Tumor suppressor genes that reduce metastatic potential have been described in a variety of different
tumor types. One of the main
tumor metastasis suppressor genes is nm-23, which is a
nucleoside diphosphate kinase. Two isotypes, nm-23H1 and nm-23H2, have been cloned and map to chromosome 17q21.3. In a variety of
tumors, including
colon cancer and
breast cancer, loss of expression of nm-23 is associated with
lymph node metastasis. In other organ systems, however, this relationship is not seen. In
head and neck squamous cell carcinomas (
HNSCC), there have been conflicting results regarding the association between nm-23
protein expression and metastatic potential. To further explore the
tumor metastasis suppressor function of nm-23 in
HNSCC, we studied high-stage laryngeal
carcinomas,
tumors with and without cervical
lymph node metastasis for nm-23
protein expression and loss of heterozygosity of the gene locus. Twenty-five cases were included (11 cases with and 14 cases without
metastasis). Loss of heterozygosity for the nm-23 gene locus was seen in 7 of 22 (32%) informative
tumors. Using immunohistochemistry, most
tumors expressed nm-23, though decreased expression was seen in 10 of 25 (40%) cases. Only 2
tumors showed negative expression. We did not find a correlation between either
protein expression or loss of heterozygosity with metastatic disease or any other adverse prognostic factors in this group of high-stage laryngeal
squamous cell carcinomas. These data imply that nm-23 may be tumor suppressor gene involved in
HNSCC but that it may not function as a
tumor metastasis suppressor in high-stage laryngeal
carcinoma.