The c-Rel subunit of NF-kappa B is a crucial regulator of phenotype and motility of HaCaT keratinocytes

Abstract

The transcription factor NF-kappa B exerts key functions in epidermal homeostasis and carcinogenesis. Its c-Rel subunit is expressed in squamous cell carcinoma, and c-Rel down-regulation results in increased apoptosis, G2/M cell cycle delay with reduced proliferation and aberrant mitotic spindle formation. To further study the impact of c-Rel on essential keratinocyte features such as migration and epithelial morphology, c-Rel was down-regulated in HaCaT keratinocytes by a siRNA approach. This inhibition of c-Rel impaired the keratinocyte-typical clustered growth leading to a more scattered appearance of the cultures. The cells were more spindle-shaped and elongated, albeit without expression changes of markers characteristic for epithelial mesenchymal transition. In addition, wound healing-related migration and adhesion to type I collagen, fibronectin, laminin and vitronectin were significantly impaired. On the sub-cellular level, these functional features were not associated with quantitatively altered adhesion receptor or Rho-GTPase expression, but rather with a significantly reduced length of cell-matrix adhesion complexes and altered appearance of filamentous actin. Thus, our studies support a role for c-Rel in processes crucial for keratinocyte integrity and malignant transformation such as adhesion and migration.