hTERT methylation and expression in gastric cancer

Gastric cancer is the second most prevalent cause of cancer death worldwide. DNA methylation is a common event in gastric carcinogenesis. hTERT seems to be the rate-limiting determinant of telomerase activation, which is responsible for stability and life span. hTERT hypermethylation has been associated with telomerase expression. In the present study, we investigated the promoter methylation status and hTERT protein expression in gastric cancer and normal mucosa samples. One hundred and nine gastric cancer and 53 normal mucosa samples were investigated through methylation-specific PCR. Immunohistochemistry was analysed using peroxidase in 55 gastric cancer and 18 normal gastric mucosa samples. This is the first study evaluating hTERT methylation status in gastric carcinogenesis. We did not observe hTERT protein expression in normal gastric mucosa. Moreover, hTERT expression was observed in 80% of tumours and was associated with gastric cancer (p?<?0.0001). Partial methylation was the most frequent pattern in gastric samples, even in normal mucosa. The frequency of specimens presenting hypermethylation was significantly higher in tumours than in normal mucosa samples (p?=?0.0002), although the presence of hypermethylated promoter was not associated with a higher frequency of hTERT expression. A low correlation between hTERT protein expression and methylation was verified in gastric cancer samples. There was a clear difference in the frequency of hTERT expression and methylation within tumoral and non-tumoral tissues. Methylation status and telomerase expression may be useful for the diagnosis of gastric cancer and may have an impact on the anti-telomerase strategy for cancer therapy.     

Telomerase activity in breast cancer in Western India (Gujarat)

The purpose of this study was to examine the association of telomerase activity with clinical and histopathological prognostic variables in primary breast cancer (n=64). Telomerase activity in breast cancer was also compared with that in benign (n=10) and non-malignant tissues (n=8; post-lumpectomy tissues histopathologically defined as containing no residual tumor). The parameter was assessed using the Telomerase PCR ELISA kit. Values above OD 0.120 were considered positive. Estrogen and progesterone receptors (ER and PgR) were assayed by the dextran-coated charcoal method and levels >10 fmol/mg cytosol protein were taken as positive. Telomerase activity was detected in 20% and 50% of the patients with benign lesions and primary breast cancer, respectively, and in 50% of post-lumpectomy breast tissues histopathologically defined as containing no residual tumor. Telomerase activity was present in all stages of breast carcinoma and showed a significant inverse correlation with lymph node status (p=0.006), lymphatic invasion (p=0.035) and necrosis (p=0.033). Moreover, when stage II patients were grouped according to nodal involvement, a trend towards significance was observed (p=0.055). No correlation was observed with ER and PgR. The results of our study suggest that telomerase activity might be associated with the presence of cancer cells. Furthermore, telomerase activation may occur early in breast cancer and may be periodically downregulated during subsequent tumor progression.     

Superoxide dismutase in gastric adenocarcinoma: is it a clinical biomarker in the development of cancer?

Gastric cancer is the second most common cancer worldwide. The involvement of reactive oxygen species (ROS) in the pathogenesis of gastric malignancies is well known. Many human tumours have shown significant changes in the activity and expression of superoxide dismutase (SOD), which might be correlated with clinical-pathological parameters for the prognosis of human carcinoma. The aim of this study is the detection of MnSOD and CuZnSOD activity and their expression in gastric adenocarcinoma and healthy tissues. Gastric samples (adenocarcinoma and healthy tissues) harvested during endoscopy or resected during surgery were used to determine MnSOD and CuZnSOD activity and expression by spectrophotometric and Western blotting assays. The total SOD activity was significantly higher (p<0.05) in healthy mucosa with respect to gastric adenocarcinomas. No differences were found in MnSOD activity and, on the contrary, CuZnSOD activity was significantly lower (p<0.001) in cancer samples with respect to normal mucosa. The rate of MnSOD/CuZnSOD activity in adenocarcinoma was over ninefold higher than that registered in healthy tissues (p<0.05). Moreover, in adenocarcinoma MnSOD activity represented the 83% of total SOD with respect to healthy tissues where the ratio was 52% (p<0.001). On the contrary, in cancer tissues, CuZnSOD activity accounted for only 17% of the total SOD (p<0.001 if compared with the values recorded in normal mucosa). After immunoblotting, MnSOD was more expressed in adenocarcinoma with respect to normal mucosa (p<0.001), while CuZnSOD was similarly expressed in adenocarcinoma and healthy tissues. The SOD activity assay might provide a specific and sensitive method of analysis that allows the differentiation of healthy tissue from tumour tissue. The MnSOD to CuZnSOD activity ratio, and the ratio between these two isoforms and total SOD, presented in this preliminary study might be considered in the identification of cancerous from healthy control tissue.     

