环指蛋白43（RNF43）失活突变在胰腺肿瘤发生中的作用和机制

Pancreatic intraepithelial neoplasia (PanINs), intraductal papillary mucinous neoplasms (IPMN) and mucinous cystic neoplasms (MCN) are pre-neoplastic lesions of pancreatic ductal adenocarcinoma (PDAC). Mechanisms of the pre-neoplatic lesions and their malignant transformation to PDAC are not clear. Even though RNF43 loss of function mutation and KRAS gain of function mutation coexist in tumor tissues of IPMN and MCN patients, the causal relationship between RNF43 mutation and the development of pancreatic tumor and whether there is a synergistic effect of aberrant RNF43 and KRAS on oncogenesis are unknown. To elucidate the role of RNF43 in pancreatic tumorigenesis, we simulated the genetic alterations in patients by constructing a pancreatic Rnf43 knockout; Kras activation mouse model. These mice have shortened survival, higher ratio of pancreas weight to body weight, shorter tumor free time, suggesting that Rnf43 inactivation promotes the progression of Kras-induced pancreatic tumors. In this study, we will establish acute pancreatitis model using pancreatic Rnf43 knockout mice to determine the role of RNF43 deletion in acinar to ductal metaplasia. We will carry out long-term observation and pancreatic tumor pathological analysis of pancreatic Rnf43 knockout; Kras activation mice. Since RNF43 is a negative regulator of Wnt signaling pathway, we will check whether Wnt signaling pathway inhibitor prolongs the survival of these mice. RNA sequencing of pancreas tissue from these mice will be conducted to dissect the potential effectors and elucidate the mechanism of Rnf43 deletion-mediated tumorigenesis. This study may yield putative targets and novel therapeutics for pancreatic tumors with RNF43 mutations.

胰腺上皮内病变、导管内乳头状粘液瘤（IPMN)、粘液性囊腺瘤（MCN）是胰腺导管腺癌的癌前病变，但癌前病变及恶性转化的机理不明确。已知IMPN及MCN同时存在RNF43失活突变和KRAS活化突变，可RNF43缺失与胰腺肿瘤发生发展的因果关系未知，与KRAS活化是否协同效应也不明。为了模拟病人的基因突变，我们构建了胰腺Rnf43敲除;Kras活化小鼠，发现这些小鼠生存期缩短，肿瘤发生时间提前，提示Rnf43失活会促进Kras活化引发的肿瘤发展。为了确定Rnf43缺失在癌前病变中的作用，拟诱发胰腺Rnf43敲除小鼠急性胰腺炎，观察腺泡导管化；对胰腺Rnf43敲除;Kras活化小鼠进行长期观察，病理分析肿瘤组织；由于RNF43负调节Wnt，确定Wnt抑制剂能否治疗肿瘤；对这些胰腺组织进行转录组测序，发现效应分子，阐明Rnf43缺失促进Kras活化胰腺肿瘤的分子机制，发现治疗靶点和相应药物。

随着影像检查的临床广泛应用，在临床上偶然发现的无症状胰腺囊性病变（PCLs）越来越多，其中导管内乳头状粘液瘤（IPMN）偶尔会发展为胰腺导管腺癌（PDAC）。对于医护人员和PCL患者来说，无论是保守监测还是手术干预都是一个困难的临床决定。由于RNF43功能缺失突变和KRAS功能获得突变在IPMN和PDAC中存在交集，我们构建胰腺特异性Rnf43基因敲除和KrasG12D突变小鼠（Rnf43-/-;KrasG12D），模拟人类从胰腺囊肿到癌症的病理过程，探索Rnf43缺失和KrasG12D在胰腺肿瘤前起始和恶性转化中的作用。Rnf43的缺失增强了KrasG12D致癌突变小鼠IPMN和PDAC的发生和严重程度。在胰腺特异性KrasG12D和Rnf43敲除小鼠中，Wnt/β-catenin信号通路被激活，而PORCN抑制剂LGK974阻断了小鼠IPMN的起始和向PDAC的进展。由于IPMN中RNF43和KRAS突变的存在预示着PCL可能向胰腺癌的恶性转化，具有这些基因异常的患者需要监测、手术和/或用Wnt/β-catenin抑制剂靶向治疗。