免疫治疗分子标记 PD-1 Blockade in Tumors with Mismatch-Repair Deficiency-新英格兰

PD-1 与PD-l1相关的免疫治疗的疗效与肿瘤的somatic突变个数相关,也与肿瘤的Mismatch-Repair gene的沉默突变相关。
PD-1 Blockade in Tumors with Mismatch-Repair Deficiency

BACKGROUND

Somatic mutations have the potential to encode “non-self” immunogenic antigens. We hypothesized that tumors with a large number of somatic mutations due to mismatch-repair defects may be susceptible to immune checkpoint blockade.

METHODS

We conducted a phase 2 study to evaluate the clinical activity of pembrolizumab, an anti–programmed death 1 immune checkpoint inhibitor, in 41 patients with progressive metastatic carcinoma with or without mismatch-repair deficiency. Pem- brolizumab was administered intravenously at a dose of 10 mg per kilogram of body weight every 14 days in patients with mismatch repair–deficient colorectal cancers, patients with mismatch repair–proficient colorectal cancers, and patients with mis- match repair–deficient cancers that were not colorectal. The coprimary end points were the immune-related objective response rate and the 20-week immune-related progression-free survival rate.

RESULTS

The immune-related objective response rate and immune-related progression-free sur- vival rate were 40% (4 of 10 patients) and 78% (7 of 9 patients), respectively, for mis- match repair–deficient colorectal cancers and 0% (0 of 18 patients) and 11% (2 of 18 patients) for mismatch repair–proficient colorectal cancers. The median progres- sion-free survival and overall survival were not reached in the cohort with mismatch repair–deficient colorectal cancer but were 2.2 and 5.0 months, respectively, in the cohort with mismatch repair–proficient colorectal cancer (hazard ratio for disease progression or death, 0.10 [P<0.001], and hazard ratio for death, 0.22 [P=0.05]). Pa- tients with mismatch repair–deficient noncolorectal cancer had responses similar to those of patients with mismatch repair–deficient colorectal cancer (immune-related objective response rate, 71% [5 of 7 patients]; immune-related progression-free sur- vival rate, 67% [4 of 6 patients]). Whole-exome sequencing revealed a mean of 1782 somatic mutations per tumor in mismatch repair–deficient tumors, as compared with 73 in mismatch repair–proficient tumors (P=0.007), and high somatic mutation loads were associated with prolonged progression-free survival (P=0.02).

CONCLUSIONS

This study showed that mismatch-repair status predicted clinical benefit of immune checkpoint blockade with pembrolizumab. (Funded by Johns Hopkins University and others; ClinicalTrials.gov number,NCT01876511.)

参考文献:

PD-1_Blockade_in_Tumors_with_Mismatch-Repair_Deficiency
First Study Evaluating DNA Mismatch Repair as Genetic Guide for Immunotherapy Treatment with Merck’s
New Test May Identify Best Patients for Immunotherapy | Medpage Today

基因失活后,肺腺癌变肺鳞癌

这是一个谈“癌”色变的年代。肺癌堪称癌症“头号杀手”,其五年存活率仅为15%,且发病率和致死率历来一直高居恶性肿瘤榜首。在我国,每年约有40万人死于肺癌;卫生部门公布的第三次死因调查结果显示,肺癌导致的死亡人数在过去三十年中上升了465%。

根据病理学分类,肺癌大致可以分为小细胞肺癌和非小细胞肺癌;顾名思义,显微镜下观察组织切片会发现前者的细胞个头较小,而后者较大。非小细胞肺癌是肺癌的主要类型(约占肺癌的85%),其中又包括腺癌、鳞癌、腺鳞癌和大细胞癌等不同亚型。虽然都属于非小细胞肺癌,但腺癌和鳞癌具有不同的发病过程和病理学特征,而且对某些药物或治疗手段也有着不同的响应效果。

具体到某个特定肺癌患者身上,为了更好地治疗,需要弄明白这个患者是什么肺癌亚型,癌细胞发生了哪些基因突变,有什么药物是专门针对这些突变的,用药后癌细胞会不会又发生变化导致耐药?这些都是研究者关注的热点问题。

利用DNA测序技术,科学家们目前已经发现多个参与肺癌发病的驱动基因(Driver Gene)突变,包括KRAS, EGFR, LKB1等。临床上,携带EGFR突变的肺癌患者可以使用小分子化合物或抗体药物进行靶向治疗。遗憾的是,超过20%的非小细胞肺癌患者携带的是LKB1基因的失活型(缺失)突变,而且目前对这类患者尚无针对性的治疗策略。

5月1日,季红斌研究组对LKB1基因的最新研究作为封面文章(Cover Story)发表在国际肿瘤学权威学术杂志《癌症细胞(Cancer Cell)》上。封面图就是我们这个研究的隐喻——《西游记》中,被擒的孙悟空在太上老君的炼丹炉中被困49天,但依然大难不死,还练就了火眼金睛。而缺失LKB1的肺腺癌,在高活性氧簇(Reactive Oxygen Species,以下简称ROS)的恶劣环境中依然拥有超强的可塑性,甚至还能变身成鳞癌,与孙猴子的情形何其相似。

Image2—600.jpg当期《Cancer Cell》封面,孙悟空在“高氧”炼丹炉里呆过后,不但没死,还练就了火眼金睛。图片来源:李福明
LKB1:帮细胞在逆境存活的抑癌基因

LKB1基因具有两大功能:作为经典的防癌卫士(抑癌基因),它可以抑制细胞增殖和阻止肿瘤发展;当环境压力较大,细胞感到“饥饿”时,它又能使细胞合理控制营养摄取、维持代谢和氧化还原稳态。

当LKB1发生缺失突变,肺癌细胞就摆脱了LKB1的束缚,有了快速增殖的能力,然而,LKB1缺失后,癌细胞也随之失去了在营养匮乏的逆境中的适应能力。那么问题来了,缺失LKB1的肺癌细胞如何处理这一矛盾,在逆境中生存下来呢?

我们打算先在小鼠身上看看,除去了LKB1基因后,肺癌的发病过程究竟是怎样的。

如今,利用基因工程技术,我们可以在实验小鼠的肺泡细胞中改造LKB1或其它基因使其产生肿瘤。出乎意料的是,在不同的肺癌小鼠模型中,我们得到的结果不太一样。在Kras/Lkb1小鼠模型中,敲除LKB1不仅大大加速肿瘤进展,还使小鼠同时产生腺癌、鳞癌和腺鳞癌,而其它模型如Kras或Kras/p53小鼠,却只产生腺癌。
肺癌细胞的生存之道:穷则变,变则通

我们发现,Kras/Lkb1小鼠之所以会同时产生腺癌、鳞癌和腺鳞癌,其实是LKB1缺失引起了肿瘤可塑性 (Tumor Plasticity),导致腺癌向鳞癌发生转变。我们推测,这种肿瘤可塑性可能是缺失LKB1的肺腺癌细胞适应逆境生存的一种方式。

于是,我们借助基因芯片和高效液相色谱串联质谱分析,比较了Kras/Lkb1小鼠肺腺癌细胞和鳞癌细胞中的代谢指标,发现腺癌细胞确含有较高水平的活性氧簇(即ROS)。ROS包括超氧离子和过氧化氢等,它的异常积累会导致DNA受到氧化性损伤、加速细胞衰老甚至肿瘤发展。事实上,降低腺癌中的ROS水平会抑制其向鳞癌的转变。由此可见,ROS的积累给腺癌细胞带来了“危机”,它却像孙猴子一样摇身一变,成了鳞癌,并因此谋取了另一条“活路”。

Image 1 provided by Prof. Ji Hongbin’s group.png

活性氧簇水平上升促使缺失LKB1的腺癌逐渐转化为鳞癌 图片来源:李福明

为什么腺癌细胞会积累更多的ROS?同样跟LKB1基因的缺失有关。正常情况下,细胞可通过戊糖磷酸途径和脂肪酸氧化这两条代谢通路及时清除ROS并维持氧化还原态的平衡;脂肪酸氧化直接受LKB1“领导”:LKB1的缺失可导致其“消极怠工”,至于戊糖磷酸途径的活性在营养匮乏时则会下调。我们发现这两条代谢通路的活性在肺腺癌中显著下降,这就是导致ROS积累的“罪魁祸首”,恢复这两条通路的活性,就可以抑制腺癌转变为鳞癌。
寻找耐药肺癌的治疗之道

我们的肺癌小鼠模型还有另一个重要应用——开展临床前试验(Preclinical Trials)来评价某些药物或治疗策略的有效性和安全性。

我们在Kras/Lkb1小鼠模型中发现,荜茇酰胺(Piperlongumine)和苯乙双胍(Phenformin)这两种药物对缺失LKB1的肺腺癌有一定的疗效,对鳞癌却没有作用。因为这些药物可诱导ROS的积累,ROS又会促使一部分腺癌转变为鳞癌并最终产生耐药性。

由此看来,腺癌的“变身术”不仅能使自己度过“ROS危机”,更能逃脱一些药物的杀伤作用。这暗示临床上携带LKB1突变的肺腺癌有可能通过转变为肺鳞癌来逃脱某些药物治疗,这可能是一种全新的耐药方式。试想一下,一种针对肺腺癌的药物刚开始或许还有用,时间一长,当肺腺癌变成肺鳞癌之后,药物就失效了,这时或许就需要及时更换另一种针对肺鳞癌的药物。

目前,我们正在继续深入研究,希望早日找到更有效的策略来治疗缺失LKB1的肺癌,给这只大闹天宫的“孙猴子”戴上“紧箍咒”! (编辑:游识猷)

原始文献
Li, Fuming, Xiangkun Han, Fei Li, Rui Wang, Hui Wang, Yijun Gao, Xujun Wang et al. “LKB1 Inactivation Elicits a Redox Imbalance to Modulate Non-small Cell Lung Cancer Plasticity and Therapeutic Response.” Cancer Cell (2015).

ahuizotl基因进行细胞选择延长苍蝇寿命

据科学日报报道,瑞士伯尔尼大学的科研小组通过激活摧毁不健康细胞的基因,极大的延长了果蝇的生命周期。这 一结果或开启人类抗衰老研究的新可能性。长生不老一直是人类的梦想。例如,在古代神话里,永生是区别人类和神的特征之一。近期,试图延长人类寿命的生物研 究主要使用的是老鼠或者苍蝇的生物体模型。瑞士伯尔尼大学细胞生物学学院的爱德华多•莫雷诺(Eduardo Moreno)带领的研究人员小组提出了一个新方法延长苍蝇的寿命,它是基于对苍蝇体内最好细胞的优先选择来实现。这项研究被发表在期刊《细胞学》上。

