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

胰腺癌（PC）是癌症死亡的第四大原因，并且通常在已经确诊之前无法诊断。 晚期和转移O-聚糖的异常变化，如截短的 糖抗原（Tn，唾液酸化Tn/STn）通常在PC中观察到。然而，机械 这些截短的O-聚糖结构在PC进展和转移中的参与尚不清楚。因此，我们认为， 我们的研究集中在研究截短的O-聚糖在早期转移性肝癌中的机制作用。 在PC上传播。O-糖基转移酶核心1 β 1，3-半乳糖基转移酶（C1 GALT 1）催化 通过将半乳糖添加至第一糖N-乙酰半乳糖胺的粘蛋白型O-聚糖生物合成的第二步骤 (Tn)形成核心1碳水化合物结构。这样的结构通常被延长为成熟的O-聚糖 在正常组织上发现，但由于非活性的DNA，它们的延伸可能在癌症期间的Tn-聚糖阶段被截短。 C1 GALT 1活性。我们的初步数据表明，O-糖基转移酶活性的损失，C1 GALT 1， （低分化）人类PC组织的子集。此外，PC中基于CRISPR/Cas9的C1 GALT 1敲除（KO） 细胞导致异常的O-糖基化（增加的Tn和STn聚糖）。沿着聚糖改变 我们的研究还表明， C1 GALT 1 KO PC细胞的致瘤性和转移增加。我们还观察到O-聚糖截短 在C1 GALT 1模型中存在于癌症干细胞标志物CD 44上。有趣的是，C1 galt 1的敲除沿着 小鼠模型中的KrasG 12 D和Trp 53 R172 H/+突变导致早发性（3周内）和早期远处转移。 转移（10周内）。基于这些观察，我们的主要目标是研究 截短的O-聚糖在PC进展和转移中的作用。基于这些观察，我们假设 “癌症相关糖蛋白（粘蛋白和干性标记物）上的截短O-聚糖诱导了早期的 胰腺癌进展和转移性播散的发生。“为了验证这一假设， 提出了目标。第一个目的是研究C1 GALT 1表达和异常表达对功能的影响。 胰腺癌中癌症相关糖蛋白的糖基化谱。第二个目标将阐明如何 膜结合粘蛋白上的截短的O-聚糖（如Tn和STn）和干性标记物有助于 胰腺癌转移第三个目标将在体内确定截短的O-聚糖在早期肿瘤中的影响。 使用C1 galt 1敲除KC和KPC小鼠的胰腺癌转移的开始。拟议的研究将 建立截短的Tn和STn聚糖的异常表达与差异性膜- 在PC进展和转移过程中结合粘蛋白的功能。这项研究将大大有助于我们 癌症中粘蛋白糖生物学知识。总而言之，这项拟议的研究也将为发展 用于调节PC中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.