世界生命科學前沿動態(tài)周報（三十七）

（12.20-12.31/2010）
美寶國際集團:陶國新 
---2010再生科學年度進展 

 　　本次動態(tài)包括以下內容：耐力鍛煉使心肌細胞增殖的機理；癌癥干細胞基因表達高癌癥治療結果差；無需標記實時觀察活組織中分子運動；果蠅激活生殖細胞遺傳基因來產生腫瘤；癌細胞自我毀滅與自我保護的信號分子；微小RNA表達模式的整體圖譜區(qū)分干細胞類別。以及2010各期中出現(xiàn)過的比較突出的幾項再生科學進展的小結。

1. 耐力鍛煉使心肌細胞增殖的機理
【摘要】
人們都知道鍛煉身體可以促進新陳代謝，有益于心血管健康，但此前科學家對運動究竟如何影響心臟卻所知甚少。美國哈佛大學醫(yī)學院的研究人員日前報告說，他們首次從分子水平發(fā)現(xiàn)運動有益心臟健康的機理，這一發(fā)現(xiàn)將有助于開發(fā)出治療心血管疾病的新療法。研究人員通過小鼠實驗發(fā)現(xiàn)，經常運動可以使小鼠體內的C/EBPβ轉錄因子水平顯著下降，其結果會促進小鼠心臟肌肉細胞增殖，有益于心臟生長。此外，研究人員還發(fā)現(xiàn)，體內C/EBPβ水平較低的小鼠對心力衰竭具有抵抗能力。研究人員表示，這項研究對心臟肌肉再生的潛力有了深入理解。參與研究的哈佛大學醫(yī)學院教授安東尼·羅森茨魏希表示，通過這項研究可以開發(fā)出針對那些無法運動的心臟病患者的療法。這項研究成果發(fā)表在新一期美國《細胞》雜志上。（來源：新華社）

【點評】
　　該研究所發(fā)現(xiàn)的心肌增殖機理同樣有助于理解非藥物方式實現(xiàn)組織再生的機制并促進此類自然再生方法的推廣。

【原文摘錄】Cell, Volume 143, Issue 7, 1072-1083, 23 December 2010
C/EBPβ Controls Exercise-Induced Cardiac Growth and Protects against Pathological Cardiac Remodeling
Pontus Boström, Nina Mann, Jun Wu, et al.
The heart has the ability to grow in size in response to exercise, but little is known about the transcriptional mechanisms underlying physiological hypertrophy. Adult cardiomyocytes have also recently been proven to hold the potential for proliferation, a process that could be of great importance for regenerative medicine. Using a unique RT-PCR-based screen against all transcriptional components, we showed that C/EBPβ was downregulated with exercise, whereas the expression of CITED4 was increased. Reduction of C/EBPβ in vitro and in vivo resulted in a phenocopy of endurance exercise with cardiomyocyte hypertrophy and proliferation. This proliferation was mediated, at least in part, by the increased CITED4. Importantly, mice with reduced cardiac C/EBPβ levels displayed substantial resistance to cardiac failure upon pressure overload. These data indicate that C/EBPβ represses cardiomyocyte growth and proliferation in the adult mammalian heart and that reduction in C/EBPβ is a central signal in physiologic hypertrophy and proliferation.

