奥曲肽对胃癌细胞株SGC7901细胞生长抑制作用及其机制的探讨

 目的　研究生长抑素类似物奥曲肽对胃癌细胞株SGC790 1细胞的增殖、蛋白激酶B及端粒酶活性的影响。方法　应用奥曲肽作用于胃癌细胞株SGC790 1细胞不同时间后 ,检测其对体外培养胃癌细胞的抑制率 ,胃癌细胞蛋白激酶B(Akt/PKB)及端粒酶的活性。结果　奥曲肽对胃癌细胞增殖有明显抑制作用 ,呈剂量依赖性。同时能显著抑制胃癌细胞Akt/PKB的活性和端粒酶的活性 (12 ,2 4 ,4 8h均P <0 .0 1)。结论　生长抑素对胃癌细胞株SGC790 1细胞增殖有抑制作用 ,其机制与抑制Akt/PKB及端粒酶活性有关。     

Haploinsufficiency of hTERT leads to telomere dysfunction and radiosensitivity in human cancer cells

One of the most consistent differences between cancer cells and normal somatic cells is the continuous expression of telomerase, an enzyme that is important for maintenance of chromosome ends, or telomeres. It is believed that telomerase expression allows cancer cells to maintain their telomeres after many cell divisions and thereby avoid replicative senescence. We have tested this hypothesis by targeting the gene encoding the catalytic subunit of the telomerase holoenzyme, hTERT, in a human cancer cell line. Heterozygous disruption of hTERT led to a reduction in telomerase activity, telomere shortening, activation of DNA damage signaling and the appearance of a subpopulation of cells that displayed features of senescence. Targeted cells were radiosensitive, as compared with parental controls that had two intact hTERT alleles, and expressed a classical marker of senescence after irradiation. These results suggest that telomerase inhibitors might be useful in the sensitization of cancer cells to DNA damaging agents.     

The detection of telomerase activity in patients with adenocarcinoma of the pancreas by fine needle aspiration

Telomerase activation in differentiated cells is associated with cell immortalization. Detection of telomerase expression in cancer provides a potential biomarker to be evaluated in the diagnosis and prognosis of cancer patients. Analysis of telomerase activity in biopsy specimens may serve as a useful marker for the diagnosis of pancreatic adenocarcinoma. This study was conducted to determine if telomerase could be detected in fine needle aspirates from patients with pancreatic carcinoma. The telomeric repeat amplification protocol (TRAP) assay was used to determine telomerase activity from pancreatic cancer cell lines, paired tumor/normal human pancreatic tissues and specimens obtained at the time of diagnostic fine-needle aspiration (FNA) biopsies. In this report, we demonstrate that: i) telomerase activity is present in pathologically confirmed pancreatic cancer specimens, but absent in matched adjacent areas of normal pancreatic tissues; ii) telomerase activity is present in FNA samples obtained at the time of CT-guided FNA of pancreatic adenocarcinomas; and iii) this activity can be detected in material normally discarded during FNA slide preparation. Activation of telomerase can be identified in FNA specimens obtained at the time of routine cytologic diagnosis. These findings may be useful for further diagnostic or therapeutic investigations of telomerase activity in pancreatic carcinoma.     

恶性肿瘤细胞株端粒酶活性的研究

目的：探讨非放射性定量的端粒重复序列扩增法（ＴＲＡＰ）在检测人类恶性肿瘤细胞株端粒酶活性中的应用价值。方法：采用银染定量的ＴＲＡＰ方法检测ＳＭＭＣ－７７２１、Ｋ５６２、ＣＮＥ－１、Ａ５４９、ＨＬ－６０细胞 的端粒酶活性。结果：９株人类恶性细胞株中８株呈端粒酶的阳性而其经热处理的标本均为阴性。结论：非放射性银染定量的ＴＲＡＰ方法具有高可信度、特异性及敏感性。且８株人类恶性肿瘤细胞株均有端粒酶活性表达     

As2 O3对人胃癌BGC-823 细胞端粒酶的影响

 目的 观察三氧化二砷（As₂ O₃）对人胃癌BGC-823细胞端粒酶活性及端粒酶逆转录酶基因转录的影响。方法 用不同浓度的三氧化二砷作用于人胃癌BGC-823细胞，通过MTT法测定细胞活力；流式细胞术检测细胞凋亡变化；TRAP PCR ELIsA方法检测细胞端粒酶活性的变化；RT-PCR半定量方法检测细胞端粒酶hTEI汀基因mRNA的转录水平。结果 三氧化二砷可明显抑制人胃癌BGC-823细胞的生长，诱导细胞发生凋亡，抑制作用随三氧化二砷浓度的升高及作用时间的延长而增强。细胞的端粒酶活性明显下降，细胞hTERT基因的转录表达显著抑制。BGC-823细胞端粒酶活性的下调与As₂ O₃作用时间和浓度有关，呈现明显的时间-剂量效应关系。结论 As₂ O₃能够抑制人胃癌BGC-823细胞的增殖、促使细胞凋亡、抑制细胞的端粒酶活性。As₂ O₃是一种良好的端粒酶抑制剂，在肿瘤的治疗中具有一定应用价值。     

The level of telomere dysfunction determines the efficacy of telomerase-based therapeutics in a lung cancer cell line

Telomerase is the ribonucleoprotein enzyme that maintains telomeres of eukaryotic chromosomes. Activation of telomerase is a common feature of the majority of human cancers, and inhibition of this enzyme has been proposed as a novel target for cancer therapeutics. Here, we investigated the effects of telomerase inhibition in the non-small cell lung cancer cell line NCI-H460, using a genetic approach by ectopic expression of dominant-negative (DN)-hTERT. Five clones were selected in which telomerase activity was completely abolished. As a result, telomere erosion was observed leading to proliferation arrest after a lag period of 20-28 population doublings. Although overall telomere length was similar between the different clones as measured by quantitative fluorescence in situ hybridization (Q-FISH), striking differences were found in telomere length of individual chromosomes. In particular, lack of individual telomeres and formation of end-to-end fusions were variable. Interestingly, this level of individual telomere dysfunction was positively correlated with the remaining life span of the different clones in vitro. In addition, the amount of telomere dysfunction induced by DN-hTERT was twice as high compared to the small molecule telomerase inhibitor BIBR1532, which induced growth arrest after >100 population doublings. Thus, pharmacological strategies that aim at inhibition of telomerase in cancer cells should take into account that not only overall telomere shortening, but rapid induction of a high level telomere dysfunction appears to be the crucial surrogate parameter for the development of future telomerase-based therapeutics.     

胃癌细胞中端粒酶活性的表达研究

Objective To study the relationship between telomerase activity and biological behavior in human gastric cancer cells and appraise the clinical significance of detecting telomerase activity. Methods The telomerase activity in 47 gastric cancer tissue samples, their matched normal tissues, 7 gastric ulcer and 2 gastric cancer cell lines was detected using a PCR-based non-radioisotopic telomeric repeat amplification protocol (TRAP) assay. Results None of the 47 samples from normal gastric tissues expressed telomerase activity. The 41 of 47 cases of gastric cancer presented telomerase activity with an 87.2% positive rate (P<0.001). 2/2 gastric cancer cell lines and 0/7 gastric ulcer line were also positive for telomerase activity. The activity of telomerase was associated with the pathological differentiation of gastric cancer. Conclusion Telomerase activity may be related to the biological behavior of gastric cancer and can help in assessing the malignant potential of gastric cancer. Telomeras activity will be a good diagnostic marker for the detection of gastric cancer.     

Telomerase and telomere dynamics in ageing and cancer: current status and future directions

Abstract This review will focus on the clinical utilities of telomerase for human cancer diagnosis and prognosis. Much attention has been focused on control of telomerase activity in early and late stage tumours. Telomerase stabilisation may be required for cells to escape replicative senescence and to proliferate indefinitely. Because of a very strong association between telomerase and malignancy, both clinicians and pathologists expect this molecule to be a useful diagnostic and prognostic marker and a new therapeutic target. These data have greatly inspired the development of various strategies to target telomere and telomerase for cancer therapy. Finally, evidence is now emerging that G-quadruplex ligands produce rapid senescence and selective cell death. A summary of recent experimental works with new small molecules as potential inhibitors of telomerase is presented. *Supported by an unrestricted educational grant from Pfizer.     

顺铂等化疗药物对胃癌细胞端粒酶活性的影响

目的：探讨端粒酶作为化疗敏感性指标的可行性。方法：选择IC50剂量的顺铂，丝裂霉素C，阿霉素及5－氟脲嘧啶和甲酰四氢叶酸处理胃癌细胞，采用半定量TRAP－银染法检测药物处理前后胃癌细胞端粒酶活性。并应用流式细胞学检测细胞周期和细胞凋亡率。结果：顺铂，丝裂霉素C和阿霉素在诱导两细胞凋亡的同时，下调端粒酶活性，且其抑制作用呈时间依赖关系；5－氟脲嘧啶和甲酰四氢叶酸对胃癌细胞端粒酶活性无明显抑制作用，结论：化疗前后细胞端粒酶活性的变化，可作为化疗敏感性指标。     

DNA倍体和端粒酶检测对贲门癌诊断的价值

目的　探讨胃镜直视下刷取贲门黏膜脱落细胞端粒酶活性检测及DNA倍体分析对贲门癌的诊断价值。方法　采用TRAP -PCR银染定性法 ,对 72例贲门黏膜脱落细胞进行端粒酶活性分析 ,同时进行流式DNA倍体分析。结果　贲门癌组织中端粒酶的阳性率 (88.89% )明显高于贲门良性疾病组织 (11.11% ) ;贲门癌黏膜脱落细胞DNA倍体的阳性率 (77.78% )明显高于贲门良性疾病组织 (11.11% ) ;端粒酶联合DNA倍体分析对贲门癌的诊断率为 95 .5 6%。结论　贲门黏膜脱落细胞DNA倍体分析联合端粒酶活性测定 ,是诊断贲门癌特异而敏感的方法