神经酰胺与辐射诱导细胞凋亡

神经酰胺作为神经鞘脂类的主要成员之一,是一个主要调节细胞活动的第二信使以转导细胞凋亡等细胞生长抑制活动信号为主,研究表明,神经酰胺通路不同水平的功能性变化直接影响细胞的药敏感性和辐射敏感性,肿瘤细胞神经酰胺缺陷可导致肿瘤细胞对药物和电射的敏感性下降。     

肿瘤辐射敏感性与细胞凋亡

辐射敏感性是肿瘤细胞复杂的生物学现象,在辐射诱导的细胞反应中具有不同的组织细胞类型特异性。肿瘤瘤射敏感性与辐射诱导的细胞凋亡密切相关,并受P53及其相关蛋白、Bcl-2基因家族蛋白、Fas及神经鞘磷脂-神经酰胺介导的信号途径、caspases级联反应等调控。     

鞘氨醇代谢物——肿瘤治疗的新靶点

神经鞘脂类是细胞膜的结构成分之一。其代谢产物如神经酰胺、鞘氨醇、1-磷酸鞘氨醇亦是具有生物活性的信号分子,可作为第一和（或）第二信使调控着细胞的生命活动,如细胞的增殖、存活、迁移、新生血管形成。鞘氨醇激酶1是调节神经酰胺、1-磷酸鞘氨醇平衡的限速酶。近年研究表明,神经酰胺、鞘氨醇激酶1、1-磷酸鞘氨醇可调控肿瘤细胞代谢的多个环节,由此提示神经鞘脂类代谢产物可作为肿瘤治疗的新靶点。     

酸性神经鞘磷脂酶的生物学特性及其功能

神经鞘磷脂酶(SMase)可水解鞘磷脂产生神经酰胺,在人体内发挥重要作用。酸性神经鞘磷脂酶(ASMase)作为SMase最重要的一个亚型,在辐射诱导细胞凋亡、调节肿瘤细胞生长、参与Fas信号系统传递等方面均可发挥重要作用。     

UVA诱导的细胞凋亡通过神经酰胺和JNK信号通路

目的 探讨神经酰胺和JNK信号通路在UVA诱导的细胞凋亡中的作用。方法 分别用MTT法和DNA梯形条带检测细胞死亡率和细胞凋亡；Western blot分析JNK信号通路的激活情况。结果 UVA照射后，正常的淋巴细胞JY出现明显的细胞凋亡，而MS 1418细胞则没有。MS 1418来自D型Niemann-Pick病人，酸性鞘磷脂水解酶遗传性缺陷，导致神经酰胺产生受阻。给予外源性神经酰胺，两种细胞都出现明显的细胞凋亡，表明UVA诱导的细胞凋亡是通过神经酰胺介导的。UVA激活了JY而不是MS 1418细胞的JNK信号通路；给予外源性神经酰胺，两种细胞的JNK信号通路都被激活，说明神经酰胺位于JNK信号通路的上游。结论 UVA诱导的细胞凋亡依赖神经酰胺和JNK信号通路。     

预测肿瘤内在辐射敏感性方法之现状

为了实现肿瘤放射治疗的个体化,首先要选择适合于放射治疗的病人,然后再根据病人临床表现、正常组织及肿瘤组织的辐射敏感性等情况综合判断,制定出适合的治疗方案。其中,肿瘤组织原位辐射敏感性主要取决于肿瘤细胞本身固有的辐射敏感性,因而国际上众多的研究主要集中在建立快速、灵敏、准确预测肿瘤细胞辐射敏感性的方法。为了研究方便,目前大量的研究集中在体外培养肿瘤细胞株的研究上。随着预测方法的进一步成熟,研究对象必将转到临床肿瘤活检组织上来。目前的研究主要集中在以下方面。一、细胞水平１－细胞集落形成实验定量接种细…     

酸性神经鞘磷脂酶的生物学特性及其功能

神经鞘磷脂酶(sMase)可水解鞘磷脂产生神经酰胺，在人体内发挥重要作用。酸性神经鞘磷脂酶(AsMase)作为SMase最重要的一个亚型，在辐射诱导细胞凋亡、调节肿瘤细胞生长、参与Fas信号系统传递等方面均可发挥重要作用。     

