Bamberger A M, Bamberger C M, Wald M, Jensen K, Schulte H M
Institute of Hormone and Fertility Research, University of Hamburg, Germany.
Endocrine. 1997 Apr;6(2):111-6. doi: 10.1007/BF02738953.
Protein kinase C (PKc) is a key regulatory enzyme involved in the transduction of extracellular growth signals to the cell nucleus. It occurs in several isoforms, the exact functional roles of which have not been established as yet. The tumor-promoting agent 12-O-tetradecanoyl-phorbol acetate (TPA) is the classic activator of PKC and modulates the activity of the activating protein-1 (AP-1) transcription factor complex via this pathway. AP-1, in turn, induces cell proliferation in many tissues. In the present study, the PKC isoenzyme expression pattern in JEG-3 choriocarcinoma cells was analyzed. The results were compared with those obtained in HEC-1B endometrium adenocarcinoma cells, which had previously been characterized in this respect. To gain insight into the possible functional consequences of different PKC expression patterns, cell proliferation rates and AP-1 activity in response to TPA in both cell lines was studied. Western blot analysis of the PKC isoenzyme expression pattern revealed that JEG-3 cells are deficient in the PKC alpha, delta, and epsilon isoforms. These isoenzymes are strongly expressed in HEC-1B cells, with the alpha and delta being constitutively active. As opposed to HEC-1B cells, JEG-3 cells did not show an enhanced proliferation rate in response to TPA. Furthermore, TPA-treated JEG-3 cells did not exhibit any change in cell shape and refractility as observed in HEC-1B cells. AP-1 activity, as determined by a transfected AP-1-luciferase reporter plasmid, was induced 10-fold by TPA in JEG-3 cells, yet only threefold in HEC-1B cells. It is concluded from these data that differential expression of a subset of PKCs, e.g., the alpha, delta, and epsilon isoforms, may serve as an indicator of the proliferative potential in response to growth factors and mitogens. Furthermore, our data indicate that the inducibility of AP-1 activity does not necessarily reflect the proliferative capacity of a given cell type in response to classical tumor promoters such as phorbol ester.
蛋白激酶C（PKc）是一种关键的调节酶，参与将细胞外生长信号转导至细胞核。它以几种同工型存在，其确切的功能作用尚未完全明确。促癌剂12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）是PKC的经典激活剂，并通过该途径调节激活蛋白-1（AP-1）转录因子复合物的活性。反过来，AP-1在许多组织中诱导细胞增殖。在本研究中，分析了JEG-3绒毛膜癌细胞中PKC同工酶的表达模式。将结果与之前已在此方面进行过特征描述的HEC-1B子宫内膜腺癌细胞的结果进行了比较。为了深入了解不同PKC表达模式可能产生的功能后果，研究了两种细胞系中细胞增殖率以及对TPA的AP-1活性。对PKC同工酶表达模式的蛋白质印迹分析表明，JEG-3细胞缺乏PKCα、δ和ε同工型。这些同工酶在HEC-1B细胞中强烈表达，其中α和δ持续具有活性。与HEC-1B细胞不同，JEG-3细胞对TPA没有表现出增殖率增强。此外，经TPA处理的JEG-3细胞没有表现出如在HEC-1B细胞中观察到的细胞形态和折光性的任何变化。通过转染的AP-1 - 荧光素酶报告质粒测定，TPA在JEG-3细胞中诱导AP-1活性增加10倍，而在HEC-1B细胞中仅增加3倍。从这些数据可以得出结论，PKC的一个子集（例如α、δ和ε同工型）的差异表达可能作为对生长因子和有丝分裂原反应的增殖潜力的指标。此外，我们的数据表明，AP-1活性的诱导性不一定反映给定细胞类型对诸如佛波酯等经典肿瘤启动子的增殖能力。
