Kobayashi T, Ruan S, Jabbur J R, Consoli U, Clodi K, Shiku H, Owen-Schaub L B, Andreeff M, Reed J C, Zhang W
Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas 77030, USA.
Cell Death Differ. 1998 Jul;5(7):584-91. doi: 10.1038/sj.cdd.4400382.
In this study, we examined the effects of radiation and ara-C on induction of apoptosis and on the apoptosis-promoting genes p53, Bax and Fas/APO-1, in BV173 human leukemia cells, which harbor the wild-type p53 gene. It has been reported that p53 upregulates Fas/APO-1 and Bax expression. Both irradiation and ara-C treatment resulted in apoptosis and induction of p53 proteins within hours. The Bax gene was activated in irradiated and ara-C-treated BV173 cells, but Fas/APO-1 was induced only in irradiated BV173 cells. Radiation and ara-C treatment did not induce Bax or Fas/APO-1 protein expression in p53-null HL60 cells. Radiation weakly induced Fas/APO-1 expression in KBM-7 cells, which harbor a partially defective p53 gene. Both HL60 and KBM-7 cells are more resistant to radiation- and ara-C-induced apoptosis than BV173 cells. These results suggest that functional p53 is necessary for the activation of Bax and Fas/APO-1 expression. However, elevated p53 protein is not sufficient to activate Fas/APO-1 gene expression in ara-C-treated cells. Using two-dimensional gel electrophoresis, we found that the p53 proteins in irradiated and ara-C-treated BV173 cells have different isoelectric points; they converged to a single isoelectric point after in vitro treatment with phosphatase. These results suggest that different genotoxic treatments cause different phosphorylations of p53, which may account for the different levels of activation of Fas/APO-1 expression.
在本研究中，我们检测了辐射和阿糖胞苷（ara-C）对携带野生型p53基因的BV173人白血病细胞凋亡诱导以及凋亡促进基因p53、Bax和Fas/APO-1的影响。据报道，p53可上调Fas/APO-1和Bax的表达。辐射和阿糖胞苷处理均在数小时内导致细胞凋亡并诱导p53蛋白的产生。Bax基因在经辐射和阿糖胞苷处理的BV173细胞中被激活，但Fas/APO-1仅在经辐射的BV173细胞中被诱导。辐射和阿糖胞苷处理在p53基因缺失的HL60细胞中未诱导Bax或Fas/APO-1蛋白表达。辐射在携带部分缺陷型p53基因的KBM-7细胞中微弱诱导Fas/APO-1表达。HL60和KBM-7细胞对辐射和阿糖胞苷诱导的凋亡均比BV173细胞更具抗性。这些结果表明功能性p53对于激活Bax和Fas/APO-1表达是必需的。然而，在阿糖胞苷处理的细胞中，p53蛋白水平升高不足以激活Fas/APO-1基因表达。使用二维凝胶电泳，我们发现经辐射和阿糖胞苷处理的BV173细胞中的p53蛋白具有不同的等电点；在用磷酸酶进行体外处理后，它们汇聚到单一等电点。这些结果表明不同的基因毒性处理导致p53发生不同的磷酸化，这可能解释了Fas/APO-1表达的不同激活水平。
