Krupitza G, Grusch M, Braun K, Fuhrmann G, Steinbrugger R, Hulla W, Simonitsch I, Chott A, Hengstschläger M
Institute of Clinical Pathology, University of Vienna, Gene Environment Interaction, International Agency for Research on Cancer (IACR), F-69372 Lyon, Cedex 08, France.
Cell Death Differ. 1998 Sep;5(9):758-64. doi: 10.1038/sj.cdd.4400417.
Tumor necrosis factor (TNFs) have been shown to be synthesized by ovarian carcinomas, and may therefore affect tumor cells in an autocrine manner. Therefore, we investigated the effects of recombinant TNFs on ovarian carcinoma cells N.1 and examined expression of the proto-oncogenes c-myc and cdc25A which are known to play a prominent role in apoptosis. TNFalpha elicited apoptosis in N.1 cells within 72 h which was shown by typical morphological changes, DNA fragmentation and signature type cleavage of poly(ADP-ribose) polymerase into a 89 kDa proteolytic peptide. TNFalpha-induced apoptosis was accompanied by constitutive c-Myc expression, although the mRNA level of phosphatase cdc25A was suppressed within 24 h of TNFalpha treatment and the protein level decreased after 48 h. Cdc25A tyrosine phosphatase is an activator of the cdk2-cyclin E complex which allows for cell cycle progression. As expected, we found TNFalpha-mediated Cdc25A down-regulation to inhibit Cdk2 activity. Cdc25A suppression was related to TNFalpha-induced apoptosis but not to a TNFalpha-induced G0 arrest because cyclin D1 expression was unaffected and the gene gas6 (growth arrest specific 6) was not induced. Arresting cells by treatment with genistein prevented TNFalpha-triggered apoptosis and inhibited c-myc expression. TNFalpha-induced apoptosis is not accompanied by cell cycle arrest which may be due to constitutive c-Myc expression, although Cdc25A and Cdk2 activity is also down-regulated. High c-Myc and low Cdc25A activity might present conflicting signals to the cell cycle machinery which are incompatible with cell survival.
肿瘤坏死因子（TNFs）已被证明可由卵巢癌合成，因此可能以自分泌方式影响肿瘤细胞。因此，我们研究了重组TNFs对卵巢癌细胞N.1的影响，并检测了原癌基因c-myc和cdc25A的表达，已知这两个基因在细胞凋亡中起重要作用。TNFα在72小时内诱导N.1细胞凋亡，表现为典型的形态学改变、DNA片段化以及聚（ADP-核糖）聚合酶裂解为89 kDa蛋白水解肽的特征性裂解。TNFα诱导的凋亡伴随着c-Myc的组成性表达，尽管在TNFα处理24小时内磷酸酶cdc25A的mRNA水平受到抑制，48小时后蛋白水平下降。Cdc25A酪氨酸磷酸酶是cdk2-细胞周期蛋白E复合物的激活剂，可促进细胞周期进程。正如预期的那样，我们发现TNFα介导的Cdc25A下调抑制了Cdk2活性。Cdc25A的抑制与TNFα诱导的凋亡有关，但与TNFα诱导的G0期停滞无关，因为细胞周期蛋白D1的表达未受影响且未诱导生长停滞特异性6（gas6）基因。用染料木黄酮处理使细胞停滞可防止TNFα触发的凋亡并抑制c-myc表达。TNFα诱导的凋亡不伴有细胞周期停滞，这可能是由于c-Myc的组成性表达，尽管Cdc25A和Cdk2活性也下调。高c-Myc和低Cdc25A活性可能向细胞周期机制发出相互冲突的信号，这与细胞存活不相容。
