Classical and novel forms of multidrug-resistance and the physiological functions of p-glycoproteins in mammals

P BORST*, AH SCHINKEL, JJM SMIT, E Wagenaar, L VANDEEMTER, AJ SMITH, EWHM EIJDEMS, F BAAS, GJR ZAMAN

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    166 Citations (Scopus)

    Abstract

    In this paper, we review recent work on multidrug resistance (MDR) in Amsterdam. We have generated mice homozygous for a disruption of one of their P-glycoprotein (Pgp) genes. The mutations do not interfere with viability or fertility, showing that these Pgps have no indispensable role in early development or metabolism. Mice homozygous for a disruption of their mdr2 gene, however, develop liver disease and this appears to be due to their complete inability to secrete phospholipids into bile. This suggests that the mdr2 Pgp (and, by inference, its human MDR 3 homologue) is essential for translocating phospholipids through the hepatocyte canalicular membrane in which this Pgp is located. These and other results show the importance of the genetic approach for studying drug metabolism. MDR is not only caused by increased activity of Pgps. When the human non-small cell lung carcinoma cell line SW-1573 is selected in vitro for low level doxorubicin resistance, the resistant variants are nearly always multidrug resistant, but this is not due to increased Pgp activity. Only when resistance is pushed to higher levels does activation of the MDR1 Pgp gene occur. This suggests that clinically relevant levels of drug resistance in some cells may be caused predominantly by non-Pgp-mediated drug resistance mechanisms. The protein responsible for MDR in the SW-1573 cells has not yet been identified and experiments are in progress to find the gene encoding it.

    Original languageEnglish
    Pages (from-to)289-299
    Number of pages11
    JournalPharmacology & Therapeutics
    Volume60
    Issue number2
    Publication statusPublished - 1993
    Event4th International Symposium on Molecular Aspects of Chemotherapy - GDANSK, Poland
    Duration: 23-Jun-199325-Jun-1993

    Keywords

    • MULTIDRUG RESISTANCE
    • P-GLYCOPROTEINS
    • LIVER DISEASE
    • STEROID METABOLISM
    • BLOOD-BRAIN-BARRIER
    • CANCER CELL-LINES
    • MDR GENE FAMILY
    • DRUG-RESISTANCE
    • ENDOTHELIAL-CELLS
    • COMPLEMENTARY-DNA
    • EXPRESSION
    • TRANSPORTER
    • LIVER
    • TISSUES

    Cite this