Tumor Cell Growth Suppression by Tannic Acid

Tannic acid was cultured together with tumor cells that had originated from human malignant tumors (HCT-15 & AGS). Significant suppression of tumor growth was observed. The 50% suppression was observed at the concentration between 50 micrograms/ml and 12.5 micrograms/ml. When tannic acid was injected into HCT-15 cells by electroporation at 1180 mu p and 200 ohm, the suppression rate was 34.3% at the concentration of 50 micrograms/ml in HBS solution. The suppression rate of cells only in contact with tannic acid solution for one hour under the same conditions as used for electroporation, was 26.1%. Histographic findings suggested that tannic acid almost completely blocked the S phase of the cell cycle.