Prognostic evaluation of metallothionein expression in human colorectal neoplasms

Aim-To investigate the role of metallothionein in colorectal tumours and th e possible relation with other factors associated with tumour progression: expression of cathepsin D (CD), CD44, p53, Rb, bcl-2, c-erbB-2, epidermal g rowth factor receptor (EGFR), proliferation indices (Ki-67, proliferating c ell nuclear antigen (PCNA)), and conventional clinicopathological variables . Methods-The immunohistochemical expression of metallothionein was investiga ted in 23 cases of colorectal adenoma and 94 adenocarcinomas. Metallothione in expression was examined by the avidin-biotin peroxidase immunoperoxidase (ABC) using the monoclonal mouse antibody E9, on formalin fixed, paraffin embedded tissue. Results-Positive metallothionein expression (> 5% of neoplastic cells) was observed in 30.4% of adenomas and 25.5% of adenocarcinomas, while 8.7% of a denomas and 14.9% carcinomas showed focal metallothionein positivity In con trast, 60.9% of adenomas and 59.6% of carcinomas almost completely lacked m etallothionein expression. In the series of adenocarcinomas, metallothionei n expression was inversely correlated with CD44 in neoplastic cells (p = 0. 01). There was no statistically significant difference of metallothionein e xpression, or the other variables examined, between adenocarcinomas and ade nomas. Conclusions-Metallothionein expression does not seem to indicate aggressive biological behaviour in colorectal adenocarcinomas, in comparison with the other types of carcinoma. The inverse correlation with CD44 could suggest that the decreased metallothionein expression may contribute to the metasta tic spread of the lymph node involvement in colorectal cancer. Metallothion ein expression does not seem to represent an independent prognostic marker in colorectal cancer.