胰腺神经内分泌肿瘤罕见但发病率增加。散发性胰腺神经内分泌肿瘤发病机制不明, 因多数为恶性, 预后较差。目前缺乏可靠的分子标志物判断预后。文献报道PHLDA3基因失活导致小鼠胰岛增生, 然而能否导致胰腺神经内分泌肿瘤发生, 尚无定论。申请人以往的研究发现胰岛素瘤和胃泌素瘤(均为胰腺神经内分泌肿瘤)发生1q31 (含PHLDA3基因) 杂合缺失(LOH)。我们发现该肿瘤PHLDA3蛋白表达下调和肿瘤转移显著相关; 肿瘤中存在基因甲基化。我们敲除大鼠PHLDA3基因发现大鼠胰腺胰岛增生。提示该基因异常和胰腺神经内分泌肿瘤发生有关。本研究目的是明确PHLDA3基因失活能否导致该肿瘤发生, 肿瘤中该基因表达能否判断预后。研究包括：1、建立大鼠PHLDA3基因敲除模型, 观察大鼠能否发生胰腺神经内分泌肿瘤; 二、在300 例肿瘤和对照中检测该基因表达与否和患者的预后关系。

Pancreatic neuroendocrine tumors are rare with the incidence and prevalence increased. The molecular tumorigenesis of sporadic pancreatic neuroendocrine tumors is unknown. The prognosis of the disease is poor due to the malignancy of most tumors. There is a lack of reliable molecular biomarkers for predicting prognosis. It was reported that loss of or inactivation of PHLDA3 gene resulted in hyperplasia of islets in mice, however, it is still uncertain that the gene inactivation would lead to tumorigenesis of pancreatic neuroendocrine tumors. Our previous studies showed that loss of heterozygosity at chromosome 1q31 (including PHLDA3 gene) was found in insulinomas and gastrinomas. Recently, we found that reduced expression of PHLDA3 protein in human pancreatic neuroendocrine tumors was significantly associated with metastasis, and methylation of gene promoter was also found in tumors. We knocked out PHLDA3 gene in rats and found the hyperplasia of islets in rats. These data suggested that abnormality of PHLDA3 gene correlated with pathogenesis of pancreatic neuroendocrine tumors. The aims of present project are to investigate whether inactivation of PHLDA3 gene resulted in tumorigenesis of pancreatic neuroendocrine tumors and to evaluate the prognostic value of gene expression in tumors. We will establish rat models of PHLDA3 knock-out to demonstrate whether pancreatic neuroendocrine tumor occur in rats. Moreover, we also detect the PHLDA3 gene expression in 300 tumor specimens and their control tissues to study the prognostic value of the gene expression in patients with pancreatic neuroendocrine tumor.

胰腺神经内分泌肿瘤发生、发展的分子机制不明, 目前缺乏可靠的预后的分子标志物。本研究的目的旨在探讨PHLDA3基因敲除后能否导致PNETs发生, 从而揭示部分散发性PNETs发生的分子机制。同时明确该基因是否在人类的PNETs中异常和表达缺失，检测该基因的表达是否可以判断PNETs患者的预后。 我们发现PHLDA3基因敲除可导致大鼠胰岛增生, 胰岛显著大于对照组，更为重要的是PHLDA3基因敲除可导致大鼠发生胰腺神经内分泌肿瘤, 而基因野生型的大鼠无肿瘤生成。表明PHLDA3基因是与胰腺神经内分泌肿瘤发生相关的抑癌基因。 该结果未见文献报道。通过免疫组化测定胰腺神经内分泌肿瘤和瘤旁组织中PHLDA3 蛋白的表达, 结合临床资料和患者随访, 发现PHLDA3蛋白表达阴性和胰腺神经内分泌肿瘤患者总生存时间短显著相关 (log rank, P= 0.012), 提示该基因蛋白有可能是潜在的预后分子标志物。此外, 用甲基化特异PCR的方法测定了胰腺神经内分泌肿瘤和瘤旁组织中PHLDA3基因启动子甲基化状态, 发现胰腺神经内分泌肿瘤组织中存在高比例甲基化。 同时我们检测胰腺神经内分泌肿瘤中 PHLDA3基因的染色体杂合缺失(LOH)。 发现26% (9/35) 的胰腺神经内分泌肿瘤发生了LOH。结合动物基因敲除的实验结果和临床研究, 提示PHLDA3基因是与胰腺神经内分泌肿瘤相关的抑癌基因。