In the present study we used a rat mesenteric lymphatic endothelial cell line which expressed the lymphatic markers Lyve-1 and Prox-1 but not the angiogenesis marker CD31 and a COX-2 expressing murine breast cancer cell line C3L5 to study the roles of soluble tumor cell products on lymphangiogenesis. This evidence concerns the gene PECAM1 and breast cancer.