Two-stage genome-wide 5-hydroxymethylcytosine (5hmC) reprogramming during colorectal carcinogenesis and liver metastasis

本研究旨在探讨5hmC在结肠癌中的作用。我们已经知道，正常结肠细胞中5hmC的水平比结肠癌细胞高得多，之前对其他癌症的研究表明，刺激细胞产生更多5hmC会导致肿瘤生长缓慢。因此，5hmC被认为是许多癌症的潜在诊断生物标志物。然而，并不是所有癌症的表现都是一样的，对于5hmC的缺失实际上是如何导致结肠癌的，人们仍然知之甚少。我们的目标是确定靶向5hmC是否是治疗结肠癌的一种可行的治疗方案。我们有两个研究目标：1.发现5hmC在结肠癌进展中所起的作用。为了发现5hmC水平的变化如何影响转移，为了第一个目标，我们将研究5hmC功能的两个特定模型。第一个问题是，降低5hmC水平是否会影响RNA的产生方式(“剪接”)。有证据表明，当5hmC存在于剪接位附近时，5hmC有助于成功的剪接，因此，假设当5hmC被移除时，剪接可能发生异常是合乎逻辑的。几种癌症都有一群剪接异常的RNA变种，这些变种可以驱动癌细胞，使它们能够持续分裂并成为侵袭性细胞。第二个模型基于的研究结果表明，5hmC的产生是正常结肠细胞发育所必需的。结肠内排列着一系列名为绒毛的指状突起，在绒毛的底部有一池结肠干细胞，能够发育成成熟的结肠细胞。这些干细胞只有很少的5hmC，当它们发育成形成成熟绒毛的细胞时，就会获得5hmC。结肠癌细胞有许多与结肠干细胞相似的特征，包括缺乏5hmC。因此，我们正在测试5hmC的缺乏是否有助于癌细胞保持干细胞样并持续分裂。对于第二个目标，我们有证据表明，当结肠癌细胞扩散(转移)到肝脏时，5hmC水平实际上可能会增加。在转移过程中，为了迁移到不同的部位，细胞会改变形状。这种形状变化过程与胚胎发育过程中发生的过程相同，当时细胞迁移到不同的区域，以形成各种器官。参与产生5HmC的酶在这一发育过程中起着突出的作用。因此，我们将测试经过治疗产生更多5hmC的肿瘤细胞形成转移肿瘤的能力是增强还是降低。我们还将进行补充分析，看看不能产生5HmC的癌细胞是否会变得更具侵袭性或更少。这项研究的结果将帮助我们了解这种表观遗传标记是如何发挥作用的，并告诉我们，以结肠癌中5hmC水平为靶点是否是一种安全的治疗选择，患者可能从中受益。

This research is designed to investigate the role 5hmC plays in colon cancer. We already know that levels of 5hmC are much higher in normal colon cells than colon cancer cells, and previous research into other cancers has shown that stimulating cells to produce more 5hmC leads to slower tumour growth. 5hmC is therefore seen as a potential diagnostic biomarker for many cancers. However, not all cancers behave identically and there is still very little understanding of how the loss of 5hmC actually contributes to colon cancer. Our goal is to determine whether targeting 5hmC is a viable therapeutic option for treating colon cancer specifically.We have two research objectives:1. To discover what role 5hmC plays during colon cancer progression2. To discover how changes in 5hmC levels affect metastasisFor the first objective we will investigate two specific models for 5hmC function. The first addresses whether reduced levels of 5hmC affect the way RNA is created ("spliced"). There is evidence that when present near the splice sites, 5hmC facilitates successful splicing and it is therefore logical to hypothesise that when 5hmC is removed splicing may occur aberrantly. Several cancers have a population of aberrantly spliced RNA variants that can drive cancer cells and enable them to divide continually and become invasive. The second model is based on findings that have shown that the production of 5hmC is necessary for normal colon cell development. The colon is lined with a series of finger-like projections called villi, at the base of which there is a pool of colon stem cells capable of developing into mature colon cells. These stem cells have very little 5hmC and acquire 5hmC when they develop into the cells that form the mature villi. Colon cancer cells have many similar features to colon stem cells including a lack of 5hmC. Therefore we are testing whether the lack of 5hmC helps cancer cells to remain stem-like and continually divide.For the second objective we have evidence that 5hmC levels might actually increase when colon cancer cells spread ("metastasise") to the liver. During metastasis cells change their shape in order to migrate to different sites. This shape-changing process is the same process that occurs during embryonic development when cells migrate to different regions in order to form various organs. The enzymes involved in producing 5hmC play a prominent role during this developmental process. We will therefore test whether tumour cells that have been treated to produce more 5hmC have an increased or decreased ability to form metastatic tumours. We will also do the complementary analysis to see whether cancer cells with an inability to produce 5hmC can become more or less invasive. The outcome of this research will help us understand how this epigenetic mark works and also tell us whether targeting 5hmC levels in colon cancer is a safe therapeutic option from which patients would be likely to benefit.