The effect of all-trans retinoic acid (ATRA) on the expression of vascular endothelial growth factor (VEGF) and VEGF receptors of human colon cancer LoVo cell line

All-trans retinoic acid (ATRA) was found to inhibit cell growth, induce differentiation and enhance apoptosis in a variety of malignant solid tumors. Retinoic acid is effective in inhibiting the expression of vascular endothelial growth factor (VEGF) in some cancer. In this study, we investigated the effect of ATRA on the expression of VEGF and its receptors in LoVo cells, and its possible mechanisms. LoVo cells were treated with ATRA at different concentrations for different time, and with exogenous recombinant human VEGF(165) or VEGF(165) + ATRA. Cell viability was measured by microtitration (MTT) assay. Cell cycle and apoptosis were evaluated by flow cytometry (FCM). The expression of VEGF in LoVo cells were detected by ELISA technique and Western blot, and its receptors by flow cytometry. ATRA greatly inhibited the proliferation of LoVo cells in dose-and time-dependent manners; inhibition rate of the cells decreased significantly after treatment with ATRA. ATRA could dose-dependently block the VEGF(165)-induced cell growth. FCM results show that ATRA induced apoptosis of LoVo cells with concomitant decrease of expressed VEGF and its receptors. The mechanism involved in down regulation of VEGF and its receptors may be related to apoptosis. ATRA could also disturb the stimulating effect of VEGF(165) on the growth of LoVo cells. These results suggest that ATRA can delay growth of LoVo cells by inhibiting the paracrine and autocrine pathways.