世界生命科学前沿动态周报（十四）

（06.21 --06.27 / 2010）
美宝国际集团:陶国新 

　　本周动态包括以下内容：自体角膜缘干细胞移植治愈角膜烧伤导致的失明；吉非替尼药物显著提高表皮生长因子受体突变的晚期非小细胞肺癌患者的生存期；研究发现RNA的新功能；有效的吞噬作用需要ATGL调节的三酰甘油水解；Smed-prep基因是涡虫的头部和大脑适当再生的基本要素；环孢霉素A治疗成为诱发肝脏移植病人新癌症的因素。
1. 自体角膜缘干细胞移植治愈角膜烧伤导致的失明
【摘要】
　　新英格兰医学杂志提前在线发表的一篇文章讲述了通过移植自体角膜缘干细胞来再生角膜治愈角膜烧伤导致的失明，107例眼睛有82例完全有效，14例部分有效，无效的都发生在移植后第一年。到目前为止移植后新生的角膜正常工作已达十年。这是迄今为止此类研究时间最长规模最大的一次。 每年干细胞移植把希望带给了全世界数千因强效清洁剂或其他化学物质烧伤角膜的患者。 这一方法不能治疗涉及视网膜的视神经损伤或黄斑变性患者，也不能治疗双目完全失明患者，因为此类患者没有可供移植的健康角膜缘组织。
【点评】
　　尽管还只能治疗一部分角膜烧伤导致失明的患者，自体角膜缘干细胞移植已经是为数不多的能在临床应用的自体干细胞移植治疗技术。

【原文摘录】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. 吉非替尼药物显著提高表皮生长因子受体突变的晚期非小细胞肺癌患者的生存期
【摘要】新华网 发布时间：2010-6-24 16:34:46
　　日本研究人员最新临床试验发现，对于一种具有特定基因突变特征的晚期非小细胞肺癌患者，肺癌药物易瑞沙（通用名吉非替尼）比标准的肺癌化疗药物更加有效，可使患者生存期延长一倍。肺癌有两种主要类型：小细胞肺癌和非小细胞肺癌，其中后者占肺癌病例的75%。日本东北大学研究小组6月24日在新一期美国《新英格兰医学杂志》上介绍说，某些非小细胞肺癌患者，其基因变异会导致一种名为“表皮生长因子受体（EGFR）”的特殊蛋白质在某些癌细胞表面过多分布，导致癌细胞增殖。在日本，大约67%的女性肺癌患者和15%的男性肺癌患者出现这种基因变异，标准化疗治疗的生存期仅为13.9个月。研究人员将230名具有这一基因变异的晚期非小细胞肺癌患者分为两组，其中一组从一开始就利用易瑞沙进行治疗，对照组则是在标准化疗不起作用后再使用易瑞沙。结果表明，从一开始就使用易瑞沙治疗的患者平均生存期为30.5个月，比标准化疗治疗的生存期延长了一倍多；对照组的生存期平均为23.6个月，也延长近一倍。易瑞沙可以阻断EGFR向肺癌细胞发送增殖信号，从而抑制癌症发展。研究人员说，针对这类肺癌患者使用易瑞沙治疗，患者对药物的反应更好，从而提高了疗效。
【点评】
特异性更高的药物吉非替尼能显著提高具有特定基因突变特征的晚期非小细胞肺癌患者生存期，但是依然无法阻止癌症的进展，更不能治愈。

【原文摘录】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. 研究发现RNA的新功能
【摘要】
　　分子生物学的中心法则认为遗传信息通过信使RNA从DNA传递到功能蛋白。这暗示信使RNA只有编码蛋白一种功能。现在，哈佛医学院的一个癌症遗传学研究组发现RNA有更多的作用。除了编码蛋白，信使RNA还能够互相交流，从而具有调节作用，即使是那些非编码RNA也能够互相交流。这一发现大大丰富了功能基因库信息。
【点评】
这一发现丰富了功能基因库信息，另一方面，它也说明了基因调控体系的复杂性，解释了为什么基因治疗迄今没有成功的临床实践。

