Objective: Angiogenesis is one of the important steps in tumor progression and is a necessary condition for tumor growth over 1-2mm size. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor, secreted by various cancers, and many reports have demonstrated a close association between VEGF and tumor growth. Recently, it was reported that overexpression of Id1 (inhibitor of DNA binding) induced VEGF secretion in prostate cancer cells. In the present study, we aimed to investigate whether Id proteins would regulate VEGF secretion in human gastric cancer cells.

Methods: The gastric cancer cell line, MKN45, was used. For the knockdown of Id, the siRNA targeted for either Id1 or Id3 (Ambion) or both were transfected into MKN45 according to the manufacturer’s recommendations. Negative control siRNAwas also transfected into MKN45 under the same conditions. The VEGF secretion by Id knockdown MKN45 cells was investigated by ELISA. Additionally, the activity of the secreted VEGF was investigated by evaluating the proliferative activity of human umbilical vein endothelial cells (HUVECs).

Results: The Ids knockdown in MKN45 cells was confirmed by western blotting analysis. The VEGF secretion was reduced in Id1 and Id3 knockdown MKN45 cells, compared to control and the parental cells. Also the proliferative activity of HUVECs cultured in the growth medium of Id1 and Id3 knockdown MKN45 cells was reduced.

Conclusions: Id proteins regulate VEGF secretion of gastric cancer. Downregulation of Id1 and Id3 in gastric cancer cells suppressed VEGF secretion. From the present results, we concluded that Id proteins play a pivotal role in the angiogenesis of gastric cancer and, consequently, downregulation of Ids would be a novel strategy for the prevention and treatment of gastric cancer.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA