Aberrantly secreted glycoproteins as markers of liver cancer

描述（由申请人提供）：我们与其他人沿着发现，随着肝细胞癌（HCC）的发展，岩藻糖基化水平增加。为了确定这种岩藻糖基化增加的起源，我们对肝癌组织、周围非肿瘤组织进行了N-连接聚糖分析，并将其与来自未患病成人肝脏的组织进行了比较。令人惊讶的是，在三个供体组中没有观察到岩藻糖基化水平的差异，这表明在患有HCC的那些人的血清中观察到的岩藻糖基化水平增加不是癌组织中岩藻糖基化蛋白合成增加的结果。此外，在组织中观察到的岩藻糖基化水平远高于在肝源性血清糖蛋白中观察到的水平。另一方面，与周围组织或非患病肝脏相比，在HCC组织中观察到四触角聚糖水平增加。我们的合作者最近的工作表明，岩藻糖基化控制了糖蛋白的极化分泌，并将其分泌引导到胆汁的顶端。事实上，胆汁糖型比血清中的岩藻糖基化程度更高，与HCC患者血清中观察到的非常相似。我们的假设是，负责我们观察到的分支增加的<$1，6-N-乙酰葡糖胺转移酶V（MGAT-5）的过度表达导致紧密的血胆屏障的丧失和岩藻糖基化蛋白质释放到血液中。这一假设，沿着使用这些知识来寻找新的HCC生物标志物，将在3个目标中进行测试。首先，我们将研究MGAT-5在加强核心岩藻糖基化蛋白的极化分泌中的作用。假设我们在HCC组织中观察到的MGAT-5的过表达导致血胆屏障的缺陷和岩藻糖基化蛋白异常释放到血液中。在具体目标2中，我们将对胆汁进行糖蛋白质组学分析，以获得HCC的标志物。这里的逻辑是，所有肝细胞都有能力分泌到血流或毛细胆管中，最终形成胆管。肝细胞极性的丧失将导致血液中岩藻糖基化蛋白的异常出现。在具体目标3中，我们将在1500例患者的队列中检查我们识别的生物标志物区分HCC患者和肝硬化患者的能力。将确定这些标志物与AFP和其他HCC的潜在生物标志物相比区分HCC与肝硬化的能力。

DESCRIPTION (provided by applicant): We, along with others, have shown increased levels of fucosylation with the development of hepatocellular carcinoma (HCC). In an effort to determine the origin of this increased fucosylation, we have performed N-linked glycan analysis of HCC tissue, the surrounding non tumor tissue, and compared this to tissue from a non-diseased adult liver. Surprisingly, no difference in the level of fucosylation was observed from the three donor groups, suggesting that the increased levels of fucosylation observed in the serum of those with HCC is not the result of increased synthesis of fucosylated proteins in the cancer tissue. In addition, the level of fucosylation observed in tissue was much higher than that observed on liver derived serum glycoproteins. On the other hand, increased levels of a tetra-antennary glycan were observed in the HCC tissue as compared to the surrounding tissue or to the non-diseased livers. Recent work by our collaborator has suggested that fucosylation controls the polarized secretion of glycoproteins and directs their secretion apically into the bil. Indeed, bile glycoforms are more heavily fucosylated than in serum and closely resemble those observed in the serum of HCC patients. It is our hypothesis that the over-expression of ¿ 1,6-N-acetylglucosaminyltransferase V (MGAT-5), which is responsible for the increased branching we have observed, leads to a loss of a tight blood-biliary barrier and the release of fucosylated proteins into the blood. This hypothesis, along with the use of this knowledge to find new biomarkers of HCC, will be tested in 3 aims. First we will examine the role of MGAT-5 in enforcing the polarized secretion of core fucosylated proteins. It is hypothesized that the overexpression of MGAT-5 that we observe in HCC tissue leads to a defect in the blood- biliary barrier and the aberrant release of fucosylated proteins into the blood. In specific aim 2 we will perform glycoproteomic analysis of bile for markers of HCC. The logic here is that all hepatocytes have the ability to secrete into the blood stream or into the bile capillaries, which eventually forms the bile ducts. Loss of hepatocyte polarity will lead to the aberrant appearance of fucosylated proteins in the blood. In specific Aim 3 we will examine the ability of our identifid biomarkers to differentiate patients with HCC from patients with liver cirrhosis in a cohort of 1500 patients. The ability of these markers to distinguish HCC from cirrhosis as compared to AFP and other potential biomarkers of HCC will be determined.