低剂量率照射下肿瘤细胞抑癌基因表达和细胞凋亡研究进展

低剂量率照射能够增强p53、p21等抑癌基因的表达,并可通过肿瘤细胞G2-M期阻滞和bcl-2等基因的改变引起细胞凋亡,从而达到治疗肿瘤的目的.     

胃癌组织ING1抑癌基因表达及其生物学意义探讨

目的:探讨生长抑制因子1(ING1)基因表达及其与胃癌临床病理特征的关系。方法:荧光定量PCR技术和免疫印迹技术检测70例胃腺癌组织及癌旁对照胃黏膜组织中ING1基因的表达水平,并分析其与胃癌患者临床特征的关系。结果:70例癌组织中有57例(81.43%)ING1基因mRNA表达明显下调,其中4例组织为ING1表达缺失,与癌旁正常胃黏膜比较差异有统计学意义,P<0.01。ING1基因表达与胃癌患者的性别无明显相关性,与胃癌的分化程度、肿瘤累及深度以及淋巴结转移有关。结论:ING1在人胃癌细胞中表达下调,其表达水平与分化程度、肿瘤累及深度以及淋巴结转移有关。     

鼻咽癌组织照射前后细胞凋亡的临床意义初探

目的 采用末端脱氧核苷酸转移酶介导的脱氧核苷酸切口末端标记（ＴＮＵＥＬ）法检测鼻咽癌患者不同剂量照射前后肿瘤细胞凋亡的变化,并初步探讨其潜在临床意义。方法 将接受根治性放射治疗的病理证实为鼻咽低分化鳞状细胞癌的２５例患者分为５个组。５个组分别在分割剂量１．９Ｇｙ／次照射１～５次后３～６ｈ活极取鼻咽癌肿瘤组织。采用ＴＵＮＥＬ免疫组织化学法检测鼻咽癌组织放射治疗前、后肿瘤细胞凋亡。结果 放射治疗前、后     

survivin和livin与肿瘤细胞凋亡

细胞凋亡的过程通过多种信号转导实现,并由许多凋亡相关基因调节控制。凋亡蛋白抑制因子(IAP)与肿瘤细胞的无限增殖关系密切。新近发现的IAP包括survivin、livin与肿瘤密切相关,其抗凋亡机制有待进一步研究。     

抗肿瘤放疗与细胞凋亡

放射治疗是肿瘤综合治疗手段之一，但是由于肿瘤细胞可产生对射线的抗拒作用，最后导致肿瘤治疗失败。本文就射线诱发细胞凋亡现象，作用机制以及有丝分裂死亡关系和临床转归进行了综述，以期探讨射线对肿瘤的杀伤机制，进而指导临床肿瘤放疗。     

低剂量率辐射生物效应及诱导凋亡研究进展

剂量或剂量率下降到一定域值则不能激活DNA损伤感受器,从而导致射线对细胞的杀伤作用增强,表现出“超放射敏感性”。凋亡被认为是低剂量率照射引起细胞死亡的主要形式。辐射诱导凋亡存在剂量率效应。细胞凋亡受许多癌基因和抑癌基因的调控,Bcl-2作为抗凋亡基因其下调有利于诱导凋亡。Bax为促凋亡基因,其表达提高可抑制Bcl-2的功能而促进凋亡,有利于肿瘤细胞死亡,抑制肿瘤的发生发展。     

低剂量率辐射生物效应及诱导凋亡研究进展

剂量或剂量率下降到一定域值则不能激活DNA损伤感受器,从而导致射线对细胞的杀伤作用增强,表现出“超放射敏感性”。凋亡被认为是低剂量率照射引起细胞死亡的主要形式。辐射诱导凋亡存在剂量率效应。细胞凋亡受许多癌基因和抑癌基因的调控,Bcl-2作为抗凋亡基因其下调有利于诱导凋亡。Bax为促凋亡基因,其表达提高可抑制Bcl-2的功能而促进凋亡,有利于肿瘤细胞死亡,抑制肿瘤的发生发展。     

抑癌基因LKB1的研究进展

LKB1是一种丝一苏氨基酸蛋白激酶的变异，多见于一种常染色体显性遗传疾病，以错构瘤为主的肠道息肉症。同时可伴有其它类型的良性肿瘤，叫Peutz-Jeghers综合征。自从1998年被发现以来，许多学者把研究重点放在其鉴定和一种调节细胞生长的因子上。同时分析它调节细胞的功能．在这篇综述中，我们详述一些最近令人振奋的研究成果：Lkb1作为一种肿瘤抑制基因可能是通过改变细胞的凋亡而起作用，在体内是通过与其它蛋白相互作用如磷酸化或甲基化而控制细胞。     

Discrimination of human tumor radioresponsiveness using low-dose rate irradiation

Purpose: Evaluation of the theoretical and practical value of using low-dose rate (LDR) irradiation to increase the resolution of radiosensitivity testing of primary human tumors using clonogenic assays.

