Role of tumor‐associated lymphatic endothelial cells in metastasis: A study of epithelial ovarian tumor in vitro

(Cancer Sci 2010; 101: 679–685) Tumor‐associated lymphatic endothelial cells (TLEC) could play a key role in the process of tumor metastasis. The aim of this study was to investigate the effect of TLECs that were isolated from human epithelial ovarian tumor (EOT) on ovarian cancer cell line CAOV‐3 in vitro. First, TLECs in EOT were detected by immunochemistry and flow cytometry, then marked by lymphatic endothelial cell (LEC) marker LYVE‐1, isolated by magnetic beads, and cultured in vitro. The cells were identified by immunostaining of LEC markers LYVE‐1, Prox‐1, Podoplanin, VEGFR‐3, and pan‐endothelial cell marker CD31. TLECs from EOT can be detected, cultured, and identified in vitro successfully. The effects of TLECs on invasion and migration of CAOV‐3 cells were investigated by 12‐well Boyden chamber; the proliferation effect was studied by counting the Trypan blue exclusion cell number. Furthermore, changes in MMP‐2/9 secreted by CAOV‐3 cells treated with TLEC were shown using real‐time PCR and zymography, and TIMP‐1/2 was detected by real‐time PCR. In vitro, TLECs can enhance invasion and migration of CAOV‐3 cells, but have no significant effect on proliferation. It was clear that the expression of MMP‐9 increased and TIMP‐2 decreased in CAOV‐3 cells treated by TLECs, and the increasing of MMP‐9 was confirmed by zymography. TLECs from EOT can enhance migration and invasion of human ovarian carcinoma cell line in vitro, and the possible mechanism was through activation of MMP‐9/TIMP‐2.