世界生命科學(xué)前沿動態(tài)周報（十四）

（06.21 --06.27 / 2010）
美寶國際集團(tuán):陶國新 

　　本周動態(tài)包括以下內(nèi)容：自體角膜緣干細(xì)胞移植治愈角膜燒傷導(dǎo)致的失明；吉非替尼藥物顯著提高表皮生長因子受體突變的晚期非小細(xì)胞肺癌患者的生存期；研究發(fā)現(xiàn)RNA的新功能；有效的吞噬作用需要ATGL調(diào)節(jié)的三酰甘油水解；Smed-prep基因是渦蟲的頭部和大腦適當(dāng)再生的基本要素；環(huán)孢霉素A治療成為誘發(fā)肝臟移植病人新癌癥的因素。
1. 自體角膜緣干細(xì)胞移植治愈角膜燒傷導(dǎo)致的失明
【摘要】
　　新英格蘭醫(yī)學(xué)雜志提前在線發(fā)表的一篇文章講述了通過移植自體角膜緣干細(xì)胞來再生角膜治愈角膜燒傷導(dǎo)致的失明，107例眼睛有82例完全有效，14例部分有效，無效的都發(fā)生在移植后第一年。到目前為止移植后新生的角膜正常工作已達(dá)十年。這是迄今為止此類研究時間最長規(guī)模最大的一次。 每年干細(xì)胞移植把希望帶給了全世界數(shù)千因強(qiáng)效清潔劑或其他化學(xué)物質(zhì)燒傷角膜的患者。 這一方法不能治療涉及視網(wǎng)膜的視神經(jīng)損傷或黃斑變性患者，也不能治療雙目完全失明患者，因?yàn)榇祟惢颊邲]有可供移植的健康角膜緣組織。
【點(diǎn)評】
　　盡管還只能治療一部分角膜燒傷導(dǎo)致失明的患者，自體角膜緣干細(xì)胞移植已經(jīng)是為數(shù)不多的能在臨床應(yīng)用的自體干細(xì)胞移植治療技術(shù)。

【原文摘錄】Published at www.nejm.org June 23, 2010 (10.1056/NEJMoa0905955)
Limbal Stem-Cell Therapy and Long-Term Corneal Regeneration
Paolo Rama, M.D., Stanislav Matuska, M.D., Giorgio Paganoni, M.D., Alessandra Spinelli, M.D., Michele De Luca, M.D., and Graziella Pellegrini, Ph.D.
Background Corneal renewal and repair are mediated by stem cells of the limbus, the narrow zone between the cornea and the bulbar conjunctiva. Ocular burns may destroy the limbus, causing limbal stem-cell deficiency. We investigated the long-term clinical results of cell therapy in patients with burn-related corneal destruction associated with limbal stem-cell deficiency, a highly disabling ocular disease.
Methods We used autologous limbal stem cells cultivated on fibrin to treat 112 patients with corneal damage, most of whom had burn-dependent limbal stem-cell deficiency. Clinical results were assessed by means of Kaplan–Meier, Kruskal–Wallis, and univariate and multivariate logistic-regression analyses. We also assessed the clinical outcome according to the percentage of holoclone-forming stem cells, detected as cells that stain intensely (p63-bright cells) in the cultures.
Results Permanent restoration of a transparent, renewing corneal epithelium was attained in 76.6% of eyes. The failures occurred within the first year. Restored eyes remained stable over time, with up to 10 years of follow-up (mean, 2.91±1.99; median, 1.93). In post hoc analyses, success — that is, the generation of normal epithelium on donor stroma — was associated with the percentage of p63-bright holoclone-forming stem cells in culture. Cultures in which p63-bright cells constituted more than 3% of the total number of clonogenic cells were associated with successful transplantation in 78% of patients. In contrast, cultures in which such cells made up 3% or less of the total number of cells were associated with successful transplantation in only 11% of patients. Graft failure was also associated with the type of initial ocular damage and postoperative complications.
Conclusions Cultures of limbal stem cells represent a source of cells for transplantation in the treatment of destruction of the human cornea due to burns.