线粒体DNA4977bp缺失和彗星分析评价肿瘤细胞的辐射敏感性

目的 探讨mtDNA4977bp缺失和彗星分析用于肿瘤细胞辐射敏感性检测的可行性。方法 选取3种不同肿瘤细胞株:肝癌细胞(HepG₂)、食管癌细胞(EC-9706)和乳腺癌细胞(MCF-7)。采用MTT法检测肿瘤细胞经γ射线照射后的存活分数(SF);巢式PCR法测肿瘤细胞的mtDNA4977bp缺失率;单细胞凝胶电泳(SCGE)检测肿瘤细胞的DNA断裂水平。结果 用MTT法发现HepG₂ 和EC-9706细胞的辐射敏感性高于MCF-7细胞。8 Gy照射后HepG₂和EC-9706 mtDNA4977bp缺失率明显高于MCF-7细胞(P<0.05),证实HepG₂和EC-9706细胞的辐射敏感性高于MCF-7细胞。多种方法分析结果说明3种肿瘤细胞在8Gy照后表现出的辐射敏感性差异有统计学意义。结论 多种生物学指标的综合应用,可能更加客观准确地评价肿瘤细胞的辐射敏感性。     

端粒、端粒酶和辐射的研究进展

目前肿瘤的治疗主要以手术、放射治疗及化疗为主，其中有50％～70％的肿瘤患者需要接受放射治疗。但由于肿瘤细胞放射敏感性的不同，放射治疗效果差异较大，因而检测肿瘤细胞放射敏感性对指导临床治疗尤为重要。染色体是细胞遗传信息的中心，也是放射损伤的主要靶点。端粒是染色体的重要结构，而端粒酶则是大部分细胞合成端粒的必需条件，     

p53状态与人类肿瘤细胞系放射敏感性的关系

ｐ５３状态与人类肿瘤细胞系放射敏感性的关系［英］／ＳｉｌｅｓＥ…∥ＢｒＪＣａｎｃｅｒ．－１９９６，７３（１）．－５８１～５８８用放射敏感性不同的８种人类肿瘤细胞系，观察辐射前后ｐ５３水平的变化和辐射诱导的细胞延迟、细胞凋亡与细胞的放射敏感性的关系。肿...     

Initiation of ionizing radiation-induced apoptosis: DNA damage-mediated or does ceramide have a role?

PURPOSE: To critically review the data supporting membrane damage-induced increases in ceramide levels as the primary initiator of ionizing radiation-induced apoptosis and to point out that there is compelling evidence supporting the involvement of DNA damage in this process. CONCLUSIONS: There is now a significant literature suggesting that irradiation of cells can quickly lead to a modest, transitory increase in the level of the putative second messenger ceramide. These results have been used to support the views that membrane damage is the primary trigger for radiation-induced apoptosis and that DNA damage is irrelevant to this process. It is argued, however, that the data are inadequate to support such conclusions because it is questionable whether the induced levels of ceramide are toxic and because the ceramide hypothesis cannot convincingly explain the delayed apoptosis, dependent on events such as mitosis, that is shown by many cell lines. In contrast, it is suggested that the sensitivity of some cell types to the induction of apoptosis by DNA-targeted radiation damage, the relationship between p53 status and radiation response, and the influence of enzymatic DNA repair capability on susceptibility to apoptosis, argue strongly that DNA damage is relevant to the triggering of apoptosis.     

Radiation-induced EGFR-signaling and control of DNA-damage repair

PURPOSE: Over the last decade evidence has accumulated indicating that cell membrane-bound growth factor receptor of the erbB family and especially the epidermal growth factor receptor EGFR (erbB1) mediates resistance of tumor cells to both chemo- and radiotherapy when mutated or overexpressed. More recently a novel link between EGFR signaling pathways and DNA repair mechanisms, especially non-homologous end joining (NHEJ) repair could be demonstrated. The following review summarizes the current knowledge on the role of EGFR and its downstream signaling pathways in the regulation of cellular radiation response and DNA repair. CONCLUSION: The novel findings on radiation-induced EGFR-signaling and its involvement in regulating DNA-double strand break repair need further investigations of the detailed mechanisms involved. The results to be obtained may not only improve our knowledge on basic mechanisms of radiation sensitivity/resistance but also will promote translational approaches to test new strategies for clinically applicable molecular targeting.     

Multimodality molecular imaging of apoptosis in oncology

OBJECTIVE: The purposes of this review are to describe the signaling pathways of and the cellular changes that occur with apoptosis and other forms of cell death, summarize tracers and modalities used for imaging of apoptosis, delineate the relation between apoptosis and inhibition of protein translation, and describe spectroscopic technologies that entail high-frequency ultrasound and infrared and midinfrared light in characterizing the intracellular events of apoptosis. CONCLUSION: Apoptosis is a highly orchestrated set of biochemical and morphologic cellular events. These events present many potential targets for the imaging of apoptosis in vivo. Imaging of apoptosis can facilitate early assessment of anticancer treatment before tumor shrinkage, which may increase the effectiveness of delivery of chemotherapy and radiation therapy and speed drug development.     

Radiation-induced EGFR-signaling and control of DNA-damage repair

Purpose: Over the last decade evidence has accumulated indicating that cell membrane-bound growth factor receptor of the erbB family and especially the epidermal growth factor receptor EGFR (erbB1) mediates resistance of tumor cells to both chemo- and radiotherapy when mutated or overexpressed. More recently a novel link between EGFR signaling pathways and DNA repair mechanisms, especially non-homologous end joining (NHEJ) repair could be demonstrated. The following review summarizes the current knowledge on the role of EGFR and its downstream signaling pathways in the regulation of cellular radiation response and DNA repair.

Conclusion: The novel findings on radiation-induced EGFR-signaling and its involvement in regulating DNA-double strand break repair need further investigations of the detailed mechanisms involved. The results to be obtained may not only improve our knowledge on basic mechanisms of radiation sensitivity/resistance but also will promote translational approaches to test new strategies for clinically applicable molecular targeting.     

整合素介导的细胞信号转导与肿瘤辐射敏感性

整合素作为重要的细胞黏附分子,可介导细胞的信号转导,在细胞的黏附、迁移、增殖、分化等生长活动中发挥重要作用。同时,在电离辐射条件下,整合素介导的细胞信号转导可在肿瘤细胞内激活多种蛋白激酶,启动不同的信号通路,调控基因表达,维持肿瘤细胞的存活,降低肿瘤的辐射敏感性。因此,深入了解整合素及其所介导的细胞信号转导途径,有利于新型辐射增敏剂的研究,对肿瘤治疗具有积极意义。     

Involvement of Wnt signaling in the injury of murine mesenchymal stem cells exposed to X-radiation

Abstract Purpose: To investigate the injury of murine mesenchymal stem cells (mMSC) exposed to 4 Gy X-radiation and the role of canonical and non-canonical wingless-type (Wnt) signaling in the radiation injury. Materials and methods: C3H10T1/2 cells were submitted to 4 Gy X-radiation. At different time points after radiation, Hoechst33258 staining and Annexin V-fluorescein isothiocyanate (FITC) flow cytometry analysis were performed to assess cellular apoptosis. Senescence-associated β-galactosidase (SA-β-gal) staining was performed to analyze cellular senescence. Cell cycle was measured by flow cytometry. P53, p21, Wnt3a, Wnt5a, sonic hedgehog (Shh) mRNA was detected by Real time polymerase chain reaction (PCR) and Wnt5a protein was determined by Western blot. Results: A time-dependent cellular apoptosis was observed with a peak level 12 hours after radiation. Cellular senescence was detected 72 h after radiation. A remarkable up-regulation of Wnt5a mRNA expression (～ 269-fold) and protein expression was seen 72 h after radiation. Conclusions: The effect of 4 Gy X-radiation to mMSC was time-dependent in the form of cellular apoptosis in the early period and cellular senescence in the late period. Non-canonical Wnt signaling may be involved in mMSC senescence induced by 4 Gy X-radiation.     

DNA依赖性蛋白激酶催化亚基在电离辐射诱发HeLa细胞自噬中的作用

目的：了解DNA依赖性蛋白激酶催化亚基（ DNA-PKcs）在电离辐射诱发细胞自噬中的作用。方法通过慢病毒载体（ pSicoR ）构建DNA-PKcs短发夹RNA （ shRNA ）表达载体,并转染HeLa细胞敲低DNA-PKcs表达。CCK-8实验检测细胞增殖活性及细胞放射敏感性,免疫印迹检测自噬相关蛋白表达,免疫荧光实验检测自噬标志物GFP-LC3的表达。结果成功构建shRNA敲低DNA-PKcs表达的HeLa细胞模型,通过该细胞模型观察到抑制DNA-PKcs蛋白表达导致细胞增殖能力降低、放射敏感性增高。 P62和LC3蛋白表达变化,以及细胞内绿色荧光蛋白（ GFP）-LC3免疫荧光斑检测结果显示,DNA-PKcs基因敲低后,明显增加X射线诱发细胞自噬。抑制DNA-PKcs导致哺乳动物西罗莫司（雷帕霉素）靶蛋白（ mTOR）第2481位丝氨酸磷酸化水平降低。结论抑制DNA-PKcs增强受照射宫颈癌HeLa细胞的自噬及放射敏感性,mTOR信号通路可能参与DNA-PKcs对自噬的调节作用。