Predictive and prognostic values of BubR1 and synuclein-gamma expression in breast cancer

The aim of this study is to determine the expression level of spindle assembly checkpoint (SAC) proteins-BubR1 and synuclein-gamma (SNCG) in human breast cancer tissues and to test whether there is a relationship between their expression levels and clinicopathologic parameters including respons to taxanes, tumor grade, estrogen receptor (ER) pozitivity, HER2 status, and overall survival (OS). We analyzed retrospectively paraffin-embedded tissue sections from 55 breast cancer patients whose clinical outcomes had been tracked after taxane treatment in neoadjuvan and metastatic setting. The expression status of BubR1 and SNCG was defined by immunohistochemistry (IHC) using the anti-BubR1 and anti-SNCG antibody. The BubR1 and SNCG was overexpressed in 38% and 62% of the study group, respectively. There was borderline significant correlation between low BubR1 expression and increased taxane sensitivity (P=0.05). In contrast, high SNCG expression was significantly associated with decreased taxane sensitivity (P=0.01). There was no association between the clinicopathologic parameters including histologic grade, ER positivity and HER2 status and the level of these proteins. However, triple negative tumors showed significantly more high BubR1 expression than those other molecular subtypes (P=0.04). Kaplan-Meier survival analysis failed to show a significant correlation between expression levels of BubR1 and SNCG and overall survival although patients with low levels of both proteins had a marginally longer survival time compared to those with high levels. In summary, our data suggest that both BubR1 and SNCG may be promising predictive marker rather than prognostic marker in patients with breast cancer.