【原文摘录】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调节的三酰甘油水解
【摘要】
　　巨噬细胞吞噬作用是宿主防御的必需生物学过程，需要大量能量。至今葡萄糖被认为是巨噬细胞中ATP产生过程的主要底物。一项针对游离脂肪酸在此过程中相对贡献的研究揭示，脂肪甘油三酯脂肪酶（ATGL），一种许多组织中脂滴相关三酰甘油水解的限速酶，它缺失时巨噬细胞无法有效水解细胞三酰甘油储备导致细胞游离脂肪酸浓度下降和脂滴集聚，细胞游离脂肪酸浓度下降导致了细胞ATP浓度的下降损害吞噬作用。添加外源性葡萄糖也无法完全补偿这一损害。这一发现暗示巨噬细胞的吞噬作用依赖细胞游离脂肪酸和将其从脂滴储备中水解释放出来的ATGL。这一新机理将ATGL调节的脂类分解与宿主防御中吞噬细胞的功能联系起来，也开启了研究ATGL在免疫反应、炎症和动脉硬化中作用的大门。
【点评】
这一发现从能量供应的角度说明了脂肪对宿主防御免疫功能的重要性。

【原文摘录】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基因是涡虫的头部和大脑适当再生的基本要素
【摘要】《PLoS遗传学》 发布时间：2010-6-25 10:47:03
　　英国科学家宣布，他们已经发现了涡虫的身体某些部位在被截掉后能够再生的基因。
　　英国诺丁汉大学的科学家对涡虫身体部位的再生能力进行了研究，这些部位包括头部和大脑，有一天这项研究有可能会使老化或受损的人体器官和组织再生成为可能。诺丁汉大学生物学院的英国研究委员会成员阿齐兹•亚布巴克博士是这项研究的领导者，该研究显示，一种被称作“Smed-prep”的基因显然是导致涡虫的头部和大脑适当再生的基本要素。
　　涡虫具有在被截断后，身体部位再生的独特能力，这些部位包括头部和大脑。它们含有成熟干细胞，这些细胞经常分裂，变成身体缺失的所有类型的细胞。该研究显示，当涡虫的身体部位进行再生时，是一套基因在控制这一过程，使它们在正确位置再生出大小、形状和方位保持原状的肢体。该研究成果发表在4月22日的《公共科学图书馆•遗传学》（PLoS Genetics）杂志上。
　　研究人员表示，Smed-prep是组成涡虫头部的细胞正确分化和定位的必要因素，也是确定头部位置的关键。他们还发现，尽管Smed- prep的出现是导致头部和大脑处于正确位置的决定因素，但是涡虫干细胞会在其他不相干的基因影响下，形成脑细胞。不过研究人员表示，即便如此，如果没有Smed-prep，这些细胞是无法自行组织起来，形成正常大脑的。
　　参与这项研究的研究生丹尼尔•菲利克斯22日说：“从分子层面了解组织的改造和再生，对再生医学的研究至关重要。涡虫因其强大的再生能力而特别出名，它们能在头部被砍掉以后再生一个新的出来。通过Smed-prep的同源异位基因，我们确定了第一种对再生期间获得上述结果和模式起关键作用的基因。这是一项振奋人心的研究项目，能参加这项研究，并把它作为我的论文课题，我感到非常幸运。”（来源：新浪科技 任秋凌）
【点评】
这一研究增进了对涡虫强大再生能力的了解，虽然目前还看不出能对人体的再生有多大影响，希望将来有助于促进人体再生的研究。

【原文摘录】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. 环孢霉素治疗成为诱发新癌症的因素
【摘要】
　　荷兰研究人员日前发现在肝脏移植的病人中环孢霉素治疗是引起新发癌症的显著风险因子。过去三十年来，肝脏移植后一年生存率显著增长到超过80%，相反的，长期效果没有任何改进。恶性肿瘤是肝脏移植后的一个主要死因，而且据报道与免疫抑制剂的强度和累积剂量有直接关系。象环孢霉素或他克莫司这类钙调磷酸酶抑制剂是器官移植后免疫抑制治疗的基石。该研究涉及20年内385例肝脏移植病例。在移植后第1、5、10和15年新癌症的发生率分别是2.9% ± 0.9%, 10.5% ± 1.8%, 19.4% ± 3.0%, and 33.6% ± 6.8%。
【点评】
　　这一研究暗示了器官移植后的免疫抑制治疗会导致病人死于新发癌症，极大降低了器官移植的价值。

【原文摘录】 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.