Expression of breast cancer specific gene-1 (BCSG-1/gamma-synuclein) is associated with tumour grade but not with clinical outcome of patients with breast cancer.

This study examined the expression and distribution of BCSG-1 in human breast cancer tissue. IHC revealed that BCSG-1 was primarily seen as a cytosolic protein, weakly staining normal mammary epithelial cells but increased in breast tumour cells. Q-PCR revealed that node negative and positive tumours had similar levels of BCSG-1 transcript and BCSG-1/CK19 ratio. There were significantly higher levels in grade 2 and grade 3 tumours compared to grade 1. Patients with NPI (Nottingham prognostic indicator) < 3.4, had a predicted 80% 15-year survival. After a 10-year follow-up, no significant difference was seen between tumours from patients remaining disease-free and those who died of breast cancer. The levels of BCSG-1 significantly correlated with an associated molecule, transglutaminase-3 (r = 0.307, P < 0.05), and weakly with transglutaminase-7 (r = 0.183). BCSG-1 is increased in breast tumour cells, is negatively associated with tumour grade and significantly correlates with levels of transglutaminase-3.