Increased Expression of nm23 Protein in Colorectal Adenocarcinoma

Abstract

Some studies have shown that abnormalities of the nm23 gene or its expression may be important in tumor dissemination, suggesting that the gene may have metastasis suppressing activity. The purpose of this study was to determine if the level of nm23 protein expression is altered with progression and dissemination in colorectal adenocarcinoma. Using immunohistochemistry and a monoclonal antibody, NCL-nm23, nm23 protein expression was examined in human primary colorectal adenocarcinoma (n = 100), some with lymph node metastasis (n = 71) and matching normal non-neoplastic colorectal mucosa (n = 100). We found that nm23 protein expression was significantly different between normal colorectal mucosa and primary colorectal carcinoma (p = 0.0001: χ2 test with continuity correction). Almost half of the cases of primary colorectal carcinoma (47/100; 47%) and a similar proportion of the lymphnode metastases (38/71 cases; 54%) had strong nm23 immunostaining. In contrast, only a minority of the normal colorectal mucosal tissues (9/100 cases; 9%) showed strong nm23 expression. However, no significant difference was found between primary colorectal carcinoma and lymph node metastases. Intracase comparisons revealed that the majority of cases (84/100; 84%) had more nm23 immunoreactivity in the primary carcinoma tissues than in the normal mucosa. Reduced nm23 immunoreactivity in the metastasis, when compared to the primary tumor tissues, was found in less than half of the cases (29/71; 41%). In summary, nm23 protein immunoreactivity appears increased in colorectal carcinoma compared to normal colorectal tissues, but no significant difference was seen in nm23 expression between primary colorectal carcinoma and metastatic carcinoma tissues. This suggests that increased nm23 expression may be important in early colorectal carcinoma but not necessarily in later progression or dissemination of the tumor. A large proportion of metastatic carcinomas paradoxically had increased nm23 protein immunoreactivity, contradicting its postulated metastasis-suppressing role. (The J Histotechnol 23:133, 2000)