Induction of G1 arrest and apoptosis by Scutellaria barbata in the human promyelocytic leukemia HL-60 cell line.
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 time-dependent inhibition of growth and a G1 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, cyclin-dependent 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-G1 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.
Kim
Eun-Kyung
EK
Department of Biochemistry, Medical School and Institute for Medical Sciences, Chonbuk National University, Jeonbuk, Korea.
Kwon
Kang-Beom
KB
Han
Mi-Jeong
MJ
Song
Mi-Young
MY
Lee
Ji-Hyun
JH
Ko
Youn-Suk
YS
Shin
Byung-Cheal
BC
Yu
Jiahua
J
Lee
Young-Rae
YR
Ryu
Do-Gon
DG
Park
Jin-Woo
JW
Park
Byung-Hyun
BH
D017209:Apoptosis / Q000187:drug effects*; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005562:Formazans / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects*; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000188:drug therapy*; D008517:Phytotherapy; D010936:Plant Extracts / Q000378:metabolism* / Q000627:therapeutic use*; D031363:Scutellaria
D005562:Formazans; D010936:Plant Extracts