Endocrine Abstracts

Many studies have been demonstrated that baicalin, a kind of flavonoid isolated from an important medicinal plant Scutellariae Radix, could inhibit tumorigenesis, but the molecular mechanisms are poorly understood. So this study was designed to investigate whether baicalin could perturb the cell cycle progression on insulinoma cell line, RINm5F, from American Type Culture Collection and discuss the possibly molecular mechanisms. After baicalin treatment, changes in morphology of some of RINm5F cells were apparent. By using MTT assay and flow cytometry analysis, we found that baicalin could be inhibiting of RINm5F cell proliferation and could arrest the cell cycle at G1/S checkpoint in dose-dependent manner and time-dependent manner. To investigate the mechanism of cell cycle arrest by baicalin, we observed the effect of baicalin on the transcription activity of cyclin D1gene, one of a major group of cell cycle regulatory gene. The findings suggested that baicalin could inhibit cyclin D1 protein expression in dose-dependent manner, as revealed by luciferase reporter system analysis and Western blot. As we known, NF-kappa B can control the expression of cyclin D1. Here we detected the effect of baicalin on the transactivities of NF-kappa B. We found that baicalin down-regulate the activities of NF-kappa B in insulinoma cell line. The results taken together provide direct evidence that baicalin may inhibit insulinoma cell line proliferation by suppressing the transactivities of NF-kappa B and down-regulation the transcription of cyclin D1 might be involved in these events.