IGF I survival effects on p53 induced apoptosis

最近的研究表明，IGF-IR活性与P53功能可能密切相关。这些研究表明，caspase9的激活是p53作用的关键下游效应，并且caspase9的激活是p53依赖的细胞死亡所必需的。Caspase 9也是Akt的底物，Akt是一种由IGF-I激活的激酶。AKT对caspase 9的磷酸化抑制caspase 9的活性。因此，IGF-I和Akt可能通过调节caspase来抑制953诱导的细胞死亡。我们的实验室拥有关键的工具来表征IGF-IR和Akt在抑制P53依赖的细胞死亡中的重要性和活性。我们推测，阻断IGF-I诱导的Akt活性将增加P53下游靶标caspase 9和APAF-1介导的细胞死亡。通过这样做，我们希望在过度表达mtp53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依赖的细胞死亡相关的特征。我们将通过四个目标实现这一目标。目的1确定P53诱导MCF-7乳腺癌细胞凋亡是否与Apaf-1/Caspase 9/细胞色素C复合体的形成有关。目的2将确定IGF-IR诱导Akt是否使caspase 9磷酸化，以及caspse 9磷酸化是否抑制P53诱导的细胞凋亡。目的3将确定caspase 9和APAF-1的诱导表达是否会导致MCF-7细胞在照射或依托泊苷处理后过度表达mtp53或m.M.-2而导致细胞死亡。细胞也将被IGF-I处理，以确认IGF-IR的生存效应是通过抑制caspase9的活性而发生的。Aim 43将独立于Wt 953鉴定导致caspase 9裂解的因素。显然，如果确定了不需要p53就能导致caspase切割的治疗方法，这将对预测表达mtp53或过表达m.M.-2的乳腺肿瘤药物的疗效有很大的临床益处。如果Caspase 9能够独立于P53发挥作用，这将表明Wt P53缺陷的癌细胞最终可能通过靶向下游的Caspase 9而对DNA损伤剂重新敏感。P53功能丧失或M.M.-2表达增加在人类乳腺肿瘤中经常被观察到，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-I或Akt的作用可能会很好地增强这些新治疗策略的效率。通过P53下游靶点增强反应和抑制乳腺癌细胞的IGF-I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.