title: Protocatechuic acid induces cell death in HepG2 hepatocellular carcinoma cells through a c-Jun N-terminal kinase-dependent mechanism.
abstract: Protocatechuic acid (PCA), chlorogenic acid (CA) and luteolin (LT) are plant phenols found in Chinese medicinal herbs such as Lonicera japonica. Cytotoxicity assays showed that PCA, CA and LT (at 100 micromol/L) effectively killed the HepG2 hepatocellular carcinoma cells. Among these three naturally occurring compounds, only PCA was capable of stimulating the c-Jun N-terminal kinase (JNK) and p38 subgroups of the mitogen-activated protein kinase (MAPK) family. Coincidently, PCA-induced cell death was rescued by specific inhibitors for JNK and p38, while the cytotoxicities of CA and LT were partially eliminated by the antioxidant effect of N-acetyl-L-cysteine (NAC). Further investigation demonstrated that the aqueous extract of Lonicera japonica also triggered HepG2 cell death in a JNK-dependent manner, but the amount of PCA alone in this herbal extract was insufficient to contribute the subsequent cytotoxic effect. Collectively, our results suggest that PCA is a naturally occurring compound capable of inducing JNK-dependent hepatocellular carcinoma cell death.
authors.affiliation: Department of Biochemistry, Molecular Neuroscience Center, Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. boyung@ust.hk
authors.forename: E C H
authors.initials: EC
authors.lastname: Yip
authors.forename: A S L
authors.initials: AS
authors.lastname: Chan
authors.forename: H
authors.initials: H
authors.lastname: Pang
authors.forename: Y K
authors.initials: YK
authors.lastname: Tam
authors.forename: Y H
authors.initials: YH
authors.lastname: Wong
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy*; D016923:Cell Death; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D006801:Humans; D062385:Hydroxybenzoates / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008113:Liver Neoplasms / Q000188:drug therapy*; D031239:Lonicera / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008956:Models, Chemical; D010766:Phosphorylation; D010936:Plant Extracts / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D062385:Hydroxybenzoates; D010936:Plant Extracts; C009091:protocatechuic acid; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases