Galectin-8 induces partial epithelial–mesenchymal transition with invasive tumorigenic capabilities involving a FAK/EGFR/proteasome pathway in Madin–Darby canine kidney cells

Abstract

Epithelial cells can acquire invasive and tumorigenic capabilities through epithelial–mesenchymal-transition (EMT). The glycan-binding protein galectin-8 (Gal-8) activates selective β1-integrins involved in EMT and is overexpressed by certain carcinomas. Here we show that Gal-8 overexpression or exogenous addition promotes proliferation, migration, and invasion in nontumoral Madin–Darby canine kidney (MDCK) cells, involving focal-adhesion kinase (FAK)-mediated transactivation of the epidermal growth factor receptor (EGFR), likely triggered by α5β1integrin binding. Under subconfluent conditions, Gal-8–overexpressing MDCK cells (MDCK-Gal-8H) display hallmarks of EMT, including decreased E-cadherin and up-regulated expression of vimentin, fibronectin, and Snail, as well as increased β-catenin activity. Changes related to migration/invasion included higher expression of α5β1 integrin, extracellular matrix-degrading MMP13 and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) protease systems. Gal-8–stimulated FAK/EGFR pathway leads to proteasome overactivity characteristic of cancer cells. Yet MDCK-Gal-8H cells still develop apical/basolateral polarity reverting EMT markers and proteasome activity under confluence. This is due to the opposite segregation of Gal-8 secretion (apical) and β1-integrins distribution (basolateral). Strikingly, MDCK-Gal-8H cells acquired tumorigenic potential, as reflected in anchorage-independent growth in soft agar and tumor generation in immunodeficient NSG mice. Therefore, Gal-8 can promote oncogenic-like transformation of epithelial cells through partial and reversible EMT, accompanied by higher proliferation, migration/invasion, and tumorigenic properties.

Galectin‐8 mediates fibrogenesis induced by cyclosporine in human gingival fibroblasts

“…Both substrates stimulated HGF adhesion at a similar level ( Figure 3C). Lactose, used to inhibit the interaction between galectins and carbohydrates, 18 reduced HGF adhesion over Gal-8, but not on fibronectin ( Figure 3C).…”

“…For SDS-PAGE, 50 µg of total protein from the cell lysate was used; these were prepared in loading buffer and heated at 95°C for 5 minutes. 18…”

“…To further explore the functional consequence of Gal-8 interaction with β1-integrin, we assessed cell adhesion, which is well known to involve activation of β1-integrins. 18 Given that α5β1-integrin is one of the main fibronectin receptors, 28,31 we compared the adhesion of HGF to Gal-8-or fibronectin-covered culture plates. Both substrates stimulated HGF adhesion at a similar level ( Figure 3C).…”

“…[15][16][17] We recently described that Gal-8 induces partial epithelial mesenchymal transition (EMT) that includes an increased expression of fibronectin. 18 EMT is crucial in organogenesis, tissue repair, cancer, and fibrosis. 19 Gal-8 has also been found to bind to type II TGF-β receptor (TGFβ-RII) and to activate the transforming growth factor β (TGF-β) signaling pathway, 20 which is indeed crucially involved in fibrogenesis in different tissues.…”

Dependence and Guidance Receptors—DCC and Neogenin—In Partial EMT and the Actions of Serine Proteases

“…With the growing recognition of partial EMTs (76-83) some initiating factors are being identified including phosphatidylinositol-3-kinase (84), TGF-β (85-87), galectins (88), or altered expression of PTEN (89). Some groups define partial EMT with respect to mismatch between cell protein profile and phenotypic behavior (90) while others are attempting to define RNA fragments which regulate protein expression.…”