Expression of tumor suppressor gene PRDM1 in lung cancers

OBJECTIVE: To determine the expression of tumor suppressor gene PRDM1 in lung cancers. METHODS: Forty-five cases were enrolled in this study, including squamous cell carcinoma (20 cases), adenocarcinoma (15 cases), and small cell cancer (10 cases). PRDM1 protein was detected in paraffin-embedded tissue by immunohistochemistry. Tumor cells in lung cancers were further selected by laser microdissection for RT-PCR analysis. PRDM1 protein in frozen tissue was also detected by Western blot. RESULTS: (1) PRDM1 protein was found in paraffin-embedded tissues in 90.0% (18/20) of squamous cell carcinoma, 13.3% (2/15) of adenocarcinoma, and 0 (0/10) small cell lung cancer. Squamous cell carcinoma predominantly expressed PRDM1 protein ( P < 0.01). (2) Gene product of PRDM1 DNA binding region was not found in microdissected tumor cells, but an abnormal PRDM1 protein about 70 KD was detected simultaneously in whole tumor tissue. CONCLUSION: PRDM1 may be considered as a specific biomarker in pulmonary squamous cell carcinoma. The abnormal PRDM1 expression both at transcriptional and protein levels indicated that this tumor suppressor gene lost its function, which may become a new target in the strategy of treatment for lung cancers.