2. 癌癥干細胞基因表達高癌癥治療結果差
【摘要】  
　　據美國物理學家組織網12月22日（北京時間）報道，斯坦福大學研究人員通過對白血病干細胞的基因表達方式研究發(fā)現(xiàn)，癌癥干細胞基因表達水平更高的病人比表達水平低的病人預后效果要差很多，該發(fā)現(xiàn)首次通過臨床數據證明了癌癥干細胞概念。醫(yī)療人員可據此預測群體病人的治療結果，并幫助開發(fā)新的臨床療法。研究發(fā)表在12月22日的《美國醫(yī)學會雜志》（JAMA）上。幾年前提出的癌癥干細胞概念認為，某些癌癥起源于一小撮自我更新能力很強的細胞，這一小撮細胞即是癌癥干細胞。這些癌癥干細胞能不斷補充生成新的癌癥細胞，癌癥要徹底治療，必須清除這些干細胞。癌癥干細胞對抗治療已經在一些固狀腫瘤和血癌的動物模型中得到驗證，雖然有大量實驗室證據支持，但至今還缺乏臨床證據。論文合著者、斯坦福癌癥中心醫(yī)務部艾什·埃里沙德和同事拉文達·馬杰提今年9月曾在實驗室小鼠中，對非霍奇森淋巴瘤癌癥干細胞表面發(fā)現(xiàn)的蛋白質CD47研究發(fā)現(xiàn)，CD47是癌癥干細胞的“保護傘”，有了它，很多藥物對這些細胞無效。CD47在其他幾種癌癥干細胞中也存在。馬杰提認為這些動物實驗中發(fā)現(xiàn)的證據在人體中也應該存在。他們用兩種能識別白血病干細胞的表面標記，從7個白血病患者的腫瘤樣本中分離出這些白血病干細胞，將腫瘤干細胞和其他腫瘤細胞的基因表達方式進行了對比，結果有52%的基因表達不同。癌癥干細胞基因表達方式和正常的血液干細胞很相似，不僅能自我更新，還能像正常干細胞在需要時候才分裂。為了逃避那些針對迅速分裂細胞的傳統(tǒng)治療方法，它會選擇少量分裂，潛伏著，等待機會“東山再起”。
　　研究人員還對來自1000多位急性骨髓白血病病人的4組腫瘤樣本進行了對比研究，發(fā)現(xiàn)在“癌癥干細胞基因高表達”和“治療結果差”之間存在很強的相關性。在一組德國樣本中，高表達病人3年內死亡的絕對風險高達78%，而低表達病人僅為57%。同樣，無病生存率、某個時期再度惡化可能性、對抗初次治療頑固性等指標也如此。論文第一作者、斯坦福大學癌癥系統(tǒng)生物學中心安德魯·簡托斯表示，白血病干細胞的信號越強，病人壽命越短，病情惡化得越快，治療效果就更差。目前，研究小組正在繼續(xù)研究數據，以最終從各種結合抗體療法中確定哪些療法對癌癥干細胞高表達基因信號的病人最有效。（來源：科技日報 發(fā)布時間：2010-12-23 10:20:47）

【點評】
　　該研究發(fā)現(xiàn)了白血病干細胞基因的高表達與急性粒細胞白血病的治療效果差之間有獨立的相關性，但是并沒有證明癌癥干細胞是腫瘤發(fā)生的起因。

【原文摘錄】 JAMA. 2010;304(24):2706-2715. doi: 10.1001/jama.2010.1862
Association of a Leukemic Stem Cell Gene Expression Signature With Clinical Outcomes in Acute Myeloid Leukemia
Andrew J. Gentles, Sylvia K. Plevritis, Ravindra Majeti, Ash A. Alizadeh
Abstract
Context In many cancers, specific subpopulations of cells appear to be uniquely capable of initiating and maintaining tumors. The strongest support for this cancer stem cell model comes from transplantation assays in immunodeficient mice, which indicate that human acute myeloid leukemia (AML) is driven by self-renewing leukemic stem cells (LSCs). This model has significant implications for the development of novel therapies, but its clinical relevance has yet to be determined.
Objective To identify an LSC gene expression signature and test its association with clinical outcomes in AML.
Design, Setting, and Patients Retrospective study of global gene expression (microarray) profiles of LSC-enriched subpopulations from primary AML and normal patient samples, which were obtained at a US medical center between April 2005 and July 2007, and validation data sets of global transcriptional profiles of AML tumors from 4 independent cohorts (n = 1047).
Main Outcome Measures Identification of genes discriminating LSC-enriched populations from other subpopulations in AML tumors; and association of LSC-specific genes with overall, event-free, and relapse-free survival and with therapeutic response.
Results Expression levels of 52 genes distinguished LSC-enriched populations from other subpopulations in cell-sorted AML samples. An LSC score summarizing expression of these genes in bulk primary AML tumor samples was associated with clinical outcomes in the 4 independent patient cohorts. High LSC scores were associated with worse overall, event-free, and relapse-free survival among patients with either normal karyotypes or chromosomal abnormalities. For the largest cohort of patients with normal karyotypes (n = 163), the LSC score was significantly associated with overall survival as a continuous variable (hazard ratio [HR], 1.15; 95% confidence interval [CI], 1.08-1.22; log-likelihood P <.001). The absolute risk of death by 3 years was 57% (95% CI, 43%-67%) for the low LSC score group compared with 78% (95% CI, 66%-86%) for the high LSC score group (HR, 1.9 [95% CI, 1.3-2.7]; log-rank P = .002). In another cohort with available data on event-free survival for 70 patients with normal karyotypes, the risk of an event by 3 years was 48% (95% CI, 27%-63%) in the low LSC score group vs 81% (95% CI, 60%-91% ) in the high LSC score group (HR, 2.4 [95% CI, 1.3-4.5]; log-rank P = .006). In multivariate Cox regression including age, mutations in FLT3 and NPM1, and cytogenetic abnormalities, the HRs for LSC score in the 3 cohorts with data on all variables were 1.07 (95% CI, 1.01-1.13; P = .02), 1.10 (95% CI, 1.03-1.17; P = .005), and 1.17 (95% CI, 1.05-1.30; P = .005).
Conclusion High expression of an LSC gene signature is independently associated with adverse outcomes in patients with AML.