The scientists found that a gene called ahuizotl, or ‘azot’ acts like a sort of cellular quality control, helping to weed out unhealthy or malfunctioning cells. Fruit flies, like the one pictured, were given an extra copy of this gene that targets unhealthy cells. During tests the flies lived 60% longer lives

Read more: http://www.dailymail.co.uk/sciencetech/article-2913648/Have-scientists-Elixir-Youth-Gene-destroys-unhealthy-cells-extend-life-flies-60-cent.html#ixzz3PKxvicN4
Immortality has long been a dream for humans. For example, in many ancient mythologies, immortality is one of the traits that distinguishes humans from the gods. More recently, biological research has tried to prolong human lifespan using model organisms such as mice or flies. Researchers at the Institute of Cell Biology from the University of Bern in Switzerland, led by Eduardo Moreno, have developed a new method to extend lifespan of flies based on improved selection of the best cells within the body. Their work appeared in the journal Cell.
“Our bodies are composed of several trillion cells,” explains Moreno, “and during aging those cells accumulate random errors due to stress or external insults, like UV-light from the sun.” But those errors do not affect all cells at the same time and with the same intensity: “Because some cells are more affected than others, we reasoned that selecting the less affected cells and eliminating the damaged ones could be a good strategy to maintain tissue health and therefore delay aging and prolong lifespan.”
A cellular quality control mechanism
To test their hypothesis, the researchers used Drosophila melanogaster flies. The first challenge was to find out which cells within the organs of Drosophila were healthier. Morenos team identified a gene which was activated in less healthy cells. They called the gene ahuizotl (azot) after a mythological Aztec creature selectively targeting fishing boats to protect the fish population of lakes, because the function of the gene was also to selectively target less healthy or less fit cells to protect the integrity and health of the organs like the brain or the gut.
Normally, there are two copies of this gene in each cell. By inserting a third copy, the researchers were able to select better cells more efficiently. The consequences of this improved cell quality control mechanism were, according to Moreno, “very exciting”: The flies appeared to maintain tissue health better, aged slower and had longer lifespans. “Our flies had median lifespans 50 to 60 percent longer than normal flies,” said Christa Rhiner, one of the authors of the study.
Could azot also slow down the human aging process?
However, the potential of the results goes beyond creating Methuselah flies, the researchers say: Because the gene azot is conserved in humans, this opens the possibility that selecting the healthier or fitter cells within organs could in the future be used as an anti aging mechanism. For example, it could prevent neuro- and tissue degeneration produced in our bodies over time.

瑞士伯尔尼大学爱德华多•莫雷诺的研究小组提出了一个新方法延长苍蝇的寿命

“我 们的身体是由几万亿个细胞组成,” 莫雷诺解释道。“在衰老过程中,这些细胞会积累因压力或外界刺激,例如太阳的紫外线光,而产生的随机错误。”但这些细胞并不会以相同的程度同时影响所有细 胞。“有些细胞比其它细胞更容易受到影响,我们由此推断选择影响较小的细胞,并消灭受损细胞应该是维持组织健康从而延缓衰老和延长寿命的好策略。”

细胞质量控制机制

为 了测试他们的假说,研究人员使用了黑腹果蝇(Drosophila melanogaster)作为实验对象。第一个面临的挑战便是找出黑腹果蝇器官里更健康的细胞。莫雷诺研究小组鉴别了在不那么健康的细胞里激活的基因, 他们将这个基因称为水猴ahuizotl(azot),以中美洲神话中的食人水怪Aztec为名,这个神话生物会选择性的攻击渔船以保护湖泊里的鱼类,而 这一基因的功能也是选择性的攻击不那么健康或者不太合适的细胞以保护器官,例如大脑和内脏的完整性和健康。

正 常来说,每一个细胞里有这个基因的两份副本。通过插入第三份副本,研究人员能够更高效的选择更好的细胞。莫雷诺表示这个改善细胞质量控制机制“令人感到兴 奋”,苍蝇似乎能够更好的维持组织健康,衰老的更慢,且具有更长的寿命。“我们的苍蝇的寿命比正常苍蝇长了50%至60%,”研究合作作者之一、伯尔尼大 学细胞生物学讲师克里斯塔•莱茵(Christa Rhiner)博士这样说道。

Azot是否也能减缓人类衰老过程?

然而,这一结果的潜在可能性远不止如此,研究人员表示由于人类体内也保存有Azot,这开启了一种新的可能性:也即在未来将选择更健康或者更合适的细胞作为一种抗衰老机制。例如,它可以预防人类身体随着衰老而产生的神经或者组织恶化。

Refereance:

Elimination of Unfit Cells Maintains Tissue Health and Prolongs Lifespan

Highlights
•Fitness-based cell culling maintains tissue health
•Azot ensures the elimination of less fit cells
•Lack of azot accelerates tissue degeneration
•Improving the efficiency of cell selection extends lifespan
Summary
Viable yet damaged cells can accumulate during development and aging. Although eliminating those cells may benefit organ function, identification of this less fit cell population remains challenging. Previously, we identified a molecular mechanism, based on “fitness fingerprints” displayed on cell membranes, which allows direct fitness comparison among cells in Drosophila. Here, we study the physiological consequences of efficient cell selection for the whole organism. We find that fitness-based cell culling is naturally used to maintain tissue health, delay aging, and extend lifespan in Drosophila. We identify a gene, azot, which ensures the elimination of less fit cells. Lack of azot increases morphological malformations and susceptibility to random mutations and accelerates tissue degeneration. On the contrary, improving the efficiency of cell selection is beneficial for tissue health and extends lifespan.

 

Science:定向深度测序技术让致病突变无处可逃

今年8月,美国波士顿儿童医院的科研人员在一项研究中深入检测了临床基因测试无法确认病因的158名脑畸形患者的DNA。在高灵敏度测序的帮助下,研究团队发现了只在每个人很少一部分细胞中发生的8个致病基因突变。对于传统基因诊断测试来说,它们实在是太过于微小。

这 类细胞基因变异又称嵌合突变,存在于每个人的身体中,并且早就为人所熟知。不过现在,基因技术使得“抓获”在少部分细胞中存在的特定突变成为可能。10 月,国立卫生研究院(NIH)将开始评审旨在寻找脑组织中基因变异的基金申请,而这有可能帮助解释一些神经精神病学疾病。同时,随着研究人员发现更多关于 嵌合突变的案例,他们正在怀疑到底有多少与基因相关的病因还保持着隐身状态,即使是面对最好的临床测试。

在 过去,基因疾病研究一直关注的是通过生殖细胞系遗传下来的突变,其被看作是身为携带者的父母或卵子和精子形成过程中发生基因错误而留下的“遗产”。一旦胚 胎开始发育,每次细胞分裂时基因错误都有可能发生。NIH国家基因组研究所遗传学家Leslie Biesecker介绍说,由于随后细胞会增殖并扩展它们的突变,因此每个身体都成为一种“微型进化试验场”。拥有特定突变的细胞数量取决于这些突变发生 的时间和地点以及其改变细胞功能的方式。很多这样的突变都是良性的,但有些会引发疾病。

对 于引发疾病的嵌合突变的系统寻找才刚刚开始。Biesecker表示,这种现象在有些病例中很明显。例如,对于多发性骨纤维营养不良症,异常细胞会通过一 个人皮肤上的斑块或形状表现出来。不过,任何一种基因疾病都可能与嵌合突变有关。研究表明,从多发性骨纤维营养不良症,到血友病和心律失常,嵌合突变会在 几十种条件下发生。

在一些疾病如唐氏综合征中,相较于影响全身细胞的突变,嵌合突变产生的症状要轻一些。还有一些如大脑过分发育导致的巨脑畸形综合征,胚系突变总是致命的。根据一项最新研究,甚至很少量的变异细胞就足以引发损害人身心健康的症状。

找到这些稀有的突变并非易事。为检测某一特定基因或完整基因组,研究人员通常从大量细胞中提取DNA,然后对其进行多次测序。从这些反复测定的序列中,测序仪基本上会就DNA链上每个碱基的可能身份达成共识。

为 从普通基因组中检测到突变,研究人员不得不增加测定的序列数量。然而,尽管DNA测序变得快速和廉价,但在测序覆盖度(一个基因组有多少碱基被测定)和深 度(基因组中每个碱基被测定的次数)之间出现了权衡问题。波士顿儿童医院神经学家和遗传学家Christopher Walsh介绍说,在全基因组测序中,通常会测定50~60次。只在很少一部分测定序列中出现的突变,会被看作测序仪固有误差率的一部分,而非取样细胞间 DNA序列上的真实差异。

这 就是Walsh和同事最近在研究脑畸形患者时所做的事情。引发脑畸形的已知遗传因素中,没有一个出现在标准临床测试中。然而,针对少数候选基因区域进行的 平均300次深度测序,使该研究团队有能力辨别那些被误认为测序错误的突变。在8个突变中,有5个只在非常少量的细胞中出现,以至于利用仍是验证突变“黄 金标准”的传统桑格DNA测序完全检测不到它们。8月,该研究团队在《新英格兰医学杂志》上发表了相关成果。Walsh表示,深度测序或许最终可以让科学 家找到隐藏在一些慢性神经疾病,如智障和自闭症背后的基因嵌合突变。

寻 找嵌合突变的其他研究人员正在追求一种更加灵敏和有针对性的方法,即基于聚合酶链反应(PCR)的技术,它能探测只在不到1%的细胞中存在的突变。该类测 试只会显示其在设计时指向的某个单一突变,而不是一个特定基因所有的变异。不过,在一项针对拥有基因疾病儿童的健康父母的最新研究中,一种类似的PCR方 法被证实可以显示很多突变。

起 初,这些父母的基因突变被检测为阴性,而在孩子的所有细胞中都检测到了突变。但领导该项研究的贝勒医学院遗传学家Pawel Stankiewicz介绍说,在4%的病例中,少量亲代细胞含有突变,而它们也有可能出现在卵子或精子中。相关成果曾在7月份在线发表于《美国人类遗传 学杂志》。然而,当基因实验室测试这些父母,看其是否为疾病的基因载体时,却常常无法对生殖细胞系组织进行取样。Stankiewicz表示,对精子进行 测序是不切实际的,而获取卵子涉及侵入性活检。为更准确地为家庭提供指导,实验室需要更加复杂的测试。

不 过,像Walsh和贝勒医学院团队使用的诸如此类的高灵敏度测序方法,在高校实验室和研究型医院之外并不常见。Walsh解释说,部分原因在于要想确认一 个在DNA样本中极少出现的序列是真实的致病突变而非测序错误,是一件非常复杂和耗费时间的事情。同时,由于目前深度测序基因组将注意力缩小到一系列已知 候选基因或特定突变上,研究人员只得受限于对那些遗传因素已了解得较多的疾病。Walsh预测,DNA测试技术的改进将最终带来针对嵌合突变的更加广泛的 搜寻。

Harmful mutations can fly under the radar

Scientists have long known that the human body is a mosaic: All of our cells don’t contain exactly the same genome. Every     time a cell divides, genetic errors can occur, leading to variations in the DNA sequence that may proliferate and—in some    cases—cause disease. Now that genetic sequencing and ther technologies have made it easier to recognize mutations that occur    in only a subset of cells, researchers are finding more and more harmful mutations hidden among unaffected cells. These findings  suggest that in some cases, standard genetic tests in the clinic may be overlooking the underlying cause of genetic disease    and underestimating a person’s risk of passing such mutations on to their children.

