Patients with lung cancer have a poor prognosis because of the high metastatic potential of the neoplasm. Therefore, identifying new molecular targets for anti-metastatic therapy is very important. To identify novel key factors of tumor metastasis in lung cancer, we established the gene expression profiles of two adenocarcinoma cell line variants, PC9/f9 and PC9/f14, by use of genome-wide human cDNA microarray analysis and comparing these profiles with that of the parental cell line, PC9. The PC9/f9 and PC9/f14 cell lines were selected for analysis because of their high metastatic potential. We identified five genes in the highly metastatic cell lines that showed a significantly enhanced or reduced expression and that had not been reported to be involved in metastasis of lung cancer. One of the overexpressed genes that was identified encoded the beta-galactoside-binding protein LGALS3 (Galectin 3). LGALS3 has been reported to be overexpressed in a variety of human cancers, but not in lung cancer, and to be involved in tumor metastasis. We examined the expression of LGALS3 by use of real-time quantitative reverse transcription-polymerase chain reaction in 38 lung cancer cell lines and in tumor tissue obtained by thoracoscopic biopsy. A population (10/30) of the non-small-cell lung cancers examined was found to overexpress the LGALS3 gene at levels three times higher than those of normal epithelial cells. In contrast, all small-cell lung cancers either failed to express the gene or expressed it at a very low level. The mean of the relative expression of the LGALS3 gene in non-small-cell lung cancer (3.065 +/- 3.976) was significantly higher than those of small-cell lung cancer (0.02 +/- 0.03) (P < 0.025). This is the first report of alterations of LGALS3 gene expression in lung cancer. These results, together with the previous reports on Galectin 3 function, suggest that Galectin 3 may play a role in the process of metastasis in non-small-cell lung cancer that overexpresses Galectin 3, but not in small-cell cancer. Accordingly, LGALS3 may be a phenotypic marker that excludes small-cell lung cancer and may represent a novel target molecule in non-small-cell lung cancer therapy.
Copyright 2003 Wiley-Liss, Inc.