Möllerström et al. BMC Cancer 2010, 10:296 http://www.biomedcentral.com/1471-2407/10/296 Page 5 of 11 Table 3: Difference in protein expression between tumours from 5-year overall survivors and tumours from deceased patients Dead patients Protein expression positive (%) Protein AdipoR1 Adora1 BTG2 CD46 -membrane only 19 -cytoplasm only 52 26 30 61 16 Protein expression negative (%) 74 70 39 81 48 84 Alive patients Protein expression positive (%) 17 23 82 44 68 14 Protein expression negative (%) 83 77 18 56 32 86 3 8 6 6 6 4 not available (No P-value dead vs. of samples) alive patients 0.29 0.47 0.026* 0.013* 0.14 0.77 P-values were calculated using a two-tailed Fisher's exact test. The samples designated as not available had few tumour cells, large tissue loss or affluence of necrotic tissue. significantly more prevalent in tumours from alive patients compared to tumours from dead patients. Fur- thermore, a multivariate analysis showed that a model containing BTG2 expression in combination with HER2 expression, patient age and Ki67 expression performed better, i.e. revealed a higher prediction accuracy, than a model containing the currently used prognostic markers (tumour size, nodal status, HER2 expression, hormone receptor status, histological grade, and patient age). In this model, BTG2 expression as well as HER2 expression and patient age were highly significant (P < 0.0001), whereas Ki67 expression displayed a lower significance (P = 0.013). These results further strengthen that BTG2 expression could be a useful complement to the currently used markers, and in addition, suggest Ki67 expression as a useful marker of breast cancer survival. This is the first report of a large quantitative analysis demonstrating that BTG2 expression is associated with breast cancer patient survival. A portion of the samples demonstrated cell membrane specific expression only, several showed only cytoplasm expression, and many of the samples showed expression in both the cell membrane and the cytoplasm (Figure 1). One sample showed distinct expression of BTG2 in the cytoplasm and cell membrane in one area and in another area BTG2 was exclusively expressed in the cell mem- brane (Figure 2). In previous studies of BTG2, the sub- cellular location of the protein was diverse. The protein has been reported to be located in the cytoplasm [15-17] and in the nucleus [18]. Immunostained lung, kidney and small intestine tissue display cell membrane expression of BTG2 in one report [19]. In the present investigation, we Figure 1 Sub-cellular location of the BTG2 protein in this study. Brown colour represents BTG2 staining. BTG2 protein immunohistochemistry staining using tissue microarrays show exclusive cell membrane specific expression (A), exclusive cytoplasm expression (B), and both cell membrane and cytoplasm expression of BTG2 in the same sample (C).