世界生命科學前沿動態(tài)周報（十）

2010年-05月-30日來源：mebo

（05.24--05.30 / 2010）
美寶國際集團:陶國新

　　本周動態(tài)包括以下內(nèi)容：新型DNA抗癌疫苗; 首次發(fā)現(xiàn)可發(fā)育成卵的干細胞; 脂肪干細胞分化為心肌細胞; CD95 促進腫瘤生長；核糖核酸干擾可抑制癌癥活躍基因；人體干細胞成功造出人工牙齒。

1. 新型DNA抗癌疫苗

【摘要】新華網(wǎng) 發(fā)布時間：2010-5-25 16:44:42
瑞典卡羅林斯卡醫(yī)學院日前發(fā)表公告說，該機構(gòu)研究人員研制出一種可抑制惡性腫瘤生長的新型DNA（脫氧核糖核酸）疫苗，實驗顯示這種疫苗無副作用。當惡性腫瘤超過幾個毫米時，需要形成新的血管為腫瘤提供營養(yǎng)和氧氣。因此，阻止血管的生長是治療惡性腫瘤的思路之一。蛋白質(zhì)DLL4是形成血管的必要成分，如果能抑制腫瘤細胞中的DLL4蛋白質(zhì)，將使新血管失去功能，從而大大減緩腫瘤的生長速度。
研究人員據(jù)此研制出了這種DNA疫苗。經(jīng)對患有乳腺癌的小白鼠進行試驗，證明接種疫苗的小白鼠體內(nèi)產(chǎn)生了可抑制DLL4蛋白質(zhì)的抗體，阻止了體內(nèi)乳腺腫瘤的生長，而且沒有引起任何不良反應(yīng)，也未影響小白鼠的傷口愈合。研究人員皮耶特拉斯稱，選擇乳腺癌作為試驗?zāi)繕耸且驗槿橄倌[瘤帶有大量的DLL4蛋白質(zhì)。研究人員希望能將這種疫苗用于乳腺癌的術(shù)后治療，防止腫瘤復發(fā)。
【點評】點評：小鼠通過接種DNA疫苗，產(chǎn)生抗體抑制惡性腫瘤新生血管必需的DLL4蛋白質(zhì)，從而阻止腫瘤生長。該疫苗對于減緩腫瘤生長和防止腫瘤復發(fā)可能有作用，但是由于不能直接作用于腫瘤細胞，還不可能根除癌癥。

【原文摘錄】Oncogene , (24 May 2010) | doi:10.1038/onc.2010.176
Therapeutic efficacy of a DNA vaccine targeting the endothelial tip cell antigen delta-like 4 in mammary carcinoma
BK Haller, A Bråve, E Wallgard, P Roswall, VG Sunkari, U Mattson, D Hallengärd, S-B Catrina, M Hellström och K Pietras
The Notch ligand delta-like ligand 4 (DLL4) is an essential component expressed by endothelial tip cells during angiogenic sprouting. We have described a conceptually novel therapeutic strategy for targeting tumor angiogenesis and endothelial tip cells based on DNA vaccination against DLL4. Immunization with DLL4-encoding plasmid DNA by in vivo electroporation severely retarded the growth of orthotopically implanted mammary carcinomas in mice by induction of a nonproductive angiogenic response. Mechanistically, vaccination brought about a break in tolerance against the self-antigen, DLL4, as evidenced by the production of inhibitory and inherently therapeutic antibodies against mouse DLL4. Importantly, no evidence for a delayed wound healing response, or for toxicity associated with pharmacological blockade of DLL4 signaling, was noted in mice immunized with the DLL4 vaccine. We have thus developed a well-tolerated DNA vaccination strategy targeting the endothelial tip cells and the antigen DLL4 with proven therapeutic efficacy in mouse models of mammary carcinoma; a disease that has been reported to dramatically induce the expression of DLL4. Conceivably, induction of immunity toward principal mediators of pathological angiogenesis could provide protection against recurrent malignant disease in the adjuvant setting.

2. 首次發(fā)現(xiàn)可發(fā)育成卵的干細胞

【摘要】新華網(wǎng) 2010-5-25 9:39:40
日本一個研究小組日前發(fā)現(xiàn)，在雌鳉魚的卵巢內(nèi)存在可發(fā)育成鳉魚卵的干細胞。有關(guān)成果已經(jīng)刊登在最新一期的美國《科學》雜志網(wǎng)絡(luò)版上。這一成果是日本自然科學研究機構(gòu)基礎(chǔ)生物學研究所的研究人員獲得的?；A(chǔ)生物學研究所日前發(fā)表公告說，在脊椎動物中，已經(jīng)發(fā)現(xiàn)雄性的精巢中存在發(fā)育成精子的干細胞，但是在卵巢中發(fā)現(xiàn)會發(fā)育成卵的干細胞則屬世界首次。研究小組對雌性鳉魚進行基因操作，使其卵巢內(nèi)的卵發(fā)出紅光，結(jié)果發(fā)現(xiàn)了很多即將發(fā)育為卵的細胞。利用綠色熒光蛋白質(zhì)給這些細胞做上標記以后，研究人員發(fā)現(xiàn)許多新形成的卵也會發(fā)出綠色熒光，這說明這些細胞的確發(fā)育成了卵，因此這些細胞就是干細胞。
【點評】點評：世界首次在脊椎動物卵巢中發(fā)現(xiàn)會發(fā)育成卵的干細胞。由于沒有直接證據(jù)顯示成體脊椎動物卵巢中有生殖干細胞，這些發(fā)育成卵的干細胞很可能是從卵巢中的體細胞原位轉(zhuǎn)變的。

【原文摘錄】Science DOI: 10.1126/science.1185473
Identification of Germline Stem Cells in the Ovary of the Teleost Medaka
Shuhei Nakamura,1 Kayo Kobayashi,1 Toshiya Nishimura,1,2 Shin-ichi Higashijima,3,4 Minoru Tanaka1,2,*

Germline stem cells continually produce sperm in vertebrate testes, whereas there is no direct evidence showing that germline stem cells are present in adult vertebrate ovaries. Using transgenic methods and clonal analysis, we identified germline stem cells that supported oogenesis and the production of offspring in the ovaries of adult medaka fish. Early-stage germ cells were localized in clusters along interwoven threadlike cords of sox9b-expressing somatic cells (termed "germinal cradles") where the germ cells developed. Germline stem cells gave rise to germ cells that divided to produce cysts, which then underwent cell death or separated to form follicles. Our results provide insight into germline stem cell biology of medaka and provide a model system for studying vertebrate stem cell niches.

3. 脂肪干細胞分化為心肌細胞

【摘要】西班牙研究人員首次從人類脂肪組織中分離出成熟的干細胞，讓這些細胞暫時暴露于人類的心房細胞中，隨后再對這些細胞重新進行培養(yǎng)。經(jīng)過12天的培養(yǎng)，這些細胞向著心肌細胞的表型方向分化，這可以通過以下方面得到證明：這些細胞從形態(tài)上發(fā)生了改變，表現(xiàn)為帶有纖維紋和分枝的雙核細胞；免疫熒光檢查發(fā)現(xiàn)，它們帶有心臟特有的標記；RT - PCR檢測證明，這些細胞存在心肌基因；它們有逆轉(zhuǎn)錄表達。這樣，這些干細胞獲得了一個心臟的表型。未來可通過這項技術(shù)從患者身上直接提取細胞來再生心肌細胞。但是醫(yī)生們表示，目前這項研究還處于初期階段，要用于治療還有很長一段時間。
【點評】點評：干細胞分化的決定受到其所處生理環(huán)境的調(diào)控，這類調(diào)控也決定了其在體外培養(yǎng)時的分化方向。

【原文摘錄】Cytotherapy DOI: 10.3109/14653240903548202

Human cardiac tissue induces transdifferentiation of adult stem cells towards cardiomyocytes
Background aims. The goal was to induce the transdifferentiation (or conversion) of human adipose-derived stem cells to cardiomyocytes using an intracellular extract obtained from adult human heart tissue. Methods. Human adult stem cells from lipoaspirates were transiently permeabilized, exposed to human atrial extracts and allowed to recover in culture. Results. After 21 days, the cells acquired a cardiomyocyte phenotype, as demonstrated by morphologic changes (appearance of binucleate, striated cells and branching fibers), immunofluorescence detection of cardiac-specific markers (connexin-43, sarcomeric α-actinin, cardiac troponin I and T, and desmin) and the presence of cardiomyocyte-related genes analyzed by reverse transcription–polymerase chain reaction (cardiac myosin light chain 1, α-cardiac actin, cardiac troponin T and cardiac β-myosin). Conclusions. We have demonstrated for the first time that adult cardiomyocytes obtained from human donors retain the capacity to induce cardiomyocyte differentiation of mesenchymal stromal cells. The use of autologous extracts for reprogramming adult stem cells may have potential therapeutic implications for treating heart disease.

