Antibacterial Activity of Kaempferia rotunda Rhizome Lectin and Its Induction of Apoptosis in Ehrlich Ascites Carcinoma Cells

The tuberous rhizome Kaempferia rotunda Linn. has been used as food and traditional medicinal plant, and the purified K. rotunda lectin (KRL) showed antiproliferative activity against Ehrlich ascites carcinoma cells [1]. In the present study, KRL showed agglutination activity against Escherichia coli and Staphylococcus aureus, with partial inhibition of their growth. MTT assay was used to investigate the effect of KRL on EAC cells in vitro in RPMI-1640 medium, and it was found that lectin inhibited 6.2-50.5 % cell growth at the range of 7.5-120 mu g/ml protein concentration. The cell cycle arrest at G(0)/G(1) phase of EAC cells was also determined by flow cytometry after treatment with lectin. The apoptotic cell morphological changes of the treated EAC cells were confirmed by fluorescence and optical microscope. In the presence of caspase-3 inhibitor, the cell growth inhibition of the lectin was reduced significantly. RT-PCR was used to evaluate the expression of apoptosis-related genes, bcl-2, bcl-X, and bax. Bax gene expression was intensively increased with the despaired of bcl-X gene expression and significant decrease of bcl-2 gene expression in the cells treated with KRL. Thus, lectin induced apoptotic cell death in Ehrlich ascites carcinoma cells.