Regulation of MDR1 promoter activity in human breast carcinoma cells by protein kinase C isozymes α and θ

被引:60
作者
Gill, PK [1 ]
Gescher, A [1 ]
Gant, TW [1 ]
机构
[1] Univ Leicester, MRC, Toxicol Unit, Leicester LE1 9HN, Leics, England
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 2001年 / 268卷 / 15期
关键词
protein kinase C; multidrug resistance; P-glycoprotein; regulations; transcription;
D O I
10.1046/j.1432-1327.2001.02326.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Increased levels of the protein kinase C (PKC) isoenzymes alpha and theta occur in conjunction with MDR1 gene expression in cells and tissues that have acquired a multidrug resistance (MDR) phenotype. Studies using PKC activators or antisense strategies against PKC suggest that activation of PKC engenders MDR1 gene transcription. In this study the potential roles of PKC-alpha and PKC-theta in MDR1 gene transcriptional regulation were explored. Human-derived MCF-7 breast cancer cells that lack constitutive expression of PKC-alpha or PKC-theta at detectable levels were transfected with full-length PKC-alpha or PKC-theta genes driven by the ecdysone promoter. Stable transfectants were selected by use of the appropriate antibiotics. Treatment of these cells with ponasterone A induced expression of PKC that was catalytically active and underwent translocation and downregulation on exposure to 12-O-tetradecanoyl-13-phorbol acetate (TPA), These cells were used to analyse PKC-mediated regulation of the MDR1 promoter by further transient transfection with either 1073 bp of the MDR1 gene promoter or deletion fragments thereof to -8 bp, each linked to a chloramphenicol acetyl transferase (CAT) reporter gene. In PKC-alpha expressing cells TPA caused activation of all promoter fragments to -29 bp. This finding suggests that TPA-inducible MDR1 transcription mediated through the TPA responsive factor early growth response 1 (EGR-1) in this region of the promoter may be due to activation of PKC-alpha. In contrast, PKC-theta activated only two MDR1 fragments, -982 and -612 bp. The effect of TPA on reporter gene expression was attenuated by the PKC inhibitor GF 109203X. These data suggest that MDR1 promoter transcription can be regulated by PKC-alpha and PKC-theta. The results support the search for therapeutic strategies directed specifically against PKC-theta to ameliorate resistance of tumours against cytotoxic agents.
引用
收藏
页码:4151 / 4157
页数:7
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