The Saponin Monomer of Dwarf Lilyturf Tuber, DT-13, Reduces Human Breast Cancer Cell Adhesion and Migration during Hypoxia via Regulation of Tissue Factor

Adhesion and migration of tumor cells are crucial steps in tumor invasion and metastasis. In the present study, we investigated the effects of saponin monomer 13 of dwarf lilyturf tuber (DT-13) on metastasis of human breast cancer cells (MDA-MB-435) during hypoxia. The effects and molecular mechanisms of DT-13 on MDA-MB-435 cells metastatic phenotype in vitro and in vivo were evaluated by RNA interference; quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot assays. DT-13 had no significant effects on cell adhesion and migration under normoxia conditions. Under hypoxic conditions, IVIDA-MB-435 adhesion to vitronectin was inhibited by about 43.5% or 60.8% after exposure of the cells to DT-13 at 1 mu M or 10 mu M, respectively. DT-13 decreased the migratory response by hypoxia at 1 or 10 mu M, and inhibition ratios were 20% and 30%, respectively. DT-13 inhibited hypoxia-induced expression of alpha v beta 3 integrin, tissue factor (TF) and early growth response gene-1 (Egr-1) and decreased excretion of matrix metalloproteinase 9 (MMP-9) of MDA-MB-435 cells under hypoxic conditions. After Egr-1 short interference RNA (siRNA) treatment, DT-13 could still inhibit the up-regulation of TF mRNA and protein levels and its pro-coagulant activity (PCA) under hypoxia. In nude mice, DT-13 decreased extravasation of MDA-MB-435 cells in the lung after tail vein injection. Our data suggest that DT-13 inhibits MDA-MB-435 cells metastasis during hypoxia via regulation of TF, and the effect of DT-13 on TF is partly mediated by Egr-1.