Imaging Liver Cancer Proliferation

 描述（由申请人提供）：肝细胞癌（HCC）是全球癌症死亡的第三大原因。目前在肿瘤学应用中使用的主要PET示踪剂2-[18 F]-氟-2-脱氧-D-葡萄糖（FDG）已被证明对HCC成像无效，因为许多HCC与周围肝组织相比未显示差异性FDG摄取。用PET成像鉴别具有快速生长（增殖）的侵袭性肝脏病变也被证明是困难的，因为主要由于葡萄糖醛酸化（导致高肝脏背景摄取），为增殖成像开发的几种胸苷类似物（胸苷激酶（TK）的所有底物）在肝脏中效果不佳。我们建议研究一种新开发的示踪剂1-（2 '-脱氧-2'-[18 F]-氟-β-D-阿拉伯呋喃糖基）胞嘧啶（[18 F]-FAC，一种对脱氧胞苷激酶（dCK）比TK更具特异性的底物），它显示出较低的肝脏背景吸收。将添加修饰剂四氢尿苷（THU，胞苷脱氨酶（CDA）的抑制剂），以抑制肝脏CDA的酶活性并维持肝脏中的FAC活性。基于令人鼓舞的初步临床前结果和临床生物分布研究，我们计划建立这种[18F]-FAC和THU组合用于HCC增殖的PET成像。我们的中心假设是FAC摄取与HCC中dCK依赖性增殖相关;[18 F]-FAC-PET（THU）可用于识别侵袭性HCC并预测对dCK依赖性治疗的反应。我们将通过以下具体目标来检验这一假设。目标1：使用临床相关的土拨鼠HCC模型确认HCC中[18 F]-FAC摄取的机制;目的2：验证HCC患者中[18 F]-FAC-PET（THU）的摄取;目的3：探索[18 F]-FAC-PET（THU）作为伴随成像生物标志物用于预测新型dCK依赖性治疗（如THU-地西他滨的新型治疗组合）应答的效用。

 DESCRIPTION (provided by applicant): Hepatocellular Carcinoma (HCC) is the third leading cause of cancer deaths worldwide. The main PET tracer currently used in oncology applications, 2-[18F]-fluoro-2-deoxy-D-glucose (FDG), has been shown to be ineffective for imaging HCC since many HCCs do not show differential FDG uptake comparing to the surrounding hepatic tissues. Identification of aggressive liver lesions with rapid growth (proliferation) with PET imaging also proves to be difficult since several thymidine analogs (all substrates of thymidine kinase (TK)) developed for proliferation imaging did not work well in the liver due mainly to glucuronidation, which leads to a high liver background uptake. We propose to investigate a newly developed tracer, 1-(2'-deoxy- 2'-[18F]-fluoro-β-D-arabinofuranosyl)cytosine ([18F]-FAC, a substrate more specific for deoxycytidine kinase (dCK) than for TK), which displays a lower liver background uptake. A modifier, tetrahydrouridine (THU, an inhibitor of cytidine deaminase (CDA)), will be added to suppress enzymatic activity of hepatic CDA and maintain FAC activity in the liver. We plan to establish this [18F]-FAC and THU combination for PET imaging of proliferation in HCC based on encouraging preliminary pre-clinical results and clinical biodistribution studies. Our central hypothesis is that FAC uptak is correlated with dCK-dependent proliferation in HCC; and [18F]-FAC-PET (THU) can be used to identify aggressive HCC and to predict response to dCK-dependent treatment. We will test this hypothesis via the following Specific Aims. Aim 1: To confirm the mechanism of [18F]-FAC uptake in HCC with a clinically relevant woodchuck model of HCC; Aim 2: To validate [18F]-FAC-PET (THU) uptake in patients with HCC; Aim 3: To explore the utility of [18F]-FAC-PET (THU) as a companion imaging biomarker for predicting the response to novel dCK-dependent treatment such as the new therapeutic combination of THU-decitabine.