Objective  To determine the expression of f Bmi-1, PTEN, and E-cadherin in colorectal cancer, and analyze the correlation among Bmi-1, PTEN and E-cadherin.

  Methods  Western blot analysis was performed to detect Bmi-1 expression in five colorectal cancer biopsies and matched adjacent noncancerous tissues. Real-time reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the protein and mRNA levels of Bmi-1, PTEN, and E-cadherin in 28 colorectal cancer biopsies and matched adjacent non-cancerous tissues. The protein levels of Bmi-1, PTEN, and E-cadherin in 28 paraffin-embedded colorectal cancer tissues were detected via immunohistochemistry. Statistical analysis was performed to evaluate the association among Bmi-1, PTEN, and E-cadherin at both the mRNA level and the protein level.

  Results  Bmi-1 was clearly upregulated in the 5 colorectal cancer biopsies and their matched adjacent non-cancerous tissues. Bmi-1 mRNA was upregulated in 89.3% (25/28) of colorectal cancer biopsies compared with the adjacent noncancerous tissues. PTEN and E-cadherin mRNA were downregulated in 82.1% (23/28) of colorectal cancer biopsies compared with adjacent noncancerous tissues. High Bmi-1 mRNA expression was significantly correlated with low levels of PTEN and E-cadherin mRNA. Immunohistochemistry and statistical analyses revealed that high Bmi-1 protein expression was significantly associated with low levels of PTEN and E-cadherin.

  Conclusion  This study provided evidence of the negative regulation of PTEN and E-cadherin by Bmi-1 at the clinical tissue level. Bmi-1 is a biomarker for colorectal cancer progression and metastasis and may be used as a therapeutic target.