Methods and Materials: Fourteen human tumor cell lines were assessed for surviving fraction at 2–8 Gy (SF₂–SF₈) using low-dose rate irradiation and a clonogenic assay. Further data were collected from the literature for 64 low-dose rate irradiation survival curves from human tumor cell lines. The data were grouped into five different radioresponsiveness categories (A–E). An analysis was made of the ability of the graded survival levels to discriminate between the different radioresponse groups and compared with previous analyses for high-dose rate SF₂. Fifteen human cervical carcinoma specimens were analysed for SF₂ and SF_3.5 following high- and low-dose rate irradiation.

Results: Low-dose rate irradiation increased the spread of tumor cell line radiosensitivity data and the ability to discriminate between radioresponse groups was greater at low than at high-dose rates. Using low-dose rate irradiation on primary tumor specimens and a soft agar clonogenic assay decreased the success rate in obtaining data. The latter dropped from 70% for high-dose rate SF₂ to 51% for low-dose rate SF_3.5.

Conclusions: The work on cell lines illustrates that low-dose rate irradiation does improve the ability of clonogenic radiosensitivity measurements to discriminate between tumors of different radioresponsiveness groups. However, using low-dose rate irradiation on primary human tumors with a soft agar clonogenic assay was not practical because of reducing the success rate for obtaining data for radiosensitivity measurements.     

Delayed expression of apoptosis in human lymphoma cells undergoing low-dose taxol-induced mitotic stress

The links between low-dose range taxol-induced mitotic arrest and the subsequent engagement of apoptosis are important for identifying the routes to therapeutic action. Here we have investigated the timing of cell-cycle perturbation and cell death responses following continuous exposure to clinically relevant drug concentrations (1-20 nM). Following 8 h of exposure to taxol, the cell line DoHH2 (p53 wild type) exhibited mitotic arrest and engagement of apoptosis, whereas the cell line SU-DHL-4 (p53 mutant) breached cell-cycle arrest with progression to an abnormal cycle and a 24 h delay in the engagement of apoptosis. Imaging showed equivalent dysfunction of mitotic spindles in both cell lines. The results of kinetic analyses indicated that although cell death may occur at different stages of progression through mitosis and subsequent cell cycles, the overall kinetics of cell death relate to the rate of arrival at a critical event window in the cell cycle. We propose a simple model of low-dose taxol-induced cell death for cycling populations in which mitotic stress acts as a primary trigger for apoptosis with equivalent but potentially delayed outcomes. This view provides a rationale for the clinical effectiveness of this agent, independent of the initial capacity of the tumour cell to engage apoptosis due, for example, to mutant p53 expression. The results provide a perspective for the design of combination regimens that include low-dose taxol and a component that may disturb mitotic delivery.     

Induction of G2 arrest and apoptosis of raji cells by continuous low-dose beta irradiation with 188Re-perrhenate

Continuous irradiation with exponentially reducing beta-rays induces cell death, known as apoptosis. The aim of this study was to investigate the G2 arrest and apoptosis caused by the beta-ray emitted by the radioisotope (188)Re. Doses of 0.4 Gy (3.7 MBq), 4 Gy (37 MBq), and 40 Gy (370 MBq), were added to Blymphoma Raji cells, and cell viability, apoptosis, and DNA cell-cycle changes were assayed. (188)Re showed time- and dose-dependent effects on cell viability and on cell apoptosis and necrosis. At a (188)Re dose of 0.4 Gy, G(2) cell-cycle arrest was observed after 16 hours, and 4,6-diamidino-2-phenylindole (DAPI) staining indicated a slow, time-dependent increase in apoptotic bodies. At a (188)Re dose of 40 Gy, DNA fragmentation was observed at 2 hours, indicative of early damage in the nucleus. In summary, our results showed that continuous irradiation with low-dose beta-rays induced G(2) arrest and progressive apoptosis, which may be characteristic mechanisms of radionuclide therapy.     

Fundamental and clinical studies of low-dose total body irradiation in tumor control

Total body irradiation of 10 rad showed an enhancement effect on tumor cell killing when given 12 hours before local tumor irradiation. In order to clarify the mechanism of this kind of effect, some immunological studies were performed using several immunological procedures, and the results suggested that 10 rad of total body irradiation caused increasing tumor immunity in irradiated tumor bearing mice. Clinical trials in some patients with advanced tumors are now being undertaken on the basis of these experimental data, and the effect of total body irradiation tumor control appears promising although it is too early to draw conclusions.     

