Open Access Research article

Prognostic relevance of Bmi-1 expression and autoantibodies in esophageal squamous cell carcinoma

Wan-li Liu1,2†, Xian-zhi Guo3†, Lan-jun Zhang1,4, Jun-ye Wang1,4, Ge Zhang5, Su Guan1,2, Yu-min Chen5, Qing-li Kong1,2, Li-hua Xu1,2, Man-zhi Li1,2, Li-bing Song1,2 and Mu-sheng Zeng1,2*

Author Affiliations

1 Department of Experimental Research, Sun Yat-sen University cancer center, Guangzhou, China

2 State Key Laboratory of Oncology in South China, Guangzhou, China

3 Department of Medical Oncology, The Central Hospital of Xuhui District, Shanghai, China

4 Department of Thoracic Surgery, Sun Yat-sen University cancer center, Guangzhou, China

5 School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China

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BMC Cancer 2010, 10:467 doi:10.1186/1471-2407-10-467

Published: 1 September 2010

Abstract

Background

Overexpression of Bmi-1 has been observed in a variety of cancers, and it has been suggested to be an independent prognostic marker for the patients. The objective of this study was to determine the level of Bmi-1 expression or its autoantibodies in human esophageal squamous cell carcinoma (ESCC) and to correlate it with clinicopathologic data.

Methods

We first examined Bmi-1 expression in ESCC cell lines and tumor samples by RT-PCR and Western blot analysis. We then analyzed Bmi-1 protein expression in 171 clinicopathologically characterized ESCC cases by immunohistochemistry. In addition, we detected its autoantibodies in sera of patients with ESCC by ELISA.

Results

We found that Bmi-1 expression was higher in the immortalized cells, cancer cell lines and most cancer tissue than in non-tumorous control tissue at both mRNA and protein level. In addition, Bmi-1 expression was observed in 64.3% (110 of 171) archive ESCC specimen by immunohistochemistry analysis, and the location of Bmi-1 in ESCC was in the nuclei instead of cytoplasm of tumor cells. There was a significant difference of Bmi-1 expression in patients categorized according to stage (P = 0.003) and pN classification (P = 0.047). Multivariate analysis suggested that Bmi-1 expression was an independent prognostic marker for ESCC patients. A prognostic significance of Bmi-1 was also found in the subgroup of T3~T4 and N1 tumor classification. Bmi-1 autoantibodies were detected in sera of 39.0% (62 of 159) ESCC patients. The correlations between anti-Bmi-1 antibodies and tumor stage (P = 0.040), or lymph node status (P < 0.001) were significant.

Conclusions

Our results suggest that Bmi-1 protein is a valuable marker of ESCC progression. The presence of Bmi-1 autoantibodies in sera from patients with ESCC may have clinical utility in esophageal cancer diagnosis.