Small intestine neuroendocrine tumors (SI-NETs) and lung carcinoids (LCs) are relatively indolent tumors, which originate from neuroendocrine (NE) cells of the diffuse NE system. Metastases can spread before diagnosis. Thus, potential cures become unavailable, which entitles new biomarker development. Indeed, we aimed at developing Ma2 autoantibodies and olfactory receptor 51E1 (OR51E1) as potential novel biomarkers and exploring other candidate protein markers in patients’ serum. First, we established a sensitive, specific and reliable anti-Ma2 indirect ELISA to distinguish SI-NET patients from healthy controls. We detected longer progression-free and recurrence-free survivals in patients expressing low anti-Ma2 titers. Moreover, a high anti-Ma2 titer was more sensitive than chromogranin A for the risk of recurrence after radical operation of SI-NET patients. We then investigated OR51E1 expression in SI-NETs and LCs. OR51E1 mRNA expression, analyzed by quantitative real-time PCR, was high in microdissected SI-NET cells, in LC cell lines and in frozen LC specimens. Immunohistochemistry (IHC) showed abundant OR51E1 protein expression in SI-NETs. OR51E1 co-expressed with vesicular-monoamine-transporter-1 in the majority of normal and neoplastic enterochromaffin cells. Furthermore, the study on LCs revealed that OR51E1, somatostatin receptor (SSTR) 2, SSTR3, and SSTR5 are expressed in 85%, 71%, 25% and 39% of typical carcinoids (TCs), whereas in 86%, 79%, 43% and 36% of atypical carcinoids (ACs). Based on the proposed IHC scoring system, in the LC cases, where all SSTR subtypes were absent, membrane OR51E1 expression was detected in 10 out of 17 TCs and 1 out of 2 ACs. Moreover, higher OR51E1 scores were detected in 5 out of 6 OctreoScan-negative LC lesions. In addition, the last presented study used a novel suspension bead array, which targeted 124 unique proteins, by using Human Protein Atlas antibodies, to profile biotinylated serum samples from SI-NET patients and healthy controls. We showed 9 proteins, IGFBP2, IGF1, SHKBP1, ETS1, IL1α, STX2, MAML3, EGR3 and XIAP as significant contributors to tumor classification. In conclusion, we proposed Ma2 autoantibodies as a sensitive circulating marker for SI-NET recurrence; OR51E1 as a candidate therapeutic target for SI-NETs; whereas as a novel diagnostic marker for LCs and 9 serum proteins as novel potential SI-NET markers. / 小肠神经内分泌肿瘤(SI-NET)和肺类癌(LC)是起源于不同神经内分泌细胞的生长缓慢的肿瘤。肿瘤往往于诊断前已经转移。这导致目前缺乏有效的治疗方法，同时也使得对于新的生物标记物的研发变得有意义。因此，我们在本论文中分别研究了Ma2自身抗体(抗Ma2)，以及潜在的新型生物标记物嗅觉受体51E1(OR51E1)。我们还探讨了患者血清中的其他候选蛋白标记物。 首先，我们建立了一个灵敏特异而可靠的抗Ma2间接酶联免疫吸附试验，用以区分SI-NET患者组和健康对照组。在表达低滴度抗Ma2的患者中，我们检测到了较长的病情无恶化存活率以及肿瘤无复发存活率。此外，高滴度抗Ma2比嗜铬粒蛋白A更为灵敏地检测到了SI-NET患者根治手术后复发的风险。     接下来，我们研究了SI-NET和LC患者肿瘤中的OR51E1受体蛋白的表达。我们用实时定量PCR技术检测到了OR51E1信使核糖核酸在显微切除的SI-NET肿瘤细胞中，以及在LC细胞系和冷冻LC标本中的高度表达。免疫组化结果显示出OR51E1蛋白在SI-NET肿瘤组织中的高度表达。OR51E1与囊泡单胺转运蛋白1在大多数正常和肿瘤的肠嗜铬细胞中可共表达。 另外，我们针对LC患者的研究显示，OR51E1受体蛋白以及促生长素抑制素受体(SSTR)2，SSTR3和SSTR5分别在85％，71％，25％和39％的典型性肺类癌(TC)，以及86％，79％，43％和36的非典型性肺类癌(AC)中表达。基于我们我提出的免疫组化结果得分系统，在无SSTR表达的LC中，OR51E1蛋白在17个TC中的10个以及2个AC中的1个中呈细胞膜表达。而且，在6个OctreoScan显象呈阴性的LC中，有5个OR51E1免疫组化得分很高。     此外，在本论文最后的一项研究中，我们采用了一种新型的悬浮磁珠阵列技术，通过使用来自于人类蛋白质图谱项目的针对124种独特蛋白质的抗体，对SI-NET患者和健康对照组的用生物素标记过的血清样本进行了分析。结果显示，通过利用9种蛋白，即IGFBP2，IGF1，SHKBP1，ETS1，STX2，IL1α，MAML3，EGR3和XIAP，我们可以显著的对肿瘤进行分类。     综上所述，我们提出Ma2自身抗体可作为一个体液中灵敏的生物标记物用以暗示SI-NET肿瘤的复发; OR51E1受体蛋白可作为一个在SI-NET治疗中所能用及的候选生物靶分子，并在LC中作为一种新型的潜在生物标记物。此外，我们在SI-NET患者血清中检测到了9种新的候选标记物蛋白。