Up-regulated cytoplasmic expression, with reduced membranous distribution, of thesrc substrate p120ctn in gastric carcinoma

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Abstract
P120ctn is a substrate of the tyrosine kinase pp60 src. Tyrosine kinases such as src localize to the adherens junctions and phosphorylate junctional proteins in both normal and transformed cells.1 p120ctn forms a complex with E-cadherin at the adherens junction and is phosphorylated by ligands such as epidermal growth factor receptor as well as pp60 src. Phosphorylation of p120ctn has been shown to correlate with cell transformation. The aim of this study was to investigate in vivo expression of p120ctn in gastric carcinoma and to examine any relationship to pathological characteristics and patient survival. Immunohistochemical staining for p120ctn was performed in 68 gastric carcinoma specimens (19 diffuse, 49 intestinal type), in 22 lymph node metastases, and in gastric mucosal biopsies from 16 patients with gastric dysplasia and ten healthy controls. Up-regulation of p120ctn cytoplasmic staining was seen in six (37 per cent) of the gastric dysplasia cases and in 45 (66 per cent) tumours (89 per cent of diffuse and 57 per cent of intestinal tumours). Loss of membranous distribution of staining for p120ctn was seen in 22 (32 per cent) tumours (52 per cent of diffuse and 24 per cent of intestinal tumours). The staining pattern in the primary tumour showed no correlation with tumour type, grade, or stage, or patient survival. Of 22 lymph node metastases examined, 13 (60 per cent) showed loss of membranous staining. In conclusion, staining for p120ctn in gastric carcinoma and dysplasia revealed marked up-regulation of cytoplasmic staining, sometimes associated with reduced membranous expression. Up-regulation of expression of p120ctn has not previously been described in human epithelial malignancy. The significance of these findings is uncertain, but they may reflect a change in tyrosine kinase signal transduction pathways, and a role for p120ctn in ligand-induced mitogenic signalling and cell transformation. Copyright © 1999 John Wiley & Sons, Ltd.