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Nm23‐H1 expression of metastatic tumors in the lymph nodes is a prognostic indicator of oral squamous cell carcinoma

We recently reported that low Nm23‐H1 expression of primary oral squamous cell carcinoma (OSCC) was correlated with the occurrence of lymphatic metastasis. However, little is known about whether Nm23‐H1 level of metastatic tumors in the cervical lymph nodes is reduced in comparison with primary oral cancers and its significance for patients' prognosis. By immunohistochemistry, we analyzed the Nm23‐H1 expression in 52 pairs of OSCC specimens from primary oral cancers and their metastatic lymph nodes. Western blot analysis further confirmed the immunohistochemical interpretation. To verify the effects of Nm23‐H1 on cell migration and invasion, we established several stable clones derived from a human OSCC cell line (SAS) by knockdown and overexpression. Wound‐healing closure, transwell migration and invasion assays were performed to determine cell motility, migratory and invasive activities. Western blot analysis was carried out to evaluate cyclin A expression of OSCC cells with the altered Nm23‐H1 levels following knockdown and overexpression. By immunohistochemistry, Nm23‐H1 expression of metastatic lymph nodes was significantly lower than that of their primary oral cancers, supporting a role of Nm23‐H1 in metastasis suppression. Negative Nm23‐H1 interpretation of OSCC specimens, in either primary oral cancers or metastatic lymph nodes, indicated a poor survival outcome of patients. On the basis of in vitro studies of Nm23‐H1 knockdown and overexpression, we demonstrated an inverse correlation between Nm23‐H1 expression and the invasiveness of OSCC cells. Moreover, we observed the concomitant reduction in Nm23‐H1 and cyclin A levels of metastatic tumors in both results of in vitro OSCC cells and ex vivo tumor specimens. © 2007 Wiley‐Liss, Inc.