title: Involvement of p53 in oroxylin A-induced apoptosis in cancer cells.
abstract: Oroxylin A, a naturally occurring monoflavonoid extracted from Scutellariae radix, exhibits anticancer activity and induces apoptosis in human hepatocellular carcinoma HepG2 cells according to our previous data. In this study, we investigate whether p53 is involved in oroxylin A-triggered viability inhibition and apoptosis induction in cancer cells. In a panel of different cancer cell lines, more potent inhibitory effects of oroxylin A were observed in wtp53 cells than those in mtp53 or p53-null cells. Moreover, p53-siRNA-transfected HepG2 cells showed lower levels of apoptosis induced by oroxylin A than control-siRNA-transfected cells. Likewise, after oroxylin A treatment, p53-null K-562 cells displayed promoted apoptosis rate when transfected with wtp53 plasmid. Western blot and real-time RT-PCR assay revealed that oroxylin A markedly upregulated p53 protein expression in HepG2 and p53-overexpressing K-562 cells, but had no influence on p53 mRNA synthesis. Furthermore, after co-treatment with cycloheximide, oroxylin A still exerted a little effect on p53 expression. The negative regulator of p53, MDM2 protein was detected, and downregulated expression was observed. In the presence of MG132, an inhibitor of proteasome-mediated proteolysis, no change in p53 expression was obtained. Additionally, the antioxidant N-acetyl-L-cysteine could obviously abrogate p53 stabilization triggered by oroxylin A. Therefore, it is summarized that oroxylin A stabilized p53 expression and induced apoptosis at the posttranslational level via downregulating MDM2 expression and interfering MDM2-modulated proteasome-related p53 degradation. This indicated that oroxylin A could be served as a potential, novel agent candidate for cancer therapy.
authors.affiliation: Jiangsu Key Laboratory of Carcinogenesis and Intervention, China Pharmaceutical University, Nanjing, People's Republic of China.
authors.forename: Rong
authors.initials: R
authors.lastname: Mu
authors.forename: Qi
authors.initials: Q
authors.lastname: Qi
authors.forename: Hongyan
authors.initials: H
authors.lastname: Gu
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Yang
authors.forename: Jingjing
authors.initials: J
authors.lastname: Rong
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Na
authors.initials: N
authors.lastname: Lu
authors.forename: Qidong
authors.initials: Q
authors.lastname: You
authors.forename: Qinglong
authors.initials: Q
authors.lastname: Guo
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000037:antagonists & inhibitors; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D031364:Scutellaria baicalensis / Q000737:chemistry; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; D005419:Flavonoids; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; C080669:5,7-dihydroxy-6-methoxy-2-phenylchromen-4-one; D016660:NAD(P)H Dehydrogenase (Quinone); C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D000111:Acetylcysteine