 

埃博拉:一篇论文,五位作者牺牲

今 年的埃博拉病毒疫情是有史以来最严重的大爆发,截至8月20日,已有超过2600例感染,其中1400多人死亡。追根溯源,这次埃博拉病毒爆发始于何处, 又是如何传播的呢?来自美国博德研究所(Broad Institute of MIT)和哈佛大学的研究者,联合塞拉利昂卫生部以及世界各地的科学家们,对99个埃博拉病毒基因组进行了测序,从结果中推断出了关于此次疫情的来源和传 播模式。研究论文今天发表在《科学》(Science)杂志上。然而,截自论文发布时,已有5位作者不幸牺牲。就此,果壳网对论文的共同作者,博德研究所 的克里斯蒂安·安德森(Kristian G. Andersen)和丹尼尔·朴(Danny Park)等人进行了采访。

 

窥视疫情来源

 

以往的埃博拉病毒病爆发仅限于中非的偏远地区,其中最大的疫情(318例)发生在1976年。2014年的爆发则出现在西非地区,从2月开始于几内亚,在3月和5月分别扩散到了邻国利比里亚和塞拉利昂,7月底到达尼日利亚。感染病例数增加迅速,倍增时间仅为34.8天。

 

凯内马公立医院里用于监测埃博拉的聚合酶链式反应(PCR)引物。图片来源:论文作者之一的史蒂芬·盖尔(Stephen Gire)

 

在 严重疫情还未扑灭的情况下,有关病毒流行及时而准确的信息就显得尤为重要。研究者们急需了解这次埃博拉大爆发的起因、时间和传播方式,以及病毒的动态和演 化进程。而其中的关键性人物,是一名由于高热和流产到塞拉利昂凯内马医院就诊的年轻女性。她被检测确认感染了埃博拉病毒,成为塞拉利昂境内确认的首个病 例。

 

经过调查,塞拉利昂卫生部的人员最终确认,该名妇女是由于参加了因感染埃博拉病毒而死的草药医生葬礼感染上病毒,葬礼上还有其他13名妇女,正是她们将病毒从几内亚传播到了塞拉利昂。

 

分析结果还显示,塞拉利昂境内的埃博拉疫情由两株不同的埃博拉病毒引起,几乎同时从几内亚传入。而其中一株在由一名染病的护士传播到其他人身上时,突变形成了第三株病毒。这第三株病毒则由开车运送这名护士以及照顾她的其他人进一步传播开来。

 

根 据系统发生学的比较结果,研究者推测此次的埃博拉病毒的源头则可以追溯到1976年的那次大爆发。此次爆发的埃博拉病毒可能是由中非地区的病毒在过去10 年间分支出来,并经由动物宿主传播的。虽然研究者们还不确定到底是哪种动物导致了病毒的传播,但是果蝠(fruit bat)是头号疑犯,因为至少有一种果蝠的生活区域横跨了中非直到几内亚。

 

了 解病毒的来源和传播可以防止疫情更大范围的扩散。“我们的研究结果表明,在某个时候,一个人从动物宿主身上受到感染,而之后的所有病例均为人与人之间的传 播。然而,如果要进一步研究这个问题,则需要对来自几内亚、塞拉利昂和利比里亚的样品进行进一步测序,来分析是否有其它动物传人的例子发生。”研究者对果 壳网说:“在受埃博拉疫情影响的人口中,许多都以丛林肉为重要的蛋白质和营养物质来源,这种行为本身就容易产生健康问题。但如果我们观察的结果是真的,那 么我们应该将关注重点更多地放在防止人与人之间的传播上。”

 

高通量测序

 

为 了了解埃博拉病毒在感染者体内的演化情况,研究人员通过高通量测序的方法,对99份样品中的埃博拉病毒基因组进行了测序,测序深度高达约2000×(注: 测序深度为测序得到的碱基总量与基因组大小的比值,它是评价测序量的指标之一)。这些样品来自塞拉利昂的78名病人(包括了那12名参加了葬礼的女性), 其中的一部分病人不止一次提供样品,使得研究者们能够更好地分析病毒在同一个体中如何变化。

 

测 序及分析结果共找出了395个基因突变,与以往有记录的埃博拉病毒相比,出现了341个碱基替换突变。研究人员还在这次埃博拉爆发的病毒样本中找到55个 单核苷酸多态性位点。实验结果表明,病毒在扩散的过程中基因突变速度较快,突变位点包含了一些基于PCR诊断测试的重要位置——这些位点会影响测试结果的 准确度。研究论文共同作者,来自哈佛大学的研究者史蒂芬·盖尔(Stephen Gire)说,这一结果对及时改进测试盒中PCR引物的序列有参考价值。在疫情爆发过程中,“我们也观察到了埃博拉病毒基因组的演化。研究结果显示,疫情 爆发时病毒基因组的演化速度大约是无疫情时的两倍。”研究者说。

 

来自哈佛大学的研究者史蒂芬·盖尔(Stephen Gire)正向塞拉利昂的凯内马公立医院运送用于检测埃博拉病毒的实验室安全设备和试剂。图片来源:论文作者之一的内森·约兹维亚克(Nathan Yozwiak)

 

“基 因监测在疾病爆发时非常重要。其他科学家建议我们要深入研究那些测序结果中的罕见突变,这些突变可能在利用传统测序方法时无法被检测出来。它们可能从一个 宿主中开始出现,但由于无法用传统方法检测,到流行起来时就为时已晚。”研究着告诉果壳网说,“因此,能够在突变刚开始发生时就能将其找出,对于跟踪突变 的产生,以及预测将来会有什么突变出现都非常重要。”

 

这 些结果可能对研究药物和疫苗的靶点有重要意义。安德森和同事们第一时间向科学界公布数据,并迅速收到了反馈。“来自斯克里普斯研究所的科学家们对这些序列 进行了结构预测,并与ZMapp的实验性抗体混合剂中的抗体结构进行了对比,以便为了解2014埃博拉病毒的变化提供结构线索。”研究者介绍道。

 

下一步,研究者们希望了解2014埃博拉病毒基因组中与以往不同的突变与其感染和传播能力较强是否有关。

 

众志成城

 

参与研究的科学家们表示,此项工作非常艰难,但是多亏了许多个人和组织的共同努力才得以实现。包括凯内马公立医院和塞拉利昂卫生部对此次疫情的迅速反应,以及在博德研究所、哈佛大学和杜兰大学的团队成员们日以继夜地工作,让整个科学界在短时间内就可以看到实验数据。

 

另一个重要因素,则是博德研究所在对其它病原体进行测序研究过程中建立起的研究方法和设施基础,“我们能够利用已有的测序方法(例如用于拉萨热和登革热病毒的方法)来进行高效的测序,才能让数据能够几乎实时地发表。”研究者对果壳网说。

 

研 究者认为,要完全控制这次疫情,还需要更多的支持、培训、基础建设以及资金资助。由于人与人之间的传播为本次疫情的扩散方式,因此对感染病人的隔离以及加 强对与病人有接触的人群追踪十分重要。在将来,还需要培训更多的当地科学家和医生,并研制可靠且易用的诊断方法,来进行早期埃博拉感染的检测。“假如感染 病例能在本地被快速准确的检出,也许疫情就能在爆发前被扼杀。”

 

为 了加快响应计划,研究团队在研究论文发表之前已将全长测序结果上传到了美国国家生物技术信息中心(NCBI)的DNA序列数据库中,以便全球的科学家们都 能获得这些最新数据。“在疫情发生时,研究数据的共享十分关键。这就是我们选择在获得数据并进行过质检后马上发出的原因,其他的研究者们也采取了同样的做 法。而我们十分希望在将来,数据的开放获取能成为常规做法。”

 

研 究者们还希望与出现疫情的其他国家的研究者们合作,从而对那些地区的病毒情况有所了解。德国汉堡Bernhard Nocht热带医学研究所的史蒂芬·君特(Stephan Günther)手上有来自几内亚病人的样品,身在利比里亚的其他研究者们也收集了样品,但由于所有人都还在奋力遏制疫情蔓延,他们暂时还没有时间对这些 样品进行测序。

 

在 塞拉利昂凯内马,部分参与本论文工作的研究者合影。左二舍克·汗(Sheik Humarr Khan,已牺牲)、右三奥古斯丁·戈巴(Augustine Goba)、右二克里斯蒂安·安德森(Kristian Anderson)、右一史蒂芬·盖尔(Stephen Gire)。图片来源:论文通讯作者之一帕蒂斯·萨贝提(Pardis Sabeti)。图片来源:论文通讯作者帕蒂斯·萨贝提(Pardis C. Sabeti)

 

本 次研究集结了超过50名来自4个国家的共同作者参与病毒样品的采集和序列分析工作。不幸的是,其中5名作者已在抗击埃博拉的战斗中不幸牺牲——他们均为塞 拉利昂凯内马医院的医护人员,包括舍克·汗(Sheik Humarr Khan)、穆罕默德·富拉(Mohamed Fullah)、穆巴鲁·方妮(Mbalu Fonnie)、阿列克斯·莫依格波(Alex Moigboi)和阿丽斯·科沃玛(Alice Kovoma)。

 

Nature 中国食管鳞状细胞癌的遗传图谱

领导这一研究的是中国医学科学院肿瘤医院肿瘤研究所的赫捷(Jie He)教授。其长期从事肺癌、食管癌等胸部肿瘤疾病的早诊早治、外科治疗及综合治疗,并在食管癌、肺癌综合治疗大型研究中取得较大成果。于2013年当选为中国科学院院士。
外 显子组测序 (Exome sequencing)是近年发展起来的一种利用序列捕获技术将全基因组外显子区域DNA捕捉并富集后进行高通量测序的基因组分析方法。是一种选择基因组 的编码序列的高效策略,相对于基因组测序其成本较低。目前,外显子组测序已经在米勒综合症、歌舞伎综合症、重型颅脑畸形等孟德尔疾病的研究中得到成功应 用。还有其它一些癌症和复杂性疾病也应用外显子组测序观察到高度相关的突变。
这些研究结果详细描绘出了食管鳞状细胞癌的突变景观,表明了一些表观遗传调控因子突变有可能具有潜在的预后及治疗意义。

