We recently discovered a novel gene and named it EG-1 (endothelial derived gene-1). Previously, we have demonstrated that the expression of EG-1 is significantly elevated in the epithelial cells of breast cancer, colorectal cancer, and prostate cancer. We have also shown that EG-1 stimulates cellular proliferation both in vitro and in vivo. Here, we report that inhibition of EG-1 blocks cellular proliferation in vitro and in vivo. As endogenous EG-1 expression was knocked down by specific siRNA's, human breast tumor cellular proliferation was significantly inhibited. A subcutaneous xenograft assay was carried out in a nude mouse model. We found that mice injected with MCF-7 human breast cancer cells infected with siRNA lentivirus had significantly smaller tumors, in comparison with those injected with cells infected by control lentivirus carrying an empty vector alone. Furthermore, rabbit polyclonal antibodies against EG-1 resulted in significantly decreased in vitro proliferation of MCF-7, T47-D, MDA-MB-231, and MDA-MB-361 human breast cancer cells, in comparison to treatment with pre-immune rabbit serum. These observations suggest that the novel gene EG-1 may be a potential target for successful cancer therapy.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]