VEGFC Upregulates Trans-Lymphatic Colorectal Cancer Metastasis in the Liver via Recruiting Bone Marrow Derived Cells

While colorectal cancer liver metastasis (CRCLM) is major cause of death of colorectal cancer, the mechanism of intrahepatic dissemination (trans-lymphatic metastasis) is not fully elucidated. Lymphangiogenesis can be the mechanism of the dissemination, but there are few evidences to prove it. In this study, we attempted to clarify the mechanism using syngeneic murine CRCLM model, especially focusing on vascular endothelial growth factor C (VEGFC), a promoter of lymphangiogenesis. We confirmed that 1) intrahepatic metastasis of CRCLM via lymphatic vessels was seen and lymphangiogenesis was upregulated in the CRCLM-bearing liver, 2) the degree of lymphangiogenesis and CRCLM was significantly correlated with the expression of VEGFC in colorectal cancer (CRC) cells and 3) macrophage inflammatory protein-1α (MIP-1α) was released from CRC cells under the stimulation of VEGFC and induced migration of immature bone marrow derived cells into the liver and differentiation into macrophage, which promoted dissemination of CRCLM. These findings suggest the possibility of therapeutic strategy targeting VEGFC / MIP-1α for diminishing CRCLM. In conclusion, VEGFC in CRC cells promoted trans-lymphatic metastasis of CRCLM by upregulation of lymphangiogenesis directly and indirectly via induction of macrophages derived from bone marrow cells. 4 samples: hepatic macrophage with treatment (n=2) and hepatic macrophage without treatment (n=2).