3. 無需標記實時觀察活組織中分子運動
【摘要】  
　　美國哈佛大學科學家將受激拉曼散射（SRS）顯微鏡和核磁共振成像（MRI）技術結合，研制出一種最新的生物醫(yī)學成像設備，極大拓展了SRS顯微鏡的視野。其速度之快精度之高，如同“視頻”，足以使科學家直接目睹分子在活組織中的運動。研究論文發(fā)表在最新一期《科學》雜志上?！按饲?，SRS顯微鏡每分鐘只能拍攝一幅畫面，用于活的動物或人體就太慢了?！惫鸫髮W化學與化學生物學教授謝曉亮說，“我們大大提高了采集數據的速度，使拍攝達到了視頻速率?！毖芯啃〗M還用這種新型SRS顯微鏡追蹤藥物在皮膚下的移動，其能清晰顯示出藥物實時吸收情況。如與內鏡檢查術結合，還能一層一層觀察組織的三維結構。新型SRS顯微鏡的工作原理是探測原子之間化學鍵的內在震動，由于融合了MRI技術，在透視深度上更適合拍攝體內器官和其他大目標，既可廣泛用于拍攝器官和組織結構的靜態(tài)圖像，也能在亞細胞水平以流動畫面觀察細胞中的蛋白質、脂質和水。
　　同多種常用的觀察生物分子的技術相比，新型SRS顯微鏡優(yōu)勢明顯。它能采集分析照射生物樣本的近30%激光，比傳統(tǒng)SRS顯微鏡高出30倍；并且不需要插入熒光標記，避免了綠色熒光標記蛋白質擾亂生物路徑或壓住較小生物分子的問題。此外，傳統(tǒng)的紅外顯微鏡空間分辨率太低，并需要給樣本脫水；自然的拉曼顯微鏡需要很高的激光能量，整體耗時很長，在活樣本中的應用受到限制；相干反斯托克拉曼散射顯微鏡在拍攝除了脂質以外的大多數分子時對比度不夠，而新型SRS顯微鏡都能突破這些局限。研究人員表示，新型SRS顯微鏡在醫(yī)療領域的應用前景廣闊。比如，手術之前必須將樣本送檢以用于組織分析，這個過程大約要花20分鐘，其間病人需要等在手術臺上，而新技術可提供實時掃描透視，有助于加速外科手術，清除腫瘤和其他損傷。謝曉亮說：“這一項目開始于11年前，核磁共振技術花了30多年才用于臨床，我們期望這種SRS顯微鏡盡早應用于醫(yī)院。”來源：科技日報 常麗君

【點評】
　　該項技術將會極大的促進生理生化尤其是新陳代謝的研究，如能成熟地運用于人體，對于人體生理學及醫(yī)學研究將有巨大的幫助。

【原文摘錄】 Science Vol. 330 no. 6009 pp. 1368-1370 DOI: 10.1126/science.1197236
Video-Rate Molecular Imaging in Vivo with Stimulated Raman Scattering
Brian G. Saar1,Christian W. Freudiger, Jay Reichman, et al.
Optical imaging in vivo with molecular specificity is important in biomedicine because of its high spatial resolution and sensitivity compared with magnetic resonance imaging. Stimulated Raman scattering (SRS) microscopy allows highly sensitive optical imaging based on vibrational spectroscopy without adding toxic or perturbative labels. However, SRS imaging in living animals and humans has not been feasible because light cannot be collected through thick tissues, and motion-blur arises from slow imaging based on backscattered light. In this work, we enable in vivo SRS imaging by substantially enhancing the collection of the backscattered signal and increasing the imaging speed by three orders of magnitude to video rate. This approach allows label-free in vivo imaging of water, lipid, and protein in skin and mapping of penetration pathways of topically applied drugs in mice and humans.

