Truncated O-glycan-dependent mechanisms inducing metastatic dissemination in pancreatic cancer

胰腺癌(PC)是导致癌症死亡的第四大原因，通常直到确诊后才被诊断出来。 晚期和转移。O-葡聚糖的异常变化，如截短的表达增加 糖类抗原(TN，唾液酸化的TN/STN)常见于PC。然而，机械论 这些截短的O-糖链结构在前列腺癌进展和转移中的作用还没有得到充分的研究。因此， 我们的研究集中在研究截短的O-糖链在早期转移中的机制作用。 在PC上传播。O-糖基转移酶核心1β1，3-半乳糖基转移酶(C1GALT1)催化 在第一糖N-乙酰半乳糖胺中加入半乳糖生物合成粘液型O-葡聚糖的第二步 (TN)形成核心1碳水化合物结构。这种结构通常被拉长为成熟的O-葡聚糖 在正常组织中发现，但在癌症期间，由于不活跃，它们的延伸可能在TN-多糖阶段被截断 C1GALT1活性。我们的初步数据显示，O-糖基转移酶活性C1GALT1在 (低分化的)人类PC组织的子集。此外，PC中基于CRISPR/Cas9的C1GALT1基因敲除(KO) 细胞产生异常的O-糖基化(TN和STN糖链增加)。伴随着糖链的变化 在致癌糖蛋白(粘蛋白糖蛋白和癌症干细胞标记物)上，我们的研究也表明 C1GALT1 KO PC细胞成瘤性和转移性增强。我们还观察到O-葡聚糖的截断 在C1GALT1模型中，存在于肿瘤干细胞标记物CD44上。有趣的是，C1galt1和 KrasG12D和Trp53R172H/+突变导致小鼠早期发病(3周内)和早期远处 PC转移(10周内)。基于这些观察，我们的主要目标是研究 截短型O-糖链在前列腺癌进展和转移中的作用。基于这些观察结果，我们假设 癌症相关糖蛋白(粘蛋白和茎干标志物)上的截短O-糖链诱导早期 胰腺癌进展和转移扩散的开始。为了验证这一假说，以下是 提出了目标。第一个目的是研究C1GALT1的表达和异常对功能的影响 胰腺癌中肿瘤相关糖蛋白的糖基化特征。第二个目标将阐明如何 膜结合粘蛋白和茎标记上的截短O-糖链(如TN和STN)有助于 胰腺癌转移。第三个目标将在体内确定截短的O-葡聚糖在早期的影响 用C1galt1基因敲除KC和KPC小鼠研究胰腺癌转移。拟议的研究将 建立截短的TN和STN糖链的异常表达与差异膜- 结合粘蛋白在前列腺癌进展和转移中的作用。这项研究将对我们的 癌症中的粘蛋白糖生物学知识。总之，这项拟议的研究也将为发展 调节PC膜结合粘蛋白功能的新疗法。

Pancreatic cancer (PC) is the fourth leading cause of cancer death and often goes undiagnosed until it has already advanced and metastasized. Aberrant changes in O-glycans, such as increased expression of truncated carbohydrate antigens (Tn, sialylated Tn/STn), are commonly observed in PC. However, the mechanistic involvement of these truncated O-glycan structures in PC progression and metastasis is under-explored. Hence, our study is focused on investigating the mechanistic role of truncated O-glycans during early metastatic dissemination in PC. The O-glycosyltransferase Core 1 β1,3-Galactosyltransferase (C1GALT1) catalyzes the second step of mucin-type O-glycan biosynthesis by adding galactose to the first sugar N-acetylgalactosamine (Tn) that forms the Core 1 carbohydrate structure. Such structures are usually elongated to mature O-glycans found on normal tissue, but their extension may be truncated at the Tn-glycan stage during cancer due to inactive C1GALT1 activity. Our preliminary data demonstrated the loss of O-glycosyltransferase activity, C1GALT1, in a subset of (poorly differentiated) human PC tissue. Further, CRISPR/Cas9-based C1GALT1 knockout (KO) in PC cells resulted in aberrant O-glycosylation (increased Tn and STn glycans). Along with glycan alterations presented upon oncogenic glycoproteins (mucin glycoproteins and cancer stem cell markers), our studies also indicate increased tumorigenicity and metastasis of C1GALT1 KO PC cells. We have also observed O-glycan truncation present on CD44, a cancer stem cell marker, in C1GALT1 models. Interestingly, knockout of C1galt1 along with KrasG12D and Trp53R172H/+ mutations in mouse models resulted in early-onset (in 3 weeks) and early distant metastasis (in 10 weeks) of PC. Based on these observations, our major goal is to investigate the mechanistic role of truncated O-glycans in PC progression and metastasis. Based on these observations, we hypothesize that "Truncated O-glycans on cancer-associated glycoproteins (mucins and stemness markers) induce the early onset of progression and metastatic dissemination in pancreatic cancer." To test this hypothesis, the following aims are proposed. The first aim will investigate the functional impact of C1GALT1 expression and aberrant glycosylation profile on cancer-associated glycoproteins in pancreatic cancer. The second aim will elucidate how truncated O-glycans (such as Tn and STn) on membrane-bound mucins and stemness markers facilitate pancreatic cancer metastasis. The third aim will determine, in vivo, the impact of truncated O-glycans in the early onset of pancreatic cancer metastasis using C1galt1 knockout KC and KPC mice. The proposed studies will establish the association of aberrant expression of truncated Tn and STn glycans with differential membrane- bound mucin function during PC progression and metastasis. This study will significantly contribute to our knowledge of mucin glycobiology in cancer. Altogether, this proposed study will also pave the way for developing novel therapeutics for modulating membrane-bound mucin function in PC.