Expression of a P-glycoprotein gene is inducible in a multidrug-resistant human leukemia cell line |
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Authors: | V Gekeler G Frese H Diddens H Probst |
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Institution: | 1. Department of Pharmacy, Anhui Provincial Hospital, 17 Lujiang Road, Hefei, Anhui 230001, China;2. Institute for Liver Diseases of Anhui Medical University (AMU), Anhui Institute of Innovative Drugs, Anhui Key Laboratory of Bioactivity of Natural Products, School of Pharmacy, Anhui Medical University, Hefei, Anhui 230032, China |
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Abstract: | A human T lymphoblastoid CCRF-CEM cell line exhibiting cross resistance to a variety of drugs was selected with increasing doses of actinomycin D. A subline, designated CCRF ACTD400+, was permanently cultured in the presence of 400 ng/ml Actinomycin D for several months. Using a fragment of the human mdr1 cDNA we found high expression of a 5 kb mRNA species which was not detectable in the sensitive parental CCRF-CEM cell line. The extent of the mdr-mRNA expression in resistant cells, however, depended on the presence or absence of actinomycin D in the culture medium: when the inhibitor was omitted, the expression decreased to about 60% after one month. In reverse, the steady state level of the P-glycoprotein mRNA increased about 2.5-fold within 72 h after the original dose of the drug was added again. In further experiments we recorded the actinomycin D or adriamycin dose response curves of the variously treated sublines by evaluation of 3H]uridine or 3H]thymidine incorporation, respectively, into acid insoluble material. Consistently, the drug sensitivity of the respective macromolecular synthesis was found to decrease with increasing mdr-mRNA levels. |
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