2. 吉非替尼藥物顯著提高表皮生長因子受體突變的晚期非小細(xì)胞肺癌患者的生存期
【摘要】新華網(wǎng) 發(fā)布時間：2010-6-24 16:34:46
　　日本研究人員最新臨床試驗(yàn)發(fā)現(xiàn)，對于一種具有特定基因突變特征的晚期非小細(xì)胞肺癌患者，肺癌藥物易瑞沙（通用名吉非替尼）比標(biāo)準(zhǔn)的肺癌化療藥物更加有效，可使患者生存期延長一倍。肺癌有兩種主要類型：小細(xì)胞肺癌和非小細(xì)胞肺癌，其中后者占肺癌病例的75%。日本東北大學(xué)研究小組6月24日在新一期美國《新英格蘭醫(yī)學(xué)雜志》上介紹說，某些非小細(xì)胞肺癌患者，其基因變異會導(dǎo)致一種名為“表皮生長因子受體（EGFR）”的特殊蛋白質(zhì)在某些癌細(xì)胞表面過多分布，導(dǎo)致癌細(xì)胞增殖。在日本，大約67%的女性肺癌患者和15%的男性肺癌患者出現(xiàn)這種基因變異，標(biāo)準(zhǔn)化療治療的生存期僅為13.9個月。研究人員將230名具有這一基因變異的晚期非小細(xì)胞肺癌患者分為兩組，其中一組從一開始就利用易瑞沙進(jìn)行治療，對照組則是在標(biāo)準(zhǔn)化療不起作用后再使用易瑞沙。結(jié)果表明，從一開始就使用易瑞沙治療的患者平均生存期為30.5個月，比標(biāo)準(zhǔn)化療治療的生存期延長了一倍多；對照組的生存期平均為23.6個月，也延長近一倍。易瑞沙可以阻斷EGFR向肺癌細(xì)胞發(fā)送增殖信號，從而抑制癌癥發(fā)展。研究人員說，針對這類肺癌患者使用易瑞沙治療，患者對藥物的反應(yīng)更好，從而提高了療效。
【點(diǎn)評】
特異性更高的藥物吉非替尼能顯著提高具有特定基因突變特征的晚期非小細(xì)胞肺癌患者生存期，但是依然無法阻止癌癥的進(jìn)展，更不能治愈。

【原文摘錄】The New England Journal of Medicine 362(25):2380-2388.
Gefitinib or Chemotherapy for Non–Small-Cell Lung Cancer with Mutated EGFR
Makoto Maemondo, Akira Inoue, Kunihiko Kobayashi, et al.
Background Non–small-cell lung cancer with sensitive mutations of the epidermal growth factor receptor (EGFR) is highly responsive to EGFR tyrosine kinase inhibitors such as gefitinib, but little is known about how its efficacy and safety profile compares with that of standard chemotherapy.
Methods We randomly assigned 230 patients with metastatic, non–small-cell lung cancer and EGFR mutations who had not previously received chemotherapy to receive gefitinib or carboplatin–paclitaxel. The primary end point was progression-free survival; secondary end points included overall survival, response rate, and toxic effects.
Results In the planned interim analysis of data for the first 200 patients, progression-free survival was significantly longer in the gefitinib group than in the standard-chemotherapy group (hazard ratio for death or disease progression with gefitinib, 0.36; P<0.001), resulting in early termination of the study. The gefitinib group had a significantly longer median progression-free survival (10.8 months, vs. 5.4 months in the chemotherapy group; hazard ratio, 0.30; 95% confidence interval, 0.22 to 0.41; P<0.001), as well as a higher response rate (73.7% vs. 30.7%, P<0.001). The median overall survival was 30.5 months in the gefitinib group and 23.6 months in the chemotherapy group (P=0.31). The most common adverse events in the gefitinib group were rash (71.1%) and elevated aminotransferase levels (55.3%), and in the chemotherapy group, neutropenia (77.0%), anemia (64.6%), appetite loss (56.6%), and sensory neuropathy (54.9%). One patient receiving gefitinib died from interstitial lung disease.
Conclusions First-line gefitinib for patients with advanced non–small-cell lung cancer who were selected on the basis of EGFR mutations improved progression-free survival, with acceptable toxicity, as compared with standard chemotherapy. (UMIN-CTR number, C000000376.)

