Salivary Acinar Cell Apoptosis: Regulation of p53 by Akt

描述(申请人提供)：头颈癌放射治疗后发生的唾液腺功能减退降低了抗癌治疗的效果，降低了这些患者的生活质量。这项应用旨在了解伽玛射线诱导的唾液腺细胞凋亡是否可以被调节以防止唾液腺功能障碍。我们实验室的数据显示，单次5Gy射线照射24小时后，25-30%的唾液腺泡细胞发生了凋亡。在唾液腺中表达活化Akt的转基因小鼠头部和颈部照射后，细胞凋亡和唾液腺功能障碍减少。这些数据表明，细胞凋亡可能导致辐射引起的唾液腺功能障碍。基于这一线索，我们确定了激活Akt的分子是否可以抑制辐射诱导的唾液腺功能障碍。新的数据表明，在辐射前给小鼠注射胰岛素样生长因子-1(IGF-1)可以激活Akt，并抑制辐射小鼠的唾液功能障碍。这是第一次证明，辐射引起的唾液腺功能障碍可以通过简单的预处理来预防。在这项应用中，我们将确定IGF-1预防辐射引起的唾液腺功能障碍的治疗参数。将确定IGF-1重复治疗的剂量、时机和在预防连续照射引起的功能障碍方面的效果。我们已经证明，激活的Akt通过Akt-&gt；MDM2-&gt；p53途径抑制唾液腺泡细胞的凋亡。我们推测IGF-1通过同样的途径抑制唾液腺泡细胞的凋亡。我们建议在体外和体内进行演示。在接受IGF-1治疗和放射治疗之前，将使用组织特异性重组来消除小鼠唾液腺中的MDM2，以确认IGF-1抑制唾液腺功能障碍的途径。我们还推测IGF-1和MYR-Aktl可能通过改变调控细胞凋亡的基因的表达来抑制细胞凋亡。DNA微阵列将被用来识别辐射后IGF-1治疗和MYR-Akt1转基因小鼠唾液腺中表达发生变化的基因。我们可以在体外检测这些候选基因在抑制细胞凋亡中的作用，使用载体过表达这些基因，或者使用siRNA载体来消除这些基因的表达。这些研究将确定使用IGF-1预防唾液腺功能障碍的参数，确定IGF-1抑制唾液腺功能障碍的机制，并确定可用于加强唾液腺免受辐射损伤的新的治疗靶点。临床前动物模型的发展允许开发预防辐射引起的唾液腺功能障碍的治疗方法，这对口腔健康具有重要的临床意义。

DESCRIPTION (provided by applicant): The salivary gland hypofunction that occurs following irradiation for treatment of head and neck cancer decreases the effectiveness of anti-cancer therapies and diminishes the quality of life for these patients. This application is directed towards understanding whether gamma-irradiation induced apoptosis in the salivary gland can be modulated to prevent salivary gland dysfunction. Data from our lab indicate that 25-30% of salivary acinar cells are apoptotic 24 hours post irradiation with a single dose of 5 Gy. Head and neck irradiation of transgenic mice that express activated Akt in the salivary gland results in diminished apoptosis and salivary gland dysfunction following irradiation. These data suggest apoptosis may cause irradiation-induced salivary gland dysfunction. Based upon this lead we determined whether molecules that activate Akt can suppress irradiation-induced salivary gland dysfunction. New data demonstrates that injection of mice with insulin-like growth factor-1 (IGF-1) prior to irradiation activates Akt, and suppresses salivary dysfunction in irradiated mice. This is the first demonstration that irradiation-induced salivary gland dysfunction can be prevented by a simple pretreatment. In this application we will determine the parameters of treatment with IGF-1 that prevent irradiation-induced salivary gland dysfunction. Dose, timing, and the effect of repeated treatment with IGF-1 in preventing dysfunction resulting from serial irradiation will be determined. We have demonstrated that activated Akt suppresses apoptosis of salivary acinar cells by an Akt-> mdm2-> p53 pathway. We posit that IGF-1 suppresses salivary acinar cell apoptosis by this same pathway. We propose to demonstrate in vitro and in vivo. Tissue-specific recombination will be used to eliminate mdm2 from the salivary glands of mice prior to treatment with IGF-1 and irradiation to confirm the pathway by which IGF-1 functions to suppress salivary gland dysfunction. We also posit that IGF-1 and myr-Aktl may suppress apoptosis by altering the expression of genes that regulate apoptosis. DNA microarrays will be used to identify genes whose expression is altered in the salivary glands of IGF-1-treated and myr-Akt1 transgenic mice following irradiation. We can examine the role of these candidate genes in suppressing apoptosis in vitro using vectors to overexpress these genes, or siRNA vectors to eliminate expression of these genes. These studies will establish the parameters for the use of IGF-1 to prevent salivary gland dysfunction, identify the mechanism by which IGF-1 suppresses salivary gland dysfunction, and identify new therapeutic targets that could be used to enhance protection of the salivary gland from -irradiation-induced damage. The development of a pre-clinical animal model that allows development of therapies that prevent irradiation-induced salivary gland dysfunction is great clinical significance to oral health.