The study of telomerase activity in gastric cancer

Telomerase activity was examined in tissue specimens from patients with gastric adenocarcinomas and gastric lymphoma using a modified TRAP (telomeric repeat amplification protocol) assay. Telomerase activity was found in 16 of 18 (89%) patients with gastric adenocarcinomas and gastric lymphoma, whereas it was not detected in a patient with noncancerous gastric mucosa. Almost all analyzed specimens had “high” and “very high” levels of telomerase activity. Telomerase is almost certainly associated with the process of malignant transformation and it can be an important marker for diagnostics of gastric cancer.     

hTERT基因片段的克隆,表达和抗hTERTy抗体用于端粒酶及hTER …

Telomerase is an important biomarker in cancer cells. It is active in germline cells, most of cancer tissues and cell lines, but not in most somatic tissues. Telomerase is composed of two components, and while hTER is present in normal and tumor cells, expression of hTERT appears to be highly regulated and correlates with telomerase activity. In order to detect the telomerase enzyme and hTERT protein, anti-hTERT polyclonal antibodies were produced in this study. A segment of hTERT cDNA was amplified by RT-PCR and cloned into the multi-cloning site of the GST gene fusion vector pGEX-5X-3. After the recombinant plasmid was expressed in E. coli BL21, the fusion protein was purified for immunization. Extracts from several cultured cells were analyzed by Western blot, and the results indicated that telomerase enzyme and hTERT protein could be specifically detected by this anti-hTERT antibod'. Thus, a simple and effective method was primarily established for the immunodetection of telomerase enzyme and hTERT protein.     

The telomerase activities in several organs and strains of rats with ageing

Telomerase activity is known to be implicated both in cell immortalization and carcinogenesis. Telomerase activity has not been detected in most human somatic tissues. However, we previously confirmed that the activity is present both in methylazoxymethanol acetate-induced rat colonic adenocarcinoma and non-treated colonic mucosa, presumably indicating the tissue-specific activity of the enzyme in rats. To determine the standard activity of rat telomerase in various organs in relation to differences in sex, age and strain, we examined the activity by using the telomeric repeat amplification protocol (TRAP) assay. The testis, liver, and colon mucosa showed the activity. The brain had very low or negative activity in 5-week-old male rats of the F344, SD, Wistar, Donryu or ACI strains. Age (5-week-old and 9-month-old) or sex difference for the activity was not apparent in rats of these strains. In general, telomerase activity in the fetal brain, liver and kidney was stronger than in the adult organ. The telomerase activity of each organ was different from that of human. This difference may indicate that the rat has a specific mechanism for maintaining the telomeric repeats of the chromosome even in somatic tissues. The basic information resulting from this study may be useful for the study of the role of telomerase in tumorigenesis in animal experiment models.     

hTERT基因片段的克隆、表达和抗hTERT抗体用于端粒酶及hTERT检测的研究

端粒酶是一种重要的肿瘤生物学标志,其活性在生殖细胞、绝大多数肿瘤细胞和体外培养的永生细胞可以测知,但在大多数体细胞中不易测出。人端粒酶由两部分组成,包括hTERC和hTERT,hTERC在正常细胞和肿瘤细胞中均有表达,而hTERT的表达似乎受到严格的调控且和端粒酶活性一致。为了检测肿瘤细胞中端粒酶及hTERT的表达,我们制备了抗hTERT蛋白的特异性多克隆抗体。首先用RT-PCR方法克隆了hTERTcDNA的一个片段,将其连接到GST融合表达载体pGEX-5X-3后在大肠杆菌中融合表达。将纯化的融合蛋白抗原免疫动物,制备抗hTERT蛋白的多克隆抗体。不同的细胞抽提物用该抗体进行了Westernblot分析,结果表明该抗体可特异识别端粒酶阳性细胞株中的hTERT及端粒酶,为端粒酶及hTERT的检测初步提供了一个简单有效的检测手段。     

Changes in serum markers indicative of health effects in vineyard workers following exposure to the fungicide mancozeb: an Italian study

