PATTERNS OF MUCI TISSUE EXPRESSION DEFINED BY AN ANTI MUCI CYTOPLASMIC TAIL MONOCLONAL ANTIBODY IN BREAST CANCER.

MUC I is a highly glycosylated mucin with a large extracellular domain, a transmembrane fraction as well as a 72-aminoacid cytoplasmic tail (CT). The present research was developed to study the pattern of MUC 1 mucin expression in breast carcinoma with an anti MUCI cytoplasmic tail (CT) MAb since it is a reliable indicator of the abundance of cell-associated MUC1. A total of 98 pretreatment tumor samples were obtained from breast cancer patients; all cases were typed as invasive adenocarcinoma; disease staging, histopathological type and grade of differentiation were established. Samples from normal and benign conditions were also included. Immunohistochemistry (IHC) was performed following standard procedures. The pattern of reaction was classified as lineal when the plasmatic membrane was reactive, cytoplasmic and mixed. Subcellular fractions were prepared followed by SDS-PAGE and Western blots analysis. The antibody employed was CT2 monoclonal antibody (MAb) directed against the last 17 aminoacids of the MUCI-CT. IHC showed a high percentage of positive staining in about 90% specimens; frequently, 50% or more tumor cells stained either with a homogeneous distribution, or restricted to some areas of the sample. Benign and normal samples showed a more restrictive pattern usually confined to the plasmatic membrane. By Western blot, subcellular fractions derived from malignant samples showed different bands of reaction at approximately 30 kDa (the most intense), at 60-50 and at 180 kDa. Conclusions: the pattern of expression of MUC I CT in breast epithelium may constitute a better indicator for MUC 1 production since it does not depend on glycosylation. [ABSTRACT FROM AUTHOR]