title: Asiatic acid, a triterpene, induces apoptosis and cell cycle arrest through activation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase pathways in human breast cancer cells.
abstract: This study first investigates the anticancer effect of asiatic acid in two human breast cancer cell lines, MCF-7 and MDA-MB-231. Asiatic acid exhibited effective cell growth inhibition by inducing cancer cells to undergo S-G2/M phase arrest and apoptosis. Blockade of cell cycle was associated with increased p21/WAF1 levels and reduced amounts of cyclinB1, cyclinA, Cdc2, and Cdc25C in a p53-independent manner. Asiatic acid also reduced Cdc2 function by increasing the association of p21/WAF1/Cdc2 complex and the level of inactivated phospho-Cdc2 and phospho-Cdc25C. Asiatic acid treatment triggered the mitochondrial apoptotic pathway indicated by changing Bax/Bcl-2 ratios, cytochrome c release, and caspase-9 activation, but it did not act on Fas/Fas ligand pathways and the activation of caspase-8. We also found that mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK1/2), and p38, but not c-Jun NH2-terminal kinase (JNK), are critical mediators in asiatic acid-induced cell growth inhibition. U0126 [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene] or SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole], specific inhibitors of mitogen-activated protein kinase kinase and p38 kinase activities, significantly decreased or delayed apoptosis. Asiatic acid was likely to confine the breast cancer cells in the S-G2/M phase mainly through the p38 pathway, because both SB203580 and p38 small interfering RNA (siRNA) inhibition significantly attenuated the accumulation of inactive phospho-Cdc2 and phospho-Cdc25C proteins and the cell numbers of S-G2/M phase. Moreover, U0126 and ERK siRNA inhibition completely suppressed asiatic acid-induced Bcl-2 phosphorylation and Bax up-regulation, and caspase-9 activation. Together, these results imply a critical role for ERK1/2 and p38 but not JNK, p53, and Fas/Fas ligand in asiatic acid-induced S-G2/M arrest and apoptosis of human breast cancer cells.
authors.affiliation: Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, 100 Shih-Chuan 1st Rd., Kaohsiung 807, Taiwan, Republic of China.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Hsu
authors.forename: Po-Lin
authors.initials: PL
authors.lastname: Kuo
authors.forename: Liang-Tzung
authors.initials: LT
authors.lastname: Lin
authors.forename: Chun-Ching
authors.initials: CC
authors.lastname: Lin
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000502:physiology*; D053222:Fas Ligand Protein; D005260:Female; D016158:Genes, p53 / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism; D053978:Pentacyclic Triterpenes; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects; D014315:Triterpenes / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000502:physiology*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D053978:Pentacyclic Triterpenes; D014315:Triterpenes; C017032:asiatic acid; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases