世界生命科學(xué)前沿動態(tài)周報（三十二）

（11.15 -- 11.21 / 2010）
美寶國際集團(tuán):陶國新 

　　本周動態(tài)包括以下內(nèi)容：黑色素瘤與腫瘤干細(xì)胞模型不符；科學(xué)家研制出新型細(xì)胞培養(yǎng)系統(tǒng)；研究揭示miRNA在先天免疫中作用；研究揭示肺炎感染人體反應(yīng)機(jī)制；FTO基因過度活躍可導(dǎo)致肥胖；維生素D不足可導(dǎo)致白血病惡化。

1. 黑色素瘤與腫瘤干細(xì)胞模型不符

【摘要】ScienceDaily (Nov. 15, 2010)
　　美國Michigan大學(xué)的研究人員發(fā)現(xiàn)大多數(shù)類型的黑色素瘤細(xì)胞都能形成惡性腫瘤，為黑色素瘤這一最致命的皮膚癌不符合越來越流行的腫瘤干細(xì)胞模型提供了新證據(jù)。另外，研究人員還發(fā)現(xiàn)黑色素瘤細(xì)胞能通過開關(guān)不同的基因改變自身形狀而成為神秘的變形者來逃避治療。

【點評】
　　該發(fā)現(xiàn)作為一個反證表明癌癥發(fā)生的腫瘤干細(xì)胞模型可能是錯誤的，癌癥的起因依然有待闡明。

【原文摘錄】Cancer Cell, 2010; 18 (5): 510-523 DOI: 10.1016/j.ccr.2010.10.012
Phenotypic Heterogeneity among Tumorigenic Melanoma Cells from Patients that Is Reversible and Not Hierarchically Organized.
Elsa Quintana, Mark Shackleton, Hannah R. Foster, et al.
We investigated whether melanoma is hierarchically organized into phenotypically distinct subpopulations of tumorigenic and nontumorigenic cells or whether most melanoma cells retain tumorigenic capacity, irrespective of their phenotype. We found 28% of single melanoma cells obtained directly from patients formed tumors in NOD/SCID IL2Rnull mice. All stage II, III, and IV melanomas obtained directly from patients had common tumorigenic cells. All tumorigenic cells appeared to have unlimited tumorigenic capacity on serial transplantation. We were unable to find any large subpopulation of melanoma cells that lacked tumorigenic potential. None of 22 heterogeneously expressed markers, including CD271 and ABCB5, enriched tumorigenic cells. Some melanomas metastasized in mice, irrespective of whether they arose from CD271 or CD271+ cells. Many markers appeared to be reversibly expressed by tumorigenic melanoma cells.

2. 科學(xué)家研制出新型細(xì)胞培養(yǎng)系統(tǒng)
 
【摘要】
　　美國威斯康辛大學(xué)麥迪遜分校的科學(xué)家們近日開發(fā)出一套新細(xì)胞培養(yǎng)系統(tǒng)，有望為細(xì)胞治療提供更加一致和安全的細(xì)胞培養(yǎng)物。11月14日的《自然—方法學(xué)》刊登了這一成果。領(lǐng)導(dǎo)這項研究的Laura Kiessling教授表示這套系統(tǒng)并不昂貴，可承擔(dān)多能細(xì)胞培養(yǎng)中的大量預(yù)估工作。這項技術(shù)“很簡單”，“任何人都能使用”。目前，大部分人類胚胎干細(xì)胞的培養(yǎng)都是作為實驗室研究用途的，而通常所采用的培養(yǎng)方法又容易造成各種污染。這套新系統(tǒng)采用一種化學(xué)合成制得的可與干細(xì)胞相結(jié)合的蛋白片段底物，并通過與特定培養(yǎng)基結(jié)合，可將細(xì)胞培養(yǎng)固定在未分化階段達(dá)三個月或者更長時間。據(jù)報告顯示，該系統(tǒng)亦可用于誘導(dǎo)多功能干細(xì)胞培養(yǎng)?！翱茖W(xué)家現(xiàn)在普遍采用的培養(yǎng)系統(tǒng)都有著非特定的缺點，并且缺乏一致性，以致出現(xiàn)質(zhì)量差異”， 領(lǐng)導(dǎo)這項研究的Laura Kiessling教授解釋，“我們研發(fā)的這套系統(tǒng)特定性很好，而且并不貴”。（科學(xué)網(wǎng) 張笑/編譯）