4.  果蠅激活生殖細胞遺傳基因來產生腫瘤
【摘要】  
　　巴塞羅那的 科學家近日在Science上報道他們發(fā)現(xiàn)了果蠅幼蟲利用生殖細胞的遺傳程序來催生腦部腫瘤。關閉涉及到的相關基因就會保持健康的大腦，這是首次發(fā)現(xiàn)關閉這些相關基因可以使果蠅腦部腫瘤消失。說明這些生殖細胞的遺傳基因對于此類腫瘤的發(fā)生有關鍵作用。此前十年積累的數據顯示某些腫瘤如黑色素瘤和某些類癌的癌細胞會激活生殖細胞的遺傳基因。

【點評】
　　這項研究說明癌基因并不一定是癌癥發(fā)生的原因，生殖基因的激活也可能引發(fā)癌癥?；蚣せ畹纳碚{控是否正常是很重要的。

【原文摘錄】 Science, December 23, 2010 DOI: 10.1126/science.1195481
Ectopic expression of germline genes drives malignant brain tumor growth in Drosophila.
Janic A, Mendizabal L, Llamazares S, Rossell D, Gonzalez C.
Model organisms such as the fruit fly Drosophila melanogaster can help to elucidate the molecular basis of complex diseases such as cancer. Mutations in the Drosophila gene lethal (3) malignant brain tumor cause malignant growth in the larval brain. Here we show that l(3)mbt tumors exhibited a soma-to-germline transformation through the ectopic expression of genes normally required for germline stemness, fitness, or longevity. Orthologs of some of these genes were also expressed in human somatic tumors. In addition, inactivation of any of the germline genes nanos, vasa, piwi, or aubergine suppressed l(3)mbt malignant growth. Our results demonstrate that germline traits are necessary for tumor growth in this Drosophila model and suggest that inactivation of germline genes might have tumor-suppressing effects in other species.

5.  癌細胞自我毀滅與自我保護的信號分子
【摘要】
　　斯坦福大學醫(yī)學院的研究人員發(fā)現(xiàn)許多癌細胞自身帶有自我毀滅的種子--細胞表面一種名為鈣網素的蛋白—能召集循環(huán)系統(tǒng)的巨噬細胞來吞食消化他們。而絕大多數癌細胞沒有被毀滅是因為他們同時表達另一種信號蛋白CD47對抗鈣網素的作用。

【點評】
　　CD47與鈣網素的作用及二者平衡的調節(jié)會促進癌癥免疫療法的發(fā)展。

【原文摘錄】 Sci Transl Med 22 December 2010: Vol. 2, Issue 63, p. 63ra94
Calreticulin Is the Dominant Pro-Phagocytic Signal on Multiple Human Cancers and Is Counterbalanced by CD47
M. P. Chao, S. Jaiswal, R. Weissman-Tsukamoto, et al.
Under normal physiological conditions, cellular homeostasis is partly regulated by a balance of pro- and anti-phagocytic signals. CD47, which prevents cancer cell phagocytosis by the innate immune system, is highly expressed on several human cancers including acute myeloid leukemia, non-Hodgkin’s lymphoma, and bladder cancer. Blocking CD47 with a monoclonal antibody results in phagocytosis of cancer cells and leads to in vivo tumor elimination, yet normal cells remain mostly unaffected. Thus, we postulated that cancer cells must also display a potent pro-phagocytic signal. Here, we identified calreticulin as a pro-phagocytic signal that was highly expressed on the surface of several human cancers, but was minimally expressed on most normal cells. Increased CD47 expression correlated with high amounts of calreticulin on cancer cells and was necessary for protection from calreticulin-mediated phagocytosis. Blocking the interaction of target cell calreticulin with its receptor, low-density lipoprotein receptor–related protein, on phagocytic cells prevented anti-CD47 antibody–mediated phagocytosis. Furthermore, increased calreticulin expression was an adverse prognostic factor in diverse tumors including neuroblastoma, bladder cancer, and non-Hodgkin’s lymphoma. These findings identify calreticulin as the dominant pro-phagocytic signal on several human cancers, provide an explanation for the selective targeting of tumor cells by anti-CD47 antibody, and highlight the balance between pro- and anti-phagocytic signals in the immune evasion of cancer.

