Ursolic acid inhibits proliferation and induces apoptosis of HT-29 colon cancer cells by inhibiting the EGFR/MAPK pathway.
OBJECTIVE
To investigate the effects of ursolic acid on the proliferation and apoptosis of human HT-29 colon cancer cells.


METHODS
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry assays were performed to evaluate the effects of ursolic acid on the growth and apoptosis of HT-29 cells. Western blot analysis was applied to investigate the inhibitory effects of ursolic acid on the phosphorylation of the epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (p38 MAPK), and the activity of B cell leukemia-2 (Bcl-2), B cell leukemia-xL (Bcl-xL), caspase-3, and caspase-9.


RESULTS
Ursolic acid inhibited the growth of HT-29 cells in dose- and time-dependent manners. The median inhibition concentration (IC50) values for 24, 48, and 72 h treatment were 26, 20, and 18 micromol/L, respectively. The apoptotic rates of 10, 20, and 40 micromol/L ursolic acid treatments for 24 h were 5.74%, 14.49%, and 33.05%, and for 48 h were 9%, 21.39%, and 40.49%, respectively. Ursolic acid suppressed the phosphorylation of EGFR, ERK1/2, p38 MAPK, and JNK, which is well correlated with its growth inhibitory effect. 10, 20, and 40 micromol/L ursolic acid significantly inhibited the proliferation of EGF-stimulated HT-29 cells (P<0.05). Cell proliferation was most significantly inhibited when treated with 10 and 20 micromol/L ursolic acid combined with 200 nmol/L AG 1478 or 10 micromol/L U0126 (P<0.01). Besides, it also down-regulated the expression of Bcl-2 and Bcl-xL and activated caspase-3 and caspase-9.


CONCLUSIONS
Ursolic acid induces apoptosis in HT-29 cells by suppressing the EGFR/MAPK pathway, suggesting that it may be a potent agent for the treatment of colorectal cancer.
Shan
Jian-zhen
JZ
Department of Traditional Chinese Medicine, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China. zhang1873@gmail.com
Xuan
Yan-yan
YY
Zheng
Shu
S
Dong
Qi
Q
Zhang
Su-zhan
SZ
D017209:Apoptosis / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D066246:ErbB Receptors / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D014315:Triterpenes / Q000008:administration & dosage*; D000097245:Ursolic Acid
D066246:ErbB Receptors; D014315:Triterpenes; D000097245:Ursolic Acid; C512478:EGFR protein, human