Expression of Bmi-1 is a prognostic marker in bladder cancer.
BACKGROUND
The molecular mechanisms of the development and progression of bladder cancer are poorly understood. The objective of this study was to analyze the expression of Bmi-1 protein and its clinical significance in human bladder cancer.


METHODS
We examined the expression of Bmi-1 mRNA and Bmi-1 protein by RT-PCR and Western blot, respectively in 14 paired bladder cancers and the adjacent normal tissues. The expression of Bmi-1 protein in 137 specimens of bladder cancer and 30 specimens of adjacent normal bladder tissue was determined by immunohistochemistry. Statistical analyses were applied to test the relationship between expression of Bmi-1, and clinicopathologic features and prognosis.


RESULTS
Expression of Bmi-1 mRNA and protein was higher in bladder cancers than in the adjacent normal tissues in 14 paired samples (P < 0.01). By immunohistochemical examination, five of 30 adjacent normal bladder specimens (16.7%) versus 75 of 137 bladder cancers (54.3%) showed Bmi-1 protein expression (P < 0.05). Bmi-1 protein expression was intense in 20.6%, 54.3%, and 78.8% of tumors of histopathological stages G1, G2, and G3, respectively (P < 0.05). Expression of Bmi-1 protein was greater in invasive bladder cancers than in superficial bladder cancers (81.5% versus 32.5%, P < 0.05). In invasive bladder cancers, the expression of Bmi-1 protein in progression-free cancers was similar to that of cancers that have progressed (80.0% versus 82.4%, P > 0.5). In superficial bladder cancers, the expression of Bmi-1 protein in recurrent cases was higher than in recurrence-free cases (62.5% versus 13.7%, P < 0.05). Bmi-1 expression was positively correlated with tumor classification and TNM stage (P < 0.05), but not with tumor number (P > 0.05). Five-year survival in the group with higher Bmi-1 expression was 50.8%, while it was 78.5% in the group with lower Bmi-1 expression (P < 0.05). Patients with higher Bmi-1 expression had shorter survival time, whereas patients with lower Bmi-1 expression had longer survival time (P < 0.05).


CONCLUSIONS
Expression of Bmi-1 was greater in bladder cancers than in the adjacent normal tissues. The examination of Bmi-1 protein expression is potentially valuable in prognostic evaluation of bladder cancer.
Qin
Zi-Ke
ZK
State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, PR China. qinzike@263.net
Yang
Jian-An
JA
Ye
Yun-Lin
YL
Zhang
Xing
X
Xu
Li-Hua
LH
Zhou
Fang-Jian
FJ
Han
Hui
H
Liu
Zuo-Wei
ZW
Song
Li-Bing
LB
Zeng
Mu-Sheng
MS
D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D015153:Blotting, Western; D002295:Carcinoma, Transitional Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D016612:Paraffin Embedding; D063150:Polycomb Repressive Complex 1; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate; D001749:Urinary Bladder Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D055815:Young Adult
C069077:BMI1 protein, human; D014408:Biomarkers, Tumor; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1