IGF I survival effects on p53 induced apoptosis

近年来的研究表明IGF-IR活性与p53功能可能密切相关。这些研究表明，caspase 9的激活是p53作用的关键下游效应，并且caspase 9的激活是p53依赖性细胞死亡所必需的。Caspase 9也是Akt的底物，Akt是一种由igf - 1激活的激酶。Akt磷酸化caspase 9抑制caspase 9活性。因此，IGF-I和Akt可能通过调节caspase抑制953诱导的细胞死亡。我们的实验室有关键的工具来表征IGF-IR和Akt在抑制p53依赖性细胞死亡中的重要性和活性。我们假设阻断igf -1诱导的Akt活性会增加p53下游靶点caspase 9和Apaf-1介导的细胞死亡。在这样做的过程中，我们期望在过度表达Mt p53或mdm-2的乳腺肿瘤细胞中重建对DNA损伤的敏感性，这是与p53依赖细胞死亡相关的特征。我们将从四个方面来实现这一目标。目的1将确定p53诱导的凋亡是否与MCF-7乳腺癌细胞中Apaf-1/Caspase 9 /细胞色素C复合物的形成有关。目的2将确定IGF-IR诱导的Akt是否磷酸化caspase 9，以及caspase 9磷酸化是否抑制p53诱导的细胞凋亡。Aim 3将确定caspase 9和Apaf-1的诱导表达是否会导致过度表达Mt p53或mm -2的MCF-7细胞在照射或顶糖苷处理后死亡。细胞也将用IGF-I处理，以证实IGF-IR的存活效应是通过抑制caspases 9的活性发生的。Aim 43将鉴定不依赖于wt953而导致caspase 9分裂的因子。显然，如果能确定不需要p53就能导致半胱天冬酶裂解的治疗方法，那么在预测药物对乳腺肿瘤中表达Mt p53或过表达mm -2的女性的疗效方面，将具有很大的临床益处。如果caspase 9可以独立于p53发挥作用，这表明缺乏Wt p53的癌细胞可能最终通过靶向下游caspase 9对DNA损伤剂重新敏感。在人类乳腺肿瘤中经常观察到p53功能的丧失或mm -2表达的增加，对这些异常如何影响治疗反应的理解的进展可能对乳腺癌患者具有广泛的意义。抑制igf - 1或Akt的作用可能会提高这些新治疗策略的效率。通过p53下游靶点增强反应和抑制IGF-I对乳腺癌细胞的生存特性是这些进展的基石。

Recent studies suggest that IGF-IR activity and p53 function may be closely related. These studies demonstrate that activation of caspase 9 is a critical downstream effect of p53 action and that caspases 9 activation is required for p53 dependent cell death. Caspase 9 is also a substrate of Akt, a kinase activated by IGF-I. Akt phosphorylation of caspase 9 represses caspase 9 activity. Thus, IGF-I and Akt may inhibit 953 induced cell death via modulation of caspase. Our lab has key tools available to characterize the importance and activity of IGF-IR and Akt in the inhibition of p53 dependent cell death. We hypothesize that blocking IGF-I induced Akt activity will augment cell death mediated by the p53 downstream targets, caspase 9 and Apaf-1. In doing so, we expect to reconstitute sensitivity to DNA damage, a characteristic associated with p53 dependent cell death, in breast tumor cells that overexpress Mt p53 or mdm-2. We will achieve this goal in four Aims. Aim 1 will determine if p53 induced apoptosis is associated with Apaf-1/Caspase 9 /Cytochrome C complex formation in MCF-7 breast cancer cells. Aim 2 will determine if IGF-IR induced Akt phosphorylates caspase 9 and if caspse 9 phosphorylation inhibits p53- induced apoptosis. Aim 3 will determine if inducible expression if caspase 9 and Apaf-1 results in cell death after irradiation or etopside treatment of MCF-7 cells over expressing either Mt p53 or m.m.-2. Cells will also be treated with IGF-I To confirm that IGF-IR survival effects occur through inhibition of caspases 9 activity. Aim 4 3will identify agents that cause caspase 9 cleavage independent of Wt 953. Clearly, if treatments are identified which result in caspase cleavage without the requirement of p53 this would be of great clinical benefit in predicting efficacy of agents in women with breast tumors express Mt p53 or overexpress m.m.-2. If caspase 9 can function independently of p53 this would suggest that cancer cells deficient in Wt p53 may ultimately be resensitized to DNA damaging agents by targeting downstream caspase 9. The loss of p53 function or increased m.m.-2 expression is frequently observed in human breast tumors and advances in the understanding of how these aberrations affect response to treatment are likely to have broad implications to breast cancer patients. Inhibition of IGF-I Or Akt action may well augment the efficiency of these new therapeutic strategies. Enhancing responses through p53 downstream targets and inhibiting IGF-I survival properties on breast cancer cells are cornerstone to these advances.