The Evaluation Of A Novel Anti-tumor Monoclonal Antibody, WL5, And The Identification And Function Analysis Of Its Target Antigen

The WL5antibody is an anti-colorectal cancer antibody secreted by the WL5hybridoma clone which was established in our lab. In this study, we investigated thespecificity and therapeutic efficacy of WL5antibody. Besides, the target antigen ofWL5antibody was identified and its functional role in cell adhesion and migrationwas researched.Flow cytometric analysis showed that WL5specifically binds to the HT29,LS180and SW620colorectal cancer cell lines. Immunohistochemical analysisperformed on a tissue microarray demonstrated that the WL5antibody could detect9of10colorectal carcinoma tissue samples, while the corresponding tumor-adjacenttissues were negative for WL5staining, indicating a better specificity and sensitivityof the WL5antibody in colorectal carcinoma diagnosis than the CEA antibody whichis used commonly in clinic. Furthermore, WL5could mediate antibody dependentcell-mediated cytotoxicity (ADCC) to kill tumor cells. For tumor-bearing nude mice,the tumor volume has a25%reduction in WL5-treated group, which is a similarantitumor activity as adriamycin (22%reduction). But the WL5-treatment avoided thecardiomyopathy, gastrointestinal mucositisand reduction in peripheral white bloodcell counts associated with prolonged adriamycin treatment. The glycoprotein,carcinoembryonic antigen-related cell adhesion molecule1(CEACAM1), wasidentified as the target antigen of WL5antibody through immunoprecipitation andmass spectrometric analyses, which might provide a potential biomarker andtherapeutic target for colorectal cancer.CEACAM1is a member of the immunoglobulin super family and has beenobserved to have two paradoxical functions: tumor suppression and the promotion oftumor invasion. In the present study, we discovered that CEACAM1functions as anadhesion inhibitor and a migration promoter. The CEACAM1transfected cells, either293-CEACAM1or LOVO/trans-CEACAM1, was proved to have lower adhesion rate.Furthermore, HT29/siRNA-CEACAM1cells had a higher adhesion rate than HT29cells. Additionally,293-CEACAM1LOVO/trans-CEACAM1cells exhibited bettermotility in a trans-well migration assay. N-cadherin expression levels were positively correlated with CEACAM1in293-CEACAM1, LOVO/trans-CEACAM1andHT29/siRNA-CEACAM1cells. When the N-cadherin protein on cell surface wereblocked by a GC-4antibody, the adhesive capacities of293-CEACAM1andLOVO/trans-CEACAM1were recovered and the motilities of them were suppressed,which suggested that CEACAM1functioned through N-cadherin.