title: Proteolysis of integrin alpha5 and beta1 subunits involved in retinoic acid-induced apoptosis in human hepatoma Hep3B cells.
abstract: Our previous report demonstrated that all-trans-retinoic acid (ATRA) induces detachment and death under serum starvation in several human tumor cell lines. In this study, we examined the influence of cell-extracellular matrix interaction on the ability of ATRA to induce apoptosis. Plating of human hepatoma Hep3B cells onto poly-hydroxyethylmethacrylate-coated plates in the absence of serum resulted in the acceleration of ATRA-induced apoptosis. In contrast, ATRA-induced apoptosis was significantly suppressed by plating cells onto Matrigel-coated plates but not suppressed by culturing onto collagen-, laminin-, vitronectin-, or fibronectin-coated plates. Exogenously added soluble collagen, laminin, fibronectin, vitronectin or Matrigel failed to suppress ATRA-induced apoptosis. Results from the adhesion assay indicated that the cell attachment to fibronectin was significantly inhibited by ATRA. Treatment with perturbing antibody against integrin alpha5 or beta1 subunits resulted in promotion of ATRA-induced apoptosis. Moreover, the proteolytic cleavage of alpha5beta1 integrin and focal adhesion kinase (FAK) proteins is linked to the early phase of the ATRA-induced apoptotic process. Furthermore, ATRA-induced detachment, death, and cleavage of alpha5beta1 integrin and FAK were drastically suppressed by plating cells onto Matrigel-coated plates. These findings provide evidence that abrogation of cell adhesion, through proteolysis of alpha5beta1 integrin and FAK, is closely linked to ATRA-induced apoptosis in Hep3B cells.
authors.affiliation: Department of Education and Research, Taichung Veterans General Hospital, No. 160, Section 3, Chung-Gang Road, Taichung 40705, Taiwan. h2326@vghtc.vghtc.gov.tw
authors.forename: S L
authors.initials: SL
authors.lastname: Hsu
authors.forename: C C
authors.initials: CC
authors.lastname: Cheng
authors.forename: Y R
authors.initials: YR
authors.lastname: Shi
authors.forename: C W
authors.initials: CW
authors.lastname: Chiang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology*; D001672:Biocompatible Materials / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D002448:Cell Adhesion / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology; D004338:Drug Combinations; D004347:Drug Interactions; D016326:Extracellular Matrix Proteins / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007797:Laminin / Q000494:pharmacology; D008113:Liver Neoplasms; D010447:Peptide Hydrolases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011509:Proteoglycans / Q000494:pharmacology; D017469:Receptors, Fibronectin / Q000378:metabolism* / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001672:Biocompatible Materials; D004338:Drug Combinations; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D007797:Laminin; D011509:Proteoglycans; D017469:Receptors, Fibronectin; C059485:matrigel; D014212:Tretinoin; D003094:Collagen; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D010447:Peptide Hydrolases