 

Genetic landscape of esophageal squamous cell carcinomaEsophageal squamous cell carcinoma (ESCC) is one of the deadliest cancers1. We performed exome sequencing on 113 tumor-normal pairs, yielding a mean of 82 non-silent mutations per tumor, and 8 cell lines. The mutational profile of ESCC closely resembles those of squamous cell carcinomas of other tissues but differs from that of esophageal adenocarcinoma. Genes involved in cell cycle and apoptosis regulation were mutated in 99% of cases by somatic alternations of TP53 (93%), CCND1 (33%), CDKN2A (20%), NFE2L2 (10%) and RB1 (9%). Histone modifier genes were frequently mutated, including KMT2D (also called MLL2; 19%), KMT2C (MLL3; 6%), KDM6A (7%), EP300 (10%) and CREBBP (6%). EP300 mutations were associated with poor survival. The Hippo and Notch pathways were dysregulated by mutations in FAT1, FAT2, FAT3 or FAT4 (27%) or AJUBA (JUB; 7%) and NOTCH1, NOTCH2 or NOTCH3 (22%) or FBXW7 (5%), respectively. These results define the mutational landscape of ESCC and highlight mutations in epigenetic modulators with prognostic and potentially therapeutic implications.
Genetic landscape of esophageal squamous cell carcinoma.pdf 

Nature:循环血DNA指导癌症治疗

2012年,Charles Swanton被迫面对一种癌症的“肮脏”把戏。当时,他与同事在英国癌症研究中心伦敦研究所测序从少量肾脏肿瘤中提取的DNA,以期找到一些不同的变异,但是单一肿瘤的遗传多样性的宽度让他们十分震惊。一端的细胞就与另一端的细胞存在差别,只有1/3的突变遍及整块肿瘤。扩散到其他部位的继发性肿瘤又出现了不同。
最终,Swanton研究小组公布了一种看上去难以逾越的多样性。“诚实地说,我还是很郁闷。如果我们进行了更高分辨率的试验,这些复杂性将更严重。”
通过发展和改善针对血流中肿瘤DNA的测量和测序技术,科学家正把血瓶变为“液体活检”。随着时间的推移,此类血液样本将告诉临床医生治疗是否会起作用以及肿瘤是否会进化出抗性。
约翰斯·霍普金斯大学遗传肿瘤学家Victor Velculescu指出,如果研究人员清楚这些障碍,液体活检将帮助临床医生更好地选择疗法和调整决策。此外,相关研究将提供新的治疗靶点。“这将有助于实现个体化治疗。它将是游戏规则改变者。”Velculescu说。
1948年,科学家第一次报告了人体血液中存在DNA循环;1977年,明确提出癌症患者血液中的DNA循环。人们又花费17年时间指出,这些DNA出现了与癌症有关的突变。
这一发现使得医生可以在孕期初期不干扰胎儿的前提下检查胎儿性别,并能不依靠侵入性试验筛查唐氏综合征等发育性疾病。这也成为妇产诊断学领域的革命性成果。
但过去10年间科学家发展出了更灵敏的技术,能在片刻间探测和量化DNA数量。例如,即使ctDNA与健康细胞DNA的比例为1/10000, 一个名为BEAMing的技术也能将其检测出来。
更好的生物标识
但ctDNA出现假阳性的几率更低,因为它是由具有癌细胞印记的突变和其他遗传变化定义的。尽管大多数蛋白质生物标识能在血液中存在数周,而ctDNA的半衰期不到两个小时,因此,后者呈现的是肿瘤目前的情况。剑桥团队与约翰斯·霍普金斯团队分别发现,在监测乳癌和肠癌时,与蛋白质生物标识相比,ctDNA更加敏感,并且在追踪肿瘤消失、扩散和复发时,ctDNA也更准确。
而让科学家最为兴奋的是能够随时观察肿瘤发展和改变,Diaz指出:“它能帮助我们回答之前没有人能回答的肿瘤学问题。”
检测抗性能让医生避免患者服用有毒、昂贵且没有效用的药物。而且,通过识别抗性背后的突变,研究人员能发现有效的替代选择和药物组合。“希望我们能将癌症从致命性疾病变为慢性病。”Velculescu说。
尽管存在希望,ctDNA在临床上还未准备好成为主角。首先,最敏感的ctDNA探测技术依靠的是寻找对那些突变的认知。这些认知可能来自于活体检查、测序突变、设计患者个性化分子探针、使用这些探针分析血样。替代选择是使用外显子组测序。这要求之前对肿瘤没有认知,但是以探测稀有突变片段所需要的深度来测序和分析每个样本,则成本过高。
与所有的ctDNA活体监测技术一样,Diehn的方法无法监测初期癌症。在一个小型研究中,它检测出了所有II期或更晚的肺癌,但I期肿瘤只检测出一半。这个可以理解——晚期肿瘤会释放更多DNA,但这限制了ctDNA作为癌症筛查工具的潜力。
不过,即便ctDNA无法影响结局,科学家表示,它也是一个无价的研究工具,并且临床医生可以常规地对其进行收集。正如Rosenfeld所说的,知道这些信息要比不知道好。当前,他说,“我们正在黑暗中摸索。但如果有个工具能让你看到发生了什么,那你为什么不这样做?”

Cancer biomarkers: Written in blood

In 2012, Charles Swanton was forced to confront one of cancer’s dirtiest tricks. When he and his team at the Cancer Research UK London Research Institute sequenced DNA from a handful of kidney tumours, they expected to find a lot of different mutations, but the breadth of genetic diversity within even a single tumour shocked them. Cells from one end differed from those at the other and only one-third of the mutations were shared throughout the whole mass. Secondary tumours that had spread and taken root elsewhere in the patients’ bodies were different again1.

Hundreds of sea-floor methane plumes spotted by sonar
Imprint of primordial monster star found
Neanderthals: Bone technique redrafts prehistory

The results confirmed that the standard prognostic procedure for cancer, the tissue biopsy, is woefully inadequate — like trying to gauge a nation’s behaviour by surveying a single street. A biopsy could miss mutations just centimetres away that might radically change a person’s chances for survival. And although biopsies can provide data about specific mutations that might make a tumour vulnerable to targeted therapies, that information is static and bound to become inaccurate as the cancer evolves.

Swanton and his team laid bare a diversity that seemed insurmountable. “I am still quite depressed about it, if I’m honest,” he says. “And if we had higher-resolution assays, the complexity would be far worse.”

But researchers have found ways to get a richer view of a patient’s cancer, and even track it over time. When cancer cells rupture and die, they release their contents, including circulating tumour DNA (ctDNA): genome fragments that float freely through the bloodstream. Debris from normal cells is normally mopped up and destroyed by ‘cleaning cells’ such as macrophages, but tumours are so large and their cells multiply so quickly that the cleaners cannot cope completely.

By developing and refining techniques for measuring and sequencing tumour DNA in the bloodstream, scientists are turning vials of blood into ‘liquid biopsies’ — portraits of a cancer that are much more comprehensive than the keyhole peeps that conventional biopsies provide. Taken over time, such blood samples would show clinicians whether treatments are working and whether tumours are evolving resistance.

As ever, there are caveats. Levels of ctDNA vary a lot from person to person and can be hard to detect, especially for small tumours in their early stages. And most studies so far have dealt with only handfuls or dozens of patients, with just a few types of cancer. Although the results are promising, they must be validated in larger studies before it will be clear whether ctDNA truly offers an accurate view — and, more importantly, whether it can save or improve lives. “Just monitoring your tumour isn’t good enough,” says Luis Diaz, an oncologist at Johns Hopkins University in Baltimore, Maryland. “The challenge that we face is finding true utility.”

If researchers can clear those hurdles, liquid biopsies could help clinicians to make better choices for treatment and to adjust those decisions as conditions change, says Victor Velculescu, a genetic oncologist at Johns Hopkins. Moreover, the work might provide new therapeutic targets. “It will help bring personalized medicine to reality,” says Velculescu. “It’s a game-changer.”
Delayed action

Scientists first reported finding DNA circulating in human blood in 1948 (ref. 2), and specifically in the blood of people with cancer in 1977 (ref. 3). It took another 17 years to show that this DNA bore mutations that are hallmarks of cancer — proof that it originated from the tumours4, 5.

The first practical use of circulating DNA came in another field. Dennis Lo, a chemical pathologist now at the Chinese University of Hong Kong, reasoned that if tumours could flood the blood with DNA, surely fetuses could, too. In 1997, he successfully showed that pregnant women carrying male babies had fetal Y chromosomes in their blood6. That discovery allowed doctors to check a baby’s sex early in gestation without disturbing the fetus, and ultimately to screen for developmental disorders such as Down’s syndrome without resorting to invasive testing. It has revolutionized the field of prenatal diagnostics (see Nature 507, 19; 2014).

“Cancer has been slower to catch on,” says Nitzan Rosenfeld, a genomicist at the Cancer Research UK Cambridge Institute. This is partly because tumour DNA is much harder to detect than fetal DNA. There is typically less of it in the blood, and the amounts are extremely variable. In people with very advanced cancers, tumours might be the source of most of the circulating DNA in the blood, but more commonly, ctDNA makes up barely 1% of the total and possibly as little as 0.01%. Early sequencing technologies were not up to the task of detecting it — at least, not consistently or reliably enough to use ctDNA as a biomarker.

“It’ll help us answer questions in oncology That have never been answered before.”

But the past decade has brought sensitive techniques that can detect and quantify minute amounts of DNA. For example, an amplification method known as BEAMing — which fastens circulating DNA to magnetic beads that can then be isolated and counted — can detect ctDNA even if it is outnumbered by healthy cell DNA by a factor of 10,000 to 1.

Genetic oncologists Bert Vogelstein and Kenneth Kinzler at Johns Hopkins developed the technique, and in 2007 they described7 using it to track ctDNA in 18 people who were being treated for bowel cancer. After surgery, the patients’ ctDNA levels fell by 99%, but in many cases the signal did not disappear completely. In all but one of the people with detectable ctDNA at the first follow-up appointment, the tumours eventually returned. None of the people with undetectable levels after surgery experienced a recurrence.