4. CD95 促進腫瘤生長

【摘要】CD95 原來一直被認為是凋亡受體蛋白，通過誘導細胞凋亡來調(diào)節(jié)組織內(nèi)穩(wěn)態(tài)，是癌細胞殺手?，F(xiàn)在發(fā)現(xiàn)，自相矛盾的是，癌細胞的正常生長也離不開它。沒有它，小鼠的卵巢癌和肝癌發(fā)病率和腫瘤體積都降低了。
【點評】點評：發(fā)現(xiàn)CD95 受體蛋白在癌癥發(fā)展中有促進作用，在癌癥治療中應(yīng)該抑制其活性而非原來認為的增強其活性。

【原文摘錄】Nature 465, 492–496 (27 May 2010) doi:10.1038/nature09075

CD95 promotes tumour growth
Lina Chen, Sun-Mi Park, Alexei V. Tumanov, Annika Hau, Kenjiro Sawada, Christine Feig, Jerrold R. Turner, Yang-Xin Fu, Iris L. Romero, Ernst Lengyel & Marcus E. Peter
CD95 (also called Fas and APO-1) is a prototypical death receptor that regulates tissue homeostasis mainly in the immune system through the induction of apoptosis1, 2, 3. During cancer progression CD95 is frequently downregulated or cells are rendered apoptosis resistant4, 5, raising the possibility that loss of CD95 is part of a mechanism for tumour evasion. However, complete loss of CD95 is rarely seen in human cancers4 and many cancer cells express large quantities of CD95 and are highly sensitive to CD95-mediated apoptosis in vitro. Furthermore, cancer patients frequently have elevated levels of the physiological ligand for CD95, CD95L6. These data raise the possibility that CD95 could actually promote the growth of tumours through its non-apoptotic activities7. Here we show that cancer cells in general, regardless of their CD95 apoptosis sensitivity, depend on constitutive activity of CD95, stimulated by cancer-produced CD95L, for optimal growth. Consistently, loss of CD95 in mouse models of ovarian cancer and liver cancer reduces cancer incidence as well as the size of the tumours. The tumorigenic activity of CD95 is mediated by a pathway involving JNK and Jun. These results demonstrate that CD95 has a growth-promoting role during tumorigenesis and indicate that efforts to inhibit its activity rather than to enhance it should be considered during cancer therapy.

5. 核糖核酸干擾可抑制癌癥活躍基因

【摘要】2010年05月29日 09:15:13 　來源：科技日報
加拿大麥吉爾大學生物化學系研究人員發(fā)現(xiàn)，與核糖核酸相結(jié)合的一種蛋白質(zhì)片斷能夠控制基因的正常表達，其中包括那些在癌癥中活躍的基因。專家認為，這是癌癥研究工作的一項重要突破，可立即將其應(yīng)用到實驗室的研究工作中，并且使目前各國科學家廣泛開展的癌癥個性化治療工作向前推進了一大步。相關(guān)研究成果發(fā)表在5月26日《自然》雜志網(wǎng)絡(luò)版上。人類細胞需要在合適的時間生產(chǎn)出適度數(shù)量的正常蛋白以維持其健康。細胞對蛋白生產(chǎn)進行有效控制時，所采用的重要手段之一就是依靠“核糖核酸干擾”?！昂颂呛怂岣蓴_”是基因靜默的一種形式，即小片段核糖核酸（又稱微核糖核酸）與它們的遺傳密碼結(jié)合，以阻斷特殊蛋白的生產(chǎn)。然而，不是核糖核酸的任何片段都能夠按此方式行事。
麥吉爾大學的哈?！だZ爾博士與同事合作，使用結(jié)構(gòu)生物學揭開了Argonaute蛋白中的一小段，即“核糖核酸干擾”的關(guān)鍵分子如何能夠選擇正確的微核糖核酸的奧秘。研究人員發(fā)現(xiàn)，“核糖核酸干擾”可以促使Argonaute蛋白增加基因靜默。拉賈爾博士認為，“核糖核酸干擾”可以作為可行的治療方法，來抑制那些在癌癥等疾病中顯得特別活躍的特殊基因。他表示現(xiàn)在已經(jīng)掌握了修改微核糖核酸的方法，可以使其更具效力，并有希望基于此開發(fā)出治療藥物。研究人員認為，該發(fā)現(xiàn)要進入實際治療還需時日，但它為有目的地控制那些非正常蛋白的生產(chǎn)提供了有效方法。麥吉爾大學生化系主任湯姆斯博士認為，醫(yī)學界一直期盼有朝一日可以結(jié)束依靠化療方法治療癌癥，而該項發(fā)現(xiàn)朝著癌癥患者個性化基因治療方向邁出了重要的一步。（記者杜華斌）
【點評】點評：核糖核酸干擾（RNAi）是可行的抑制那些在癌癥等疾病中特別活躍的特殊基因的方法，但只是臨時關(guān)閉這類基因而不能消除導致其特別活躍的因素，很難根除癌癥。

【原文摘錄】Nature advance online publication 26 May 2010 | doi:10.1038/nature09039
Structural basis for 5′-nucleotide base-specific recognition of guide RNA by human AGO2
Filipp Frank1,2,3, Nahum Sonenberg1,2 & Bhushan Nagar1,3

MicroRNAs (miRNAs) mediate post-transcriptional gene regulation through association with Argonaute proteins (AGOs)1. Crystal structures of archaeal and bacterial homologues of AGOs have shown that the MID (middle) domain mediates the interaction with the phosphorylated 5′ end of the miRNA guide strand and this interaction is thought to be independent of the identity of the 5′ nucleotide in these systems2,3. However, analysis of the known sequences of eukaryotic miRNAs and co-immunoprecipitation experiments indicate that there is a clear bias for U or A at the 5′ position4,5,6,7. Here we report the crystal structure of a MID domain from a eukaryotic AGO protein, human AGO2. The structure, in complex with nucleoside monophosphates (AMP, CMP, GMP, and UMP) mimicking the 5′ end of miRNAs, shows that there are specific contacts made between the base of UMP or AMP and a rigid loop in the MID domain. Notably, the structure of the loop discriminates against CMP and GMP and dissociation constants calculated from NMR titration experiments confirm these results, showing that AMP (0.26 mM) and UMP (0.12 mM) bind with up to 30-fold higher affinity than either CMP (3.6 mM) or GMP (3.3 mM). This study provides structural evidence for nucleotide-specific interactions in the MID domain of eukaryotic AGO proteins and explains the observed preference for U or A at the 5′ end of miRNAs.

6. 人體干細胞成功造出人工牙齒

【摘要】網(wǎng)易探索2010-5-28 5:18:39
哥倫比亞大學醫(yī)學中心5月25日宣布牙齒再生技術(shù)獲得新突破，研究人員成功在動物口腔內(nèi)進行了牙齒再生實驗，這意味著未來人們就可將該技術(shù)應(yīng)用于臨床實驗領(lǐng)域。
杰瑞米·毛（Jeremy Mao）博士負責帶領(lǐng)哥倫比亞大學醫(yī)學中心組織工程學及再生藥物實驗室的研究人員從事該課題的研究，他們找到一種新的技術(shù)，只需在患者口腔內(nèi)植入一個托架，并將患者體內(nèi)的干細胞引導至需要牙齒再生的地方，就可以實現(xiàn)真正意義上的“牙齒再生”。用于植入患者口腔的托架將全部采用天然材料制成，并將被放置在失去牙齒的牙洞內(nèi)。在生長的過程中，該托架將與其周圍的牙洞組織逐漸融合，甚至還會令牙周韌帶及齒槽骨再生。而這些正是傳統(tǒng)種牙方法所無法帶來的。
【點評】點評：干細胞分化的決定受到其所處生理環(huán)境的調(diào)控，在沒有移植細胞的情況下，在牙齒托架和再生誘導物的作用下，體內(nèi)細胞遷移過來再生新牙齒。

【原文摘錄】Journal of Dental Research, May 2010; vol. 0: pp. 0022034510370803v1.
Anatomically Shaped Tooth and Periodontal Regeneration by Cell Homing

K. Kim, C.H. Lee, B.K. Kim, and J.J. Mao
Tooth regeneration by cell delivery encounters translational hurdles. We hypothesized that anatomically correct teeth can regenerate in scaffolds without cell transplantation. Novel, anatomically shaped human molar scaffolds and rat incisor scaffolds were fabricated by 3D bioprinting from a hybrid of poly--caprolactone and hydroxyapatite with 200-μm-diameter interconnecting microchannels. In each of 22 rats, an incisor scaffold was implanted orthotopically following mandibular incisor extraction, whereas a human molar scaffold was implanted ectopically into the dorsum. Stromal-derived factor-1 (SDF1) and bone morphogenetic protein-7 (BMP7) were delivered in scaffold microchannels. After 9 weeks, a putative periodontal ligament and new bone regenerated at the interface of rat incisor scaffold with native alveolar bone. SDF1 and BMP7 delivery not only recruited significantly more endogenous cells, but also elaborated greater angiogenesis than growthfactor-free control scaffolds. Regeneration of tooth-like structures and periodontal integration by cell homing provide an alternative to cell delivery, and may accelerate clinical applications.