Mechanisms Regulating Reversal of Malignancy

描述(由申请人提供)：我们的长期目标是建立逆转创业症的成功治疗方法的潜在机制，识别损害逆转的遗传和分子事件，识别预测性生物标记物，并将结果转化为人。该项目将利用乳腺癌和唾液腺癌的独特条件小鼠模型来确定p53在针对核受体维甲酸X受体α(RXRpha)和过氧化物酶体增殖物激活受体伽马(PPARGamma)的药理分化治疗中的作用。逆转癌前疾病是癌症预防治疗计划的目标之一。早期阻断恶性过程比治疗完全发展甚至可能转移的癌症更可取。这一建议的中心假设是，配体诱导的上皮细胞中RXRpha和PPARGamma的激活可以通过涉及蛋白磷酸酶2A(PP2A)活性下调的再分化过程来推动难治性异型增生的解决。第二个假设是，正常的P53功能参与了RXRpha和/或PPARγ激动剂启动的再分化过程。假说：RXRpha和/或PPARGamma在体内上皮细胞癌中的药理激活导致疾病成功逆转的机制是通过下调PP2Ac、DP-1磷酸化、降低CDK-2、增加p27、增加P53活性和减少细胞外基质中胶原的产生而介导的细胞周期停滞和分化。在ERα阳性的乳腺创业症中被激活的其他机制包括ERα和细胞周期蛋白D1的下调，BRCA1的上调和随着细胞外基质的变化而减少的胶原产生。具体目标：1.测试药物RXRpha和/或PPARγ激动剂单独或联合是否能够通过下调PP2Ac表达并继而获得DP-1磷酸化、CDK-2丢失和p27表达增加来重新分化GRID小鼠难治性发育不良唾液组织。1.b.测试正常的P53表达水平是否有助于这些药物的成功逆转。2.测试药物RXRpha和/或PPARGamma激动剂单独或联合是否通过下调PP2Ac、增加DP-1磷酸化、增加p27和CDK-2和/或通过丢失ERpha、细胞周期蛋白D1和增加BRCA1来重新分化CEM小鼠中表达ERpha的导管增生和DCIS。比较RXRpha和/或PPARγ激动剂与ERpha拮抗剂他莫昔芬和有条件下调ERpha转基因的组织学和分子反应。2.b.检测P53的正常表达是否有助于药物RXR和/或PPARγ激动剂、ERpha拮抗剂他莫昔芬和/或有条件下调ERpha转基因的成功逆转。2.c.测试药物RXRpha和/或PPARGamma激动剂单独或联合使用是否可以预防ERpha导管增生和DCIS的发展。

DESCRIPTION (provided by applicant): Our long-range goal is to establish the mechanisms underlying successful therapeutic approaches to reverse preneoplasia, identify genetic and molecular events that impair reversal, identify predictive biomarkers and translate results to people. This Project will exploit unique conditional mouse models of breast and salivary gland cancer to define the role of p53 in pharmacological differentiation therapies that target nuclear receptors Retinoid X Receptor alpha (RXRalpha) and Peroxisome proliferator-activated receptor gamma (PPARgamma). Reversal of premalignant disease is one goal of cancer prevention treatment programs. Interruption of the malignant process at an early stage is preferable to treating the fully developed and perhaps metastatic cancer. The central hypothesis of this proposal is that ligand induced activation of RXRalpha and PPARgamma in epithelial cells can impel resolution of refractory dysplasia through a re-differentiation process that involves down-regulation of Protein Phosphatase 2A (PP2A) activity. A secondary hypothesis is that normal p53 function contributes to the re-differentiation process initiated by RXRalpha and/or PPARgamma agonists. Hypothesis: The mechanism by which pharmacological activation of RXRalpha and/or PPARgamma in epithelial cell preneoplasia in vivo leads to successful disease reversal is through cell cycle arrest and differentiation mediated by down- regulation of PP2Ac, DP-1 phosphorylation, decreased CDK-2, increased p27, increased p53 activity, and decreased collagen production with changes in the extracelllalr matrix. Additional mechanisms that will be activated in ERalpha positive mammary preneoplasia include down-regulation of ERalpha and cyclin D1, up- regulation of Brca1 and decreased collagen production with changes in the extracellular matrix. Specific Aims: 1. a. Test if pharmacological RXRalpha and/or PPARgamma agonists alone or in combination are able to redifferentiate refractory dysplastic salivary tissue in GRIDS mice through down-regulation of PP2Ac expression with secondary gain of DP-1 phosphorylation, loss of CDK-2, and increased p27 expression. 1. b. Test if normal p53 expression levels contribute to successful reversal by these pharmacological agents. 2. a. Test if pharmacological RXRalpha and/or PPARgamma agonists alone or in combination redifferentiate ERalpha-expressing ductal hyperplasia and DCIS in CERM mice through down-regulation of PP2Ac, gain of DP-1 phosphorylation, increased p27 and loss of CDK-2 and/or through loss of ERalpha, cyclin D1 and increased Brca1. Compare histological and molecular responses to the RXRalpha and/or PPARgamma agonists with the ERalpha antagonist tamoxifen and conditional down-regulation of the ERalpha transgene. 2. b. Test if normal p53 expression contributes to successful reversal by pharmacological RXR and/or PPARgamma agonists, the ERalpha antagonist tamoxifen and/or conditional down-regulation of the ERalpha transgene. 2. c. Test if pharmacological RXRalpha and/or PPARgamma agonists alone or in combination prevent development of ERalpha ductal hyperplasia and DCIS.