Function of HSP90 and p23 in the telomerase complex of thyroid tumors

Recently, studies on endocrine tumors revealed a potential role of telomerase in the dedifferentiation and/or malignant transition of these tumors. Telomerase is a ribonucleoprotein complex that includes the telomerase RNA component (hTR), the telomerase-associated protein (TP1), and the telomerase catalytic subunit (hTERT). Previously, the chaperones p23 and HSP90 have been described as additional telomerase regulators. To test whether the interactions of these genes are reflected in the dedifferentiation of thyroid tumors, we determined their mRNA and/or protein expression in 30 normal (tumor-free) thyroid tissues (NT), 35 follicular adenomas (FAD), 42 papillary carcinomas (PTC), 38 follicular carcinomas (FTC), 25 poorly differentiated carcinomas (PDTC), and 34 undifferentiated carcinomas (UTC). We then compared the results with telomerase activity. RT-PCR analysis revealed that TP1 was ubiquitously expressed. hTR was found in 50-94% of malignant tumors, in contrast to 7% of NT and 26% of FAD. hTERT was clearly associated with aggressive biological behavior. Ninety-two to 100% of the malignant tumors were positive for hTERT protein, whereas NT and FAD were negative in 100% and 94%, respectively. HSP90 mRNA and protein showed a close relationship to hTERT. p23 protein was negative in NT and positive in 3% of FAD, 39% of FTC, 40% of PTC, 44% of PDTC and 47% of UTC. High telomerase activity was measurable in hTERT and HSP90-positive tissues only. Our data show that the common expression of hTERT and HSP90 regulates telomerase activity in thyroid carcinomas. Chaperone p23 is involved in the telomeric complex to a lesser extent, but its expression is stronger in carcinomas than in non-malignant thyroid tissues. The expression profile of telomerase components represents an additional prognostic marker that may identify more aggressive thyroid tumors.     

hTERT基因反义核酸对Raji细胞端粒酶活性的影响

目的:观察人端粒酶逆转录酶(hTERT)基因的全硫代修饰反义寡核苷酸(ASODN)对Raji细胞端粒酶活性的影响。方法: 端粒酶聚合酶链反应-酶联免疫测定法检测Raji细胞的端粒酶活性；采用逆转录-聚合酶链反应方法检测hTERT基因mRNA的表达水平；以间接免疫荧光标记法通过流式细胞仪检测hTERT蛋白表达含量的变化。结果:hTERTASODN作用于Raji细胞后，hTERTmRNA表达水平明显降低，ASODN与Raji细胞共同孵育48h，hTERT蛋白表达阳性率降为50.15%±3.49%，72hhTERT蛋白表达阳性率降为33.35%±2.75%。而hTERT正义核酸作用24、48、72h对hTERT蛋白表达阳性率(65%)无显著影响(P＞0.05)。hTERT基因ASODN作用于Raji细胞48h，其端粒酶活性明显降低，作用72h，端粒酶活性明显受到抑制，分别与正义寡核苷酸组、空白对照组相比有显著差异(P＜0.05)。结论:hTERT基因反义寡核苷酸特异性地抑制Raji细胞的端粒酶活性。     

Differential expression of telomerase activity in neuroendocrine lung tumours: correlation with gene product immunophenotyping

Telomerase activity was examined by the telomeric repeat amplification protocol (TRAP) assay in 38 neuroendocrine (NE) lung tumours. A significantly (p = 0.001) different frequency of telomerase positivity was observed among different histological tumour types. Specifically, a positive TRAP signal was observed in 14 of 15 (93%) small cell lung cancers (SCLCs), 7 of 8 (87%) large-cell NE carcinomas (LCNECs), and only 1 of 15 (7%) typical carcinoid tumours. When telomerase activity was correlated with the gene product-based immunophenotypic profile of individual tumours, it was found that the absence of telomerase activity was associated with a lack of bcl-2, p53, and c-kit expression, and characterized by a low proliferation index consistent with the absence of cdk-4 expression and the presence of the cdk inhibitor Rb. Such a phenotype was appreciable in most of the carcinoid tumours. Conversely, telomerase-positive tumours generally showed an immunophenotype consistent with gene product alterations (including high expression of bcl-2, p53, and c-kit, and loss of Rb) and were characterized by a high proliferation index. These telomerase data support the previously reported evidence for two genetically unrelated groups of NE lung tumours (SCLC, and to some extent LCNEC, versus carcinoid tumours) that have distinct phenotypic profiles.     

Quantitative measurement of telomerase activity and localization of its catalytic subunit (hTERT) in chronic inflammation of capsule formation around various model implants and in sarcomas in a rat model

Telomerase is upregulated in some preneoplastic lesions and overexpressed in the majority of malignant tumors, but absent in most nonneoplastic somatic tissues. We analyzed telomerase activity using TRAP-assay in capsule tissues in a rat model with chronic inflammation and in tumor, and visualized the catalytic subunit of telomerase (hTERT) by immunhistochemistry. Significant elevated telomerase activity was found in tumor tissue compared with nonneoplastic tissue (p = 0.047). Cases with a strong inflammation in capsule tissue showed a specific telomerase activity. In these cases, there were no significant differences in telomerase activities compared with malignant tumor tissue. We demonstrate elevated telomerase activity and its diagnostic limits around model implants in a rat model, and visualize its expression not only in malignant tissue but also in inflammatory cells. So the quantitative measurement of telomerase activity should not be applied in general as a marker for malignancy in capsule tissue.     

Prognostic implication of telomerase activity in patients with brain tumors

Telomerase adds telomeric repeats to the ends of telomeres to compensate for their progressive loss. A favorable prognosis is associated with low or no telomerase in some tumors. The authors investigated whether telomerase activity is associated with survival of patients with brain tumors. Sixty-two consecutive patients with brain tumors underwent surgery, and their surgical specimens were investigated. The patients were pathologically categorized as group I (aggressive group) and group II (non-aggressive group). Telomerase activity was examined by the telomeric repeat amplification protocol (TRAP) assay. The median time was calculated in association with overall survival and progression-free survival in each group. The significant difference was noted in telomerase activity between high-grade gliomas and lowgrade gliomas (p=0.022). Telomerase activity was significantly associated with the median overall survival and progression-free survival in all tumors of the aggressive group. On the other hand, the median overall survival in the non-aggressive group was not dependent on telomerase activity, while the median progression-free survival was. Our data suggests that telomerase is an important prognostic indicator of survival in patients with brain tumors.     

Localization of telomerase hTERT protein and hTR in benign mucosa, dysplasia, and squamous cell carcinoma of the cervix

Telomerase has been detected by telomerase repeat amplification protocol (TRAP) assay in cervical dysplasia and squamous cell carcinoma but not in most normal cervical tissues. In the present study, the cellular localization of the protein catalytic subunit of telomerase (hTERT) and the RNA component (hTR) were investigated by a sensitive immunohistochemical technique and by in situ hybridization, respectively. hTERT protein was detected in all diagnostic categories of cervical specimens. hTERT was localized predominantly to the lower suprabasal levels of normal squamous mucosa but was detected throughout virtually all levels of the lesional epithelium in low-grade squamous intraepithelial lesions (LSILs), high-grade squamous intraepithelial lesions (HSILs), and squamous cell carcinoma (SCC). Telomerase expression correlated with hTERT detection in SCC and HSIL but was not detected by TRAP assay in most samples of normal mucosa or LSIL. The distribution of hTR correlated with the localization of hTERT in HSIL and SCC but was restricted to the basal and suprabasal cell layers in normal mucosa and LSIL.