Expression of the nm23-2/NDP kinase alpha gene in rat mammary and oral carcinoma cells of varying metastatic potential

Isolation of a novel gene showing reduced expression in metastatic colorectal carcinoma cell lines and carcinomas

To investigate genes involved in metastatic stages of cancer, we analyzed expression of mRNAs in three cell lines derived from murine colon adenocarcinoma 26 by means of a differential display method. Each of these lines exhibits distinct metastatic characteristics. Among many bands representing different expression patterns in the display, we confirmed by northern analysis that a gene corresponding to one amplified fragment, termed grm2 (gene related to metastasis 2), was expressed more abundantly in NL4, the derivative with the lowest metastatic potential, than in cell lines NL17, an experimentally metastatic derivative, and in NL22, a spontaneously metastatic derivative. Using the grm2 fragment as a probe, we isolated murine cDNA clones and subsequently human cDNA clones corresponding to the GRM2 gene. The human and mouse homologues both encode proteins of 600 amino-acid residues, which show weak homologies to proteins belonging to the myosin family. When we examined the expression levels of this novel gene in human colon cancers and in corresponding metastatic foci, we found that in more than half of these tissues, expression was significantly reduced in association with malignant potential. Our results imply that in humans the GRM2 gene product may regulate the metastatic phenotype of some colorectal cancers.

NM23 expression in metastasis of malignant melanoma is a predictive prognostic parameter correlated with survival

The management of patients presenting with metastatic malignant melanoma (MM) is hampered by the substantial variability in survival of these patients and the lack of prognostic markers. In the search for a reliable predictive parameter, we have investigated the expression of the nm23 gene, considered to be a major regulator of the metastatic process. We have analysed by Northern blot the nm23 mRNA level in tumour tissue obtained from metastases of 20 stage II and ten stage III patients with MM. Normal human tissues and benign naevi were simultaneously examined. The level of nm23 expression was highly heterogeneous in MM metastases, with a mean value which was higher than the mean level in normal tissues and naevi. Correlative study was focused on the overall survival following resection of the metastasis in which nm23 Northern blot analysis was performed. Patients displaying higher nm23 expression in metastatic tissue (above the mean level) tended to have a longer survival than others (P = 0.08), and this difference was significant for patients presenting with isolated regional lymph node involvement (P = 0.035). The time from biopsy of the primary MM to the appearance of the first lymph node metastasis also showed a positive correlation with the nm23 mRNA level in this metastasis. The present study is not only in accordance with previous reports showing that the nm23 gene may be implicated in MM progression, but also suggests the reliable value of nm23 expression as a prognostic marker for patients presenting with metastatic MM.