title: Distinct signaling pathways regulate differential opioid effects on actin cytoskeleton in malignant MCF7 and nonmalignant MCF12A human breast epithelial cells.
abstract: The mechanisms through which opioids regulate the activity of malignant breast epithelial cells are currently unknown. In the present study we report the differential actin cytoskeleton reorganization induced by opioids in malignant (MCF7) and nonmalignant (MCF12A) breast epithelial cells expressing functional opioid receptors. Exposure of MCF7 cells to the opioid agonist alpha(s1) casomorphin induced important actin assembly and reorganization, including the formation of filopodia and lamellipodia. In contrast, incubation of MCF12A cells with alpha(s1) casomorphin revealed a partial but transient disassembly of actin microfilaments. Immunoprecipitation and immunoblot analyses showed rapid phosphorylation of focal adhesion kinase (FAK) and vinculin in opioid-treated MCF7 cells. Moreover, FAK associates with phosphatidylinositol-3 (PI-3 kinase), the latter being subsequently phosphorylated and activated. In addition, a substantial activation of the small GTPase Rac1 was observed. Pretreatment of MCF7 cells with the specific PI-3 kinase inhibitor wortmannin abolished both the activation of Rac1 and actin reorganization, while the opioid-induced phosphorylation of FAK and vinculin remained unaffected. Interestingly, in opioid-treated MCF12A cells this signaling cascade remained inactive, while we identified rapid phosphorylation of actin regulating the protein villin. Finally, opioids differentially inhibited cell motility in each cell line. Our data suggest a distinct, opioid-induced, signaling pathway activated in malignant breast epithelial cells, leading to important actin reorganization. These findings may indicate a potential antineoplastic role of opiates, based on the activation of differential signaling mechanisms.
authors.affiliation: Department of Biochemistry, School of Medicine, University of Crete, GR-71110 Heraklion, Greece.
authors.forename: Galatea
authors.initials: G
authors.lastname: Kallergi
authors.forename: Anna
authors.initials: A
authors.lastname: Tsapara
authors.forename: Marilena
authors.initials: M
authors.lastname: Kampa
authors.forename: Evangelia A
authors.initials: EA
authors.lastname: Papakonstanti
authors.forename: Kostas
authors.initials: K
authors.lastname: Krasagakis
authors.forename: Elias
authors.initials: E
authors.lastname: Castanas
authors.forename: Christos
authors.initials: C
authors.lastname: Stournaras
mesh_terms: D000199:Actins / Q000187:drug effects*; D000970:Antineoplastic Agents / Q000494:pharmacology; D001943:Breast Neoplasms / Q000473:pathology*; D002364:Caseins / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D018613:Microscopy, Confocal; D009294:Narcotics / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D016596:Vinculin / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D000970:Antineoplastic Agents; D002364:Caseins; D009294:Narcotics; D010446:Peptide Fragments; C102368:alpha(S1)-casomorphin; D016596:Vinculin; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D020744:rac GTP-Binding Proteins