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The multidrug resistance‐associated protein (MRP) is over‐expressed and functional in rat hepatoma cells
Author(s) -
Payen Léa,
Courtois Arnaud,
Vernhet Laurent,
Guillouzo André,
Fardel Olivier
Publication year - 1999
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19990505)81:3<479::aid-ijc24>3.0.co;2-s
Subject(s) - efflux , blot , multiple drug resistance , northern blot , calcein , microbiology and biotechnology , multidrug resistance associated proteins , multidrug resistance associated protein 2 , abcc1 , western blot , biology , cell culture , cancer cell , gene expression , transporter , chemistry , biochemistry , drug resistance , cancer , gene , atp binding cassette transporter , genetics , membrane
Expression of multidrug‐resistance‐associated protein (MRP), a drug efflux pump transporting a wide range of xenobiotics, including anti‐cancer drugs and chemical carcinogens, and present at low levels in normal hepatocytes, was investigated in rat hepatoma cells. Northern‐blot analysis allowed detection of high levels of MRP mRNA in rat diethylnitrosamine‐induced hepatocarcinomas when compared with normal liver. Similarly, elevated expression of MRP transcripts were evidenced in 6 rat hepatoma cell lines of different origins, especially in HTC cells, that, in contrast, failed to express mRNA of the canalicular multispecific organic anion transporter (cMOAT), an efflux pump sharing numerous substrates with MRP. HTC cells were also found by Western blotting to display much higher amounts of MRP than those observed in normal hepatocytes. In contrast, the MRP gene copy number was similar both in hepatoma HTC cells and in hepatocytes, as assessed by Southern blotting. Analysis of MRP‐related transport using 3 types of MRP substrates, namely, the fluorescent glutathione‐bimane, the anionic dye calcein and the cationic anti‐cancer drug vincristine, demonstrated that HTC cells displayed cellular efflux of these 3 compounds, an efflux strongly inhibited by MRP modulators such as indomethacin. These results indicate that MRP is over‐expressed and functional in rat hepatoma cells and may therefore be included in the de‐toxifying pathways that are altered during hepatocarcinogenesis and are thus thought to contribute to the known multidrug resistance of liver tumors. Int. J. Cancer 81:479–485, 1999. © 1999 Wiley‐Liss, Inc.