Transport properties of the multidrug resistance‐associated protein (MRP) in human tumour cells

Abstract

In this paper we demonstrate that the expression of the multidrug resistance-associated protein (MRP) in a variety of intact human tumour cells results in the ATP-dependent, mutually exclusive extrusion of both the acetoxymethyl ester and the free anion forms of the fluorescent dye calcein, as well as that of a fluorescent pyrenemaleimide-glutathione conjugate. The MRP-dependent transport of all these three model compounds closely correlates with the expression level of MRP and is cross-inhibited by hydrophobic anticancer drugs, by reversing agents for MDR1, and also by compounds not influencing MDR1, such as hydrophobic anions, alkylating agents, and inhibitors of organic anion transporters. Cellular glutathione depletion affects neither the MRP-dependent extrusion of calcein AM or free calcein, nor its modulation by most hydrophobic or anionic compounds, although eliminating the cross-inhibitory effect of glutathione conjugates. These results suggest that the outward pumping of both hydrophobic uncharged and water-soluble anionic compounds, including glutathione conjugates, is an inherent property of MRP, and offer sensitive methods for the functional diagnostics of this transport protein as well as for the rapid screening of drugresistance modulating agents.

Vinblastine and sulfinpyrazone export by the multidrug resistance protein MRP2 is associated with glutathione export

“…These results are in agreement with earlier findings that these compounds are inhibitors of drug transport by MRP1 (Feller et al, 1995;Evers et al, 1996;Holló et al, 1996;Heijn et al, 1997). Benzbromarone also blocked GSH export in the MDCKII-MRP2 cells, and probenecid gave a partial inhibition.…”

MRP proteins as potential mediators of heavy metal resistance in zebrafish cells

“…Previous studies have shown that calcein AM and rhodamine 123 are substrates of some MRP proteins (Dogan et al, 2004;Hollo et al, 1996;Twentyman et al, 1994). Thus, accumulation of these fluorescent substrates in ZF4 cells treated with or without MRP specific inhibitors was determined to address whether ZF4 cells possess MRP-like transport activity.…”

Molecular and functional MDR1‐Pgp and MRPs expression in human glioblastoma multiforme cell lines

“…27,28 Cells were plated onto 24-multiwell plates and were pre-incubated for 30 min without (control) or with 10 M indomethacin or 1 mM probenecid at 37°C in the culture medium. After 30 min, 3 [H]-vincristine or 3 [H]-etoposide was added to the culture medium in order to obtain a final extracellular concentration of 100 nM and 5 M, respectively.…”