PROGNOSTIC-SIGNIFICANCE OF NM23 PROTEIN EXPRESSION IN MALIGNANT-MELANOMA - AN IMMUNOHISTOCHEMICAL STUDY

The NM23 genes, encoding for the red blood cell nucleoside diphosphate kinases A and B, have been found to serve as metastasis-suppressor ge nes in experimental animal models of tumour progression, and in some, but not all cancers in man. To investigate the role of NM23 in the pro gression of human malignant melanoma, we studied the expression and di stribution of the nm23 protein with a sensitive immunohistochemical te chnique and a well-characterized monoclonal antibody in 41 benign pigm ent cell lesions and 71 uniformly treated malignant melanomas with a l ong follow up-up. In benign naevi, the junctional nests frequently exp ressed nm23 protein, whereas the immunoreactivity tended to decrease w hen the lesions matured. All malignant melanomas expressed nm23 protei n in their vertical phases, and the towards the deeper parts of the le sion. No relation was found between nm23 expression and patient outcom e. In addition, nm23 was found in activated lymphoid cells, and this f eature was significantly associated with a brisk lymphocytic stroma re sponse in malignant melanomas. Our data are at variance with previous mRNA studies on malignant melanoma, and indicate that routine immunehi stochemical analysis for nm23 protein on paraffin embedded tumour tiss ue cannot reliably be used as a prognostic marker for patients sufferi ng from malignant melanoma. In contrast, our findings suggest that the nm23 protein in pigment cell lesions is related to the proliferative or activated state of pigment cells, rather than to their metastatic p otential.