OBJECTIVETo study the effect of cyclooxygenase-2 (COX-2) on lymphangiogenesis in breast cancer.

METHODSBy the means of immunohistochemistry, COX-2, vascular endothelial growth factor-C (VEGF-C) and D2-40 were examined in the tissue samples of primary tumors from 94 patients underwent surgical resections for breast cancer from November 1998 to March 2002. Eighty-three patients were followed-up. The expressions of VEGF-C mRNA and protein were detected by reverse transcription polymerase chain reaction (RT-PCR) and Western blot in MDA-MB-231 cell lines by the treatment of selective COX-2 inhibitor Nimesulide at different doses. The expressions of VEGF-C protein were evaluated in MDA-MB-231 cells treated by PGE2 (1 microg/ml) and Trastuzumab (1 microg/ml), respectively.

RESULTSCOX-2 over-expression was observed in 46.8% of surgical specimens (44/94), while VEGF-C overexpression occurred in 51.1% of tumor samples (48/94). COX-2 was strongly correlated with VEGF-C expression (P < 0.01), micro-lymphatic vessels (P = 0.032) and metastatic lymph nodes (P = 0. 035). Patients with COX-2 positive tumors had a significant shorter survival time than those with negative tumors did, including disease-free survival (P = 0.010) and overall survival (P = 0.040). Nimesulide could down-regulate the expressions of VEGF-C mRNA and protein in a does-dependent manner, while PGE2 could up-regulate the expressions. The expression of VEGF-C protein up-regulated by PGE2 treatment was decreased by Trastuzumab.

CONCLUSIONSCOX-2 over-expression can up-regulate the expression of VEGF-C. VEGF-C might promote lymph node metastasis by a lymph-angiogenic pathway, then affect the prognosis of the patients with breast cancer.