Antitumor Effects of Ginkgolic Acid in Human Cancer Cell Occur via Cell Cycle Arrest and Decrease the Bcl-2/Bax Ratio to Induce Apoptosis

Background: Ginkgolic acids (GAs), extracted from the seed coat of Ginkgo biloba L. Our previous study has shown that GA monomer could inhibit the growth of Hep-2 significantly and induce the fragmentation of the chromosomal DNA. To further assess the antitumor potential and turn it into a candidate new antitumor drug, the antitumor mechanism of GA was investigated. Method: The cytotoxicity and antitumor effect of GA monomer were assayed by MTT colorimetric assay with nontumorogenic MC-3T3-E1 as well as tumorogenic Hep-2 and Tac8113 cell lines. The effect of GA monomer on the proliferation of tumor cell lines was analyzed with MTT colorimetric and CFSE labeled assay. Cell cycle distribution and measurement of the percentage of apoptotic cells were performed by flow cytometry following stained with propidium iodide, annexin V-FITC. The expression of apoptotic proteins Bcl-2, Bax and caspase-3 was analyzed with Western blot. Result: GA only inhibited the growth of tumorogenic cell lines in a both dose-and time-dependent manner. Tumor cells were treated with GA for 72 h, 70.53 +/- 4.54% Hep2 and 63.5 +/- 7.2% Tca8113 cells were retarded at GO/G1 phase, and the percentage of apoptosis was 40.4 +/- 1.58 and 38.4 +/- 1.7%, respectively. GA-treated activated caspase-3 downregulated the expression of anti-apoptotic Bcl-2 protein and upregulated the expression of pro-apoptotic Bax protein, eventually leading to a decrease in the Bcl-2/Bax ratio in tumor cells. Conclusions: The antitumor action of GA was due to inhibiting the proliferation in a manner of inhibiting division, retarding the progress of cell cycle and inducing apoptosis, making GA a candidate as new antitumor drug. Copyright (C) 2010 S. Karger AG, Basel