VTN and neoplasm: These higher amounts of complement proteins may be linked to enhanced expression and production of complement by the liver, however, local increases in expression of complement genes in tumors and organs targeted by metastasis contribute to augmented levels of complement fragments because endothelial and immune cells synthesize complement fragments (89, 90) and these cells are an integral component of the tumor microenvironment (81, 91) and the premetastatic niche (26).