Combined therapy of experimental pancreatic cancer with CYP2B1 producing cells: low-dose ifosfamide and local tumor irradiation

Local therapy of pancreatic cancer with microencapsulated CYP2B1-producing cells and ifosfamide showed an effect both on the primary tumor and on distant metastatases. This possibly represents a consequence of the activation of immune response. Other studies have demonstrated that local tumor irradiation leads to the activation of the intratumoral lymphocyte infiltration. The aim of our study was to investigate the efficacy of the combined therapy with low-dose irradiation, ifosfamide and CYP2B1-producing cells. Syngenic pancreatic cancer was induced in 38 Lewis-rats by subcutaneous inoculation of 1 x 10(6) (DSL6A) tumor cells. Microencapsulated CYP2B1-producing cells were injected peritumorally 10--12 weeks after tumor implantation. Animals were randomized to the following groups: 1) control (NaCl, 1 ml i.p.), 2) ifosfamide (50 mg/kg, i.p., (3x/week), 3) local irradiation with 5 Gy and 4) ifosfamide plus irradiation. The tumor growth was monitored for 3 weeks. The tumor infiltration with CD4+, CD8+, NK-cells, microvessel density and proliferation rates were investigated by immunohistochemistry. Cytokine plasma level for TNF-alpha were measured by ELISA. Seven of 9 animals in the group of combined therapy showed an objective response to the therapy. The therapy with ifosfamide or radiation alone showed 5 and 3 responders, respectively. The mean tumor volume was significantly reduced after combined ifosfamide plus radiation therapy in the first week, whereas monotherapy with ifosfamide or radiation significantly decreased tumor growth earliest after 2 and 3 weeks, respectively. The high plasma level of TNF-alpha in the control group was significantly reduced after combined ifosfamide/irradiation treatment. The lymphocyte infiltration and tumor proliferation were not significantly different between the groups. Microvascular density was significantly increased after ifosfamide and ifosfamide plus irradiation therapy. The combination of ifosfamide/CYP2B1-producing cells and irradiation showed an earlier therapeutical effect on the growth of rat pancreatic cancer than the irradiation or ifosfamide alone. There was no evidence of late activation of lymphocyte infiltration and PCNA-positive tumor cells.     

胃癌细胞中Cullin1基因表达与肿瘤细胞凋亡的关系

目的:探讨胃癌组织及细胞中Cullin1基因表达水平及其对凋亡的影响及其机制。方法:在TCGA（The Cancer Genome Atlas）数据库下载胃癌数据,分析胃癌组织与正常组织中Cullin1表达差异。应用实时荧光定量PCR（qRT-PCR）技术检测36例胃癌及正常组织中Cullin1基因表达。合成小干扰RNA（Cullin1-siRNA）转染胃癌细胞系AGS,抑制Cullin1表达;四甲基偶氮唑盐比色法（MTT）检测细胞的增殖活性;流式细胞仪实验检测细胞凋亡率;qRT-PCR和蛋白印迹（Western blot）检测转染各组细胞Cullin1、Bcl2、Bax和Survivin、Livin基因mRNA和蛋白表达。结果:生物信息学结果显示,Cullin1基因在胃癌组织中表达水平明显高于正常组织（P＜0.01）;不同T分期的胃癌组织中Cullin1基因表达存在差异（P=0.026）。qRT-PCR结果显示验证结果与生物信息学结果符合。Cullin1-siRNA能有效沉默AGS细胞Cullin1基因的表达;有效抑制AGS细胞Cullin1表达后,转染组细胞的活性明显低于NS-siRNA组和空白对照组;凋亡率在Cullin1-siRNA组明显高于NS-siRNA组、空白对照组。Cullin1-siRNA转染后AGS中Cullin1和Bcl2、Survivin、Livin基因和蛋白表达下调,而Bax基因和蛋白表达上调(P＜0.05)。结论:Cullin1基因在胃癌中表达增强且与肿瘤浸润深度有关,该基因可能通过抑制胃癌细胞凋亡而发挥作用。     

甲状腺肿瘤原位细胞凋亡检测与脆性组氨酸三联体蛋白表达的临床意义

目的研究原位细胞凋亡指数(apoptosis index,AI)及抑癌蛋白脆性组氨酸三联体(FHIT)在原发性甲状腺肿瘤中表达及其与病变的关系。方法原发性甲状腺肿瘤78例(腺癌38例,腺瘤40例),分别应用原位细胞凋亡检测(TuNEL)试剂盒测定AI及应用免疫组化方法检测FHIT表达情况。结果AI及FHIT蛋白在各甲状腺肿瘤组织中均有表达,腺癌AI表达显著高于腺瘤(P<0.05),腺瘤FHIT表达高于腺癌(P<0.01),AI及FHIT蛋白表达与肿瘤大小(P<0.05及P<0.01)、腺癌转移(P<0.05及P<0.05)具有相关性。结论AI、FHIT的表达与甲状腺肿瘤显著相关,它们在原发性甲状腺癌病变中高度表达,检测AI及FHIT水平对于鉴别原发性甲状腺肿瘤良恶性具有重要参考意义,其表达水平可能是判断甲状腺癌预后的观测指标。