3. 研究發(fā)現(xiàn)RNA的新功能
【摘要】
　　分子生物學(xué)的中心法則認(rèn)為遺傳信息通過信使RNA從DNA傳遞到功能蛋白。這暗示信使RNA只有編碼蛋白一種功能?，F(xiàn)在，哈佛醫(yī)學(xué)院的一個癌癥遺傳學(xué)研究組發(fā)現(xiàn)RNA有更多的作用。除了編碼蛋白，信使RNA還能夠互相交流，從而具有調(diào)節(jié)作用，即使是那些非編碼RNA也能夠互相交流。這一發(fā)現(xiàn)大大豐富了功能基因庫信息。
【點(diǎn)評】
這一發(fā)現(xiàn)豐富了功能基因庫信息，另一方面，它也說明了基因調(diào)控體系的復(fù)雜性，解釋了為什么基因治療迄今沒有成功的臨床實(shí)踐。

【原文摘錄】Nature 465(7301):1033–1038, doi:10.1038/nature09144
A coding-independent function of gene and pseudogene mRNAs regulates tumour biology
Laura Poliseno, Leonardo Salmena, Jiangwen Zhang, Brett Carver, William J. Haveman & Pier Paolo Pandolfi
The canonical role of messenger RNA (mRNA) is to deliver protein-coding information to sites of protein synthesis. However, given that microRNAs bind to RNAs, we hypothesized that RNAs could possess a regulatory role that relies on their ability to compete for microRNA binding, independently of their protein-coding function. As a model for the protein-coding-independent role of RNAs, we describe the functional relationship between the mRNAs produced by the PTEN tumour suppressor gene and its pseudogene PTENP1 and the critical consequences of this interaction. We find that PTENP1 is biologically active as it can regulate cellular levels of PTEN and exert a growth-suppressive role. We also show that the PTENP1 locus is selectively lost in human cancer. We extended our analysis to other cancer-related genes that possess pseudogenes, such as oncogenic KRAS. We also demonstrate that the transcripts of protein-coding genes such as PTEN are biologically active. These findings attribute a novel biological role to expressed pseudogenes, as they can regulate coding gene expression, and reveal a non-coding function for mRNAs.

4. 有效的吞噬作用需要ATGL調(diào)節(jié)的三酰甘油水解
【摘要】
　　巨噬細(xì)胞吞噬作用是宿主防御的必需生物學(xué)過程，需要大量能量。至今葡萄糖被認(rèn)為是巨噬細(xì)胞中ATP產(chǎn)生過程的主要底物。一項(xiàng)針對游離脂肪酸在此過程中相對貢獻(xiàn)的研究揭示，脂肪甘油三酯脂肪酶（ATGL），一種許多組織中脂滴相關(guān)三酰甘油水解的限速酶，它缺失時巨噬細(xì)胞無法有效水解細(xì)胞三酰甘油儲備導(dǎo)致細(xì)胞游離脂肪酸濃度下降和脂滴集聚，細(xì)胞游離脂肪酸濃度下降導(dǎo)致了細(xì)胞ATP濃度的下降損害吞噬作用。添加外源性葡萄糖也無法完全補(bǔ)償這一損害。這一發(fā)現(xiàn)暗示巨噬細(xì)胞的吞噬作用依賴細(xì)胞游離脂肪酸和將其從脂滴儲備中水解釋放出來的ATGL。這一新機(jī)理將ATGL調(diào)節(jié)的脂類分解與宿主防御中吞噬細(xì)胞的功能聯(lián)系起來，也開啟了研究ATGL在免疫反應(yīng)、炎癥和動脈硬化中作用的大門。
【點(diǎn)評】
這一發(fā)現(xiàn)從能量供應(yīng)的角度說明了脂肪對宿主防御免疫功能的重要性。

【原文摘錄】June 25, 2010 The Journal of Biological Chemistry, 285, 20192-20201.
Efficient Phagocytosis Requires Triacylglycerol Hydrolysis by Adipose Triglyceride Lipase
Prakash G. Chandak, Branislav Radović, Elma Aflaki, et al.
Macrophage phagocytosis is an essential biological process in host defense and requires large amounts of energy. To date, glucose is believed to represent the prime substrate for ATP production in macrophages. To investigate the relative contribution of free fatty acids (FFAs) in this process, we determined the phagocytosis rates in normal mouse macrophages and macrophages of adipose triglyceride lipase (ATGL)-deficient mice. ATGL was shown to be the rate-limiting enzyme for the hydrolysis of lipid droplet-associated triacylglycerol (TG) in many tissues. Here, we demonstrate that Atgl−/− macrophages fail to efficiently hydrolyze cellular TG stores leading to decreased cellular FFA concentrations and concomitant accumulation of lipid droplets, even in the absence of exogenous lipid loading. The reduced availability of FFAs results in decreased cellular ATP concentrations and impaired phagocytosis suggesting that fatty acids must first go through a cycle of esterification and re-hydrolysis before they are available as energy substrate. Exogenously added glucose cannot fully compensate for the phagocytotic defect in Atgl−/− macrophages. Hence, phagocytosis was also decreased in vivo when Atgl−/− mice were challenged with bacterial particles. These findings imply that phagocytosis in macrophages depends on the availability of FFAs and that ATGL is required for their hydrolytic release from cellular TG stores. This novel mechanism links ATGL-mediated lipolysis to macrophage function in host defense and opens the way to explore possible roles of ATGL in immune response, inflammation, and atherosclerosis.

