Abstract
Klotho is a single-pass transmembrane protein with documented anti-cancer properties. Recent reports have implicated Klotho as an inhibitor of transforming growth factor β1 induced cell migration in renal fibrosis. Overexpression of epidermal growth factor receptor (EGFR) is known to promote tumor initiation and progression in clear-cell renal cell carcinoma (cRCC). We tested our hypothesis that Klotho inhibits EGF-mediated cell migration in cRCC by interfering with the EGFR signaling complex and mitogen-activated protein kinase (MAPK) pathways. We performed cell adhesion, migration, and biochemical studies in vitro using Caki-1 cell line. In addition, we validated the cell culture studies with expression analysis of six de-identified FFPE tissues from primary and metastatic cRCC patients. Our studies show that Klotho inhibited EGF-induced Caki-1 de-adhesion and decreased spreading on collagen type 1. Klotho also inhibited EGF-induced α2β1 integrin-dependent cell migration on collagen type 1. To test the involvement of MAPK pathways in EGF-induced Caki-1 cell motility, the cells were pretreated with either SB203580, a specific p38 MAPK inhibitor, or Klotho. SB203580 blocked the EGF-induced Caki-1 cell migration. Klotho had a comparable inhibitory effect. Our FFPE clinical specimens revealed decreased Klotho mRNA expression compared to a control, non-cancer kidney tissue. The decrease in Klotho mRNA levels correlated with increased c-Src expression, while E-Cadherin was relatively reduced in metastatic FFPE specimens where Klotho was least expressed. Taken together, these results suggest that secreted Klotho inhibits EGF-induced pro-migratory cell morphological changes and migration in Caki-1 cells. Our data additionally suggest that decreased Klotho expression may be involved in cRCC metastasis.
Highlights
Klotho is a type 1 transmembrane protein with homology to β-glucosidase and was discovered as a mutated gene in a mouse showing several phenotypes resembling human aging [1, 2]
The pro-migratory function of p38 mitogen-activated protein kinase (MAPK) has been documented in certain cancers [22, 23] and the epidermal growth factor (EGF)-induced, cell migration on collagen type 1 mediated by α2β1 integrin requires p38 MAPK activation [24, 25]
We showed that suppression EGFRMAPK pathway by Klotho induced cells to adopt mesenchymal like morphology
Summary
Klotho is a type 1 transmembrane protein with homology to β-glucosidase and was discovered as a mutated gene in a mouse showing several phenotypes resembling human aging [1, 2]. Klotho is highly expressed in renal tubular cells. The approximately 120 kDa extracellular domain is released into circulation by ectodomain shedding and acts as a humoral factor [3, 4]. One of the mechanisms of action of Klotho is www.oncotarget.com its suppressive interaction with insulin and insulinlike growth factor–1 receptors (IGF-1R) [5]. This finding supported studies implicating Klotho as a tumor suppressor in breast, gastric, and pancreatic cancers [6,7,8,9]. Subsequent data indicated that Klotho inhibits transforming growth factor β1 (TGFβ1)–induced cell migration in renal fibrosis [3]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