6. 微小RNA表達模式的整體圖譜區(qū)分干細胞類別
【摘要】
　　干細胞生物學在全世界引發(fā)人們對其可以最終修復身體部位的巨大期望。盡管很多科學家認為這是可行的，但是必須克服很多障礙，包括令人擔憂的在修復器官時引發(fā)癌癥的潛在風險。而近日報道的加州大學的一項關于多能性干細胞的微小RNA表達模式的研究或許對此有所幫助。他們分析很多種多能性干細胞的微小RNA表達模式，發(fā)現(xiàn)所有的多能性干細胞微小RNA表達模式并不相同，但不是因細胞來源而異，而是具有不同的p53 體系狀態(tài)。微小RNA表達模式的整體圖譜能夠告訴你這是何種細胞，何種癌癥，是否干細胞等信息。

【點評】
　　微小RNA表達模式的整體圖譜研究也許會有助于研究人體潛能再生細胞的定位和屬性。

【原文摘錄】 Cell Stem Cell, Volume 7, Issue 6, 671-681, 3 December 2010
MicroRNA Profiling Reveals Two Distinct p53-Related Human Pluripotent Stem Cell States
Pierre Neveu, Min Jeong Kye, Shuping Qi, et al.
Highlights
miRNA profiles distinguish two categories of human pluripotent stem cells
The p53 network status distinguishes pluripotent cells independently of their origin
p53-targeting miRNAs change the classification status of iPSCs
A 2D representation of miRNA profiles tracks differentiation and reprogramming
Summary
Reprogramming methodologies have provided multiple routes for achieving pluripotency. However, pluripotency is generally considered to be an almost singular state, with subtle differences described between induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs). We profiled miRNA expression levels across 49 human cell lines, including ESCs, iPSCs, differentiated cells, and cancer cell lines. We found that the resulting miRNA profiles divided the iPSCs and hESCs examined into two distinct categories irrespective of the cell line origin. The miRNAs that defined these two pluripotency categories also distinguished cancer cells from differentiated cells. Transcriptome analysis suggested that several gene sets related to p53 distinguished these categories, and overexpression of the p53-targeting miRNAs miR-92 and miR-141 in iPSCs was sufficient to change their classification status. Thus, our results suggest a subdivision of pluripotent stem cell states that is independent of their origin but related to p53 network status.

7. 2010再生科學年度進展
　　根據與人體再生復原科學的相關程度，本年度登載的以下動態(tài)作為2010再生科學年度進展：

1.人體多能干細胞體外定向分化形成腸組織；
2.老鼠實驗表明修復端粒可以逆轉衰老；
3.蠑螈重生肢體和器官的獨特酶；
4.生長因子TGF-β2和BMP4可使成熟細胞轉化為成人干細胞；
5.生命復雜性的產生可能必須先有線粒體出現(xiàn)；
6.黃芩湯可減輕腸癌患者化療損傷；
7.細胞生長調控依靠細胞質核傳輸；
8.洞螈長壽研究或解開衰老之謎；
9.脂肪可用作細胞內在pH感受器；
10.發(fā)現(xiàn)上皮組織中神秘免疫細胞的功能和機理；
11.細胞歸巢法使兔滑膜關節(jié)面再生；
12.控制細胞分化的力學因素；
13.關鍵基因控制哺乳動物組織再生；
14.細胞運動的集體調控控制胚胎的生長；
15.首次發(fā)現(xiàn)可發(fā)育成卵的干細胞;
16.精子形成過程中的細胞在一定時期內可以變回干細胞；
17.“活體生物反應器”“原位”培養(yǎng)再生新器官；
18.發(fā)現(xiàn)斑馬魚造血干細胞生成機理。