Colorectal Cancer
Copyright ©2005 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Jan 21, 2005; 11(3): 344-347
Published online Jan 21, 2005. doi: 10.3748/wjg.v11.i3.344
Expression pattern of epithelial cell adhesion molecule on normal and malignant colon tissues
Xin Xie, Chun-Yan Wang, Yun-Xin Cao, Wei Wang, Ran Zhuang, Li-Hua Chen, Na-Na Dang, Liang Fang, Bo-Quan Jin
Xin Xie, Chun-Yan Wang, Yun-Xin Cao, Wei Wang, Ran Zhuang, Li-Hua Chen, Na-Na Dang, Liang Fang, Bo-Quan Jin, Department of Immunology, Fourth Military Medical University, Xi’an 710032, Shaanxi Province, China
Author contributions: All authors contributed equally to the work.
Supported by the National Key Basic Research Special Funds (NKBRSF), No. 2001CB510004
Correspondence to: Professor Bo-Quan Jin, Department of Immunology, Fourth Military Medical University, Xi’an 710032, Shaanxi Province, China. immu_jin@fmmu.edu.cn
Telephone: +86-29-83374598
Received: April 4, 2004
Revised: April 8, 2004
Accepted: May 13, 2004
Published online: January 21, 2005
Abstract

AIM: To investigate the expression pattern of epithelial cell adhesion molecule (Ep-CAM) on normal and malignant colon tissues to evaluate its diagnostic and therapeutic significance.

METHODS: cDNA encoding Ep-CAM extracellular domain was cloned by reverse transcription-polymerase chain reaction (RT-PCR) from excised malignant colon tissues and inserted into a glutathione S-transferase (GST)-tagged vector. Ep-CAM-GST fusion protein was induced by isopropyl-β-D-thiogalactopyranoside (IPTG) and purified with glutathione-sepharose. The Ep-CAM-GST fusion protein was mixed with Freund’s adjuvant and Balb/c mice were immunized with it. Sp2/0 myeloma cells were fused with the spleen cells of the immunized mice. After having selected by indirect ELISA, the anti-Ep-CAM monoclonal antibodies (MAbs) were generated and the corresponding ascites were obtained. Finally, the human colon carcinoma tissue array prepared from seventy individual patients was stained with the anti-Ep-CAM MAbs.

RESULTS: The isolated Ep-CAM cDNA sequence was identical to the data in GenBank. The expressed fusion protein was almost soluble and had a molecular weight (MW) of 53 ku. Four MAbs against Ep-CAM were obtained and designated as FMU-Ep1, FMU-Ep2, FMU-Ep3 and FMU-Ep4 respectively. Among them, FMU-Ep4 could recognize the natural Ep-CAM on Colo205 and SW480 cells, and all of them could be used for immunohistochemical staining of tissue sections. It was found that Ep-CAM was distributed differently in normal and various malignant colon tissues, including squamous cell carcinoma, signet-ring cell carcinoma and adenocarcinoma. In normal colon gland epithelia, Ep-CAM antigen was mainly distributed on the basolateral membrane and in the region between the basolateral membrane and the cytoplastic part near the nuclei, whereas the expression pattern of colon malignancies was mainly on the whole surface of epithelia and the expression was much higher than the normal colon tissues. The staining pattern of tissue array showed in adenocarcinoma and papillary adenocarcinoma, and the expression of Ep-CAM was increased from grade I to grade III.

CONCLUSION: MAbs against Ep-CAM might be useful for research on the structure and function of Ep-CAM and may have diagnostic and therapeutic value to various colon carcinomas.

Keywords: Colon carcinoma, Colon, Epithelial cell adhesion molecule