5. Smed-prep基因是渦蟲的頭部和大腦適當(dāng)再生的基本要素
【摘要】《PLoS遺傳學(xué)》 發(fā)布時間：2010-6-25 10:47:03
　　英國科學(xué)家宣布，他們已經(jīng)發(fā)現(xiàn)了渦蟲的身體某些部位在被截掉后能夠再生的基因。
　　英國諾丁漢大學(xué)的科學(xué)家對渦蟲身體部位的再生能力進(jìn)行了研究，這些部位包括頭部和大腦，有一天這項(xiàng)研究有可能會使老化或受損的人體器官和組織再生成為可能。諾丁漢大學(xué)生物學(xué)院的英國研究委員會成員阿齊茲•亞布巴克博士是這項(xiàng)研究的領(lǐng)導(dǎo)者，該研究顯示，一種被稱作“Smed-prep”的基因顯然是導(dǎo)致渦蟲的頭部和大腦適當(dāng)再生的基本要素。
　　渦蟲具有在被截斷后，身體部位再生的獨(dú)特能力，這些部位包括頭部和大腦。它們含有成熟干細(xì)胞，這些細(xì)胞經(jīng)常分裂，變成身體缺失的所有類型的細(xì)胞。該研究顯示，當(dāng)渦蟲的身體部位進(jìn)行再生時，是一套基因在控制這一過程，使它們在正確位置再生出大小、形狀和方位保持原狀的肢體。該研究成果發(fā)表在4月22日的《公共科學(xué)圖書館•遺傳學(xué)》（PLoS Genetics）雜志上。
　　研究人員表示，Smed-prep是組成渦蟲頭部的細(xì)胞正確分化和定位的必要因素，也是確定頭部位置的關(guān)鍵。他們還發(fā)現(xiàn)，盡管Smed- prep的出現(xiàn)是導(dǎo)致頭部和大腦處于正確位置的決定因素，但是渦蟲干細(xì)胞會在其他不相干的基因影響下，形成腦細(xì)胞。不過研究人員表示，即便如此，如果沒有Smed-prep，這些細(xì)胞是無法自行組織起來，形成正常大腦的。
　　參與這項(xiàng)研究的研究生丹尼爾•菲利克斯22日說：“從分子層面了解組織的改造和再生，對再生醫(yī)學(xué)的研究至關(guān)重要。渦蟲因其強(qiáng)大的再生能力而特別出名，它們能在頭部被砍掉以后再生一個新的出來。通過Smed-prep的同源異位基因，我們確定了第一種對再生期間獲得上述結(jié)果和模式起關(guān)鍵作用的基因。這是一項(xiàng)振奮人心的研究項(xiàng)目，能參加這項(xiàng)研究，并把它作為我的論文課題，我感到非常幸運(yùn)?！保▉碓矗盒吕丝萍?任秋凌）
【點(diǎn)評】
這一研究增進(jìn)了對渦蟲強(qiáng)大再生能力的了解，雖然目前還看不出能對人體的再生有多大影響，希望將來有助于促進(jìn)人體再生的研究。

