Identification of a New Member of the Ep-CAM (17-1A)Tumor-Associated Antigen Family

The tumor-associated antigen Ep-CAM (17-1A antigen), defined by the murine monoclonal antibody (mAb) 17-1A, has been identified as a 42-kD glycoprotein. The mAb 17-1A has been used for immunotherapy of colorectal cancer. We obtained mAb 19F4 using a synthetic peptide containing antigen determinants of 17-1A antigen. The mAb 19F4 can bind the corresponding dominants of the 17-1A antigen in ELISA. Western-blot analysis demonstrated that mAb 19F4 recognized a 50-kD protein from cell lysates of MCF-7 (breast cancer cell line). Both mAb 19F4 and 17-1A detected a 42-kD protein in the cell lysates of HT-29 (colorectal cancer cell line). The results suggest that new members of the tumor-associated antigen family 17-1A may exist.