Tissue-type transglutaminase is not a tumor-related marker.

The level of transglutaminase (TGase) expressed in various tumor cell lines was investigated. We found that each cell line could be categorized into three distinct groups, that is, (i) cell lines with low or negligible TGase activity, (ii) cell lines with significant or high TGase activity and immunoreactive to a monoclonal antibody against tissue type TGase, and (iii) cell lines with significant or high TGase activity but not immunoreactive to the antibody. Results reported here argue against the former proposal that tissue-type TGase is expressed at a lower level in malignant cells compared to the level in normal cells.