Abstract: Objective To compare growth and metastasis of breast cancer cell and osteosarcoma cell influenced by co-inoculating human lymphatic endothelial cell (HLyEC), and to analyze its mechanisms. Methods HLyEC was isolated and purified from human lymph node by magnetic beads coated with antibody against human VEGFR3. Human breast cancer cell line (MDA-MB-435) or human osteosarcoma cell line (MG-63) was inoculated alone or co-inoculated with HLyEC subcutaneously into nude mice. Weight of tumors were detected; the peri-tumor lymphatic vessel density was shown by Evans blue, the intra-tumor lymphatic vessel density and origin of intra-tumor lymphatic endothelial cell were evaluated by immunohistochemistry for human and mouse PDPN. And the metastasis clones on lungs was counted. The effect of MDA-MB-435 and MG-63 condition medium on proliferation of HLyEC was evaluated by MTT assay. Results The growth of MDA-MB-435 but not MG-63 was promoted by co-inoculating HLyEC with much higher weight of tumor. The peri-tumor and intra-tumor lymphatic vessel density of MDA-MB-435 were increased by co-inoculating HLyEC, both hPDPN- and mPDPN-positive lymphatic vessels were found in MDA-MB-435 co-inoculating with HLyEC group. But co-inoculating HLyEC has no effect on lymphatic vessels density of MG-63. Neither hPDPN- nor mPDPN-positive lymphatic vessels were found in MG-63 tumor. And many metastasis clones were visible on lungs only at MDA-MB-435 co-inoculating with HLyEC group. The result of MTT assay showed that the proliferation of HLyEC was increased by condition medium of MDA-MB-435 but not MG-63. Conclusion Breast cancer has active lymphangiogenesis which might contribute to its growth and metastasis.

Key words: lymphatic endothelium, breast cancer, osteosarcoma, lymphaniogenesis, metastasis