Expression of the candidate tumor suppressor gene nm23 in the bronchial system of patients with squamous cell lung cancer.

OBJECTIVE A number of oncogenes and tumor suppressor genes participating in tumorigenesis have been identified, one of them being nm23. The expression of the candidate tumor suppressor gene nm23 depends on the cell type of tumors. Both, reduced expression as well as overexpression of nm23 is associated with a high potential of malignancy. In a variety of tumor cell lines secretion of the nm23 protein can be detected. In an earlier investigation we showed, that the nm23 expression in squamous cell lung carcinoma is considerably elevated. In order to establish the potential diagnostic value of this finding we investigated the nm23 expression in healthy and diseased lungs in patients with squamous cell lung cancers. METHODS We examined bronchial lavage samples of 20 patients with bronchogenic squamous cell carcinoma. The lavage was separately performed in the bronchus of the tumor bearing lobe and in the corresponding bronchus of the unaffected contralateral lung. RESULTS Using Western blot analysis we found 2-7 fold elevated amount of nm23 protein in bronchial lavage of the tumor bearing lung in comparison to the healthy side. This finding was neither related to tumor stage nor to tumor location. Thus we have a strong hint that the nm23 protein is secreted by the bronchogenic squamous cell carcinoma. CONCLUSIONS With respect to these results the proof of nm23 protein in bronchial lavage fluid might be of relevance to establish the diagnosis when pulmonary nodules of unknown etiology are found.