Objective: Serine proteases are redundant enzymes implicated in the extracellular modulation required for tumor growth and invasion. Tumor-associated differentially expressed gene-14 (TADG-14) is a novel transmembrane serine protease recently reported by our group to be highly overexpressed in ovarian carcinomas. The goal of this study was to investigate the frequency of expression of the TADG-14 gene in human cervical tumors.
Study design: TADG-14 expression was evaluated in 19 cervical cancer cell lines (11 primary and 8 established cell lines) as well as in 8 normal cervical keratinocyte cultures by reverse transcriptase polymerase chain reaction. In addition, to validate gene expression data at the protein level, TADG-14 expression was evaluated by immunohistochemistry on paraffin-embedded tissue from which all 11 primary tumor cell lines were established.
Results: TADG-14 was found to be highly expressed in 82% (9/11) primary cervical cancer cell lines and in 87% (7/8) established cervical cancer cell lines by reverse transcriptase-polymerase chain reaction. Expression of TADG-14 by primary squamous cervical tumors was 100% (6/6), whereas 60% (3/5) of primary adenocarcinomas expressed TADG-14. In contrast, none of the normal cervical keratinocyte control cultures (n=4) or flash frozen normal cervical biopsy specimens (n=4) expressed TADG-14. Immunohistochemistry staining of paraffin-embedded cervical cancer specimens confirmed TADG-14 expression in tumor cells and its absence on normal cervical epithelial cells.
Conclusion: Cervical cancer expressed a high level of TADG-14, suggesting that this protease may play an important role in invasion and metastasis. Because TADG-14 appears only in abundance in tumor tissue and contains a secretion signal sequence, suggesting that TADG-14 is secreted, it may prove to be a useful diagnostic tool for the early detection of recurrent/persistent cervical cancer after standard treatment or as a novel molecular target for cervical cancer therapy.