Gastric cancer is the second most common cancer worldwide. The involvement of reactive oxygen species (ROS) in the pathogenesis of gastric malignancies is well known. Many human tumours have shown significant changes in the activity and expression of superoxide dismutase (SOD), which might be correlated with clinical–pathological parameters for the prognosis of human carcinoma. The aim of this study is the detection of MnSOD and CuZnSOD activity and their expression in gastric adenocarcinoma and healthy tissues. Gastric samples (adenocarcinoma and healthy tissues) harvested during endoscopy or resected during surgery were used to determine MnSOD and CuZnSOD activity and expression by spectrophotometric and Western blotting assays. The total SOD activity was significantly higher (p<0.05) in healthy mucosa with respect to gastric adenocarcinomas. No differences were found in MnSOD activity and, on the contrary, CuZnSOD activity was significantly lower (p<0.001) in cancer samples with respect to normal mucosa. The rate of MnSOD/CuZnSOD activity in adenocarcinoma was over ninefold higher than that registered in healthy tissues (p<0.05). Moreover, in adenocarcinoma MnSOD activity represented the 83% of total SOD with respect to healthy tissues where the ratio was 52% (p<0.001). On the contrary, in cancer tissues, CuZnSOD activity accounted for only 17% of the total SOD (p<0.001 if compared with the values recorded in normal mucosa). After immunoblotting, MnSOD was more expressed in adenocarcinoma with respect to normal mucosa (p<0.001), while CuZnSOD was similarly expressed in adenocarcinoma and healthy tissues. The SOD activity assay might provide a specific and sensitive method of analysis that allows the differentiation of healthy tissue from tumour tissue. The MnSOD to CuZnSOD activity ratio, and the ratio between these two isoforms and total SOD, presented in this preliminary study might be considered in the identification of cancerous from healthy control tissue.     

Adenovirus-mediated suicide SCLC gene therapy using the increased activity of the hTERT promoter by the MMRE and SV40 enhancer

Telomerase is a ribonucleoprotein complex of which the function is to add telomeric repeats to chromosomal ends. Telomerase consists of two essential components, the telomerase RNA template (hTR) and the catalytic subunit (hTERT). hTERT is expressed only in cells and tissues positive for telomerase activity, i.e., tumor or stem cells. The aim of this study was to use increased telomerase promoter activity in small-cell lung cancer (SCLC) gene therapy. The hTERT promoter and Myc-Max response elements (MMRE) in pGL3-Control vector containing SV40 enhancer resulted in strong expression of the luciferase gene only in telomerase positive and myc overexpressing SCLC cell line but not in normal human cell line. To investigate the possibility of the utilization of the MMRE, hTERT promoter, and SV40 enhancer in targeted SCLC gene therapy, adenovirus vector expressing HSV-TK controlled by the MMRE, hTERT promoter, and SV40 enhancer for the induction of telomerase positive and myc-overexpressing cancer specific cell death was constructed. SCLC cells infected with Ad-MMRE-hT-TK-enh were significantly suppressed and induced apoptosis more than those of Ad-hT-TK or Ad-hT-TK-enh infected cells. Telomerase and c-myc are activated in 60 approximately 80% of SCLC, so the increased activity of telomerase promoter can be used for targeted SCLC gene therapy. These results show that the MMRE, hTERT promoter, and SV40 enhancer can be used in SCLC targeted cancer gene therapy.     

以端粒酶为靶标抗癌药物筛选模型建立及端粒酶抑制剂筛选

新药研究与开发离不开筛选模型 ,而筛选模型的关键是寻找、确定和制备药物筛选靶———药靶 .近来研究表明 ,端粒酶与恶性肿瘤的发生和发展有着密切的关系 ,端粒酶在恶性肿瘤细胞中表达率占80 %～ 90 % ,而在正常体细胞中不表达[1～ 4 ] .这表明端粒酶在维持肿瘤细胞的增殖中起着重要作用 .抑制端粒酶的活性有可能抑制肿瘤的生长 ,因而端粒酶被认为是恶性肿瘤诊断和治疗的新靶标 .以端粒酶为抗癌药物作用的靶标 ,建立抗癌药物筛选模型 ,在分子水平上筛选针对端粒酶的抑制剂 ,进而获得特异性高、针对性强、毒副作用小的新型广谱的抗癌药物 ,…     

Activity of the Human Telomerase Catalytic Subunit (hTERT) Gene Promoter Could Be Increased by the SV40 Enhancer

Telomerase is a ribonucleoprotein complex of which the function is to add telomeric repeats to chromosomal ends. Telomerase consists of two essential components, the telomerase RNA template (hTR) and the catalytic subunit (hTERT). hTERT is expressed only in cells and tissues positive for telomerase activity, i.e., tumor and fetal cells. The aim of this study is to test the increased telomerase promoter activity for cancer gene therapy in adenovirus vector. We cloned the hTERT promoter in place of the SV40 promoter in the pGL3-contol vector to be increased by the SV40 enhancer sequences, resulting in strong expression of luc+ only in telomerase positive cancer cells. Then we transfected the constructed plasmid into a normal human cell line and several cancer cell lines. Through these experiments, we identified the selective and increased expression of the luciferase gene controlled by the hTERT promoter and the SV40 enhancer in the telomerase positive cancer cell lines. To investigate the possibility of utilizing the hTERT promoter and the SV40 enhancer in targeted cancer gene therapy, we constructed an adenovirus vector expressing HSV-TK controlled by the hTERT promoter and the SV40 enhancer for the induction of specific telomerase positive cancer cell death. NSCLC cells infected by Ad-hT-TK-enh were more significantly suppressed and induced apoptosis than those infected by Ad-hT-TK. Telomerase is activated in 80～90% of cancers, so adenovirus with increasing telomerase promoter activity might be used for targeted cancer gene therapy using suicide genes. These results show that the hTERT promoter and the SV40 enhancer might be used for targeted cancer gene therapy.     

