Expression of Lewisa, sialyl Lewis3, Lewisx and sialyl Lewisx antigens: DISCUSSION Part 2
Expression of Lea and sialyl Lea antigens in solid tumours as prognostic factors of cancer patients: Sialyl Lea also serves as a ligand for ELAM-1. Tumour cells expressing sialyl Lex and its positional isomer sialyl Lea adhere to interleukin-activated cultured endothelial cells. Takada et al investigated cancer cell lines expressing sialyl Lex and/or sialyl Lea, and found that the degree of adhesion of tumour cells to the endothelium correlated with the degree of sialyl Lex and sialyl Lea expression. This adhesion was significantly inhibited by pretreatment with antibodies to ELAM-1, sialyl Lex or sialyl Lea.
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Although sialyl Lea is expressed on many types of solid tumours, the relation between sialyl Lea expression and metastatic behaviour remains unclear. Recently, Nakayama et al and Asai et al reported that sialyl Lea antigen expression in colorectal tumours, detected immuno-histochemically by monoclonal antibody NS19-9, is a useful marker for evaluating tumour aggressiveness and the prognosis of patients with advanced colorectal cancer. However, the present study failed to prove the prognostic value of sialyl Lea antigen expression in colorectal carcinomas, and the existence of a relation between sialyl Lea antigen expression and the degree of tumour aggressiveness (TNM factors). There are several differences among the study by Nakayama et al, the study by Asai et al and the present study that may explain why different results were obtained. First, each of the three studies used different antibodies. Second, different methodologies of immunohistochemical staining were used. Third, different methods of evaluating monoclonal antibody reactivity were used. However, we believe that different results were obtained in the study by Nakayama et al and the study by Asai et al mainly because different antibodies were used. Monoclonal antibody CSLEA1, which was used in the present study, recognizes the carbohydrate structure of sialyl Lea, as does monoclonal antibody NS19-9. Monoclonal antibody CSLEA1 shows a similar, but not identical, pattern of immunohisto-chemical staining as NS19-9 in colonic, gastric and pancreatic tumours and in normal tissues, ie, CSLEA1 shows a wider range of immunoreactivity.
The relation between sialyl Lea expression, detected im-munohistochemically using monoclonal antibody NS19-9, and metastatic behaviour and subsequent outcome has been reported by Arends et al and Walker and Day. Ar-ends et al reported that the presence of sialyl Lea in gastrointestinal cancers is not correlated with parameters known to be of prognostic significance. Walker and Day found no correlation between the presence of sialyl Lea in breast carcinomas and lymph node status. Thus, the relation between sialyl Lea expression and metastatic behaviour remains unclear, although sialyl Lea is expressed in many types of solid tumours.