Lack of tissue-specificity of mucin markers in a lung-cancer model - biochemical approach.

Mucin-associated epitopes are recognized by monoclonal antibodies in the immunometric assays used for the diagnosis and monitoring of cancer. The recently developed new assays measure mucins as tumor markers, assuming 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 are based on the frequency and the intensity of expression of the single markers for a certain organ. However, this theoretical organ specificity is not absolute, since the mucins are expressed also by tumors other than those mentioned above and they may also be present in inflammatory conditions and in normal tissues. These observations were confirmed by the present study, which used an experimental model consisting of a pool of 20 lung tissue samples (10 normal and 10 cancer). The tissue 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 immunometric assays in mucin fractions separated from the tissue extract by chromatographic methods. The comparison of the chromatographic profiles and the evaluation of the mucin levels in normal and malignant lung tissue specimens confirmed the absence of tissue specificity of these biochemical parameters. Recent developments in molecular biology and the discovery of genes coding for several apomucins may open new perspectives towards the understanding of the mechanisms regulating mucin pathways.