Human prostate-specific transglutaminase gene: Promoter cloning, tissue-specific expression, and down-regulation in metastatic prostate cancer

Objectives. To investigate the tissue-specific and differential expression of the human prostate-specific transglutaminase (pTGase) gene in metastatic prostate cancer (CaP) and to study how this gene is regulated in the prost ate. Methods, Northern blot hybridization and polymerase chain reaction (PCR) we re performed using RNA from a variety of organs to confirm prostate-specifi c expression of the gene. Relative quantitative reverse transcriptase-PCR ( RT-PCR) was performed to investigate the differential expression of the gen e among normal prostates and prostates with CaP and metastatic CaP. The pTG ase gene promoter was cloned using genomic library screening and sequencing . Transfection experiments and chloramphenicol acetyltransferase (CAT) assa ys were performed to study the regulation of the gene. Results. Northern hybridization and RT-PCR confirmed that the gene is only expressed in the prostate, Relative quantitative RT-PCR demonstrated a loss of expression of the pTGase gene among men with CaP and higher Gleason gra des. In metastatic CaP tissue from;various: sites, 86% of the samples lost expression of the gene. We cloned and sequenced a 1.4-kilobase promoter reg ion of the pTGase gene. Transfection and CAT assay results supported the th eory that certain elements in:the -1 to -520 region are sufficient to direc t prostate-specific expression of the gene. Additional elements in the -520 to -1400 region may also Contribute to its prostate-specific expression. Conclusions. The results of our study demonstrate that the human pTGase gen e is only expressed in prostate tissue and that its expression is inhibited in most metastatic CaP. Prostate-specific expression of the gene is contro lled by elements in the promoter region. The observed preferential loss of pTGase gene expression in metastatic CaP may be important to the :pathogene sis and progression of this disease. (C) 1999, Elsevier Science Inc.