Studies of Folic Acid-Induced Anti-Tumor Growth Activity---Anti-Angiogensis and Anti-Cancer Cell Growth

We appreciated the grant (2007-2008) sponsored by National Science Council allowing us to conduct the experiments. Two specific aims of our previous grant proposal include (1) in vitro and in vivo studies of anti-angiogenic activity of folic acid, and (2) delineation of molecular mechanisms underlying folic acid-induced anti-angiogenesis. So far, we have finished several experiments and obtained some results including (1) folic acid at very low concentrations (0-10 M) inhibited DNA synthesis and decreased cell number in cultured human umbilical venous endothelial cells (HUVEC); (2) the protein levels of p21, but not p27, cyclins A, D1, D3 and E, cyclin-dependent kinase (CDK)2, and CDK4 in HUVEC were increased significantly after folic acid treatment; (3) the CDK2-p21 complex, but not the CDK2-p27, CDK4-p21, and CDK4-p27 complex, was increased in the folic acid-treated HUVEC; (4) the CDK2, but not CDK4, kinase activity was decreased in the folic acid-treated HUVEC; (5) Pretreatment of HUVEC with a p21, but not p27, antisense oligonucleotide reversed the folic acid-induced inhibition of [3H]thymidine incorporation into HUVEC. The in vivo study of anti-angiogenic activity of folic acid is still under investigation. The conclusion from current study is that folic acid inhibits HUVEC proliferation by increasing the level of p21 protein, which in turn inhibits CDK2 kinase activity, and finally interrupts the cell cycle. In this proposed research, we will extend the present studies and further investigate in detail how folic acid inhibited the process of angiogenesis and tumor growth. Several issues will be addressed in this study including (1) the molecular mechanisms underlying folic acid-induced increase of p21; (2) the molecular mechanisms underlying folic acid-induced endothelial cell migration; (3) role of folate transporters and folate-binding proteins in folic acid-induced anti-angiogenesis and anti-tumorigenesis; (4) in vitro and in vivo studies of anti-tumorigenic activity of folic acid; (5) effect of female sex hormones on the folic acid-induced anti-angiogenesis. We will apply the cellular and molecular biology techniques to perform in vitro and in vivo studies in examining the anti-angiogenic activity of folic acid and its molecular mechanisms underlying. The outcome of this study will help us getting insight the anti-angiogenic and anti-cancer activity of folic acid and the potential clinical applications of folic acid.