The nm23 gene is a potential metastasis-suppressor gene originally identified in a murine melanoma line. Several investigators have reported the probable inverse association of nm23 expression with disease prognosis and/or metastasis. Since there are now 2 known isotypes of human nm23, namely nm23-H I and -H2, we immunohistochemically examined expression of these isotypes in human breast-cancer tissues using monoclonal antibodies (MAbs) specific for each isotype protein.
We also analyzed expression of c-erbB-2 in the same collection of cancer tissues, in order to examine the significance of nm23 expression in comparison with c-erbB-2 expression. Of I30 tumors from breast-cancer patients, 73 (56%) and 69 (53%) positively expressed nm23-H I and -H2 respectively. Expression of c-erbB-2 was positive in 36 (28%). Expression of nm23-H I, but not nrn23-H2, was inversely associated with lymph-node metastasis (p < 0.01). Expression of c-erbB-2 was associated with Tnm stage, tumor size and lymph-node metastasis (p < 0.0 I, p < 0.05 and p < 0.05 respectively). Overall survival was better (p = 0.014) in patients in whom expression of nm23-H I was positive than in those in whom it was negative. In multivariate analyses using a Cox's proportional-hazards regression model with 9 variables, nm23-HI showed the fourth greatest contribution to patient survival following lymph-node metastasis, Tnm stage and menopausal status. No significant contribution was shown for c-erbB-2 expression. nm23-H I, but not nm23-H2, may perform a role in disease prognosis in addition to its participation in cancer metastasis. It may have value for predicting long-term survival of human breast-cancer patients.