Tissue transglutaminase expression in breast carcinomas

Tissue transglutaminase (tTG) is known to participate in multiple cellular processes, including apoptosis, cellular adhesiveness etc. Alterations of t TG expression could contribute to the development of several categories of diseases, including AIDS, cancer etc. The aim of the study was to test the pattern and relevance of tTG expression in a subset of breast carcinomas. R T-PCR has detected tTG-specific RNA message in 11 out of 25 (44%) breast ca ncer samples, tTG message was detected in 6/8 (75%) breast carcinomas with high apoptotic index, but only in 5/17 (29%) with the low one (p = 0.03). I mmunohistochemical analysis revealed that only 15% of breast carcinomas dis played tTG protein in tumor cells, while the staining of the stromal compon ents occurred in approximately one-half of the tumours tested. Surprisingly , there was no significant association between tTG RNA expression and prote in positivity. Moreover, there was no evident relationships between tTG imm unostaining and apoptotic index or clinical parameters of breast neoplasms. There are at least 2 alternative explanations for the poor concordance bet ween RNA and protein data. It is likely that the sensitivity of immunohisto chemistry is not sufficient to detect functionally relevant tTG enzyme in a ll breast cancer sections. Otherwise, tTG RNA expression does not always le ad to accumulation of its product in the tumor cells, but reflects the tran scriptional activation of other pro-apoptotic genes due to common triggerin g mechanisms.