Pruschy M, Resch H, Shi Y Q, Aalame N, Glanzmann C, Bodis S
Department of Radiation Oncology, University Hospital Zurich, Switzerland.
Br J Cancer. 1999 May;80(5-6):693-8. doi: 10.1038/sj.bjc.6690411.
p53 mutations are among the most common genetic alterations in human cancer and are frequently described in intrinsic or acquired radio- and chemotherapy resistance. Radiation-induced cell kill is not only mediated by DNA damage but also by the activation of signal transduction cascades generated at the plasma membrane like the sphingomyelin pathway. We used genetically defined wild-type p53 or p53-deficient mouse fibrosarcoma cells to investigate the p53-dependence of tumour response upon activation of the sphingomyelin pathway. Treatment of the tumour cells with neutral sphingomyelinase drastically reduced the amount of wild-type p53 fibrosarcoma cell proliferation over 72 h in a clear dose-response (0.2-1.0 U ml(-1) nSMase). Sphingomyelinase had no effect on cell proliferation in tumour cells lacking p53. Similarly, cell proliferation was abolished by C2-ceramide (5-20 microM) only in wild-type p53 cells. FACS-analysis revealed that C2-ceramide induced massive p53-dependent apoptosis (40-50% after 12-24 h) and cell cycle analysis showed a transient G1 arrest in p53-deficient tumour cells 12-24 h after C2-ceramide exposure. These results suggest that ceramide-induced apoptosis in tumour cells can be dependent on the status of p53 and imply that p53 is also important for stress-induced apoptotic signal transduction cascades generated at the plasma membrane.
p53突变是人类癌症中最常见的基因改变之一，并且在内在性或获得性放疗和化疗耐药中经常被描述。辐射诱导的细胞杀伤不仅由DNA损伤介导，还由质膜上产生的信号转导级联反应的激活介导，如鞘磷脂途径。我们使用基因定义的野生型p53或p53缺陷的小鼠纤维肉瘤细胞来研究鞘磷脂途径激活后肿瘤反应对p53的依赖性。用中性鞘磷脂酶处理肿瘤细胞在72小时内显著降低了野生型p53纤维肉瘤细胞的增殖量，呈现明显的剂量反应（0.2 - 1.0 U ml(-1) nSMase）。鞘磷脂酶对缺乏p53的肿瘤细胞的增殖没有影响。同样，仅在野生型p53细胞中，C2 - 神经酰胺（5 - 20 microM）可消除细胞增殖。流式细胞术分析显示，C2 - 神经酰胺诱导大量p53依赖性凋亡（12 - 24小时后为40 - 50%），细胞周期分析显示在C2 - 神经酰胺暴露后12 - 24小时，p53缺陷的肿瘤细胞出现短暂G1期阻滞。这些结果表明，神经酰胺诱导的肿瘤细胞凋亡可能取决于p53的状态，并意味着p53对于质膜上产生的应激诱导凋亡信号转导级联反应也很重要。
