Expression of transglutaminase-2 (TGM2) in the prognosis of female invasive breast cancer

Background Transglutaminase 2 (TGM2) is a protein expressed in several isoforms in both intra- and extra-cellular tissue compartments. It has multiple functions that are important in cancer biology and several small studies have suggested expression of TGM2 in breast cancers is associated with a poorer prognosis. The aim of this study was to evaluate the role of intra-cellular and extra-cellular TGM2 expression in breast cancer and to determine whether there were any differences by hormone receptor status. Methods We carried out TGM2 immunostaining of tissue micro-arrays comprising 2169 tumour cores and scored these for both intra- and extra-cellular and expression. Results Intra-cellular (tumour cell) TGM2 positivity was associated with a better prognosis (HR = 0.74, 95% CI 0.59–0.92) with a larger effect stronger in hormone-receptor-negative cases (HR = 0.56, 95% CI 0.37–0.85). Extra-cellular (stromal) TGM2 expression was associated with a poorer prognosis (HR = 1.47, 95% CI 1.06–2.03) with a stronger association in hormone-receptor-positive cases (HR = 1.60, 95% CI 1.09–2.34). Conclusion Tissue compartment and hormone receptor status differences in the effect of TGM2 expression on clinical outcomes of breast cancer may reflect the different functions of TGM2.