Isonishi S, Ohkawa K, Tanaka T, Howell S B
Department of Obstetrics/Gynecology, Jikei University School of Medicine, Tokyo, Japan.
Br J Cancer. 2000 Jan;82(1):34-8. doi: 10.1054/bjoc.1999.0873.
Down-regulation of protein kinase C (PKC) by 12-Otetradecanoylphorbol-13-acetate (TPA) enhances the sensitivity of human ovarian carcinoma 2008 cells to various types of platinum compounds such as cisplatin (DDP), carboplatin and (-)-(R)-2-aminomethylpyrrolidine (1,1-cyclobutanedicarboxylato)-platinum(II) monohydrate (DWA) by a factor of two- to threefold. TPA enhanced the sensitivity of the DDP-resistant 2008/C135.25 subline to each of these three drugs to the same extent as for the 2008 cells. The extent of PKC down-regulation and drug sensitization depended on the duration of TPA exposure; maximum effect was achieved with a 48 h pretreatment. Sensitization was TPA concentration-dependent and was maximal at 0.05 microM TPA. 2008 cells expressed only the PKCalpha and PKCzeta isoforms. Western blot analysis revealed that whereas the expression of PKCalpha was reduced by TPA the level of PKCzeta was not affected. These results suggest that PKCalpha is the isotype responsive to TPA in these cells and that platinum drug sensitivity can be modulated by this isoform alone. In parallel to its effect on PKCalpha, TPA decreased cellular glutathione content by 30 +/- 3 (standard deviation (s.d.) % in 2008 cells and by 41 +/- 3 (s.d.) % in 2008/C135.25 cells. TPA also increased accumulation of DDP and DWA by 70%, although this effect was limited to the 2008/C135.25 cells. TPA rendered 2008 and 2008/C135.25 cells resistant to cadmium chloride by a factor of 3.7 and 3.6-fold respectively, suggesting a significant increase in cellular metallothionein content. Although the mechanism of TPA induced sensitization is not yet fully understood, this study points to a central role for PKCalpha in modulating platinum drug sensitivity.
12-十四酰佛波醇-13-乙酸酯(TPA)对蛋白激酶C(PKC)的下调作用使人类卵巢癌2008细胞对多种铂类化合物(如顺铂(DDP)、卡铂和一水合(-)-(R)-2-氨甲基吡咯烷(1,1-环丁烷二羧酸根)铂(II)(DWA))的敏感性提高了两到三倍。TPA使耐DDP的2008/C135.25亚系对这三种药物中每种药物的敏感性提高到与2008细胞相同的程度。PKC下调和药物致敏的程度取决于TPA暴露的持续时间;48小时预处理可达到最大效果。致敏作用呈TPA浓度依赖性,在0.05 microM TPA时达到最大值。2008细胞仅表达PKCalpha和PKCzeta亚型。蛋白质印迹分析显示,虽然TPA可降低PKCalpha的表达,但PKCzeta的水平不受影响。这些结果表明,PKCalpha是这些细胞中对TPA有反应的亚型,并且铂类药物敏感性可仅由该亚型调节。与对PKCalpha的作用并行,TPA使2008细胞中的细胞内谷胱甘肽含量降低30±3(标准差(s.d.)%),使2008/C135.25细胞中的细胞内谷胱甘肽含量降低41±3(s.d.)%。TPA还使DDP和DWA的积累增加70%,尽管这种作用仅限于2008/C135.25细胞。TPA使2008和2008/C135.25细胞对氯化镉的抗性分别提高了3.7倍和3.6倍,表明细胞内金属硫蛋白含量显著增加。虽然TPA诱导致敏的机制尚未完全了解,但本研究指出PKCalpha在调节铂类药物敏感性中起核心作用。