Oridonin induces apoptosis and senescence in colorectal cancer cells by increasing histone hyperacetylation and regulation of p16, p21, p27 and c-myc.
BACKGROUND
Oridonin, a tetracycline diterpenoid compound, has the potential antitumor activities. Here, we evaluate the antitumor activity and action mechanisms of oridonin in colorectal cancer.


METHODS
Effects of oridonin on cell proliferation were determined by using a CCK-8 Kit. Cell cycle distribution was determined by flow cytometry. Apoptosis was examined by analyzing subdiploid population and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. Senescent cells were determined by senescence-associated β-galactosidase activity analysis. Semi-quantitative RT-PCR was used to examine the changes of mRNA of p16, p21, p27 and c-myc. The concomitant changes of protein expression were analyzed with Western blot. Expression of AcH3 and AcH4 were examined by immunofluorescence staining and Western blots. Effects of oridonin on colony formation of SW1116 were examined by Soft Agar assay. The in vivo efficacy of oridonin was detected using a xenograft colorectal cancer model in nude mice.


RESULTS
Oridonin induced potent growth inhibition, cell cycle arrest, apoptosis, senescence and colony-forming inhibition in three colorectal cancer cell lines in a dose-dependent manner in vitro. Daily i.p. injection of oridonin (6.25, 12.5 or 25 mg/kg) for 28 days significantly inhibited the growth of SW1116 s.c. xenografts in BABL/C nude mice. With western blot and reverse transcription-PCR, we further showed that the antitumor activities of oridonin correlated with induction of histone (H3 and H4) hyperacetylation, activation of p21, p27 and p16, and suppression of c-myc expression.


CONCLUSIONS
Oridonin possesses potent in vitro and in vivo anti-colorectal cancer activities that correlated with induction of histone hyperacetylation and regulation of pathways critical for maintaining growth inhibition and cell cycle arrest. Therefore, oridonin may represent a novel therapeutic option in colorectal cancer treatment.
NO 3 People's Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai 201900, PR China.
Feng-Hou
FH
Gao
Xiao-Hui
XH
Hu
Wei
W
Li
Hua
H
Liu
Yan-Jie
YJ
Zhang
Zhu-Ying
ZY
Guo
Mang-Hua
MH
Xu
Shi-Ting
ST
Wang
Bin
B
Jiang
Feng
F
Liu
Ying-Zheng
YZ
Zhao
Yong
Y
Fang
Fang-Yuan
FY
Chen
Ying-Li
YL
Wu
D000107:Acetylation; D000818:Animals; D017209:Apoptosis; D016922:Cellular Senescence; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D045786:Diterpenes, Kaurane / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D009363:Neoplasm Proteins / Q000235:genetics*; D009368:Neoplasm Transplantation; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D001616:beta-Galactosidase / Q000378:metabolism
C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D045786:Diterpenes, Kaurane; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D016271:Proto-Oncogene Proteins c-myc; C011959:oridonin; D050760:Cyclin-Dependent Kinase Inhibitor p27; D001616:beta-Galactosidase