Yan Ying, Haas John P, Kim Min, Sgagias Magdalene K, Cowan Kenneth H
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
J Biol Chem. 2002 Sep 6;277(36):33422-30. doi: 10.1074/jbc.M201147200. Epub 2002 Jun 24.
Mutation in the BRCA1 gene is associated with an increased risk of breast and ovarian cancer. Recent studies have shown that the BRCA1 gene product may be important in mediating responses to DNA damage and genomic instability. Previous studies have indicated that overexpression of BRCA1 can induce apoptosis or cell cycle arrest at the G(2)/M border in various cell types. Although the activation of JNK kinase has been implicated in BRCA1-induced apoptosis, the role of other members of the mitogen-activated protein kinase family in mediating the cellular response to BRCA1 has not yet been examined. In this study, we monitored the activities of three members of the MAPK family (ERK1/2, JNK, p38) in MCF-7 breast cancer cells and U2OS osteosarcoma cells after their exposure to a recombinant adenovirus expressing wild type BRCA1 (Ad.BRCA1). Overexpression of BRCA1 in MCF-7 cells resulted in arrest at the G(2)/M border; however, BRCA1 expression in U2OS cells induced apoptosis. Although BRCA1 induced JNK activation in both cell lines, there were marked differences in ERK1/2 activation in response to BRCA1 expression in these two cell lines. BRCA1-induced apoptosis in U2OS cells was associated with no activation of ERK1/2. In contrast, BRCA1 expression in MCF-7 cells resulted in the activation of both ERK1/2 and JNK. To directly assess the role of ERK1/2 in determining the cellular response to BRCA1, we used dominant negative mutants of MEK1 as well as MEK1/2 inhibitor PD98059. Our results indicate that inhibition of ERK1/2 activation resulted in increased apoptosis after BRCA1 expression in MCF-7 cells. Furthermore, BRCA1-induced apoptosis involved activation of JNK, induction of Fas-L/Fas interaction, and activation of caspases 8 and 9. The studies presented in this report indicate that the response to BRCA1 expression is determined by the regulation of both the JNK and ERK1/2 signaling pathways in cells.
BRCA1基因的突变与乳腺癌和卵巢癌风险增加相关。最近的研究表明，BRCA1基因产物在介导对DNA损伤和基因组不稳定的反应中可能很重要。先前的研究表明，BRCA1的过表达可在多种细胞类型中诱导凋亡或使细胞周期停滞在G(2)/M边界。虽然JNK激酶的激活与BRCA1诱导的凋亡有关，但丝裂原活化蛋白激酶家族的其他成员在介导细胞对BRCA1的反应中的作用尚未得到研究。在本研究中，我们监测了MCF-7乳腺癌细胞和U2OS骨肉瘤细胞在暴露于表达野生型BRCA1的重组腺病毒（Ad.BRCA1）后，丝裂原活化蛋白激酶家族三个成员（ERK1/2、JNK、p38）的活性。BRCA1在MCF-7细胞中的过表达导致细胞停滞在G(2)/M边界；然而，BRCA1在U2OS细胞中的表达诱导了凋亡。虽然BRCA1在两种细胞系中均诱导了JNK激活，但这两种细胞系中对BRCA1表达的反应在ERK1/2激活方面存在显著差异。BRCA1在U2OS细胞中诱导的凋亡与ERK1/2未激活有关。相反，BRCA1在MCF-7细胞中的表达导致ERK1/2和JNK均激活。为了直接评估ERK1/2在决定细胞对BRCA1反应中的作用，我们使用了MEK1的显性负突变体以及MEK1/2抑制剂PD98059。我们的结果表明，抑制ERK1/2激活导致BRCA1在MCF-7细胞中表达后凋亡增加。此外，BRCA1诱导的凋亡涉及JNK激活、Fas-L/Fas相互作用诱导以及半胱天冬酶8和9的激活。本报告中的研究表明，细胞对BRCA1表达的反应由JNK和ERK1/2信号通路的调节决定。