These results suggested that ctDNA can reveal how well a patient has responded to surgery and whether they need chemotherapy to finish off any lingering cancer cells. Researchers soon found similar results for other types of cancer. Rosenfeld and his Cancer Research UK colleagues James Brenton and Carlos Caldas showed that ctDNA provides a precise portrait of advanced ovarian and breast cancers8. And in the largest study yet, Diaz and other members of the Johns Hopkins group detected ctDNA in at least 75% of patients with advanced tumours, in organs as diverse as the pancreas, bladder, skin, stomach, oesophagus, liver and head and neck9. (Brain cancers were a notable exception, because the blood–brain barrier stops tumour DNA from reaching the bloodstream.)
Better biomarkers

Circulating DNA might perform better than the protein biomarkers that researchers have been seeking and refining for decades. Proteins are used in the clinic to diagnose illnesses and monitor people undergoing treatment. For example, prostate-specific antigen is a biomarker for prostate cancer, but it can give false positives because there are other reasons that the antigen can be elevated in the blood. False positives should be rarer with ctDNA because it is defined by mutations and other genomic changes that are hallmarks of cancer cells. And although most protein biomarkers stay in the blood for weeks, ctDNA has a half-life of less than two hours, so it gives a clearer view of a tumour’s present, rather than its past. The Cambridge and Johns Hopkins teams have found that ctDNA is more sensitive than protein biomarkers when it comes to detecting breast10 and bowel9 cancers, respectively, and it is more accurate at tracking tumour disappearance, spread and recurrence.

Illustration by Oliver Munday

Both teams also showed that ctDNA was more sensitive than circulating tumour cells — intact cancer cells that also travel around the bloodstream and have been an intense area of research. In a sub-study of 16 people, Diaz’s team found that where both were present, ctDNA fragments outnumbered circulating tumour cells by 50 to 1 (ref. 9). And although ctDNA was always there if the circulating cells were, 13 people with detectable tumour DNA had no trace of such cells.

But most exciting to scientists, says Diaz, is the ability to watch tumours evolve and adapt over time: “It’ll help us answer questions in oncology that have never been answered before.”

For example, why do so many targeted therapies eventually fail? Gefitinib and panitumumab are among several drugs that block the epidermal growth factor receptor (EGFR), a protein involved in cell growth and division that is overactive in a number of cancers. People taking these drugs do very well — briefly. But after a few months, their cancers almost always develop resistance, often through changes to other genes, such as KRAS, which is mutated in many cancers.

To monitor patients and decide on the next course of action, clinicians would normally need to take multiple biopsies. But people with advanced cancer often have several tumours to test, and different parts of any single tumour could be resistant in different ways. Biopsies are invasive and risky, and difficult for inaccessible and fragile organs such as the lungs. “You can’t just go to the patient and get five more biopsies after the treatment fails,” says Velculescu. Taking blood is simple in comparison.

In 2012, Diaz’s team reported11 using ctDNA to study patients who were being treated with EGFR inhibitors. The researchers found 42 different KRAS mutations that confer resistance; on average, these turned up 5 months before imaging techniques showed that the tumours were progressing. The team was specifically looking for KRAS mutations, but Rosenfeld’s group has used ctDNA to identify resistance mutations from a blind start. Last year, the researchers described how they had sequenced the complete exomes — the 1% of the genome that encodes protein — in blood samples from six people being treated for advanced breast, lung or ovarian cancers. In five cases, the unguided search revealed routes to resistance, such as mutations that prevent drugs from binding to their target proteins12.

Spotting resistance early would let clinicians take patients off toxic and expensive drugs that are unlikely to keep working. And by identifying the mutations that underlie the resistance, they could find effective alternatives or drug combinations. “The hope is that we can turn cancer from a deadly disease into a chronic one,” says Velculescu. “You treat someone with one therapy and when it stops working, you switch, or alternate back and forth.”
Clinical caveats

Despite its promise, ctDNA is not yet ready for a starring role in the clinic. For one thing, the most sensitive techniques for detecting it, such as BEAMing, rely on some knowledge of which mutations to look for. This knowledge can be provided by taking a biopsy, sequencing its mutations, designing patient-specific molecular probes that target them, and using those probes to analyse later blood samples — a laborious approach that must be repeated for each patient. The alternative is to use exome sequencing, as Rosenfeld’s team did. This requires no previous knowledge about the cancer, but it is prohibitively expensive to sequence and analyse every sample at the depth required to detect rare mutant fragments.
Related stories

Cancer crossroads
‘Pan-cancer’ study unearths tumours’ genetic trademarks
Lists of cancer mutations awash with false positives

More related stories

Maximilian Diehn, a radiation oncologist at Stanford University in California, has tried to combine the best of both worlds. His team identified a small proportion of the genome — just 0.004% — that is repeatedly mutated in lung cancers13. Whenever the researchers get a new blood sample, they sequence this fraction 10,000 times over. This picks up even rare mutant fragments, and the focused approach keeps costs down. Because almost everyone with lung cancer has at least one mutation in these regions, the method should work in almost every patient, says Diehn. The team is now working to develop similar mutation panels for other types of cancer, and to validate the technique in clinical trials — work that could take several years.

Like practically all ctDNA biopsy techniques, Diehn’s approach does not do well at picking up early forms of cancer. In a small study13, it detected every lung cancer of stage II or higher, but only half of stage I tumours. This is understandable — advanced cancers simply discharge more DNA — but it limits ctDNA’s potential as a cancer-screening tool.

Diehn says that more-sensitive techniques could overcome this problem, but Diaz disagrees. “The limiting factor is biology,” he says. “There just aren’t a lot of fragments in circulation.” And if ctDNA hints at the presence of an undetected cancer, what then? “If you detect a mutation in the circulation, you don’t know where it’s coming from,” says Diaz.

There are other unknowns, too. Does ctDNA paint a truly representative portrait of a cancer? Do tumours that have spread to other organs release as much DNA as the original tumours? Do all the cells in a tumour release as much ctDNA as each other? Diaz says that the only way to answer these questions is to do ‘warm autopsies’ — to take samples and characterize all of a person’s tumours very soon after death, and compare them with ctDNA extracted in life. “This is the heavy lifting that’ll need to be done in the field,” he says.

And the biggest question remains: does an accurate picture of tumour burden, or a real-time look at emerging mutations, actually save patients or improve their quality of life? Even if doctors discover that someone’s tumour has developed a resistance mutation, that insight is useless if there are no drugs that target the mutation. “The limitation is the reality of targeted therapies,” says Velculescu. “You get all this information — but so what? Our approaches to understanding cancer are outstripping our clinical options.”

Even if ctDNA does not yet affect outcomes, scientists say that it is an invaluable research tool, and clinicians are starting to collect it routinely. Swanton, for example, is leading a £14-million (US$24-million) lung-cancer study called TRACERx (Tracking Cancer Evolution Through Therapy), which will use both conventional biopsies and ctDNA collected once every three months. The circulating DNA may or may not provide clues that help the study participants, but at the very least, it will give Swanton a much better understanding of how lung cancer evolves, and how to control that evolution.

As Rosenfeld argues, it is better to have this information than not to. Currently, he says, “we’re groping in the dark. Why would you do that if you have a tool that allows you to see what’s happening?”

染色体异常

染色体是组成细胞核的基本物质,是基因的载体。染色体异常(chromosome abnormalities)也称染色体发育不全(chromosome dysgenesis)。美籍华人蒋有兴(1956)查明人类染色体为46条,Caspersson等(1970)首次发表人类染色体显带照片。

美籍华人蒋有兴(1956)查明人类染色体为46条Caspersson等(1970)首次发表人类染色体显带

照片自1971

染色体异常

染色体异常

巴黎国际染色体命名会议以来,已发现人类染色体数目异常和结构畸变3000余种,目前已确认染色体病综合征100余种,智力低下和生长发育迟滞是染色体病的共同特征。

最常见的染色体疾病Down综合征(Down’ssyndrome)的新生儿发病率为1/700~1/600。除Down综合征之外,13三体综合征(trisomy13syndrome)的活婴发病率为1/2000,女性多于男性,患儿母亲平均生育年龄为31岁。18三体综合征(trisomy18syndrome)的活婴发病率为1/4000女性多见患者母亲平均生育年龄为34岁。脆性X染色体综合征(fragile-Xsyndrome)估计可使1/1500的男婴受累由于女性具有两条X染色体,受累率为50%,程度较轻Klinefelter综合征(Klinefelter’ssyndrome)的染色体表型为XXY,仅见于男性。Turner综合症的染色体为XO(45X)型,仅见于女性。Williams综合征的新生儿发病率为1/2万,Prader-Willi综合征的新生儿发病率为1/2万,Rett综合征的发病率为1/1.5万~1/1万,仅见于女性。

染色体是基因的载体,染色体病即染色体异常,故而导致基因表达异常机体发育异常。染色体畸变的发病机制不明,可能由于细胞分裂后期染色体发生不分离或染色体在体内外各种因素影响下发生断裂和重新连接所致。
1、物理因素:人类所处的辐射环境,包括天然辐射和人工辐射。天然辐射包括宇宙辐射,地球辐射及人体内放射物质的辐射,人工辐射包括放射辐射和职业照射等。
电离辐射因导致染色体不分离而引人注目。有试验证明,将受照射小鼠处于MⅡ中期的卵细胞和未受照射的同期卵细胞比 较,发现不分离在受照射组中明显增高,这一现象在年龄较大的小鼠中尤为明显。人的淋巴细胞受照射或在受照射的血清内生长,发现实验组三体型频率较对照组 高,并引起双着丝粒染色体异位、缺失等染色体畸变。
2、化学因素:人们在日常生活中接触到各种各样的化学物质,有的是天然产物,有的是人工合成,它们会通过饮食、呼吸或皮肤接触等途径进入人体,而引起染色体畸变。
3、生物因素:当以病毒处理培养中的细胞时,往往会引起多种类型的染色体畸变,包括断裂、粉碎化和互换等。
4、母龄效应:胎儿在6—7个月龄时,所有卵原细胞已全部发展为初级卵母细胞,并从第一次减数分裂前期进入核网期, 此时染色体再次松散舒展,宛如同前胞核,一直维持到青春期排卵之前。这种状态可能与合成卵黄有关。到青春期时,由于FSH的周期性刺激卵母细胞,每月仅一 个完成第一极体。次级卵母细胞自卵巢排出,进入输卵管,在管内进行第二次减数分裂达到分裂中期。此时如果受精,卵子便完成第二次减数分裂,成为成熟卵子, 与精子结合成为合子,从此开始新个体发育直至分娩。随着母龄的增长,在母体内外许多因素的影响下,卵子也可能发生许多衰老变化,影响成熟分裂中同对染色体 间的相互关系和分裂后期的行动,促成了染色体间的不分离。
5、遗传因素:染色体异常常可以表现为家族性倾向,这提示染色体畸变与遗传有关。
6、自身免疫性疾病:自身免疫性疾病似乎在染色体不分离中起一定作用,如甲状腺原发性自身免疫抗体增高与家族性染色体异常之间有密切相关性。[1]

