Down-regulation of the human PRL-3 gene is associated with the metastasis of primary non-small cell lung cancer.

BACKGROUND: Phosphatase of the regenerating liver (PRL)-3 protein tyrosine phosphatase gene is expressed in colon cancer metastasis. To investigate the role of this gene in metastatic lung cancer, we compared PRL-3 gene expression between primary cancers, metastatic lung cancer, and normal lung tissue. MATERIALS AND METHODS: Five metastatic tumor and normal samples from non-small cell lung cancer patients were obtained at the National Hospital Organization Kumamoto Medical Center (Kumamoto, Japan). For a quantitative evaluation of RNA expression by PCR, we used Taqman PCR methods. RESULTS: Although PRL-3 gene expression levels in the primary lesions were slightly decreased compared with those in the normal tissues, those in the metastatic lesions were extremely down-regulated in the synchronous metastatic case. In 2 of these 3 cases, the metastatic tumors showed down-regulated PRL-3 gene expression at 10 times less than that of the normal tissue, and the other tumor showed a slightly weaker expression. CONCLUSION: These data suggest that a down-regulation of the PRL-3 gene is important in lung cancer metastasis and provide a new hypothesis of lung cancer metastases.