世界生命科学前沿动态周报（八）

（05.10—05.16 / 2010）
美宝国际集团:陶国新 

　　本周动态包括以下内容：卵巢激素孕酮驱使乳腺干细胞发生动态变化； VE琥珀酸酯可明显抑制肿瘤细胞生长；发现抑制胃癌的重要基因；细胞与组织疗法与临床应用之间的距离；成人口腔黏膜固有层里有一类新干细胞群；老鼠ips细胞12号染色体印迹基因异常沉默。

1. 卵巢激素孕酮驱使乳腺干细胞发生动态变化
【摘要】
　　 2010-5-10 9:22:45 Nature：香港玛嘉烈医院的癌症研究人员发现，卵巢激素孕酮在改变乳腺干细胞方面承担了重要的角色。老鼠研究表明，在月经的下半个周期孕酮分泌会达到峰值，此时干细胞和邻近细胞开始相互交流，驱使正常的乳腺干细胞数量扩增，这就可能导致环境改变使得癌症易于发生。直到现在，普遍观点认为在成年女性乳房中，乳腺干细胞一般是不活跃的，这项关于荷尔蒙改变乳腺干细胞的研究为乳腺癌初期的细胞生长开启了新的理解方式，有利于开发新的干细胞靶向定位方法。这是第一个关于孕酮驱使乳腺干细胞发生动态变化的证据，这种激活机制为细胞变化过程的开启提供了机会，并最终导致乳腺癌的发生。
【点评】
　　点评：发现激素对乳腺干细胞的调节作用，有助于干细胞生命规律的研究。
【原文摘录】
Nature doi:10.1038/nature09091
Progesterone induces adult mammary stem cell expansion
Purna A. Joshi1, Hartland W. Jackson1, Alexander G. Beristain1, Marco A. Di Grappa1, Patricia Mote2, Christine Clarke2, John Stingl3, Paul D. Waterhouse1 & Rama Khokha1
Reproductive history is the strongest risk factor for breast cancer after age, genetics and breast density1, 2. Increased breast cancer risk is entwined with a greater number of ovarian hormone-dependent reproductive cycles, yet the basis for this predisposition is unknown3, 4, 5. Mammary stem cells (MaSCs) are located within a specialized niche in the basal epithelial compartment that is under local and systemic regulation6. The emerging role of MaSCs in cancer initiation warrants the study of ovarian hormones in MaSC homeostasis. Here we show that the MaSC pool increases 14-fold during maximal progesterone levels at the luteal dioestrus phase of the mouse. Stem-cell-enriched CD49fhi cells amplify at dioestrus, or with exogenous progesterone, demonstrating a key role for progesterone in propelling this expansion. In aged mice, CD49fhi cells display stasis upon cessation of the reproductive cycle. Progesterone drives a series of events where luminal cells probably provide Wnt4 and RANKL signals to basal cells which in turn respond by upregulating their cognate receptors, transcriptional targets and cell cycle markers. Our findings uncover a dynamic role for progesterone in activating adult MaSCs within the mammary stem cell niche during the reproductive cycle, where MaSCs are putative targets for cell transformation events leading to breast cancer.

2. VE琥珀酸酯可明显抑制肿瘤细胞生长
【摘要】 科学时报 发布时间：2010-5-14 9:36:19
　　日前，哈尔滨医科大学公共卫生学院教授吴坤指导的课题组在寻找维生素E琥珀酸酯（VES）在肿瘤化学防治中的作用及信号传导途径的研究中发现，VES能特异性地抑制胃癌细胞的生长和DNA合成，并诱导其发生细胞凋亡和细胞分化。 课题组建立起小鼠前胃癌模型，经口灌胃或经腹腔注射VES，结果表明VES可显著降低肿瘤的数量和体积，提高实验小鼠的免疫功能；与此同时，他们在离体试验条件下，以人胃癌细胞为靶细胞，观察VES对其生长抑制情况，结果也显示，VES能明显抑制癌细胞的生长及DNA合成，促进胃癌细胞分化和诱导细胞凋亡，而对正常细胞无不良影响。 吴坤课题组进行细胞和动物实验，科学证实了VES确能遏制肿瘤细胞的生长，延长荷瘤小鼠的生存时间。这为今后VES的资源开发及临床推广应用奠定了坚实的理论基础。
【点评】
　　点评：维生素E琥珀酸酯在细胞和动物实验中显示的抑制胃癌细胞生长及诱导其分化或凋亡的功能若能在人体上也看得到，就很可能会为其在胃癌的预防性营养食品中赢来一席之地。

