Sialylation-dependent mechanisms driving pancreatic cancer progression

摘要 尽管人们几十年前就知道ST6Gal-I唾液酸转移酶在癌症中上调，但有 关于ST6Gal-I在调节肿瘤细胞行为中的功能作用的信息仍然令人震惊地匮乏。 我们小组一直处于鉴定重新编程的特定ST6Gal-I受体底物的前沿 肿瘤细胞发出信号传递干细胞样的转移表型。这些研究表明ST6Gal-I是一名大师 通过唾液酸化控制关键受体功能的调节分子，包括TNFR1、Fas、EGFR 和β-1整合素。该受体共同引导信号级联的激活，促进 标记肿瘤干细胞(CSC)的特性，如侵袭性和抗凋亡。在最近 未发表的工作，我们已经明确确认ST6Gal-I在胰腺导管中的肿瘤驱动作用 腺癌(PDAC)。我们产生了一种新的基因工程小鼠，在 胰腺，并跨越这条线到“KC”胰腺癌模型，该模型含有致癌的K-ras 在胰腺中的表达。与KC小鼠相比，ST6Gal-I过表达的KC小鼠 加速了PDAC的发展、转移和死亡率。我们假设ST6Gal-I活性有助于 在发病机制中的两个关键步骤：(1)腺泡至导管化生(ADM)，这是PDAC启动的早期事件 (目标1)和(2)PDAC转移(目标2)，这是患者死亡的主要原因。在目标1中，我们将 阐明ST6Gal-I促进ADM的分子机制，重点是ST6Gal-I的假说 激活NF-ĸB信号以诱导Sox9的表达。一部强有力的文献已经确立了对 Sox9在ADM中起着重要作用，但ST6Gal-I介导的唾液酸化控制着Sox9 表达表明肿瘤糖基化在PDAC启动中起到了转化作用。重要的是一个 ADM中的ST6Gal-I/NF-ĸB/SOX9信号轴将在(I)规范的266adm细胞模型中进行评估；(Ii) 来自我们的各种小鼠模型的上皮类器官系；以及(Iii)体内ADM模型，导管 结扎和注射雨蛙素。在目标2中，我们将询问唾液酸化依赖的信号机制 将肿瘤细胞重新编程为具有转移能力的CSC样细胞。我们的中心前提是ST6Gal-i- 介导的表皮生长因子受体、肿瘤坏死因子受体1/Fas和β1整合素的唾液酸化是改变信号转导节点的分子开关 这赋予了茎一样的特性。此外，我们将测试改变游戏规则的假设，即外显体 将活性ST6Gal-I转移到受体细胞可以对这些细胞进行重新编程，以获得转移特性。至 验证ST6Gal-I在转移中的因果作用我们将使用生物发光成像来追踪 原位植入PDAC患者器官样物质以及Suit2细胞及其细胞的转移转移 等基因转移克隆。总体而言，这些研究预计将揭示出 肿瘤细胞唾液酸化在推动PDAC进展中的作用。

Summary Although it has been known for decades that the ST6Gal-I sialyltransferase is upregulated in cancer, there is still a striking dearth of information regarding the functional role of ST6Gal-I in regulating tumor cell behavior. Our group has been at the forefront of characterizing the specific ST6Gal-I receptor substrates that reprogram tumor cell signaling to impart a stem-like, metastatic phenotype. These studies implicate ST6Gal-I as a master regulatory molecule that controls the function (via sialylation) of key receptors including TNFR1, Fas, EGFR and β1 integrin. Together this receptor cohort directs the activation of signaling cascades that promote hallmark cancer stem cell (CSC) characteristics such as invasiveness and apoptosis-resistance. In recent unpublished work, we have definitively confirmed a tumor-driver role for ST6Gal-I in pancreatic ductal adenocarcinoma (PDAC). We generated a new genetically engineered mouse with ST6Gal-I overexpression in the pancreas, and crossed this line to the “KC” pancreatic cancer model, which harbors oncogenic K-ras expression in the pancreas. Compared to KC mice, KC mice with ST6Gal-I overexpression have greatly accelerated PDAC development, metastasis, and mortality. We hypothesize that ST6Gal-I activity contributes to two critical steps in pathogenesis: (1) acinar-to-ductal metaplasia (ADM), an early event in PDAC initiation (Aim 1), and (2) PDAC metastasis (Aim 2), which is the chief cause of patient mortality. In Aim 1 we will elucidate molecular mechanisms by which ST6Gal-I promotes ADM, focusing on the hypothesis that ST6Gal-I activates NF-ĸB signaling to induce Sox9 expression. A robust literature has established that upregulation of Sox9 plays an essential role in ADM, however the finding that ST6Gal-I-mediated sialylation controls Sox9 expression points to a transformative role for tumor glycosylation in PDAC initiation. The importance of a ST6Gal-I/NF-ĸB/Sox9 signaling axis in ADM will be evaluated in: (i) the canonical 266-6 ADM cell model; (ii) epithelial organoid lines derived from our various mouse models; and (iii) the in vivo ADM models, ductal ligation and cerulein injection. In Aim 2 we will interrogate the sialylation-dependent signaling mechanisms that reprogram tumor cells into CSC-like cells with metastatic capability. Our central premise is that ST6Gal-I- mediated sialylation of EGFR, TNFR1/Fas, and β1 integrin acts as a molecular switch to alter signaling nodes that confer stem-like properties. Furthermore, we will test the game-changing hypothesis that exosomal transfer of active ST6Gal-I to recipient cells can reprogram these cells to acquire metastatic properties. To verify that ST6Gal-I plays a causal role in metastasis we will use bioluminescence imaging to track the metastatic dissemination of orthotopically implanted PDAC patient organoids, as well as Suit2 cells and their isogenic metastatic clones. In the aggregate, these studies are expected to reveal an unprecedented role for tumor cell sialylation in driving PDAC progression.