分类

⒈数量畸变包括整倍体非整倍体畸变,染色体数目增多、减少和出现三倍体等。
⒉结构畸变染色体缺失易位倒位、插入、重复和环状染色体等又可分为常染色体畸变,如Down(21三体)综合征Patau(13三体)综合征和Edward(18三体)综合征等,以及性染色体畸变如Turner综合征(XO)和先天性睾丸发育不全等。
最常见的染色体疾病Down综合征病理改变:患者脑重约较正常轻10%仅有简单的脑回结构,额叶小,颞上回皮质薄,脑白质髓鞘形成晚皮质神经元发育不全和分化低等。40岁以上患者可见Alzheimer病样神经原纤维缠结及老年斑

3临床表现编辑

Down综合症(Down’ssyndrome)也称21三体综合征(trisome21syndrome)和先天愚型等。这是人类最常见

染色体异常

染色体异常

染色体疾病新生儿发病率为1/700~1/600是精神发育迟滞最常见的原因占严重智力发育障碍病例的10%。

Seguin(1846)首先报告本病的临床表现,LangdoneDown(1866)对本病作了全面的描述,英国学者后来将本病称为Down综合症,Lejeune等(1959)证明本病由21号染色体三倍体引起并提倡用21三体综合症的名称在1970年丹佛会议上得到承认。
除Down综合症之外,其他染色体发育不全包括Patau综合征18三体综合征、猫叫(Criduchat)综合征、脆性X染色体综合征、环状染色体综合征、Klinefelter综合征、Turner综合征、Colpocephaly综合征、Williams综合征、Prader-Willi和Angelman综合征、Rett综合征等。

Down综合征

(Down’ssyndrome)的临床特征如下:⑴Down综合症患儿出生时即有某些病理特征,随年龄增长症状变得明显。颅面部表现为圆头低鼻梁上颌

染色体异常

染色体异常

骨发育不全可致面部扁平,呈微张状舌体肥大有深裂,常伸出口外故称伸舌痴呆。内眦赘皮常遮盖部分,内眦患者裂可轻微向上向外倾斜形成蒙古样,面容耳朵位置低呈卵圆形,耳垂小可见虹膜灰-白色斑点即布鲁什菲尔德点(Brushfield’sspots),囟门明显闭合晚。

愚钝综合征

患儿出生时较正常新生儿的平均身长略短,随年龄增长差异愈发明显成年患者身高很少超过正常10岁儿童。手呈短粗状,手掌宽只有一条横纹,表现为水平掌褶纹(通贯手)及其他特征性皮纹改变,如小指短而内屈呈单一褶纹(即第五指为两节),肌张力减低多数患儿3~4岁仍不会走路,婴幼儿反应迟钝或引不出进食困难患儿智力及精神发育明显异常,智商为20~70,平均40~50多在Gaussian曲线以下,90%的患儿5岁时才会说话。大多数表现沉静、温顺、易让人接近,寿命可达40岁。
有些患者可见白内障先天性心脏病或心脏病继发,脑栓塞和脑脓肿,胃肠道异常如,十二指肠狭窄等寰枢关节不稳定,剧烈运动可导致脊髓压迫,中幼粒细胞和淋巴细胞白血病的发生率高于常人患者40多岁时几乎普遍发生Alzheimer病,出现注意力不集中、寡言少语视空间定向力差记忆力及判断力下降和癫痫发作等。

13三体综合征

13三体综合征(trisomy13syndrome)也称Patau综合征,活婴发病率为1/2000,女性多

染色体异常

染色体异常

于男性,患儿母亲平均生育年龄为31岁。

患儿表现为小头前额凸出、小眼、虹膜缺损角膜浑浊、嗅觉缺失耳位低唇腭裂、毛细血管瘤、多指(趾)畸形、手指弯曲、足跟后凸右位心、脐疝听力缺陷、肌张力过高及严重精神发育迟滞等患儿多死于儿童早期。

18三体综合征

18三体综合征(trisomy18syndrome)的活婴发病率为1/4000,女性多见,患者母亲平均生育年龄为34岁。
患儿表现为生长迟缓、上睑下垂眼睑畸形耳位低小嘴小下颏皮肤斑点示指超过中指并握紧拳头、并指(趾)畸形、摇篮底足(rocker-bottomfeet)足趾大而短、室间隔缺损脐疝或腹股沟疝、胸骨短、小骨盆和肌张力增高,偶有癫痫发作、严重精神发育迟滞等常死于婴儿早期。

猫叫综合征

猫叫综合征(Criduchatsyndrome)是5号染色体短臂缺失所致。
患儿生后数周至数月出现小猫叫样哭声,严重精神发育迟滞,眼间距过远内眦赘皮折叠(epicanthalfolds)、短头畸形、满月脸、反先天愚型样睑裂歪曲,小颌肌张力减退和斜视等。

脆性X染色体综合征

脆 性X染色体综合征(fragile-Xsyndrome)是X染色体有异常易断裂的脆性部位Martin和Bell(1943)最先报道一个X连锁遗传的 精神发育迟滞大家系Lubs(1969)发现这个家系患者X染色体长臂末端有脆弱位点,证实此位点有不稳定遗传的CGG重复序列。正常人重复序列为 43~200个,患者超过200个,多余的序列可灭活编码RNA结合蛋白基因,影响蛋白表达而出现症状。
本综合征是导致遗传性精神发育迟滞最常见的原因估计可使1/1500的男婴受累。由于女性具有两条X染色

染色体异常

染色体异常

体,受累率为50%程度较轻。据估计10%以上的男性遗传性精神发育迟滞患儿有异常脆性X染 色体有时女性也受累但病情较轻,Rousseau等描述了一种简单敏感的实验方法,采用DNA分析技术在孕期及出生后对患儿进行诊断由于重复三联密码子的 长度与智力发育迟滞的程度有关因此脆性X染色体变异型偶见于智力正常的男性,患者外孙可患病。 患儿表现为典型的三联征:精神发育迟滞,特殊容貌(如长 脸、大耳宽额头鼻大而宽和高腭弓)和大睾丸等患儿身高正常,大睾丸一般出现于8~9岁,85%的患儿可有智力低下,多为中等程度常表现为行为异常,多出现 于青春期前,常见自伤性行为、多动及冲动性行为以及刻板和怪异动作、多动症多言癖,孤独症患者可有特有的拍手动作9%~45%的患儿可出现癫痫发作。 DNA检查可确诊。⑸环状染色体:环状染色体(ringchromosome)表现为精神发育迟滞伴各种身体畸形。

Klinefelter综合征

Klinefelter综合征(Klinefelter’ssyndrome)的染色体表型为XXY仅见于男性。患者身材高大,表现类似无睾丸者的外表,宽、头发及体毛稀疏、音调高、乳房女性化和小睾丸肌张力减低通常伴精神发育迟滞但程度较轻本病并发精神病哮喘内分泌功能异常如伴糖尿病几率较高。

Turner综合征

Turner综合征的染色体为XO(45X)型仅见于女性。患者身材矮小颈部有蹼脸呈三角形,小下颏乳头间距宽,指(趾)弯曲肘外翻和指甲发育不全,可伴五官距离过远内眦赘皮折叠,可有性发育迟缓及中度精神发育迟滞等。

Colpocephaly综合征

Colpocephaly综合征是少见的脑部畸形,病因很多有些是8号染色体三倍体嵌合所致,常误诊为多种类型的脑室扩张伴脑发育异常。患者表现为精神发育迟滞、痉挛状态和癫痫发作视神

染色体异常可检查发现

染色体异常可检查发现

经发育不全导致视觉异常等侧脑室枕角显著扩张,皮质灰质边缘重叠增厚,白质变薄。

Williams综合征

Williams综合征是7号染色体编码弹性蛋白基因区域存在微小缺失,新生儿发病率为1/2万,由Williams首先描述目前还不清楚脑部是否有特征性病变,曾有文献报道一例35岁的病人活检,除Alzheimer病改变外未发现其他脑异常。
患者精神发育迟滞较轻,音乐能力早熟有非凡的音乐才能对乐谱有惊人的记忆力,听一遍交响乐可全部记住;有些患者可写出大段的描写文字措辞和内容正确,但不会描绘简单事物患儿发育迟缓外貌独特,如:宽嘴、杏仁眼、孔上翻、耳朵小而尖,称为“小妖精样”外貌;性格温和对听觉刺激敏感,言语交谈能力获得较晚,可有视空间和运动能力缺陷。可有心血管畸形如主动脉瓣狭窄。

Prader-Willi及Angelman综合征

Prader-Willi综合征新生儿发病率为1/2万两性患病率均等为15号染色体q11-q13缺失所致,可采用细胞发生分析与DNA分析相结合的方法检测此染色体缺陷70%的病例是父系X染色体非遗传性缺失所致。
患儿表现为肌张力降低、腱反射消失、身材矮小、面容变形、生殖器明显发育障碍,出生时可有关节弯曲等1年后出现明显精神发育迟滞或智力低下(hypomentia),由于过度进食变得肥胖
Angelman综合征是15号染色体q11-q13缺失所致,与Prader-Willi综合征不同的是本病由母系单基因遗传缺

可产前检查预防

可产前检查预防

陷所致患儿表现为严重精神发育迟滞、小头畸形及早期出现癫痫发作等,抗癫痫药治疗不敏感,出现少见的牵线木偶样姿态和运动障碍,常想大笑或微笑样旧称“快乐木偶综合征”。

Rett综合征

Rett综合征由Rett首先(1966)描述,病因不明,呈X染色体显性遗传有人推测代谢机制参与致病发病率为1/1.5万~1/1万仅见于女性,可存活多年男性为纯合子,常不能存活。
若为女性,出生时及生后早期发育正常6~15个月时手部自主运动丧失,以后交流能力丧失身体发育迟滞、头颅增大等,典型症状为:手部徐动搓丸样刻板样运动,逐渐出现共济失调下肢强直最终丧失行走及语言能力可出现发作性过度换气和屏气、夜间呼吸节律正常和痫性发作等。
本病可误诊为Kanner孤独综合征,两者的不同点是Rett综合征早期即运动能力丧失,无注意力不集中及眼球联合运动消失。