【點評】
更加一致、穩(wěn)定和安全的細(xì)胞培養(yǎng)物對于干細(xì)胞培養(yǎng)和研究的質(zhì)量控制大有好處。這一技術(shù)可能會促進(jìn)干細(xì)胞研究領(lǐng)域的發(fā)展。

【原文摘錄】Nature Methods, 14 November 2010 DOI: 10.1038/nmeth.1532
A defined glycosaminoglycan-binding substratum for human pluripotent stem cells
Joseph R Klim, Lingyin Li, Paul J Wrighton, et al.
To exploit the full potential of human pluripotent stem cells for regenerative medicine, developmental biology and drug discovery, defined culture conditions are needed. Media of known composition that maintain human embryonic stem (hES) cells have been developed, but finding chemically defined, robust substrata has proven difficult. We used an array of self-assembled monolayers to identify peptide surfaces that sustain pluripotent stem cell self-renewal. The effective substrates displayed heparin-binding peptides, which can interact with cell-surface glycosaminoglycans and could be used with a defined medium to culture hES cells for more than 3 months. The resulting cells maintained a normal karyotype and had high levels of pluripotency markers. The peptides supported growth of eight pluripotent cell lines on a variety of scaffolds. Our results indicate that synthetic substrates that recognize cell-surface glycans can facilitate the long-term culture of pluripotent stem cells.

3. 研究揭示miRNA在先天免疫中作用
 
【摘要】
　　11月10日，國際權(quán)威學(xué)術(shù)期刊《免疫學(xué)期刊》（Journal of Immunology）在線發(fā)表了中科院上海巴斯德所最新研究成果，該成果揭示了microRNA在先天免疫中的作用以及調(diào)控機(jī)制，并研究了這種作用在地塞米松抗炎癥效應(yīng)中的地位。這項成果是博士研究生朱清源在戈寶學(xué)研究員指導(dǎo)下完成的。先天免疫中炎癥因子的調(diào)節(jié)需要被精細(xì)地控制，過多或者過少的炎癥因子都可能會造成機(jī)體的負(fù)面反應(yīng)。MAPK是負(fù)責(zé)炎癥因子產(chǎn)生的重要信號通路，可以在TLR激活的免疫反應(yīng)中通過磷酸化來誘導(dǎo)下游轉(zhuǎn)錄因子激活炎癥因子轉(zhuǎn)錄。而同時，這個信號通路的激活會導(dǎo)致MKP-1的產(chǎn)生，這是一種可以通過對MAPK進(jìn)行去磷酸化作用使炎癥反應(yīng)下調(diào)的分子。MAPK與MKP-1構(gòu)成了一個標(biāo)準(zhǔn)的負(fù)反饋調(diào)節(jié)莖環(huán)結(jié)構(gòu)。
　　研究人員發(fā)現(xiàn)一種microRNA (miR-101)可以通過靶向MKP-1 mRNA的3’- UTR來調(diào)節(jié)MAPK的反應(yīng)，進(jìn)而影響下游炎癥因子的分泌。更進(jìn)一步的實驗表明，PI3K/AKT通路可以調(diào)控miR-101的表達(dá)，從而影響MKP-1以及MAPK的表達(dá)和活化情況，這表示P3IK/AKT通路可以通過miR-101與MAPK通路進(jìn)行串?dāng)_。研究發(fā)現(xiàn)，在地塞米松的抗炎癥作用中，miR-101被抑制，至少部分是因為地塞米松導(dǎo)致MKP-1大幅度上調(diào)而降低了MAPK活化作用。這項研究為今后對細(xì)胞因子分泌引起的免疫疾病的治療策略提供了新的靶標(biāo)。此項研究得到科技部、國家自然科學(xué)基金、上海市科學(xué)技術(shù)委員會和中國科學(xué)院的資金資助，并已經(jīng)申請了相關(guān)專利。（來源：中科院上海巴斯德所）

【點評】
　　微核糖核酸miR-101 通過作用于使炎癥反應(yīng)下調(diào)的MKP-1信號通路調(diào)節(jié)巨噬細(xì)胞對細(xì)菌脂多糖的先天免疫反應(yīng)。該發(fā)現(xiàn)豐富了炎癥與免疫反應(yīng)的機(jī)理上的認(rèn)識，有助于開發(fā)新的抗炎方法。

