**6.3 TAG-72**

Immunohistochemical and immunocytochemical techniques have demonstrated preferential expression of TAG-72 known as tumor-associated glycoprotein in breast, gastrointestinal and ovarian adenocarcinomas compared to normal tissues (Denardo, 2005). Antibodies against the TAG-72 antigen particularly B72.3 and chB72.3 were evaluated in patients after careful study in human xenograft mouse models (Lorraine et al., 1998). The TAG-72 target antigen reactive with B72.3 pancarcinoma antibody has been used to target and image breast cancer (Denardo, 2005). CC49, a newer antibody to a different epitope of TAG-72, is a murine IgG1 monoclonal antibody that was labeled with Lutitium-177 by Milenic et al. (Milenic et al., 1991). He found that Lutitium-177 was an attractive alternative radionuclide with a lower energy beta emission and longer half life than 90Y. The images demonstrated the activity uptake at the site of tumor as well as in bone marrow.

#### **6.4 L6**

L6 cell surface antigen is a 24-kDa surface protein containing 3 hydrophobic transmembrane regions that are followed by a hydrophilic region (Richman & Denardo, 2001). L6 antigen is related to a number of cell surface proteins with similar predicted membrane topology that have been implicated in cell growth. L6 antigen is highly expressed in 50% of breast cancer specimens. Two mAb of this family, L6 mAb and the chimeric version (ChL6) have been studied in clinical trials (Denardo et al., 1994). 131I-Chimeric L6 antibody demonstrated therapeutic promise for patients with breast cancer (John et al., 2009).
