Expression of Bmi-1 protein in tumor tissues is associated with favorable prognosis in breast cancer patients.
OBJECTIVE
Abnormal expression of the cell cycle regulatory protein Bmi-1 has been studied in breast cancer, but the clinical relevance has not been fully elucidated. We studied the expression of Bmi-1 protein in breast cancer patients to define its clinical significance in breast cancer.


METHODS
Tissue microarrays were performed to evaluate the expression of Bmi-1 by immunohistochemistry in tumor tissues from 960 patients with stage I-III breast cancer. We assessed the relationship between the expression of Bmi-1 and pathologic prognostic indices as well as clinical long-term follow up outcome.


RESULTS
Bmi-1 was expressed in 53.2% of breast cancer patients by immunohistochemistry, and the expression of Bmi-1 was significantly correlated with favorable prognostic indices at diagnosis. In univariate analysis, patients with Bmi-1 expression showed favorable relapse-free survival (88.6+/-2.7% vs. 72.3+/-4.3%, P=0.041) and favorable overall survival (93.5+/-2.2% vs. 82.6+/-3.5%, P<0.001) than patients without Bmi-1 expression. According to multivariate analyses, Bmi-1 expression was identified as independent prognostic factor for overall survival with a statistical significance (hazard ratio of Bmi-1 (-) patients compared to Bmi-1 (+) patients, 1.744; 95% CI, 1.013-3.003; P=0.045). This correlation of Bmi-1 expression with favorable overall survival was maintained in patients underwent uniform chemotherapy, regardless of undergoing adjuvant chemotherapy. In a subset analysis according to ER status, Bmi-1 expression associated with favorable overall survival only in ER-positive patients.


CONCLUSIONS
Bmi-1 expression assessed with Immunohistochemistry may be associated with favorable overall survival in breast cancer patients, especially in patients with ER-positive breast cancer.
Choi
Young Jin
YJ
Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Ilwon-dong 50, Gangnam-gu, Seoul 135-710, Korea.
Choi
Yoon La
YL
Cho
Eun Yoon
EY
Shin
Young Kee
YK
Sung
Ki Woong
KW
Hwang
Yu Kyeong
YK
Lee
Sang Jin
SJ
Kong
Gu
G
Lee
Jeong Eon
JE
Kim
Jee Soo
JS
Kim
Jung Han
JH
Yang
Jung-Hyun
JH
Nam
Seok Jin
SJ
D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002453:Cell Cycle; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D009154:Mutation; D009367:Neoplasm Staging; D009687:Nuclear Proteins / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D063150:Polycomb Repressive Complex 1; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016896:Treatment Outcome
C069077:BMI1 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1