IGF I survival effects on p53 induced apoptosis

最近的研究表明，IGF-IR活性和p53功能可能密切相关。 这些研究表明，半胱天冬酶9的活化是p53作用的关键下游效应，并且半胱天冬酶9活化是p53依赖性细胞死亡所必需的。 半胱天冬酶9也是Akt的底物，Akt是由IGF-I激活的激酶。 caspase 9的Akt磷酸化抑制caspase 9的活性。 因此，IGF-I和Akt可以通过调节caspase抑制953诱导的细胞死亡。 我们的实验室有关键的工具可用于表征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-I诱导的Akt活性将增加由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，我们希望重建的敏感性DNA损伤，与p53依赖性细胞死亡，在乳腺癌细胞过度表达Mtp 53或mdm-2。 我们将通过四个目标来实现这一目标。 目的1将确定p53诱导的MCF-7乳腺癌细胞凋亡是否与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是否磷酸化半胱天冬酶9以及半胱天冬酶9磷酸化是否抑制p53诱导的细胞凋亡。 目的3将确定半胱天冬酶9和Apaf-1的诱导表达是否导致过表达Mt p53或m.m.-1的MCF-7细胞在辐射或依托泊苷处理后的细胞死亡。2. 还将用IGF-I处理细胞，以证实IGF-IR存活效应通过抑制半胱天冬酶9活性而发生。 目的4 3将确定代理人引起caspase 9的切割独立的野生型953。 显然，如果鉴定出导致胱天蛋白酶切割而不需要p53的治疗，这将在预测药剂在患有表达Mt p53或过表达m.m.- 2. 如果半胱天冬酶9可以独立于p53发挥作用，这将表明Wt p53缺陷的癌细胞可能最终通过靶向下游半胱天冬酶9而对DNA损伤剂再敏感。 p53功能丧失或m.m.增加- 2的表达经常在人类乳腺肿瘤中观察到，并且在理解这些畸变如何影响对治疗的反应方面的进展可能对乳腺癌患者具有广泛的意义。 IGF-I或Akt作用的抑制可以很好地增强这些新的治疗策略的效率。 通过p53下游靶点增强反应和抑制IGF-I对乳腺癌细胞的存活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.