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，是三大死亡原因之一。绝大多数与癌症相关的死亡是由于恶性肿瘤，肿瘤细胞在不同组织中的侵袭性和全身性扩散。细胞的侵袭和扩散与细胞外基质的重塑以及细胞-细胞和细胞-基质相互作用的改变相对应。在这种情况下，硫酸肝素蛋白聚糖存在于所有细胞表面和细胞外基质中起核心作用。硫酸肝素蛋白聚糖以其高结构多样性而闻名，通过与多种特定蛋白质的相互作用微调生理，并在肿瘤进展的不同方面介导关键的病理生理事件。参与硫酸肝素蛋白多糖生物合成和转化的酶的表达改变已经报道了几种癌症类型。然而，关于协调硫酸肝素蛋白聚糖的可变结构和功能特性的调节因素知之甚少。转化生长因子-ß （TGF-ß）是恶性疾病的另一个关键因素。根据细胞环境的不同，这一调节性细胞因子家族可以在癌前状态下通过抑制细胞增殖而发挥肿瘤抑制作用，或者在信号通路发生故障时作为肿瘤启动子，促进肿瘤侵袭性。最近，Jeffrey Esko教授的研究小组通过在人类黑色素瘤细胞系中使用基因靶向技术进行集群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TGF ß3与硫酸肝素蛋白聚糖表达之间存在联系。有趣的是，TGF-ß3已被证明可以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TGF ß3对硫酸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TGF-ß基因敲除突变体，（ii）通过研究改变TGF ß3 /硫酸肝素蛋白多糖轴如何影响蛋白质与硫酸肝素结合和肿瘤生长。（iii）研究TGF-ß3失活如何影响硫酸肝素蛋白多糖代谢和介导TGF-ß3反应的信号通路。本项目旨在确定硫酸肝素蛋白多糖生物合成响应TGF-ß3表达的详细分子机制。这项研究的见解可能有助于更好地理解与癌症中硫酸肝素蛋白聚糖形成改变相关的疾病，这可能反过来提出改变硫酸肝素蛋白聚糖组成和肿瘤细胞转移潜力的新方法。

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.