BMI1 and urinary bladder cancer: In addtion, in bladder cancers, a significant difference in Bmi-1 protein expression and in mRNA levels was obtained, but Bmi-1 protein was up-regulated to a much greater extent than Bmi-1 mRNA in cancer tissue compared with non-cancerous tissues, implying that the major source of Bmi-1 expression might be dysregulation at the post-transcriptional level in bladder cancers [19].