CHARACTERIZATION BY SOMATIC-CELL GENETICS OF A MONOCLONAL-ANTIBODY TO THE MDR1 GENE-PRODUCT (P-GLYCOPROTEIN) - DETERMINATION OF P-GLYCOPROTEIN EXPRESSION IN MULTI-DRUG-RESISTANT KB AND CEM CELL VARIANTS

We isolated an IgG(2a) murine monoclonal antibody (MAb) termed MAb57, specifically reactive with multi-drug-resistant (MDR) human cells. Its specificity toward the MDRI gene product (P-glycoprotein) has been demonstrated by the concordant segregation of the MAb57 epitope with the MDRI gene in interspecific mouse x human cell hybrids, and the reactivity of several different MDRI gene-expressing cells with MAb57, particularly insect cells acutely infected with a baculovirus encoding the MDRI gene. MAb57 can be used to detect, by flow cytometry, variations in the relative drug-resistance levels of several MDR KB and CEM cell variants. This immunological probe has also proven useful in selectively destroying MDR target cells in an antibody-dependent cell-mediated (ADCC) assay system as well as in detecting P-glycoprotein expression in normal and malignant tissues and cells.