Activation of kinin B receptor triggers differentiation of cultured human keratinocytes

BACKGROUND

Keratinocyte life span is modulated by receptors that control proliferation and differentiation, key processes during cutaneous tissue repair. The kinin B(1) receptor (B(1)R) has been reported in normal and pathological human skin, but so far there is no information about its role in keratinocyte biology.

OBJECTIVES

To determine the consequence of kinin B(1)R stimulation on tyrosine phosphorylation, a key signalling mechanism involved in keratinocyte proliferation and differentiation.

METHODS

Subconfluent primary cultures of human keratinocytes were used to investigate tyrosine phosphorylation, epidermal growth factor receptor (EGFR) transactivation, cell proliferation and keratinocyte differentiation. Cell proliferation was assessed by measuring bromodeoxyuridine incorporation whereas assessment of cell differentiation was based on the expression of filaggrin, cytokeratin 10 (CK10) and involucrin.

RESULTS

The major proteins phosphorylated, after B(1)R stimulation, were of molecular mass 170, 125, 89 and 70 kDa. The 170- and 125-kDa proteins were identified as EGFR and p125(FAK), respectively. Phosphorylation was greatly reduced by GF109203X and by overexposure of keratinocytes to phorbol 12-myristate 13-acetate, indicating the participation of protein kinase C. B(1)R stimulation did not increase [Ca(2+)]i, but triggered EGFR transactivation, an event that involved phosphorylation of Tyr(845), Tyr(992) and Tyr(1068) of EGFR. B(1)R stimulation did not elicit keratinocyte proliferation, but triggered cell differentiation, visualized as an increase of filaggrin, CK10 and involucrin. Blockade of EGFR tyrosine kinase by AG1478, before B(1)R stimulation, produced an additional increase in filaggrin expression.

CONCLUSIONS

The kinin B(1)R may contribute to keratinocyte differentiation and migration by triggering specific tyrosine signalling pathways or by interacting with the ErbB receptor family.

Prognostic significance of transforming growth factor alpha TGF-alpha) in human lung carcinoma: an immunohistochemical study

Despite emerging data relating oncogene expression, growth factors and/or their receptors to the etiology of lung cancer, standard clinicopathological evaluation is still used for the diagnostic and prognostic purposes. Recent studies have shown that expression of some oncogenes and growth factors/receptors may be useful as markers in routine diagnostic and prognostic processes. For example, EGF/erb-B family of peptides may play a role in lung carcinogenesis. Similarly, expression of TGF-alpha mRNA and peptide has been shown to occur in various human lung carcinomas in vivo and in vitro. However, results concerning the role of TGF-alpha in lung carcinoma are conflicting and therefore its clinical value still remains obscure. To better evaluate the potential value of TGF-alpha in clinical application we have investigated the relationship between TGF-alpha expression in 51 lung carcinomas and 26 different clinical and clinicopathological parameters. The only significant correlation noted was between TGF-alpha and venous blood erythrocytes and eosinophils. This study suggests a relationship between metastasis and aggressive behavior of lung cancer. This data shows that TGF-alpha expression can not serve as an independent tumor marker for lung cancer.