BMI1 and gastric cancer: Pearson correlation analysis showed that there was a positive correlation between the expression of Bmi-1 and miR-21 (r = 0.260, P = 0.025) as the expression of miR-21 in gastric cancer tissues with high Bmi-1 expression was higher than that in tissues with low Bmi-1 expression (Fig. 2c), while the expression of miR-34a had no obvious correlation with Bmi-1 level (r = −0.118, P = 0.318) as the expression of miR-34a was not different in gastric cancer tissues with high Bmi-1 expression from tissues with low Bmi-1 expression (Fig. 2d).