3. 发现抑制胃癌的重要基因
【摘要】 医药123 2010-5-13 13:47:02
　　上海交通大学医学院附属瑞金医院专家首次发现了5号染色体短臂上的同源盒基因IRX1对抑制胃癌细胞具有重要作用，IRX1的活性丢失可导致胃癌细胞增殖与侵袭能力增加。研究人员发现，通过转基因技术将该基因导入胃癌细胞，使IRX1基因活性恢复后，无论是体外培养的胃癌细胞，还是小鼠活体内的肿瘤细胞，其恶性增殖与侵袭能力均受到明显抑制。 该研究不仅首次提出IRX1基因在胃癌发生发展中的抑癌基因作用，还发现了另外一个重要现象，即：不但胃癌组织中可以检测到IRX1基因启动子的高甲基化，在胃癌患者的外周血游离DNA中也可以检测到IRX1基因的高甲基化。 研究人员表示，此项研究或成为胃癌诊断新型分子标志物的重要线索。
【点评】
　　点评：IRX1基因抑制胃癌的作用及其启动子的高甲基化的规律使其有助于胃癌的诊断。
【原文摘录】
Oncogene doi:10.1038/onc.2010.143
Homeobox gene IRX1 is a tumor suppressor gene in gastric carcinoma
X Guo, W Liu, Y Pan, P Ni, J Ji, L Guo, J Zhang, J Wu, J Jiang, X Chen, Q Cai, J Li, J Zhang, Q Gu, B Liu, Z Zhu and Y Yu
The IRX1 tumor suppressor gene is located on 5p15.33, a cancer susceptibility locus. Loss of heterozygosity of 5p15.33 in gastric cancer was identified in our previous work. In this study, we analyzed the molecular features and function of IRX1. We found that IRX1 expression was lost or reduced in gastric cancer. However, no mutations were identified in IRX1-encoding regions. IRX1 transcription was suppressed by hypermethylation, and the expression of IRX1 mRNA was partially restored in gastric cancer cells after 5-Aza-dC treatment. Restoring IRX1 expression in SGC-7901 and NCI-N87 gastric cancer cells inhibited growth, invasion and tumorigenesis in vitro and in vivo. We identified a number of target genes by global microarray analysis after IRX1 transfection combined with real-time PCR and chromatin immunoprecipitation assay. BDKRB2, an angiogenesis-related gene, HIST2H2BE and FGF7, cell proliferation and invasion-related genes, were identified as direct IRX1 target genes. The hypermethylation of IRX1 was not only detected in primary gastric cancer tissues but also in the peripheral blood of gastric cancer patients, suggesting IRX1 could potentially serve as a biomarker for gastric cancer.

4. 细胞与组织疗法与临床应用之间的距离
【摘要】
　　细胞与组织疗法中细胞的鉴别和定量面临着很多挑战，从管理的角度看，这类治疗不止必须安全有效还得高质量生产以便能按时运送活细胞。尽管无菌试验适用常规的生物工艺，细胞与组织疗法需要更严格的安全测试，特别是与使用动物制品、免疫反应和长时间培养导致的潜在不稳定性有关时。而且，鉴于其无限生长的潜力，计划将人类胚胎干细胞用于治疗的细胞生产者需要更加严格监控最后的纯化过程。
【点评】
　　点评：目前的细胞与组织移植的疗法面临诸多挑战，想要成功转化为临床实践还得先能克服这些挑战，能否成功还很难说。
【原文摘录】STEM CELLS 2010;28:996-1004
Concise Review: Mind the Gap: Challenges in Characterizing and Quantifying Cell- and Tissue-Based Therapies for Clinical Translation
Erin A. Rayment *¶, David J. Williams
There are many challenges associated with characterizing and quantifying cells for use in cell- and tissue-based therapies. From a regulatory perspective, these advanced treatments must not only be safe and effective but also be made by high-quality manufacturing processes that allow for on-time delivery of viable products. Although sterility assays can be adapted from conventional bioprocessing, cell- and tissue-based therapies require more stringent safety assessments, especially in relation to use of animal products, immune reaction, and potential instability due to extended culture times. Furthermore, cell manufacturers who plan to use human embryonic stem cells in their therapies need to be particularly stringent in their final purification steps, due to the unrestricted growth potential of these cells. This review summarizes the current issues in characterization and quantification for cell- and tissue-based therapies, dividing these challenges into the regulatory themes of safety, potency, and manufacturing quality. It outlines current assays in use, as well as highlights the limits of many of these product release tests. Mode of action is discussed, with particular reference to in vitro surrogate assays that can be used to provide information to correlate with proposed in vivo patient efficacy. Importantly, this review highlights the requirement for basic research to improve current knowledge on the in vivo fate of these treatments; as well as an improved stakeholder negotiation process to identify the measurement requirements that will ensure the manufacture of the best possible cell- and tissue-based therapies within the shortest timeframe for the most patient benefit.

