LACK OF TISSUE-SPECIFICITY OF MUCIN MARKERS IN A LUNG-CANCER MODEL - BIOCHEMICAL APPROACH

Mucin-associated epitopes are recognized by monoclonal antibodies in t he immunometric assays used for the diagnosis and monitoring of cancer . The recently developed new assays measure mucins as tumor markers, a ssuming that each mucin is associated with a particular tumor site, i. e. CA 15.3 and MCA with breast cancer, CA 125 with ovarian cancer, CA 19.9 and CA 195 with colon and pancreatic cancer. These associations a re based on the frequency and the intensity of expression of the singl e markers for a certain organ. However, this theoretical organ specifi city is not absolute, since the mucins are expressed also by tumors ot her than those mentioned above and they may also be present in inflamm atory conditions and in normal tissues. These observations were confir med by the present study, which used an experimental model consisting of a pool of 20 lung tissue samples (10 normal and 10 cancer). The tis sue concentrations of the mucins MCA, CA 15.3, CA 125, CA 19.9, and of the glycoprotein CEA, were measured both in malignant tissue samples and in their normal counterparts. The marker levels were detected by i mmunometric assays in mucin fractions separated from the tissue extrac t by chromatographic methods. The comparison of the chromatographic pr ofiles and the evaluation of the mucin levels in normal and malignant lung tissue specimens confirmed the absence of tissue specificity of t hese biochemical parameters. Recent developments in molecular biology and the discovery of genes coding for several apomucins may open new p erspectives towards the understanding of the mechanisms regulating muc in pathways.