肿瘤干细胞介导脑肿瘤化放疗抗拒性研究进展

目的:探讨脑肿瘤干细胞(tumor stem cells,TSCs)研究的最新进展,旨在从中获取有益的治疗信息。方法:外文文献依据PubMed检索系统,中文文献依据维普检索系统,检索年限为2002-2008年,以肿瘤干细胞、化放疗抗拒性和脑肿瘤为关键词;查询文献时使用医学主题词,筛选出肿瘤干细胞介导脑肿瘤化放疗抗拒性研究相关文献107篇,最后纳入文献22篇。结果:TSCs能通过自再生而致脑瘤发生,促进肿瘤进展,并介导化、放疗抗拒性。这意味着未来的肿瘤治疗应该靶向杀灭TSCs,才有可能彻底控制癌症。虽然一些研究支持TGS假设,但仍然有许多不确定因素,诸如理论技术及实验结果阐述等方面存在争议。结论:如果TSCs假设成立,这将对肿瘤分类及治疗产生深远影响。     

慢病毒携带的双自杀基因对淋巴瘤细胞杀伤作用的实验研究

背景与目的:慢病毒载体具有可感染非分裂细胞、目的基因整合至靶细胞基因组长期表达、免疫原性低等优点,适于体内基因治疗。本研究探讨慢病毒介导的双自杀基因对淋巴瘤细胞Raji的杀伤作用。方法:将表达慢病毒的3种质粒,即包装结构基因质粒pCMVΔ8.2、包膜基因质粒pCMV.VSVG、目的基因质粒pHR'CS.GFP或pHR'CS.CDglytk分两组(pHR'CS.Cdglytk为实验组、pHR'CS.GFP为对照组),经脂质体导入病毒包装细胞293T,包装成病毒后,收集病毒上清,浓缩后转染Raji细胞,用荧光显微镜及RT-PCR检测基因的表达。给予前体药物5-氟胞嘧啶(5-FC)和/或无环鸟苷(GCV),用MTT法测定Raji细胞的生长抑制率,检测CD和HSV-tk双自杀基因对Raji细胞的作用。结果:表达慢病毒的3种质粒可高效转染入293T细胞。荧光显微镜下观察可见大量的绿色荧光,透射电镜下观察可见富集的病毒颗粒。慢病毒介导的双自杀基因在Raji细胞中高效、稳定表达。单独使用GCV或5-FC对细胞的生长抑制率分别为51%、50%,与未转染组Raji细胞比较,差异有显著性(P<0.01);联合使用5-FC和GCV对细胞的生长抑制率为73%,明显高于单独使用5-FC或GCV(P<0.01)。结论:慢病毒介导的双自杀基因可高效稳定转染淋巴瘤细胞;双自杀基因系统较单一自杀基因系统(CD/5-FC或HSVtk/GCV)对淋巴瘤细     

双自杀基因CD和TK对K562细胞体内外杀伤作用的实验研究

目的:探讨双自杀基因CD和TK对K562细胞的体内外抑制作用及前体药物对肿瘤的杀伤作用。方法:将目的基因转染入K562细胞,MTT法观察细胞在体内外的增殖状况及5-FC/GCV对转染细胞的杀伤作用,电子显微镜观察其超微结构变化。将K562/CDgly TK和K562细胞接种于裸鼠皮下,观察各种肿瘤细胞在体内的成瘤情况及对前体药物治疗的敏感性。结果:单独使用GCV或5-FC对K562及K562/CDgly TK细胞产生明显的杀伤作用,联合应用该2种药物对肿瘤细胞的杀伤作用更强。将K562细胞和K562/CDgly TK细胞接种于小鼠皮下后小鼠成瘤率为100%,GCV或5-FC可明显抑制裸鼠体内的肿瘤形成,联合应用GCV和5-FC治疗K562/CDglyTK细胞在小鼠体内形成的肿瘤,较单独应用GCV和5-FC及对照组小鼠形成的肿瘤体积明显缩小,生存期也明显延长。结论:双自杀基因在体内外对K562细胞均有明显的抑制作用,可增加前体药物GCV和5-FC对瘤细胞的杀伤率。     

PTEN inhibits adrenomedullin expression and function in brain tumor cells

Summary To examine the role of focal adhesion kinase in human glioma cells, we studied its effects on proliferation and apoptosis using FAK antisense oligonucleotide. U251 MG cells were transfected with ODNs, sense FAK, mismatch FAK and antisense-FAK, respectively. Expression of FAK proteins were detected by Western blots and Immnofluoressence. Cell apoptosis and mitochondrial membrane potential were analyzed by flow cytometry. Caspase-3 activity was measured by spectrofluorometer. MTT assay was used to examine changes in cell proliferation. The protein expression of FAK in U251 MG cells decreased in antisense-FAK ODNs group significantly. Caspase-3 activity increased in cells treated with antisense-FAK and down-regulated when treated with caspase-3 inhibitor. The level of cell apoptosis and loss of mitochondrial membrane potential in antisense-FAK group was higher than in the mismatch sense group. Cells proliferation was inhibited by antisense-FAK, and the effects were clearly additive when antisense oligonuceotides were added to cells treated with the anticancer agents. The results suggest that antisense-FAK ODNs inhibit U251 MG cells proliferation and induce their apoptosis. It is possible that FAK via mitochondrial and caspase-3 inhibits U251 MG cells apoptosis. And antisense oligonucleotide treatment enhances U251 MG cells sensitivity to chemotherapy.     

Killing of tumor cells in vitro by macrophages from mice treated with synthetic dehydrodipeptides.

Treatment of NMRI mice i.p. with dehydrodipeptides [acetyldehydro-3-(2-thienyl)alanyltyrosine (SI); acetyldehydro-3-(2-furyl)alanyltyrosine (SII)] rendered macrophages cytolytic for several tumor cells in vitro. Normal peritoneal mouse macrophages from untreated mice not given injections of the peptides or from control mice given injections of phosphate-buffered saline were not cytotoxic. Moreover, supernatants from these in vivo-activated mouse peritoneal macrophages significantly increased the release of the cytoplasmic enzyme lactate dehydrogenase from freshly added target cells, showing that these cells had been killed. The macrophage activation to lyse tumor cells was sharply dose dependent and appeared about 48 hr after injection of the peptides. Although dehydrodipeptide SI was active in vivo at concentrations as low as 500 microgram/mouse, the same substance lacked activity in vitro at all concentrations tested up to 800 microgram/ml. Dehydrodipeptides activate macrophages through a T-cell-independent process to lyse tumor target cells. Macrophages from athymic nude (nu/nu) mice were less cytotoxic, but they still were stimulated; and the culture supernatants could kill about 50% of the tumor cells used. There are indications for a relative specific structure-activity relationship of dehydrodipeptides for inducing cytotoxic macrophages.     

The expression of the tumor suppressor gene connexin 26 is not mediated by methylation in human esophageal cancer cells

Gap junctional intercellular communication is thought to play an important role in cell differentiation and tissue homeostasis. Gap junctional intercellular communication is mediated by intercellular channels connecting adjacent cells and composed of connexin (Cx) proteins. Until now, approximately 20 different Cx have been characterized in mammals, and they are expressed in a tissue-specific manner. The downregulation of Cx expression is often observed in tumors and transformed cell lines and is believed to contribute to the loss of proliferating control. Connexin 26 (Cx26) is a Cx constitutively expressed in the normal epithelial esophageal tissue. In the majority of esophageal tumors, Cx26 expression is low or totally absent. CpG island hypermethylation is known to be associated with gene silencing in cancer. Because the promoter and exon 1 region of Cx26 are rich in CpG dinucleotides, we examined whether the loss of Cx26 expression in human esophageal TE cell lines was related to the hypermethylation of this region. We analyzed several TE cell lines derived from different human esophageal carcinomas and exhibiting different levels of Cx26 expression by using methylation-sensitive restriction digestion and Southern blot analysis. We did not find any correlation between the Cx26 expression and the methylation level of the promoter region of the Cx26 gene. Our results suggest that methylation was probably not involved as a primary mechanism of Cx26 regulation in human esophageal cancer cell lines.     

Increased resistance of tumor cells to hyperthermia mediated by integrin-linked kinase.

PURPOSE: Integrin-linked kinase (ILK) is a serine-threonine kinase associated with anchorage-independent growth and tumorigenic transformation. Previous studies indicate that overexpression of ILK is common among several types of tumors, and it is involved in the regulation of tumor cell survival under stress. In this study, we examined the effects of ILK expression on tumor cellular response to hyperthermia. EXPERIMENTAL DESIGN: We used an adenovirus-mediated approach to overexpress the ILK gene in a prostate cancer cell line and examine its effects on heat stress-induced cell death. Clonogenic survival, as well as apoptosis, was evaluated in cells that overexpress ILK. In addition, the ability to form tumors in vivo was examined in syngeneic hosts. Finally, potential molecular mechanisms of ILK-mediated resistance to heat were examined by determining the status of a variety of signal transduction pathways. RESULTS: ILK overexpression made tumor cells significantly more resistant to the cell-killing effects of hyperthermia. This was correlated at the molecular level with the down-regulation of hyperthermia-induced activation of stress-activated protein kinase/c-Jun-NH(2)-terminal kinase, p38 mitogen-activated protein kinase activities, and caspase 9. The overexpression of ILK was also shown to induce a more rapid tumor growth in a murine prostate cancer cell line CONCLUSION: ILK plays an important role in tumor growth and tumor response to hyperthermia treatment.     

Radiopotentiation of human brain tumor cells by sodium phenylacetate.

Phenylacetate (PA) inhibits the growth of tumor cells in vitro and in vivo and shows promise as a relatively nontoxic agent for cancer treatment. A recent report shows that prolonged exposure of cells to low concentrations of PA can enhance the radiation response of brain tumor cells in vitro, opening up the possibility of using this drug to improve the radiation therapy of brain tumor patients. We investigated the cytotoxicity produced by sodium phenylacetate (NaPA) alone and in combination with X-rays in SF-767 human glioblastoma cells and in two medulloblastoma cell lines, Masden and Daoy. Exposure of all three cell lines to relatively low concentrations of NaPA for up to 5 days did not enhance the subsequent cell killing produced by X-irradiation. However, enhanced cell killing was achieved by exposing either oxic or hypoxic cells to relatively high drug concentrations ( > 50-70 mM) for 1 h immediately before X-irradiation. Because central nervous system toxicity can occur in humans at serum concentrations of approximately 6 mM PA, translation of these results into clinical trials will likely require local drug-delivery strategies to achieve drug concentrations that can enhance the radiation response. The safety of such an approach with this drug has not been demonstrated.     

慢病毒转染造血干细胞介导的肿瘤基因治疗的研究进展

肿瘤基因治疗是继手术、放化疗等传统治疗方法之后出现的一种全新的肿瘤治疗方法,并在科研和临床方面取得可喜的进展。如何将肿瘤治疗基因安全高效的转移到人体内,使治疗基因在人体内长期、稳定、高效的表达是当前基因治疗实践中所遇到的重大困难。造血干细胞(hematopoieticstemcells,HSCs)因具有自我更新和定向分化能力,治疗基因转染到造血干细胞内可长期、持续、有效的杀伤肿瘤达到治疗目的。这使的造血干细胞成为基因治疗研究中最令人兴奋的靶细胞。慢病毒载体(lentivirusvector,LV)能感染大部分处于静止期的造血干细胞,因此成为一种有效的感染HSCs和进行基因治疗的工具。本文就慢病毒携带肿瘤治疗基因转染HSCs治疗肿瘤方面做一综述。     

肿瘤特异单链抗体库的构建及肿瘤血管特异性结合抗体的体内筛选

目的:研究化疗药物依托泊苷对腺病毒载体介导的外源基因在肿瘤细胞内表达水平的影响。方法:携带外源基因增强型绿色荧光蛋白(EGFP)的复制缺陷型腺病毒Ad5-CMV-EGFP(MOI为1或10)单独或联合终质量浓度为0.2、2、20、40、80、100和200μg/ml的依托泊苷感染体外培养的肿瘤细胞NCI-H446(人非小细胞肺癌细胞株)、A549(人肺腺癌细胞株)、SMMC-7721(人肝癌细胞株)、SGC7901(人胃癌细胞株)、SKBR-3(人乳腺癌细胞株)和BTT(小鼠膀胱移行上皮癌细胞株)后不同时间,流式细胞仪分析肿瘤细胞EGFP阳性率和平均荧光强度,Western blotting检测EGFP蛋白表达,RT-PCR和实时荧光定量PCR检测肿瘤细胞内EGFP的mRNA表达量和DNA拷贝数。结果:不同剂量的依托泊苷可不同程度地提高Ad5-CMV-EGFP在7种肿瘤细胞内的表达水平,但对EGFP阳性率无明显提高。10MOI的Ad5-CMV-EGFP联合40μg/ml依托泊苷分别感染肿瘤细胞NCI-H446、NCI-H460、A549、SMMC-7721、SGC7901、SKBR-3和BTT24h后,细胞内EGFP的荧光强度分别是单独感染的3.3、3.5、3.1、6.2、7.0、5.4和3.4倍。Ad5-CMV-EGFP联合应用依托泊苷后肿瘤细胞内EGFP蛋白表达增加2~5倍,EGFP mRNA表达量提高,但DNA拷贝数未见明显改变。结论:依托泊苷可提高腺病毒载体介导的外源基因在肿瘤细胞内的表达水平,该作用可能是在转录水平上发挥作用的。     

Urokinase induces receptor mediated brain tumor cell migration and invasion

The plasminogen activation (PA) system plays an important role in tumor invasion by initiating pericellular proteolysis of the extracellular matrix (ECM) and inducing cell migration. Malignant brain tumors overexpress PA members and characteristically invade by migrating on ECM-producing white matter tracts and blood vessel walls. To determine whether urokinase-type plasminogen activator (uPA) and its receptor (uPAR) directly modulate the migration of brain tumor cells, we examined six human brain tumor cell lines, 2 astrocytomas (SW1088, SW1783), 2 medullobastomas (Daoy, D341Med), and 2 glioblastomas (U87MG, U118MG), for their surface uPAR expression, endogenous PA activity, and functional proteolytic activity by an ECM-degradation assay. Migration on Transwell membranes and invasion of Matrigel was then tested by pre-incubating the cells with increasing concentrations of either uPA, the proteolytically inactive amino-terminal fragment (ATF) of uPA, or the uPAR cleaving enzyme, phosphatidylinositol-specific phospholipase C (PI-PLC).All of the cell lines, except D341Med, express surface uPAR protein and uPA activity. High levels of uPAR and uPA activity correlated with cellular degradation of ECM, cell migration, and Matrigel invasion. Cell migration and invasion were enhanced by uPA or ATF in a dose dependent manner, while PI-PLC treatment abolished the uPA effect and inhibited migration and invasion. We conclude that ligation of uPAR by uPA directly induces brain tumor cell migration, independent of uPA-mediated proteolysis; and in concert with ECM degradation, markedly enhances invasion. Conversely, removing membrane bound uPAR from the surface of the cells studied inhibited their ability to migrate and invade even in the presence of proteolytically active uPA.     

Immune cytolysis of murine tumor cells mediated by xenogeneic "immune" RNA

Using a quantitative assay for lymphocyte-mediated cytotoxicity, it was shown that normal, non-immune C3Hf/HeCr mouse spleen cells were converted to effector cells specifically cytotoxic to chemically induced C3H tumor cells by incubation in vitro with “immune” RNA extracted from the lymphoid organs of specifically immunized guineapigs. This response was specific for the tumor used to immunize the RNA donor. Cytotoxicity indices (CIs) at 0.30 to 0.54 were consistently obtained. Spleen cells incubated with RNA from guinea-pigs immunized with a different tumor, or with normal C3H tissue, failed to lyse the target cells. These immune responses were abrogated when the “immune” RNA was treated with RNase prior to incubation with the spleen cells. However, pre-treatment with DNase or pronase did not alter the activity of the “immune” RNA. “Immune” RNA to a second chemically induced C3H tumor mediated a cytotoxic response to that tumor (CI=0.45), but not to the first tumor. This clearly demonstrates that xenogeneic “immune” RNA mediates tumor-specific immune cytolysis, in vitro.     

CYTOTOXICITY OF INDIRECT IMMUNOTOXIN MEDIATED BY ANTI-GASTRIC CANCER MONOCLONAL ANTIBODIES ON TUMOR CELLS

In the present study, an indirect assay was employed to investigate 5 anti-gastric cancer monoclonal antibodies for their cytotoxic potential as ricin A chain-containing immunotoxins. The tumor cell, were treated with dilutions of tested antibody followed by ricin A chain coupled to goat anti-mouse immunoglobulin. The cytotoxic effect was determined with tetrazolium colorimetric assay. The results showed that among the 5 antibodies chosen, MGb2 and MG7 could be well used for preparation of effective A chain immunotoxins.     

Observation of the in vivo tumor cell lysis mediated by NK cells]

Natural killer cells/large granular lymphocytes (NK/LGL) separated on discontinuous Percoll gradient from rat spleen cells were injected iv to rats (7 x 10(7) cells/rat) 3 days following iv inoculation of 2 x 10(6) Walker-256 cells. Two and 4 hr after NK/LCL injection, animals were sacrificed and the lungs examined by light and immunoelectron microscopy. The latter was done using colloidal gold-labelled polyclonal antibody against purified rat LGL cytoplasmic granules. At 2 hr following iv NK/LGL, in addition to the scattered individual tumor cells and minute tumor foci, many lymphocytes were seen accumulating in the small pulmonary vessels and capillaries. This was not observed in tumor-inoculated control rats. At 4 hr, many extravasated lymphocytes reached the lung parenchyma, some of which had attached to the tumor cells. Immunoelectromicroscopically, lymphocytes were found in intimate contact with the tumor cells with the cytoplasmic gold particles clustering at the cell contact site. Gold particles could also be seen closely adherent to the plasma membrane of degenerating tumor cells. This is the first in vivo demonstration of the role of cytotoxic granules of NK cells in tumor cell lysis.     

神经干细胞和脑肿瘤干细胞研究进展

神经干细胞（NSC）是中枢神经系统（CNS）内具有自我更新和多向分化潜能的干细胞，主要存在于脑室下区域（SVZ），NSC通过自我更新和分化维持正常CNS的形态和功能。可塑性（plasticity）是NSC的重要特征，由NSC所处的微环境（microenvironment）决定。脑肿瘤干细胞（BTSC）是脑肿瘤中与NSC相似的细胞，是脑肿瘤发生和生长的细胞来源。BTSC可能起源于NSC，是NSC可塑性的表现，导致NSC向BTSC分化的机制可能是微环境作用的结果。     

神经干细胞和脑肿瘤干细胞研究进展

神经干细胞(NSC)是中枢神经系统(CNS)内具有自我更新和多向分化潜能的干细胞,主要存在于脑室下区域(SVZ),NSC通过自我更新和分化维持正常CNS的形态和功能。可塑性(plastici- ty)是NSC的重要特征,由NSC所处的微环境(microenvironment)决定。脑肿瘤干细胞(BTSC)是脑肿瘤中与NSC相似的细胞,是脑肿瘤发生和生长的细胞来源。BTSC可能起源于NSC,是NSC可塑性的表现,导致NSC向BTSC分化的机制可能是微环境作用的结果。     

树突状细胞与细胞因子诱导的杀伤细胞共培养对多药耐药肿瘤细胞系的杀伤活性

目的探讨在细胞因子诱导的杀伤细胞(CIK)表达特异性抗原的肿瘤细胞过程中,是否存在抗原特异性杀伤。方法分离健康人骨髓获得单个核细胞,分别诱导为树突状细胞(DC)和CIK细胞,将人类乳腺癌耐药细胞株MCF-7/ADR细胞的冻融物抗原冲击或未冲击DC与CIK细胞共培养(pulsed-DC CIK、DC CIK),CIK细胞单独培养作对照。用流式细胞仪分析细胞表型,用酶联免疫吸附法(ELISA)检测IL-12、和IFN-γ分泌水平,用二苯基溴化四氮唑蓝(MTT)法测定细胞毒效应。结果DC与CIK共育后,两组DC成熟表型较共育前明显提高(P=0.003、P=0.001);pulsed- DC CIK组与DC CIK组、CIK组比较,细胞表型(CD3、CD8、CD56)明显提高(P=0.003、P= 0.011),CD3 CD56 细胞明显增多(P=0.001,P<0.001),CD3 CD8 细胞亦明显增多(P=0.002, P=0.002);CD45RA表型则明显降低(P<0.001,P=0.004)。IL-12和IFN-γ水平在pulsed-DC CIK组表达最高,分别为(254±14.5)pg/ml和(3100±286)pg/ml。对有耐药抗原表达的MCF-7/ADR细胞,pulsed-DC CIK组杀伤效应最强,pulsed-DC CIK组、DC CIK组和CIK组比较,差异均有统计学意义(pulsed-DC CIK组与DC CIK组比较,P=0.039;pulsed-DC CIK组与CIK组比较,P= 0.002;DC CIK组与CIK组比较,P=0.049);而对于无P-gp抗原表达的MCF-7细胞的杀伤效应,pulsed- DC CIK组和DC CIK组之间无明显差异,但均高于CIK组,差异有统计学意义(pulsed-DC CIK组与CIK组比较,P=0.007;DC CIK组与CIK组比较,P=0.048)。结论从人骨髓培养得到DC和CIK细胞共培养后,能促进各自特征性表面标志的表达上调,并分泌大量相关细胞因子。细胞杀伤效应的明显提高及可能的特异性细胞杀伤效应,为多药耐药肿瘤的临床生物免疫治疗提供实验基础。