OVEREXPRESSION OF THE 67‐kD LAMININ RECEPTOR CORRELATES WITH TUMOUR PROGRESSION IN HUMAN COLORECTAL CARCINOMA

The high affinity 67‐kD laminin receptor (67LR) is a cell surface protein whose expression is increased in a number of human carcinoma models. To date, 67LR expression in colorectal carcinomas has been examined in a small number of cases. 67LR expression has been immunohistochemically analysed in a large series of human colorectal neoplasms, using the MLuC5 monoclonal antibody. The study included 59 samples of non‐neoplastic mucosa, 45 polyps (11 hyperplastic, 34 adenomas), 196 carcinomas, and lymph node metastases of 87 carcinomas. Epithelial cells of normal mucosa and hyperplastic polyps were negative or showed weak positivity in the paranuclear and apical areas of the cytoplasm. In adenomas and carcinomas, the staining was stronger, with a membranous or cytoplasmic pattern. The expression of 67LR correlated significantly with the progression from normal mucosa (22 per cent) to adenoma (44 per cent), carcinoma (61 per cent), and lymph node metastasis (75 per cent) (P<0·0001). Expression of the laminin receptor showed a tendency to be more frequently positive in advanced stage (III+IV; 67 per cent) when compared with early stage (I+II) carcinomas (54 per cent). The difference, however, was not statistically significant (P=0·058). In addition, 14 out of 28 (50 per cent) primary carcinomas without 67LR expression became positive in lymph node metastases, while most (86 per cent) of the MLuC5‐positive primary carcinomas were also immunoreactive in metastases. In conclusion, these results indicate that 67LR is up‐regulated in the progression of human colorectal carcinomas and may play a role in the local and metastatic progression of these tumours.