Transforming Growth Factor-β3: A Potential New Regulator of Heparan Sulfate Assembly and Functionality in Cancer

癌症是一个主要的健康问题，是导致死亡的三大原因之一。绝大多数与癌症相关的死亡是由于恶性肿瘤，即肿瘤细胞在不同组织中的侵袭性和系统性扩散。细胞侵袭和扩散与细胞外基质的重塑和细胞-细胞及细胞-基质相互作用的改变相对应。在这种情况下，存在于所有细胞表面和细胞外基质中的硫酸乙酰肝素蛋白多糖起着核心作用。硫酸乙酰肝素蛋白多糖以其高度的结构多样性而闻名，通过与多种特定蛋白质的相互作用来微调生理，并在肿瘤进展的不同方面调节关键的病理生理事件。据报道，几种癌症类型中涉及硫酸乙酰肝素蛋白多糖生物合成和周转的酶的表达发生了变化。然而，人们对调节硫酸乙酰肝素蛋白多糖的可变结构和功能特性的调控因素知之甚少。转化生长因子是恶性疾病的另一个关键因子。根据细胞环境的不同，这一调节细胞因子家族可以在癌前状态通过抑制细胞增殖来发挥肿瘤抑制作用，或者在信号通路失灵时作为肿瘤促进剂发挥作用，从而促进肿瘤的侵袭性。最近，Jeffrey Esko教授的研究小组利用基因打靶在人类黑色素瘤细胞系中进行了成簇的规则间隔短回文重复序列(CRISPR)和CRISPR相关基因9(CRISPR-Cas9)全基因组筛选，发现了转化生长因子β3和硫酸乙酰肝素蛋白多糖表达之间的联系。有趣的是，转化生长因子-β3已被证明调节几种癌症类型的侵袭和转移。因此，我们提出了一种跨学科的研究方法来研究转化生长因子3对硫酸乙酰肝素蛋白多糖形成的影响(I)通过在黑色素瘤和前列腺癌细胞中创建转化生长因子基因敲除突变体，(Ii)通过检测改变转化生长因子3/硫酸乙酰肝素蛋白聚糖轴如何影响蛋白与硫酸乙酰肝素结合和肿瘤生长，以及(Iii)通过研究失活转化生长因子-3如何影响硫酸乙酰肝素蛋白聚糖代谢和介导转化生长因子-β3反应的信号通路。这项拟议的项目旨在确定硫酸乙酰肝素蛋白多糖生物合成响应转化生长因子-β3表达的详细分子机制。这项研究的见解可能会促进更好地理解与癌症中硫酸乙酰肝素蛋白多糖形成变化相关的疾病，这反过来可能会提出改变肿瘤细胞硫酸乙酰肝素蛋白多糖组成和转移潜力的新方法。

Cancer is a major health problem being amongst the top three causes of death. The vast majority of cancer-related deaths occurs due to malignancy, the invasive and systemic spreading of tumor cells in different tissues. Cell invasion and spreading correspond with remodeling of the extracellular matrix and alterations of cell-cell and cell-matrix interactions. In this context, heparan sulfate proteoglycans present on all cell surfaces and in the extracellular matrix play a central role. Heparan sulfate proteoglycans known for their high structural diversity fine-tune physiology through interactions with a multitude of specific proteins and mediate key pathophysiological events during different aspects of tumor progression. Altered expression of enzymes involved in heparan sulfate proteoglycan biosynthesis and turnover have been reported for several cancer types. However, little is known about the regulatory factors that orchestrate the variable structural and functional properties of heparan sulfate proteoglycans. Transforming growth factor-ß (TGF-ß) is another key player in malignant disease. Depending on the cellular context, this family of regulatory cytokines can function as tumor suppressor by inhibiting cell proliferation in the premalignant state or as tumor promotor when the signaling pathway malfunctions, fostering tumor aggressiveness. Recently, a connection between TGF ß3 and heparan sulfate proteoglycan expression was discovered by Prof. Jeffrey Esko's group through a clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated gene 9 (CRISPR-Cas9) genome wide screening using gene targeting in a human melanoma cell line. Interestingly, TGF-ß3 has been shown to modulate invasion and metastasis of several cancer types. We, therefore, propose an interdisciplinary research approach to examine the impact of TGF ß3 on heparan sulfate proteoglycan formation (i) by creating TGF-ß gene knockout mutants in melanoma and prostate cancer cells, (ii) by examining how altering the TGF ß3 / heparan sulfate proteoglycan axis impacts protein binding to heparan sulfate and tumor growth, and (iii) by investigating how inactivation of TGF-ß3 impacts heparan sulfate proteoglycan metabolism and the signaling pathways that mediate TGF-ß3 responses. The proposed project aims to identify the detailed molecular mechanism underlying heparan sulfate proteoglycan biosynthesis in response to TGF-ß3 expression. Insights from this study might foster a better understanding of disorders associated with altered heparan sulfate proteoglycan formation in cancer, which might in turn suggest novel ways to alter heparan sulfate proteoglycan composition and metastatic potential of tumor cells.