【原文摘錄】The Journal of Immunology, 2010, doi:10.4049/jimmunol.1000798
MicroRNA-101 Targets MAPK Phosphatase-1 To Regulate the Activation of MAPKs in Macrophages
Qing-Yuan Zhu, Qin Liu, Jian-Xia Chen, et al.
MAPK phosphatase-1 (MKP-1) is an archetypical member of the dual-specificity phosphatase family that deactivates MAPKs. Induction of MKP-1 has been implicated in attenuating the LPS- or peptidoglycan-induced biosynthesis of proinflammatory cytokines, but the role of noncoding RNA in the expression of the MKP-1 is still poorly understood. In this study, we show that MKP-1 is a direct target of microRNA-101 (miR-101). Transfection of miR-101 attenuates induction of MKP-1 by LPS as well as prolonged activation of p38 and JNK/stress-activated protein kinase, whereas inhibition of miR-101 enhances the expression of MKP-1 and shortens p38 and JNK activation. We also found that expression of miR-101 is induced by multiple TLR ligands, including LPS, peptidoglycan, or polyinosinic-polycytidylic acid, and that inhibition of PI3K/Akt by LY294002 or Akt RNA interference blocks the induction of miR-101 by LPS in RAW264.7 macrophage cells. Moreover, treatment of cells with dexamethasone, a widely used anti-inflammatory agent, markedly inhibits miR-101 expression and enhances the expression of MKP-1 in LPS-stimulated macrophages. Together, these results indicate that miR-101 regulates the innate immune responses of macrophages to LPS through targeting MKP-1.

4. 研究揭示肺炎感染人體反應(yīng)機(jī)制
 
【摘要】
　　據(jù)英國《每日電訊報》報道，英國科學(xué)家宣布，他們發(fā)現(xiàn)了身體自然對抗引發(fā)肺炎和腦膜炎的肺炎鏈球菌的新方式，朝研制出治療肺炎和腦膜炎的通用型疫苗又前進(jìn)了一大步。該研究發(fā)表在美國《科學(xué)公共圖書館—病原體》雜志上。英國萊斯特大學(xué)和都柏林圣三一學(xué)院的研究人員在論文中以《理解上的巨大突破》為題，揭示了免疫系統(tǒng)如何對肺炎鏈球菌引發(fā)的感染作出反應(yīng)的機(jī)制。研究人員稱，他們首次發(fā)現(xiàn)，肺炎會觸發(fā)一群名叫炎性體的免疫系統(tǒng)蛋白。當(dāng)被激發(fā)時，炎性體會啟動一系列事件，導(dǎo)致包括白介素在內(nèi)的活性分子的生成以對抗感染。科學(xué)家可以據(jù)此研發(fā)出新藥物，這些藥物能觸發(fā)同樣的反應(yīng)，將疾病扼殺在萌芽狀態(tài)。萊斯特大學(xué)的阿拉斯·卡迪格魯和圣三一學(xué)院的艾德·拉弗勒認(rèn)為，這一關(guān)于毒素如何同免疫系統(tǒng)結(jié)合的新認(rèn)知意味著研究人員可以研發(fā)出新疫苗?，F(xiàn)在，對抗肺炎鏈球菌的疫苗可以防御7種不同的菌株，但新方法研發(fā)出的疫苗應(yīng)該能夠?qū)顾?2種菌株?？ǖ细耵敱硎?，這是一項非常令人興奮的發(fā)現(xiàn)，提供了一種全新的方法來對抗細(xì)菌。這個“重大突破”將幫助科學(xué)家更好地理解每年造成數(shù)百萬嬰兒死亡以及很多老年人患病和死亡的肺炎和腦膜炎這兩個罪魁禍?zhǔn)住?（來源：科技日報 劉霞）

【點評】
　　該發(fā)現(xiàn)加深了對于人體自身免疫系統(tǒng)作用機(jī)制的理解，或許有助于解決現(xiàn)代醫(yī)學(xué)面臨的抗生素困境。