并发症

染色体异常种类繁多,临床症状体征复杂多样,神经系统以外的表现各不相同具体详情可参见各病临床表现。

区分

主要根据患儿的特征性症状、体征及染色体检查。检出染色体异常可确诊。21三体所致的Down综合征与染色体易位导致Down综合征的临床表现很难区分,二者有很强的关联性,与母亲年龄有关21三体患儿母亲通常生育年龄较大,但高龄或年轻孕妇染色体易位的发生率都较低。Down综合征亚型,如嵌合型有些细胞染色体正常,有些异常。嵌合型患者可有Down综合征的典型表现有些患者智力正常。

5检查编辑

实验室检查

⒈Down综合征血清学检查可见血清素降低、白细胞中碱性、磷酸酶增高、红细胞二磷酸葡萄糖增高、过氧化物歧化酶增高50%、但与患者发育异常及智力低下无关。
⒉约1/3的Down综合征患儿母亲在妊娠4~6个月时血清甲胎蛋白含量增高,血清绒毛膜促性腺激素含量增

产前检查是关键

产前检查是关键

高、雌三醇含量降低,可提示胎儿Down综合征检查结果。阳性孕妇应行羊膜囊穿刺,检测患者羊水细胞或染色体。

其他辅助检查

孕妇行羊膜囊穿刺可发现羊水细胞染色体异常可以早期筛查Down综合征患儿及其他染色体发育不全。
染色体检查可用荧光原位杂交技术(fluorescentinsituhybridizationtechnique)检测患者羊水细胞或染色体,如Down综合征可发现21号染色体为三倍体。

治疗

染色体异常治疗困难疗效不满意,导致的先天性智能障碍的治疗,也尚无有效药物,可尝试中药治疗与康复训练。

产前检查

不同类型染色体发育不全预后不尽相同,多数预后不良智力低下和生长发育迟滞是染色体病的共同特征。染色体发育不全治疗困难疗效不满意预防显得更为重要预防措施包括推行遗传咨询、染色体检测、产前诊断和选择性人工流产等,防止患儿出生。孕妇应该定期做产前检查,如果胎儿有问题,至少能及早发现。抽羊水诊断是能检验胎儿是否患有先天染色体缺陷的其中一个方法。

染色体核型命名如下:正常男性为46,XY,正常女性为46,XX。21三体综合征(唐氏综合征)由于有一条额外的21号染色体(21三体),核型命名为男性47,XY,+21 ;女性命名为47,XX,+21 .染色体易位也可导致21三体综合征,典型的14/21平衡易位携带者母亲写为45,XX,t(14q;21q).易位染色体分别来自14q和21q(在该染色体上,q为长臂),短臂(p)已丢失.短臂缺失的5号染色体(又称为5p缺失综合征),女性的核型为46,XX,5p-.
活婴中染色体异常的发生率约为0.5%.这些染色体异常者均能在产前得以诊断.然而有创性产前诊断方法其弊大于利.因此,产前诊断仅用于高危人群.
孕妇高龄是产前细胞遗传学诊断的最常见指征.虽然染色体异常可见于各年龄组的孕妇,但随着年龄的增大,子代三体核型发生率随之增加,35岁以后呈指数级递增(表247-1),至今原因不明.由于自然流产因素,孕16~18周检出的胎儿染色体异常的发生率较存活新生儿高30%,分娩年龄在35岁以上者均应作产前诊断.然而,年龄界限是相对的,年龄较小的妇女也可考虑行产前诊断.
母亲血清异常标志物提示胎儿有21三体综合征及18三体综合征风险增高,可考虑作羊膜穿刺术(见下文).  已有异常染色体的儿童是作产前诊断的指征.如果一对夫妇已有一个存活孩子是21三体,其本次分娩年龄在30岁以下,那么再次怀21三体胎儿的风险约为 1%.对于30岁以上者,其再次怀21三体胎儿的风险与孕妇实际年龄相关(表247-1).该表假设患者没有携带罗伯逊易位的夫妇,资料仅限于其他三体核型,但子代再次染色体异常的风险大约增加1%.某些染色体异常(例如45,X;三倍体;新重排)并不增加下一次妊娠的风险.对于即使无风险增加的夫妇,如果他们有顾虑心理,也可作产前诊断.
一对夫妇可能会出现有一个表型异常但染色体状况未知的孩子,表型异常通常与染色体异常有关,这种情况会出现在30%的活婴中,而表型正常的死婴中会有5%的染色体异常.如果前一个孩子的不正常是由于异常染色体所致则有指征作产前诊断.
父母染色体异常增加了子代染色体异常的风险.父代平衡重组包括易位(罗伯逊或互换易位)和倒位(臂内和臂间倒位), 他们往往表型正常但应作遗传咨询并考虑作产前诊断.常染色体非整倍性夫妇较少见.从理论上讲,非整倍体父母的子代约50%也为非整倍体.但是母亲为21三 体者,其子代为三体型的发生率为1/3.父亲为21三体型者均不育.性染色体三体型(如47,XXY)是很常见的,他们往往伴有生育力下降.性染色体三体型的父母,其子代为非整倍体者罕见.任何具有非整倍性染色体或完全嵌合型染色体的夫妇均应作产前诊断.染色体异常的夫妇通常是在对多次自然流产或子代异常或不孕症的病因筛查中得到诊断.
反复自然流产常 提示染色体异常.至少有50%早期自然流产的胎儿染色体异常;其中约1/2是三倍体.如果首次流产的胎儿为非整倍体,再次流产的胎儿也可能为非整倍体,但 这种异常可以不在同一染色体上发生.三体症(如16三体)妊娠可能是致死的并常导致流产,但再次妊娠可能会出现表型异常和其他三体型(如18三体)的活 婴.曾有非整倍体活婴分娩史者,再次妊娠非整倍体活婴的风险增加.然而,非整倍体反复自然流产者,究竟是否增加以后非整倍体活婴的风险仍不清楚.一些遗传 学家认为,反复自然流产应作为产前诊断的指征;必要时作夫妇双方染色体重组检测

染色体异常的原因1、男性也可能造成胚胎染色体异常的原因:男性长期服用药物,是会影响精子品质,并造成胎儿之不良 影响。在正常情况下,睾丸组织与流经睾丸的血液之间有一个防护层,医学上称为血睾屏障。这一屏障可阻止血液中某些物质进入睾丸。但是很多药物却能通过血睾 屏障,影响精卵健康结合。如常见的一些免疫调节剂,等药物,其毒性作用强,可直接扰乱精子DNA的合成,包括使遗传物质成分改变,染色体异常和精子畸形。 像男性不孕症,妇女习惯性流产(早期胚胎丢失),其中部分原因就是男性精子受损的结果。
染色体异常的原因2、这些药物还可随睾丸产生的精液通过性生活排入阴道,经阴道粘膜吸收后而进入血液循环,使低体重 儿和畸形胎的发生率增高,增加围产期胎儿的死亡率。因此,在怀孕前的2~3个月和怀孕期,先生用药一定要小心,除非夫妻中有染色体异常的问题,认为若你有 这类疑虑建议夫妻双方接受抽血检查染色体有无异常。
染色体异常的原因3、怀孕的前三个月,是流产的高危险期,这种自发性的流产,多半是胎儿染色体异常所致,是一种自然 淘汰。如果不是胎儿染色体异常的自然淘汰现象,而是因为孕妇本身的问题导致流产,根本之计就是找出问题,对症下药,才能避免再次流产。萎缩卵,葡萄胎是为 胎儿的染色体异常所致:萎缩卵,葡萄胎=是萎缩性胚胎.至于萎缩卵发生的原因多为胚胎本身的问题

江西发现一例人类罕见异常染色体,此例染色体经实验鉴定,属世界首次发现。那么,这异常染色体是怎么形成呢?
江西省妇幼保健院近日从一名3岁男孩身上发现一例人类罕见异常染色体核型:46,XY,dup(4)(p12p16)。据医院产前诊断中心主管技师李宇中介绍,这一异常染色体经中国医学遗传学国家重点实验室鉴定,属世界首次发现。
李宇中分析认为,这一染色体可能是在减速分裂时,同源染色体之间非对等交换或染色单体之间非对等交换形成重复片段而产生。根据基因的致病性程度,可能会导致患者先天性的非进行性智力低下,生长发育迟缓,并伴有五官、四肢、皮纹和内脏等方面的多发畸形症状。[3]

 

 

新胃癌分型:4种分子类型更精确进行不同的靶向治疗

基于分子特征的新系统,而不是细胞和组织特点

目前的系统分类将胃癌分为两类:弥漫性和肠型。该系统采用主要细胞和组织的变化进行区分。研究人员指出,使用这个系统对胃癌分类不容易,因为癌细胞在显微镜下完全不同,即使他们来自同一肿瘤。

Adam Bass,马萨诸塞州波士顿哈佛医学院助理教授,是主要研究者之一。他解释说,新分类系统的优点:

“这个项目的一个重要进展是,我们已经确定,并制定了更加有用的分类系统,以寻找具有独特的分子特征胃癌组,并在同一时间,我们还确定了主要目标,用于不 同的病人,这将提供一个坚实的基础,对疾病和方式进行分类,使我们可以基于一些关键的分子改变,推动不同类别的癌症开展临床试验”。

在这项研究中,Bass 教授和他的同事进行了分子特征复杂的统计分析,295肿瘤六种类型的基因数据,包括DNA测序、RNA测序和蛋白质芯片。

2型(肿瘤的22%)表现出较高水平的“微卫星不稳定性”或MSI,其中突变往往积聚在DNA的重复序列。
4型(占肿瘤的50%)被归类为染色体不稳定型,因为它们表现出高水平的SCNAs。

研究人员对EBV阳性型特别感兴趣,EBV在美国是最著名的传染性单核或腺热的原因, EB病毒也被认为会导致某些癌症,包括鼻咽癌,以及某些类型的淋巴瘤。

EB病毒在少数胃癌也表达, 因为在肿瘤中EB病毒的基因被发现。这项研究还发现与EBV有关的胃癌分子特征。 例如,他们在EBV阳性肿瘤中发现的分子之一是PIK3CA基因突变率较高的倾向。该基因编码一种名为PI3激酶的蛋白质,是细胞生长和分裂,对相关癌症 的其他细胞功能很重要。

这样的发现可能提示胃癌EBV阳性可能对PI3激酶抑制剂的治疗反应,这些药物目前在美国处于临床试验的初期阶段。

该小组还与其他三个小组有一些其他有趣的发现。例如,基因组稳定亚型的肿瘤中显示基因RHOA的高频率突变,其蛋白与其它细胞蛋白相互作用以帮助细胞改变形状和迁移,  这是肿瘤生长的一个重要特征。

此外,染色体不稳定的肿瘤类型显示的频繁基因扩增,链接到受体蛋白和异常的细胞生长, 已经在使用中的药物可能会遏制他们的活动。

TCGA是由国家人类基因组研究所(NHGRI)和美国国家癌症研究所(NCI)共同管理。

Comprehensive molecular characterization of gastric adenocarcinomaGastric cancer is a leading cause of cancer deaths, but analysis of its molecular and clinical characteristics has been complicated by histological and aetiological heterogeneity. Here we describe a comprehensive molecular evaluation of 295 primary gastric adenocarcinomas as part of The Cancer Genome Atlas (TCGA) project. We propose a molecular classification dividing gastric cancer into four subtypes: tumours positive for Epstein–Barr virus, which display recurrent PIK3CA mutations, extreme DNA hypermethylation, and amplification of JAK2, CD274 (also known as PD-L1) and PDCD1LG2 (also known as PD-L2); microsatellite unstable tumours, which show elevated mutation rates, including mutations of genes encoding targetable oncogenic signalling proteins; genomically stable tumours, which are enriched for the diffuse histological variant and mutations of RHOA or fusions involving RHO-family GTPase-activating proteins; and tumours with chromosomal instability, which show marked aneuploidy and focal amplification of receptor tyrosine kinases. Identification of these subtypes provides a roadmap for patient stratification and trials of targeted therapies.


