Claudin-7 indirectly regulates the integrin/FAK signaling pathway in human colon cancer tissue

J Hum Genet. 2016 Aug;61(8):711-20. doi: 10.1038/jhg.2016.35. Epub 2016 Apr 28.

Abstract

The claudin family of proteins is integral to the structure and function of tight junctions. The role of claudin-7 (Cldn-7, CLDN7) in regulating the integrin/focal adhesion kinase (FAK)/ERK signaling pathway remains poorly understood. Therefore, we investigated differences in gene expression, primarily focusing on CLDN7 and integrin/FAK/ERK signaling pathway genes, between colon cancer and adjacent normal tissues. Quantitative real-time reverse transcription-PCR and immunohistochemistry were utilized to verify the results of mRNA and protein expression, respectively. In silico analysis was used to predict co-regulation between Cldn-7 and integrin/FAK/ERK signaling pathway components, and the STRING database was used to analyze protein-protein interaction pairs among these proteins. Meta-analysis of expression microarrays in The Cancer Genome Atlas (TCGA) database was used to identify significant correlations between Cldn-7 and components of predicted genes in the integrin/FAK/ERK signaling pathway. Our results showed marked cancer stage-specific decreases in the protein expression of Cldn-7, Gelsolin, MAPK1 and MAPK3 in colon cancer samples, and the observed changes for all proteins except Cldn-7 were in agreement with changes in the corresponding mRNA levels. Cldn-7 might indirectly regulate MAPK3 via KRT8 due to KRT8 co-expression with MAPK3 or CLDN7. Our bioinformatics methods supported the hypothesis that Cldn-7 does not directly regulate any genes in the integrin/FAK/ERK signaling pathway. These factors may participate in a common network that regulates cancer progression in which the MAPK pathway serves as the central node.

MeSH terms

  • Biomarkers
  • Claudins / genetics
  • Claudins / metabolism*
  • Cluster Analysis
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism*
  • Colonic Neoplasms / pathology
  • Computational Biology / methods
  • Focal Adhesion Kinase 1 / genetics
  • Focal Adhesion Kinase 1 / metabolism*
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic
  • Gene Regulatory Networks
  • Humans
  • Integrins / genetics
  • Integrins / metabolism*
  • Protein Transport
  • Signal Transduction*
  • Tissue Array Analysis
  • Transcriptome

Substances

  • Biomarkers
  • CLDN7 protein, human
  • Claudins
  • Integrins
  • Focal Adhesion Kinase 1
  • PTK2 protein, human