Antimarker antibodies for the external imaging of gastrointestinal cancer

Abstract

Much effort has been made over the past fifteen or more years to identify a unique cancer antigen, since it has been thought that this could serve as an indicator, or ‘marker’, in the blood for the diagnosis and monitoring of cancer. Such antigens could be restricted to a particular tumor, distributed among tumors of a specific organ or type, or common to a larger group or to all cancer types. They might share characteristics with parts or products of normal adult or of fetal cells, or even of tissues undergoing pathological changes distinct from cancer. Such substances may be secretory products, constituents of the cell surface, of the cytoplasm, or even of the cell nucleus. Examples of all these possibilities exist in the prolific literature of cancer immunology and tumor markers [1,2], and the recent introduction of hybridization techniques for the production of monoclonal antibodies has resulted in the resurgence of interest in thsis area. However, with few exceptions, such as human chorionic gonadotropin for choriocarcinoma, alpha-fetoprotein in the detection of hepatic or testicular cancer, prostatic acid phosphatase in prostatic carcinoma, and specific blood hormone levels for certain endocrine tumors [2], there are none that have the sensitivity or specificity needed for providing a definitive diagnosis of a particular cancer. In general, the major applications of tumor markers have been to determine the extent of disease, i.e., to determine disease recurrence, to evaluate the patient’s response to therapy, and as a prognostic indicator.

Dedicated to Professor Kurt Elster, Bayreuth and Erlangen, Germany, on the occasion of his 65th birthday.