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EGF-receptor tyrosine kinase inhibition induces keratinocyte growth arrest and terminal differentiation
D Peus1, L Hamacher, M R Pittelkow
1Department of Dermatology, Mayo Clinic/Foundation, Rochester, Minnesota, USA.
Abstract:
Epidermal keratinocyte growth and differentiation are regulated by specific families of growth factors and receptors. Peptide growth factors of the epidermal growth factor family stimulate proliferation of clonal density human keratinocytes and suppress markers of terminal differentiation in confluent cultures of human keratinocytes. We present evidence that selected inhibitors of activation of the type I human epidermal growth factor receptor (EGFR or HER-1), namely, neutralizing monoclonal antibody to HER-1/EGFR and the specific tyrosine kinase inhibitor PD 153035, potently inhibit proliferation of human keratinocytes in autonomously replicating subconfluent cultures. Coupled to growth arrest is the suppression of HER-1 tyrosine autophosphorylation in inhibitor-treated human keratinocytes. Proliferation and tyrosine autophosphorylation are initially reversible following removal of the inhibitor and restimulation of cells with epidermal growth factor. Sustained inactivation of HER-1 in autonomously replicating cultures of human keratinocytes induces expression of keratin 1 and keratin 10 genes, early markers of terminal differentiation. Reversal of growth inhibition by epidermal growth factor suppresses keratin 1 and keratin 10 expression. These results demonstrate that human keratinocyte terminal differentiation as well as proliferation are mediated by HER-1. Co-expression of autocrine epidermal growth factor-related ligands as well as HER-1 by human keratinocyte may function as part of the signal transduction network in epidermis to regulate cell number, replication rate, and terminal differentiation.
Insights
Epidermal Growth Factor Receptor (EGFR) inhibition halts human keratinocyte proliferation and terminal differentiation. Blocking EGFR signaling, crucial for skin cell growth, offers insights into epidermal regulation.
Area of Science:
- Dermatology
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Epidermal keratinocyte proliferation and differentiation are tightly regulated by growth factors and their receptors.
- Epidermal Growth Factor (EGF) family peptides stimulate keratinocyte proliferation and inhibit terminal differentiation markers.
Purpose of the Study:
- To investigate the role of the type I human Epidermal Growth Factor Receptor (EGFR or HER-1) in regulating human keratinocyte proliferation and differentiation.
- To determine the effects of EGFR activation inhibitors on keratinocyte behavior and gene expression.
Main Methods:
- Utilized neutralizing monoclonal antibodies against HER-1/EGFR and the tyrosine kinase inhibitor PD 153035 to block EGFR activation.
- Assessed effects on human keratinocyte proliferation, tyrosine autophosphorylation, and expression of differentiation markers (keratin 1 and keratin 10).
- Evaluated reversibility of effects upon inhibitor removal and EGF restimulation.
Main Results:
- EGFR inhibitors potently inhibited human keratinocyte proliferation and suppressed HER-1 tyrosine autophosphorylation.
- Inhibition of proliferation and autophosphorylation was reversible upon removal of inhibitors and EGF restimulation.
- Sustained EGFR inactivation induced expression of keratin 1 and keratin 10, markers of terminal differentiation, which was reversed by EGF.
Conclusions:
- Human keratinocyte proliferation and terminal differentiation are mediated by HER-1/EGFR signaling.
- EGFR plays a central role in the epidermal signal transduction network regulating keratinocyte cell number, replication rate, and differentiation.
- Autocrine signaling involving EGF-related ligands and HER-1 may be critical for maintaining epidermal homeostasis.