【原文摘錄】PLoS Genet 6(4): e1000915. doi:10.1371/journal.pgen.1000915
The TALE Class Homeobox Gene Smed-prep Defines the Anterior Compartment for Head Regeneration
Felix DA, Aboobaker AA
Planaria continue to blossom as a model system for understanding all aspects of regeneration. They provide an opportunity to understand how the replacement of missing tissues from preexisting adult tissue is orchestrated at the molecular level. When amputated along any plane, planaria are capable of regenerating all missing tissue and rescaling all structures to the new size of the animal. Recently, rapid progress has been made in understanding the developmental pathways that control planarian regeneration. In particular Wnt/beta-catenin signaling is central in promoting posterior fates and inhibiting anterior identity. Currently the mechanisms that actively promote anterior identity remain unknown. Here, Smed-prep, encoding a TALE class homeodomain, is described as the first gene necessary for correct anterior fate and patterning during planarian regeneration. Smed-prep is expressed at high levels in the anterior portion of whole animals, and Smed-prep(RNAi) leads to loss of the whole brain during anterior regeneration, but not during lateral regeneration or homeostasis in intact worms. Expression of markers of different anterior fated cells are greatly reduced or lost in Smed-prep(RNAi) animals. We find that the ectopic anterior structures induced by abrogation of Wnt signaling also require Smed-prep to form. We use double knockdown experiments with the S. mediterranea ortholog of nou-darake (that when knocked down induces ectopic brain formation) to show that Smed-prep defines an anterior fated compartment within which stem cells are permitted to assume brain fate, but is not required directly for this differentiation process. Smed-prep is the first gene clearly implicated as being necessary for promoting anterior fate and the first homeobox gene implicated in establishing positional identity during regeneration. Together our results suggest that Smed-prep is required in stem cell progeny as they form the anterior regenerative blastema and is required for specifying anterior cell fates and correct patterning.

6. 環(huán)孢霉素治療成為誘發(fā)新癌癥的因素
【摘要】
　　荷蘭研究人員日前發(fā)現(xiàn)在肝臟移植的病人中環(huán)孢霉素治療是引起新發(fā)癌癥的顯著風(fēng)險因子。過去三十年來，肝臟移植后一年生存率顯著增長到超過80%，相反的，長期效果沒有任何改進(jìn)。惡性腫瘤是肝臟移植后的一個主要死因，而且據(jù)報道與免疫抑制劑的強(qiáng)度和累積劑量有直接關(guān)系。象環(huán)孢霉素或他克莫司這類鈣調(diào)磷酸酶抑制劑是器官移植后免疫抑制治療的基石。該研究涉及20年內(nèi)385例肝臟移植病例。在移植后第1、5、10和15年新癌癥的發(fā)生率分別是2.9% ± 0.9%, 10.5% ± 1.8%, 19.4% ± 3.0%, and 33.6% ± 6.8%。
【點(diǎn)評】
　　這一研究暗示了器官移植后的免疫抑制治療會導(dǎo)致病人死于新發(fā)癌癥，極大降低了器官移植的價值。

【原文摘錄】 Liver Transplantation，2010，16（7）：837 - 846
Increased incidence of early de novo cancer in liver graft recipients treated with cyclosporine: An association with C2 monitoring and recipient age
Angela S. W. Tjon, Jerome Sint Nicolaas, Jaap Kwekkeboom，et al.
The goal of this study was to determine the risk factors for de novo cancer after liver transplantation (LTx). Retrospective analyses were performed in 385 LTx patients who underwent transplantation between 1986 and 2007. In total, 50 (13.0%) recipients developed de novo malignancy. The cumulative incidence of de novo cancer at 1, 5, 10, and 15 years after LTx was 2.9% ± 0.9%, 10.5% ± 1.8%, 19.4% ± 3.0%, and 33.6% ± 6.8%, respectively. The standardized incidence ratio of malignancy in LTx patients compared to the general population was 2.2 (95% confidence interval: 1.6-2.8). After excluding posttransplant lymphoproliferative disorder and skin cancer, patients with de novo cancer had a significantly lower survival rate compared to recipients who remained cancer-free. The identified univariate risk factors for de novo cancer were cyclosporine A (CsA) treatment, time period of LTx, and recipient age. In multivariate analysis, only CsA treatment emerged as an independent risk factor for de novo cancer, which was attributed to more aggressive cancer types. A surprising finding was that CsA treatment specifically enhanced cancer risk in patients who underwent transplantation after 2004, when C2 monitoring (blood concentration at 2 hours postdose) was introduced. In addition, these patients showed a significantly lower acute rejection rate, which might reflect a more robust immunosuppressive status caused by the CsA-C2 regimen. When age was considered, only patients 50 years had a higher cancer rate when treated with CsA compared to treatment with tacrolimus. Our data suggest that, compared to tacrolimus treatment, CsA treatment with C2 monitoring or in younger patients of 50 years is associated with a higher early de novo cancer risk after LTx.