Abstract. Scutellaria barbata has been used to treat cancer in Chinese medicine. The responsible anticancer mechanism, however, is not clear. Here we demonstrated an inhibitory mechanism due to a Scutellaria barbata extract (SBE) on a human promyelocytic leukemia cell line (HL-60) that has a mutation in the tumor suppressor gene p53. HL-60 cells were incubated with various concentrations of SBE. After a 24-h incubation, cytotoxicity and apoptosis were determined by MTT and DNA fragmentation assay, respectively. After treatment with SBE, cell cycle arrest was determined by measuring the cell number stained by 5'-bromo-2'-deoxyuridine (BrdU) and 7-amino-actinomycin D (7-AAD). Treatment of cells with SBE resulted in a concentration-and timedependent inhibition of growth and a G 1 phase arrest of the cell cycle. This effect was associated with a marked decrease in the protein expression of cyclin A, D1, D2, D3, and E and their activating partners, cyclin-dependent kinases (CDK) 2, 4, and 6 with concomitant upregulation of p21, cyclindependent kinase inhibitor. Downstream of the CDK inhibitory protein-CDK/cyclin cascade, SBE decreased phosphorylation level of retinoblastoma protein. SBE treatment also resulted in apoptosis evidenced by an increase of sub-G 1 phase cells, DNA fragmentation and degradation of the inhibitory protein for the caspase-activated deoxyribonuclease. The molecular mechanism during SBE-mediated growth inhibition in HL-60 cells may be due to modulation of the cell-cycle machinery and the induction of apoptosis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.