5. 成人口腔黏膜固有层里有一类新干细胞群
【摘要】
　　成人口腔黏膜固有层里有一类具有明显的原始神经嵴样表型的原始干细胞群，将其移植到有严重免疫缺陷的老鼠身上时形成了含有来自两种胚层细胞的肿瘤。这是第一例报道由来自良性成人身体组织的干细胞群形成混合外胚层和中胚层细胞的肿瘤。
【点评】
　　点评：干细胞移植形成肿瘤的风险难以避免。
【原文摘录】STEM CELLS 2010;28:984-995
The Lamina Propria of Adult Human Oral Mucosa Harbors a Novel Stem Cell Population
Keren Marynka-Kalmani 1, Sandra Treves 1, Miri Yafee 1, Heled Rachima 2, Yossi Gafni 1, Malkiel A. Cohen 3, Sandu Pitaru 1 *¶
The highly regenerative capacity of the human adult oral mucosa suggests the existence of a robust stem cell (SC) population in its lamina propria (OMLP). The purpose of this study was to characterize the availability, growth, immunophenotype, and potency of this presumable SC population. Cells positive for the embryonic stem cell transcription factors Oct4 and Sox2 and for p75 formed distinct cord-like structure in the OMLP. Regardless of donor age, trillions of cells, termed human oral mucosa stem cells (hOMSC), 95% of which express mesenchymal stromal cell markers, were simply, and reproducibly produced from a biopsy of 3-4 × 2 × 1 mm3. A total of 40-60% of these cells was positive for Oct4, Sox2, and Nanog and 60-80% expressed constitutively neural and neural crest SC markers. hOMSC differentiated in culture into mesodermal (osteoblastic, chondroblastic, and adipocytic), definitive endoderm and ectodermal (neuronal) lineages. Unexpectedly, hOMSC treated with dexamethasone formed tumors consisting of two germ layer-derived tissues when transplanted in severe combined immune deficiency mice. The tumors consisted of tissues produced by neural crest cells during embryogenesis - cartilage, bone, fat, striated muscle, and neural tissue. These results show that the adult OMLP harbors a primitive SC population with a distinct primitive neural-crest like phenotype and identifies the in vivo localization of putative ancestors for this population. This is the first report on ectodermal- and mesodermal-derived mixed tumors formation by a SC population derived from a nonmalignant somatic adult human tissue.

6. 老鼠ips细胞12号染色体印迹基因异常沉默
【摘要】
　　比较相同遗传来源的老鼠胚胎干细胞和诱导多能干细胞，发现大多数诱导多能干细胞的染色体12qF1上Dlk1–Dio3基因簇异常沉默，因此ips老鼠大多无法完成完整发育过程。值得注意的是，用组蛋白脱乙酰酶抑制剂处理的Dlk1–Dio3基因簇异常沉默的ips细胞该基因簇复活能支撑ips老鼠完成完整发育过程。
【 点评】
　　点评：该文再次证实ips细胞自身基因缺陷造成其无法完成完整发育过程。
【原文摘录】Nature, Volume:465,Pages:175–181 doi:10.1038/nature09017
Aberrant silencing of imprinted genes on chromosome 12qF1 in mouse induced pluripotent stem cells
Matthias Stadtfeld, Effie Apostolou, Hidenori Akutsu, et al
Induced pluripotent stem cells (iPSCs) have been generated by enforced expression of defined sets of transcription factors in somatic cells. It remains controversial whether iPSCs are molecularly and functionally equivalent to blastocyst-derived embryonic stem (ES) cells. By comparing genetically identical mouse ES cells and iPSCs, we show here that their overall messenger RNA and microRNA expression patterns are indistinguishable with the exception of a few transcripts encoded within the imprinted Dlk1–Dio3 gene cluster on chromosome 12qF1, which were aberrantly silenced in most of the iPSC clones. Consistent with a developmental role of the Dlk1–Dio3 gene cluster, these iPSC clones contributed poorly to chimaeras and failed to support the development of entirely iPSC-derived animals (‘all-iPSC mice’). In contrast, iPSC clones with normal expression of the Dlk1–Dio3 cluster contributed to high-grade chimaeras and generated viable all-iPSC mice. Notably, treatment of an iPSC clone that had silenced Dlk1–Dio3 with a histone deacetylase inhibitor reactivated the locus and rescued its ability to support full-term development of all-iPSC mice. Thus, the expression state of a single imprinted gene cluster seems to distinguish most murine iPSCs from ES cells and allows for the prospective identification of iPSC clones that have the full development potential of ES cells.