Figure 2.

Experimental demonstration of monocyte-lymphatic endothelial plasticity. (A) Transplantation of GFP-labeled bone marrow is a strategy to identify bone marrow–derived cells in diverse tissues of the recipient, including tumors. Alternatively, using Cre/Lox-mediated lineage-tracing strategy, myeloid cells expressing Cre recombinase under the myeloid specific CD11b promoter can activate a GFP reporter transgene and thus label all cells that have been passed through a CD11b-expressing lineage. Bone marrow transplantation and lineage tracing can also be combined. (B) Transplantation of GFP-labeled bone marrow into double-transgenic Rip1Tag2;Rip-VEGF-C mice that develop pancreatic β-cell tumors with a high extent of peritumoral lymphangiogenesis and lymph node metastasis. A histological section has been stained with antibodies against the lymphatic marker LYVE-1 (red) and GFP (green). DAPI staining visualizes nuclei (blue). Note a GFP⁺, bone marrow–derived cell (green) integrated in a tumor-surrounding LYVE-1⁺ lymphatic vessel (red), as indicated by an arrowhead and shown in higher-magnification insets.