Kodym Elisabeth, Kodym Reinhard, Choy Hak, Saha Debabrata
Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9183, USA.
Radiat Res. 2008 Jan;169(1):46-58. doi: 10.1667/RR0937.1.
Kodym, E., Kodym, R., Choy, H. and Saha, D. Sustained Metaphase Arrest in Response to Ionizing Radiation in a Non-small Cell Lung Cancer Cell Line. Radiat. Res. 169, 46-58 (2008). In solid tumors, non-apoptotic forms of tumor cell inactivation such as mitotic catastrophe appear to be predominant in the response to DNA-damaging agents. Despite its importance, the underlying molecular mechanisms of mitotic catastrophe have been only partially elucidated. We found that a large fraction of HCC2279 non-small cell lung cancer cells underwent mitotic catastrophe after irradiation. Cells were arrested in metaphase with chromosomal damage indicated by DNA fragments displaced from the metaphase plate and considerable numbers of residual gamma-H2AX foci. Although TP53 was nonfunctional, we detected a prompt radiation response on the level of checkpoint kinases. In contrast, CDC25A was the only checkpoint phosphatase that was responsive to radiation. CDC25B was not detectable, and CDC25C was constitutively phosphorylated at serine 216, leading to its cytoplasmic sequestration and functional inactivation. Therefore, radiation-induced mitotic catastrophe in HCC2279 cells appears to be induced by a combination of relative insufficiencies in the p53-mediated and checkpoint kinase-mediated pathways leading to premature entry into mitosis. Displaced chromosome fragments triggering an intra-M checkpoint in cells entering mitosis presumably result in a sustained metaphase arrest. The phenomenon found in these cells, which were derived directly from a human patient, might be responsible for therapy-induced genetic instability of tumors.
科迪姆，E.，科迪姆，R.，乔伊，H. 和萨哈，D. 非小细胞肺癌细胞系对电离辐射的持续性中期阻滞。《辐射研究》169，46 - 58（2008年）。在实体瘤中，肿瘤细胞失活的非凋亡形式，如有丝分裂灾难，似乎是对DNA损伤剂反应中的主要形式。尽管其很重要，但有丝分裂灾难的潜在分子机制仅得到部分阐明。我们发现，很大一部分HCC2279非小细胞肺癌细胞在照射后发生有丝分裂灾难。细胞停滞在中期，有从中期板移位的DNA片段以及大量残留的γ-H2AX灶表明存在染色体损伤。尽管TP53无功能，但我们在检查点激酶水平检测到了迅速的辐射反应。相比之下，细胞分裂周期蛋白25A（CDC25A）是唯一对辐射有反应的检查点磷酸酶。未检测到细胞分裂周期蛋白25B（CDC25B），并且细胞分裂周期蛋白25C（CDC25C）在丝氨酸216处持续磷酸化，导致其在细胞质中隔离并功能失活。因此，HCC2279细胞中辐射诱导的有丝分裂灾难似乎是由p53介导和检查点激酶介导途径的相对不足共同导致的，这些不足导致过早进入有丝分裂。在进入有丝分裂的细胞中，移位的染色体片段触发了M期内检查点，大概导致了持续性中期阻滞。在这些直接来源于人类患者的细胞中发现的这种现象，可能是肿瘤治疗诱导的基因不稳定的原因。