Activity of the human telomerase catalytic subunit (hTERT) gene promoter could be increased by the SV40 enhancer

Telomerase is a ribonucleoprotein complex of which the function is to add telomeric repeats to chromosomal ends. Telomerase consists of two essential components, the telomerase RNA template (hTR) and the catalytic subunit (hTERT). hTERT is expressed only in cells and tissues positive for telomerase activity, i.e., tumor and fetal cells. The aim of this study is to test the increased telomerase promoter activity for cancer gene therapy in adenovirus vector. We cloned the hTERT promoter in place of the SV40 promoter in the pGL3-contol vector to be increased by the SV40 enhancer sequences, resulting in strong expression of luc+ only in telomerase positive cancer cells. Then we transfected the constructed plasmid into a normal human cell line and several cancer cell lines. Through these experiments, we identified the selective and increased expression of the luciferase gene controlled by the hTERT promoter and the SV40 enhancer in the telomerase positive cancer cell lines. To investigate the possibility of utilizing the hTERT promoter and the SV40 enhancer in targeted cancer gene therapy, we constructed an adenovirus vector expressing HSV-TK controlled by the hTERT promoter and the SV40 enhancer for the induction of specific telomerase positive cancer cell death. NSCLC cells infected by Ad-hT-TK-enh were more significantly suppressed and induced apoptosis than those infected by Ad-hT-TK. Telomerase is activated in 80 approximately 90% of cancers, so adenovirus with increasing telomerase promoter activity might be used for targeted cancer gene therapy using suicide genes. These results show that the hTERT promoter and the SV40 enhancer might be used for targeted cancer gene therapy.     

Telomerase activity in human germline and embryonic tissues and cells

Telomerase is a ribonucleoprotein that synthesizes telomere repeats onto chromosome ends and is involved in maintaining telomere length in germline tissues and in immortal and cancer cells. In the present study, the temporal regulation of expression of telomerase activity was examined in human germline and somatic tissues and cells during development. Telomerase activity was detected in fetal, newborn, and adult testes and ovaries, but not in mature spermatozoa or oocytes. Blastocysts expressed high levels of telomerase activity as did most human somatic tissues at 16–20 weeks of development with the exception of human brain tissue. This activity could no longer be detected in the somatic tissues examined from the neonatal period onward. Neither placenta nor cultured fetal amniocytes contained detectable telomerase activity. Fetal tissues explanted into primary cell culture showed a dramatic decline in telomerase activity which became undetectable after the first passage in vitro. Elucidation of the regulatory pathways involved in the repression of telomerase activity during development may lead to the ability to manipulate telomerase levels and explore the consequences both for cellular aging and for the survival of cancer cells. © 1996 Wiley-Liss, Inc.     

Adenovirus-mediated suicide gene therapy using the human telomerase catalytic subunit (hTERT) gene promoter induced apoptosis of ovarian cancer cell line

Telomerase is a ribonucleoprotein complex the function of which is to add telomeric repeats (TTAGGG)(n) to chromosomal ends, and it is known to play an important role in cellular immortalization. Telomerase is highly active in most tumor cells, yet not in normal cells. As such, it may have possible applications in cancer gene therapy. Telomerase consists of two essential components, telomerase RNA template (hTR) and catalytic subunit (hTERT). hTERT is expressed only in cells and tissues positive for telomerase activity, i.e., tumor and fetal cells. We here tested the possibility of the utilization of the hTERT promoter in targeted cancer gene therapy. We cloned the hTERT promoter in the replace of the CMV promoter and sub-cloned HSV-TK gene to be controlled by hTERT gene promoter in adenovirus shuttle plasmid. Then we constructed recombinant adenovirus Ad-hT-TK, and infected them into normal and human gynecological cancer cell lines. Through these experiments, we identified the selective tumor specific cell death by Ad-hT-TK. Furthermore, FACS analysis and TUNEL assay suggests that the reduced viability is mediated through the induction of apoptosis, indicating that this approach may be a useful method for suppressing cancer growth in targeted cancer gene therapy. These results show that Ad-hT-TK could be used for gynecological cancer gene therapy.