【原文摘錄】PLoS Pathog 6(11): e1001191. doi:10.1371/journal.ppat.1001191
Pneumolysin Activates the NLRP3 Inflammasome and Promotes Proinflammatory Cytokines Independently of TLR4
McNeela EA, Burke Á, Neill DR, Baxter C, Fernandes VE, et al.
Pneumolysin (PLY) is a key Streptococcus pneumoniae virulence factor and potential candidate for inclusion in pneumococcal subunit vaccines. Dendritic cells (DC) play a key role in the initiation and instruction of adaptive immunity, but the effects of PLY on DC have not been widely investigated. Endotoxin-free PLY enhanced costimulatory molecule expression on DC but did not induce cytokine secretion. These effects have functional significance as adoptive transfer of DC exposed to PLY and antigen resulted in stronger antigen-specific T cell proliferation than transfer of DC exposed to antigen alone. PLY synergized with TLR agonists to enhance secretion of the proinflammatory cytokines IL-12, IL-23, IL-6, IL-1β, IL-1α and TNF-α by DC and enhanced cytokines including IL-17A and IFN-γ by splenocytes. PLY-induced DC maturation and cytokine secretion by DC and splenocytes was TLR4-independent. Both IL-17A and IFN-γ are required for protective immunity to pneumococcal infection and intranasal infection of mice with PLY-deficient pneumococci induced significantly less IFN-γ and IL-17A in the lungs compared to infection with wild-type bacteria. IL-1β plays a key role in promoting IL-17A and was previously shown to mediate protection against pneumococcal infection. The enhancement of IL-1β secretion by whole live S. pneumoniae and by PLY in DC required NLRP3, identifying PLY as a novel NLRP3 inflammasome activator. Furthermore, NLRP3 was required for protective immunity against respiratory infection with S. pneumoniae. These results add significantly to our understanding of the interactions between PLY and the immune system.

5. FTO基因過度活躍可導(dǎo)致肥胖
 
【摘要】
　　英國牛津大學(xué)11月15日發(fā)布的新聞公報指出，該校研究人員找到了FTO基因會導(dǎo)致肥胖的有力證據(jù)，稱FTO基因過度活躍會造成飲食過量，從而導(dǎo)致肥胖。相關(guān)成果發(fā)表在最近一期《自然—遺傳學(xué)》雜志上。FTO基因也稱肥胖基因，是一種與肥胖相關(guān)的等位基因。早在2007年，一個包括牛津大學(xué)科學(xué)家在內(nèi)的國際研究小組通過大型全基因組研究發(fā)現(xiàn)，F(xiàn)TO基因變異與肥胖有關(guān)。攜帶兩個FTO基因變異副本的人，其平均體重比擁有正常副本的人重3公斤。而在歐洲血統(tǒng)白人中，大約有16%的人攜帶兩個FTO基因變異副本。此次牛津大學(xué)和英國醫(yī)學(xué)理事會的合作研究中，研究人員希望能確定是否就是FTO基因本身活動的差異導(dǎo)致了肥胖。在實驗中，研究人員培育出具有多余FTO基因副本的小鼠，他們發(fā)現(xiàn)，這些小鼠雖然也很健康，但與其它正常小鼠相比，它們的食欲更強(qiáng)，更易飲食過量，體型也更肥碩。那些有兩個FTO基因副本的雌性小鼠，即使食譜與其它正常雌性小鼠相同，其在20周后的體重也比后者重22%；但對于雄性小鼠而言，這種體重差異則大約在10%左右。
　　該項研究的領(lǐng)導(dǎo)者、牛津大學(xué)的弗朗西斯·阿什克勞夫特教授表示，該實驗表明，F(xiàn)TO基因是與肥胖相關(guān)的重要基因，正是FTO基因過度活躍，才會造成小鼠飲食過度，從而導(dǎo)致體重大幅增加。研究論文作者之一、牛津大學(xué)的克里斯·丘奇則稱，這是研究人員第一次找到令人信服的證據(jù)證明FTO基因能夠?qū)е路逝?。而下一步，他們要致力于研究相關(guān)機(jī)制，一旦了解了FTO基因?qū)е路逝值臋C(jī)制，就可以開發(fā)出有效的肥胖治療藥物。相信這種能夠抑制基因活動的藥物將具有很好的應(yīng)用前景。（來源：科技日報 劉海英）

【點評】
　　第一次有直接證據(jù)表明FTO基因過度活躍會造成小鼠飲食過量，從而導(dǎo)致肥胖。這一發(fā)現(xiàn)有助于對肥胖及其相關(guān)代謝疾病的深入了解。

