Carcinoembryonic antigen (CEA) is a 180,000 dalton glycoprotein composed of 50% carbohydrate by weight. It is the most important tumor marker for colonic cancer, and can now be included as one member of a family of gene products which vary in their amino acid sequences, immunological properties, degree of glycosylation, and tissue distribution and expression. Objectives of this research are to investigate the structures of CEA and several of its related antigens by a combination of protein structural, immunological, and molecular cloning studies. The protein studies include chemical deglycosylation, peptide mapping, and microsequence analyses. The immunological studies involve testing of antigens and their fragments with monoclonal antibodies (Mabs) raised to intact and fragmented antigens. The Mabs will be utilized in serum immunoassays for CEA, in in vivo diagnosis of CEA producing tumors, and tested for their utility in therapy. The in vivo diagnosis reagents are DIPA-conjugated, Indium-111 labeled Mabs. The therapeutic DTPA-Mabs are labeled with Yttrium-90. We have also produced and expressed recombinant Mabs and will continue our studies on recombinant, chimeric (mouse-human) antibodies. The molecular cloning studies will focus on identifying CEA in various cDNA libraries cloned into recBC-recipients, and on identifying the CEA gene in a genomic library by the use of long, unique probes based on our amino acid sequence data and expected human codon usage. Once cloned, CEA gene probes will be used to determine the genomic organization of the gene family, and their mRNA levels in various normal and malignant tissues.