Gaynor Davies, Richard J. Ablin, Malcolm D. Mason and Wen G. Jiang

Background: Prostate transglutaminase (TGase-4), has been identified as a TGase that has a pattern of prostate specific expression. This study sought to determine (i) the level of TGase-4 in human cancer cell lines includ-ing prostate cancer cells; (ii) to investigate the effect after knocking down the expression of TGase-4 tran-script using a ribozyme transgene; (iii) to establish the effect of HGF/SF, a pro-invasion/metastasis cytokine, on the invasive capacity of TGase-4 knockdown cells.

Methods: RT-PCR and quantitative RT-PCR were used to assess the presence of TGase-4 transcript at the mRNA level in a panel of 26 cell lines including 6 prostate cancer cell lines (PC-3, DU-145, CA-HPV-10, PZ-HPV-7, PNT2C2 and PNT1A). A ribozyme transgene consisting of hammerhead ribozyme and antisense specific to TGase-4 was constructed using a pEF6 expression vector and transfected into CA-HPV-10 cell, a cell line highly expressed TGase-4. An in vitro invasion assay assessed the effects of HGF/SF on cell invasiveness.

Results: TGase-4 transcript was detected in a number of cell lines, including prostate, colorectal, lung and breast tumour cells. At the mRNA level, TGase-4 was strongly expressed in CA-HPV-10 cells with lower levels of expression seen in PC-3, DU-145, PZ-HPV-7 and PNT1A cells. TGase-4 knock-down in CA-HPV-10 cells was established at the mRNA level. HGF/SF significantly increased the invasion of wild type (21.67 + 0.88; P<0.001 vs. control 8.67 + 0.67) and control plasmid transfected cells (16.33 + 0.88; P<0.001 vs. control 7.67 + 0.88) compared with untreated cells. However, cells transfected with the TGase-4 ribozyme transgene had a reduced invasive capacity (9.33 + 0.88 P<0.01 vs. control 4.33 + 0.88) through Matrigel.

Conclusion: TGase-4 has a relatively wide profile of expression in human cancer cell lines and is strongly expressed in the low invasive CA-HPV-10 prostate cancer cell line. The molecule is associated with the invasive potential of prostate cancer cells.