Effects of Selaginella tamariscina on in vitro tumor cell growth, p53 expression, G1 arrest and in vivo gastric cell proliferation

Selaginella tamariscina, an oriental medicinal plant, was extracted using water and several organic solvents, and each fraction was assayed for its tumoricidal effects with 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT). Influences on expression of p53 tumor suppressor gene and induction of G1 arrest in the cell cycle were analyzed by Northern blotting and flow cytometry, respectively. The modifying effects of pulverized Selaginella tamariscina on cell turnover in the stomach were also investigated in rats given 150 mg/kg of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) by gavage and then fed a diet containing 5, 1 or 0% Selaginella tamariscina. Fractions I–V showed significant tumoricidal effects against cultured human leukemia cells whereas these fractions did not affect normal human lymphocytes. Among the effective fractions, the water-extracted fraction (V) efficiently increased p53 gene expression and induced G1 arrest. The 1% Selaginella tamariscina feeding caused a significant reduction (P<0.05) in the proliferating cell nuclear antigen-(PCNA) labeling index of the glandular stomach epithelium as compared with the MNNG-alone group value although 5% Selaginella tamariscina feeding was only associated with a tendency for decrease. These results suggest that Selaginella tamariscina could be a candidate chemopreventive agent against gastric cancer.