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

Abstract

We isolated an IgG2a 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.

Resistance of HIV-1 to AZT Might Also Involve the Cellular Expression of Multidrug Resistance P-Glycoprotein

“…It can be seen that P-glycoprotein is highly expressed in CEM VBL 100 as compared with the parental CEM line. This result is in keeping with previous observations11~14, 21 plates containing log2 dilution of AZT and VBL starting from 100,000 and 1,000 ng/ml, respectively. After 48 h of culture the relative growth percentage and the IC50 for drug were evaluated as described in methods.…”

Differential Effect of HIV-1 Protease Inhibitors on P-Glycoprotein Function in Multidrug-Resistant Variants of the Human CD4+ T Lymphoblastoid CEM Cell Line

“…The chemosensitization induced by ritonavir, saquinavir and indinavir was also tested in combination with Adriamycin. This anthracycline derivative compound appears to be less cytotoxic than vinblastine if we compare their respective IC50 values [24]. Nevertheless, the cytotoxic activity of Adriamycin significantly increases if MDR cells are simultaneously combined with 10 ÌgWml -1 of ritonavir.…”

“…The study on the modulation of UIC2 epitope, which is associated with the movement of P-glycoprotein during its active drug transporter function, was performed on CEM-VBL10 cells for the following reasons: (1) the relatively low number of Pglycoprotein binding sites/cell (!1W10 4 ) allows one to better appreciate the modulation of the UIC2 epitope [22], (2) this number of P-glycoprotein binding sites/cell is comparable to that calculated on circulating T lymphocytes [23], and (3) the level of P-glycoprotein expression in CEM-VBL10 cells is similar to that observed in specimens from tumors refractory to chemotherapy and showing an acquired or intrinsic MDR phenotype [24,25]. As shown in figure 1, MAb UIC2 binding was increased under physiological conditions (37°C) in the presence of 10 ÌgWml -1 of vinblastine as compared to conventional UIC2 staining in the presence of drug diluent.…”

A Strong Glutathione S-Transferase Inhibitor Overcomes the P-glycoprotein-mediated Resistance in Tumor Cells

“…P-gp Does Not Affect the NBDHEX Efflux-P-gp molecules are undetectable on the parental drug-sensitive cells, although their number progressively increases in MDR variants (11). Because the transmembrane regions of this protein are rich in highly conserved aromatic amino acids residues (17), NBDHEX could fall within the wide range of nonpolar compounds recognized as substrates by this ABC transporter.…”

“…P-gp overexpressing variants, CEM-VBL10 and CEM-VBL100, which show different relative resistance levels to vinblastine (CEM-VBL10 Ͻ10 4 and CEM-VBL100 Ͼ10 6 P-gp molecules per cell) (10,11), and U-2 OS/DX 580 cell lines resistant to doxorubicin (12).…”