title: Emodin inhibits tumor cell adhesion through disruption of the membrane lipid Raft-associated integrin signaling pathway.
abstract: Cell adhesion and spreading is a crucial step in the metastatic cascade of cancer cells, and interruption of this step is considered to be a logical strategy for prevention and treatment of tumor metastasis. Emodin is the major active component of the rhizome of Rheum palmatum L., with known anticancer activities. Here, we first found that emodin significantly inhibited cell adhesion of various human cancer cells. This inhibition was achieved through suppressing the recruitment of focal adhesion kinase (FAK) to integrin beta(1) as well as the phosphorylation of FAK followed by the decreased formation of focal adhesion complex (FAC). In understanding the underlying mechanisms, we found that emodin inhibited the lipid raft clustering and subsequent colocalization of integrin beta(1) and FAC proteins within lipid rafts. Lipid profile analysis revealed significant decrease of cholesterol and sphingolipids in raft fraction after emodin treatment. Cholesterol replenishment abolished the adverse effect of emodin on the translocation of integrin beta(1) and FAC proteins into the lipid raft fraction and cell adhesion. Therefore, data from this study provide novel evidence that emodin inhibits cell adhesion and spreading through disruption of the membrane lipid raft-associated integrin signaling pathway.
authors.affiliation: Department of Community, Occupational, and Family Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Qing
authors.initials: Q
authors.lastname: Huang
authors.forename: Han-Ming
authors.initials: HM
authors.lastname: Shen
authors.forename: Guanghou
authors.initials: G
authors.lastname: Shui
authors.forename: Markus R
authors.initials: MR
authors.lastname: Wenk
authors.forename: Choon-Nam
authors.initials: CN
authors.lastname: Ong
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism; D004642:Emodin / Q000494:pharmacology*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D022001:Focal Adhesions / Q000187:drug effects* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D016023:Integrins / Q000096:biosynthesis / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects* / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D019012:Integrin beta1; D016023:Integrins; D002784:Cholesterol; D051416:Focal Adhesion Protein-Tyrosine Kinases; D004642:Emodin