【原文摘錄】Nature Genetics DOI: doi:10.1038/ng.713
Overexpression of Fto leads to increased food intake and results in obesity
Chris Church, Lee Moir, Fiona McMurray, et al.
Genome-wide association studies have identified SNPs within FTO, the human fat mass and obesity–associated gene, that are strongly associated with obesity. Individuals homozygous for the at-risk rs9939609 A allele weigh, on average, ~3 kg more than individuals with the low-risk T allele. Mice that lack FTO function and/or Fto expression display increased energy expenditure and a lean phenotype. We show here that ubiquitous overexpression of Fto leads to a dose-dependent increase in body and fat mass, irrespective of whether mice are fed a standard or a high-fat diet. Our results suggest that increased body mass results primarily from increased food intake. Mice with increased Fto expression on a high-fat diet develop glucose intolerance. This study provides the first direct evidence that increased Fto expression causes obesity in mice.

6. 維生素D不足可導(dǎo)致白血病惡化
 
【摘要】
　　美國一項新研究發(fā)現(xiàn)，機(jī)體內(nèi)維生素D水平與白血病之間存在緊密聯(lián)系，維生素D不足可能會引起病情惡化，維生素D水平正常則會延長病人存活時間。這項研究由美國梅奧診所和艾奧瓦大學(xué)的研究人員共同完成，研究涉及390名慢性淋巴細(xì)胞白血病患者，其中30%的人在剛患病時被發(fā)現(xiàn)維生素D不足（即每毫升血液少于25毫微克）。在以后3年的跟蹤調(diào)查期間，缺乏維生素D的白血病患者的病情惡化和接受化療的幾率要比其他病人高66%，死亡風(fēng)險則要高兩倍以上。研究還發(fā)現(xiàn)，提高白血病患者的維生素D水平可延長他們的存活時間，這一結(jié)論不受與白血病發(fā)展有關(guān)因素的影響。研究人員說，他們對另一組白血病患者進(jìn)行了為期10年的研究，得出了同樣結(jié)論。研究人員指出，這一發(fā)現(xiàn)將有助于更有效地治療白血病，因為病人可以根據(jù)需要及時補(bǔ)充維生素D，這一方法既簡易可行，又不會產(chǎn)生副作用。研究人員說，他們計劃在另一項研究中調(diào)理患者的維生素D水平，看是否能以此改善病人的預(yù)后。研究報告刊登在新一期美國學(xué)術(shù)期刊《血液》雜志上。（來源：新華網(wǎng) 高原）

【點評】
　　體內(nèi)維生素D水平與白血病之間存在緊密聯(lián)系，表明了營養(yǎng)不良與癌癥發(fā)生之間一定的關(guān)聯(lián)性。

【原文摘錄】Blood; DOI 10.1182/blood-2010-07-295683.
Vitamin D insufficiency and prognosis in chronic lymphocytic leukemia (CLL)
Tait D. Shanafelt,, Matthew T. Drake, Matthew J. Maurer, et al.
Vitamin D insufficiency is common globally with low levels linked to higher cancer incidence. Although vitamin D insufficiency is related to inferior prognosis in some cancers, no data exist for chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL). We evaluated the relationship of 25(OH)D serum levels with time-to-treatment(TTT) and overall survival(OS) in newly diagnosed CLL patients participating in a prospective cohort study(discovery cohort) and a separate cohort of previously untreated patients participating in an observational study(confirmation cohort). Of 390 CLL patients in the discovery cohort, 119(30.5%) were 25(OH)D insufficient. After median follow-up of 3 years, TTT(hazard ratio[HR]=1.66; p=0.005) and OS(HR=2.39; p=0.01) were shorter for 25(OH)D insufficient patients. In the validation cohort, 61 of 153 patients(39.9%) were 25(OH)D insufficient. After median follow-up of 9.9 years, TTT(HR=1.59; p=0.05) and OS(HR 1.63; p=0.06) were again shorter for 25(OH)D insufficient patients. On pooled multivariable analysis of patients in both cohorts adjusting for age, sex, stage, CD38, ZAP-70, IGHV, CD49d, and FISH, 25(OH)D insufficiency remained an independent predictor of TTT(HR=1.47; p=0.008), although the association with OS was not significant(HR=1.47; p=0.07). Vitamin D insufficiency is associated with inferior TTT and OS in CLL patients. Whether normalizing vitamin D levels in deficient CLL patients would improve outcome merits clinical testing.