RET/PTC Mediated Thyroid Tumorigenesis and NIS Modulation

描述（由申请人提供）：RET/PTC癌基因是RET受体酪氨酸激酶的重排形式，被认为在乳头状甲状腺癌（PTC）的发病机制中起重要作用，特别是在儿科患者和既往放射暴露的患者中。本项目的长期目标是了解RET/PTC癌基因对人PTC肿瘤发生、发展和放射性碘治疗作用的潜在机制。该提案确定了三个具体目标。在目标1中，我们将研究RET/PTC 1在甲状腺肿瘤发生中的发病以及RET/PTC 1在肿瘤维持/进展中的需求。我们正在产生多西环素诱导的甲状腺靶向RET/PTC 1-荧光素酶双转基因小鼠;这样RET/PTC 1表达可以通过给予多西环素来调节，并且甲状腺肿瘤形成可以通过MS 1/2成像进行非侵入性监测。我们假设RET/PTC介导的肿瘤形成是由RET/PTC激活时甲状腺细胞的内在增殖能力调节的。在目标2中，我们将描述NIS通过磷酸化和蛋白复合物形成调节的潜在机制。我们已经确定了四个在体内磷酸化位点在NIS和已证明这四个磷酸化位点在调节NIS活性的可能意义。我们将进一步表征这四个磷酸化位点的功能意义，并确定调节这些磷酸化位点的信号转导/激酶。此外，我们将研究NIS磷酸化和NIS蛋白复合物的差异是否导致NIS细胞表面水平和NIS活性之间的不一致。在目标3中，我们将使用临床前动物模型筛选选择性增加甲状腺肿瘤中放射性碘蓄积的药物，并检查RET/PTC 1对活体动物甲状腺中放射性核素摄取和保留的影响。

DESCRIPTION (provided by applicant): The RET/PTC oncogene, a rearranged form of the RET receptor tyrosine kinase, is believed to play an important role in the pathogenesis of papillary thyroid cancer (PTC), in particular in pediatric patients and those with prior radiation exposure. The long-term goal of the proposed project is to understand the underlying mechanisms of the effects of RET/PTC oncogene on tumorigenesis, progression, and radioiodine therapy of human PTC. In this proposal, three specific aims are identified. In Aim 1, we will investigate the onset of RET/PTC1 in thyroid tumorigenesis and the requirement of RET/PTC1 in tumor maintenance/ progression. We are generating doxycycline-inducible thyroid-targeted RET/PTC 1-luciferase bi-transgenic mice; such that RET/PTC1 expression can be modulated by administration of doxycycline and thyroid tumor formation can be non-invasively monitored by MS¿1/2 imaging. We hypothesize that RET/PTC mediated tumor formation is modulated by the intrinsic proliferation capacity of thyrocytes at the time of RET/PTC activation. In Aim 2, we will delineate the underlying mechanisms of NIS modulation by phosphorylation and protein complex formation. We have identified four in vivo phosphorylation sites in NIS and have demonstrated possible significance of these four phosphorylation sites in modulating NIS activity. We will further characterize the functional significance of these four phosphorylation sites and identify signaling/kinases that modulate these phosphorylation sites. In addition, we will examine whether differences in NIS phosphorylation and NIS protein complexes contribute to the discordance between NIS cell surface levels and NIS activity. In Aim 3, we will screen for agents that selectively increase radioiodine accumulation in thyroid tumors using a pre-clinical animal model and examine RET/PTC1 effects on radionuclide uptake and retention in the thyroid of live animals.