Comprehensive molecular characterization of gastric adenocarcinoma
Gastric cancer is a leading cause of cancer deaths, but analysis of its molecular and clinical characteristics has been complicated by histological and aetiological heterogeneity. Here we describe a comprehensive molecular evaluation of 295 primary gastric adenocarcinomas as part of The Cancer Genome Atlas (TCGA) project. We propose a molecular classification dividing gastric cancer into four subtypes: tumours positive for Epstein–Barr virus, which display recurrent PIK3CA mutations, extreme DNA hypermethylation, and amplification of JAK2, CD274 (also known as PD-L1) and PDCD1LG2 (also known as PD-L2); microsatellite unstable tumours, which show elevated mutation rates, including mutations of genes encoding targetable oncogenic signalling proteins; genomically stable tumours, which are enriched for the diffuse histological variant and mutations of RHOA or fusions involving RHO-family GTPase-activating proteins; and tumours with chromosomal instability, which show marked aneuploidy and focal amplification of receptor tyrosine kinases. Identification of these subtypes provides a roadmap for patient stratification and trials of targeted therapies.

Comprehensive molecular characterization of gastric adenocarcinoma.pdf (3.69 MB,)

Cancer Cell:癌症与经典信号Notch

自 2004年科学家们确定了Notch是一种对白血病形成非常重要的癌基因之后,这一研究领域就成为了癌症热门研究方向之一,近年来研究人员投入了巨大的努 力致力于研究Notch在癌症中的作用,为此Cell出版社旗下,著名的癌症期刊Cancer Cell以“Notch in Cancer”为题,介绍了近期的研究进展。

早在100多年前,科学家们就在黑腹果蝇中发现了Notch表型,自此Notch信号成为了一种被广泛关注的关键调控因子,研究发现这种信号能在多种器官和组织中调控细胞命运。

而 且在过去二十年间,不少研究证据表明Notch信号通路与癌症发生发展存在重要关联,Notch被认为是一种癌基因。在此次专题的首篇综述文章中,作者探 讨了Notch信号通路促癌和抑癌的双方面作用,解析了Notch信号在血液癌症和实体肿瘤中分子机制。并且作者还将这些作用机制与人体癌症治疗过程中, 靶向Notch途径的治疗策略联系在了一起。

Notch信号通路与非小细胞肺癌

研究表明,在细胞和动物模型研究中,抑制Notch 1能导致肿瘤细胞死亡的增加。虽然Notch信号通路在许多类型的癌症中是重要治疗靶标,但当前的方法影响Notch家族中的所有成员,这会一直伴随着毒性。

一些新的研究证明Notch1对非小细胞肺癌是必需的,因为它抑制p53(一个著名的肿瘤抑制蛋白,被称为基因组的监护人,因为它的作用是防止突变)。p53蛋白可以修复受损细胞,或迫使细胞发生程序性细胞死亡导致肿瘤细胞死亡。

利用动物模型,研究表明抑制Notch1信号导致最初肿瘤生长减少。此外,中断 Notch 1能通过诱导p53的稳定性大大增加细胞的凋亡。

Notch与Botch

2013 年5月,约翰霍普金斯大学的科学家在《Developmental Cell》的一项研究中报道称,他们发现了一种称为Botch的蛋白,在决定干细胞是否分化为构成脑的细胞以及无数的其他组织中发挥着重要的调控作用,并 表明Botch在高尔基体内与Notch蛋白发生了互作。

但是这两者之间相互作用的机制还并不清楚,近期这一研究组又查明了Botch蛋白如何阻断Notch信号蛋白的:Botch利用一种从未见过的机制,将一个甘氨酸化学基团替代为另一个可物理性阻断furin酶活性的化学基团。

事 实上,Notch是一个四蛋白家族,在小鼠和人中具有完全相同的性能和活性。这些蛋白位于细胞周围的细胞膜中,在那里它们充当受体的作用,通过在细胞内开 启一个信号连锁反应,响应细胞外的特定信号。Notch负责很多事情,从获得干细胞,到发育成不同的器官,到帮助产生红血细胞。最大的问题是,一个看似简 单的信号系统如何能够具有如此不同的效果。

自 Notch从细胞的蛋白制造中心出现,到它能够在细胞膜内发挥作用之前,会发生几件事情。其中一件是在蛋白质的一个特定部位添加化学基团甘氨酸。之后,一 个称为furin(弗林蛋白酶)的酶可在靠近甘氨酸的部位切断Notch。Botch将甘氨酸从furin的切割点上移除。了解Botch如何作用于 Notch,可能有助于科学家们理解发育的生物化学过程。对Botch靶向的甘氨酸附近的Notch区域突变相关的一些白血病的治疗,也具有一定的影响。

 

原文摘要:

From Fly Wings to Targeted Cancer Therapies: A Centennial for Notch Signaling

Since Notch phenotypes in Drosophila melanogaster were first identified 100 years ago, Notch signaling has been extensively characterized as a regulator of cell-fate decisions in a variety of organisms and tissues. However, in the past 20 years, accumulating evidence has linked alterations in the Notch pathway to tumorigenesis. In this review, we discuss the protumorigenic and tumor-suppressive functions of Notch signaling, and dissect the molecular mechanisms that underlie these functions in hematopoietic cancers and solid tumors. Finally, we link these mechanisms and observations to possible therapeutic strategies targeting the Notch pathway in human cancers.

Complementary Genomic Screens Identify SERCA as a Therapeutic Target in NOTCH1 Mutated CancerHighlights

  • Intersecting high-throughput screens identify SERCA inhibition to modulate Notch1
  • A small-molecule SERCA inhibitor has on-target antileukemia activity in vitro
  • A SERCA inhibitor has on-target antileukemia activity in T-ALL mouse models
  • SERCA inhibition preferentially impairs the maturation of mutated Notch1 receptors

SummaryNotch1 is a rational therapeutic target in several human cancers, but as a transcriptional regulator, it poses a drug discovery challenge. To identify Notch1 modulators, we performed two cell-based, high-throughput screens for small-molecule inhibitors and cDNA enhancers of a NOTCH1 allele bearing a leukemia-associated mutation. Sarco/endoplasmic reticulum calcium ATPase (SERCA) channels emerged at the intersection of these complementary screens. SERCA inhibition preferentially impairs the maturation and activity of mutated Notch1 receptors and induces a G0/G1 arrest in NOTCH1-mutated human leukemia cells. A small-molecule SERCA inhibitor has on-target activity in two mouse models of human leukemia and interferes with Notch signaling in Drosophila. These studies “credential” SERCA as a therapeutic target in cancers associated with NOTCH1 mutations.

A Critical Role for Notch Signaling in the Formation of Cholangiocellular CarcinomasHighlights

  • •Notch signaling is frequently dysregulated in human CCCs
  • •Notch is an oncogenic driver of CCC and able to transform hepatic progenitor cells
  • •Notch induces the cyclin E promoter, causing genetic instability by increasing cyclin E expression
  • •Inhibition of Notch signaling may be a treatment option for CCC

SummaryThe incidence of cholangiocellular carcinoma (CCC) is increasing worldwide. Using a transgenic mouse model, we found that expression of the intracellular domain of Notch 1 (NICD) in mouse livers results in the formation of intrahepatic CCCs. These tumors display features of bipotential hepatic progenitor cells, indicating that intrahepatic CCC can originate from this cell type. We show that human and mouse CCCs are characterized by high expression of the cyclin E protein and identified the cyclin E gene as a direct transcriptional target of the Notch signaling pathway. Intriguingly, blocking γ-secretase activity in human CCC xenotransplants results in downregulation of cyclin E expression, induction of apoptosis, and tumor remission in vivo.

A Rare Population of CD24+ITGB4+Notchhi Cells Drives Tumor Propagation in NSCLC and Requires Notch3 for Self-RenewalHighlights

  • •CD24, ITGB4, and Notch(1–4) enrich for TPCs in murine models of NSCLC
  • •The TPC population is enriched after chemotherapy in the mouse model
  • •The gene signature of mouse TPCs correlates with a poor prognosis in human NSCLC
  • •Notch3 is required for tumor propagation in the mouse model and human NSCLC

SummarySustained tumor progression has been attributed to a distinct population of tumor-propagating cells (TPCs). To identify TPCs relevant to lung cancer pathogenesis, we investigated functional heterogeneity in tumor cells isolated from Kras-driven mouse models of non-small-cell lung cancer (NSCLC). CD24+ITGB4+Notchhi cells are capable of propagating tumor growth in both a clonogenic and an orthotopic serial transplantation assay. While all four Notch receptors mark TPCs, Notch3 plays a nonredundant role in tumor cell propagation in two mouse models and in human NSCLC. The TPC population is enriched after chemotherapy, and the gene signature of mouse TPCs correlates with poor prognosis in human NSCLC. The role of Notch3 in tumor propagation may provide a therapeutic target for NSCLC.

A Critical Role for Notch Signaling in the Formation of Cholangiocellular Carcinomas.pdf

 

Complementary Genomic Screens Identify SERCA as a Therapeutic Target in NOTCH1 M.pdf

From Fly Wings to Targeted Cancer Therapies A Centennial for Notch Signaling.pdf