 1 mL syringe is inserted directly into the cisterna chyli or the tumor-draining lymphatics for collection of pure lymph. These lymph samples can be used to analyze the lymph-derived cancer cells using highly sensitive multiomics approaches to investigate the impact of the lymph environment during cancer metastasis. The procedure requires 2 h per mouse to complete and is suitable for users with minimal expertise in small animal handling and use of microsurgical tools under a stereo microscope.