BMI1 and cancer: Results showed that the expression of Bmi-1 in cancer tissues is upregulated in 37 cases (50 %) compared with that in paired adjacent normal tissues (Additional file 6: Table S3), and Bmi-1 overexpression positively correlated with depth of invasion (T classification), vascular invasion, or neural invasion as the expression of Bmi-1 was higher in patients with deeper invasion, positive vascular invasion, or neural invasion (Table 2), which suggested that overexpression of Bmi-1 correlated with a more aggressive phenotype in GC.