title: Laminin and estradiol regulation of the plasminogen-activator system in MCF-7 breast-carcinoma cells.
abstract: We have investigated the effects of laminin, on the plasminogen-activator system of MCF-7 breast-carcinoma cells. MCF-7 cells were incubated on plastic or laminin-coated wells, and medium and cell lysate aliquots were assayed for tissue-type (tPA) and urokinase-type plasminogen activator (uPA) by a chromogenic assay in combination with anti-uPA antibodies. Cells cultured on laminin displayed a 5-fold increase in tPA activity and a 2-fold decrease in uPA activity relative to cells on plastic. These effects could be mimicked by laminin fragment P1 but not by collagen I or fibronectin. tPA activity of cells treated with estradiol (10 nM) was 3-fold higher, that of cells on laminin treated with estradiol was 15-fold higher, than that of control. Northern-blot analysis showed that tPA mRNA levels were up-regulated by estradiol and laminin, whereas PAI-1 mRNA levels were down-regulated by laminin and not affected by E2. Concomitant treatment with laminin and estradiol, decreased PAI-1 mRNA and increased tPA mRNA levels, accounting for the synergistic increase in tPA activity. Laminin exerted only a modest (approx. 2-fold) inhibitory effect on uPA mRNA levels. In the breast-carcinoma cell line MDA-MB-231, down-regulation of PAI-1 and uPA mRNA by laminin was not observed. Adhesion assays indicated that alpha2beta1 is the predominant receptor for laminin in MCF-7 cells. MDA-MB-231 cells expressed alpha2 (54%) but this integrin is not used as a laminin receptor. These results support a role for alpha2beta1 in mediating interactions of MCF-7 with LN.
authors.affiliation: Departamento de Radiologia de Faculdade de Medicina da USP, São Paulo, Brazil.
authors.forename: S
authors.initials: S
authors.lastname: Sonohara
authors.forename: R
authors.initials: R
authors.lastname: Mira-y-Lopez
authors.forename: M M
authors.initials: MM
authors.lastname: Brentani
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D002448:Cell Adhesion; D004357:Drug Synergism; D004958:Estradiol / Q000494:pharmacology*; D006801:Humans; D016023:Integrins / Q000378:metabolism; D007797:Laminin / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D010959:Tissue Plasminogen Activator / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D016023:Integrins; D007797:Laminin; D012333:RNA, Messenger; D004958:Estradiol; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator