Differential telomerase activity, expression of the telomerase catalytic sub-unit and telomerase-RNA in ovarian tumors.

Telomerase activity has been found in a variety of malignant tumors but only rarely in benign tumors or normal tissues. In this study, we investigated telomerase activation in 37 ovarian tumors, including benign, borderline and malignant neoplasms. Telomerase activity was detected using the telomeric repeat amplification protocol (TRAP) in 13/16 ovarian carcinomas, 9/10 borderline tumors and 3/11 cystadenomas/fibromas. mRNA expression of the putative human telomerase catalytic sub-unit gene (hTERT) was detected by RT-PCR in 14/15 ovarian carcinomas, 8/10 borderline tumors and 4/11 cystadenomas/fibromas. In situ hybridization was performed to evaluate telomerase-RNA (hTR) expression in the corresponding paraffin-embedded tumors. Variable expression levels of hTR were found over neoplastic tumor cells. The highest levels of hTR expression were found predominantly in ovarian carcinomas. Although the amount of telomerase activity varied, significantly high levels of telomerase activity were found predominantly in ovarian carcinomas. hTERT mRNA expression was closely associated with telomerase activity. These findings suggest that up-regulation of hTERT and hTR is important for telomerase activation during malignant-tumor progression. Telomerase activation might therefore be a valuable diagnostic parameter that could help to identify potentially progressive lesions. However, the diagnostic and therapeutic implications of telomerase activation need to be clarified in clinical trials. Int. J. Cancer (Pred. Oncol.) 84:426-431, 1999.     

Expression of telomerase genes in thyroid carcinoma

Telomerase (T) is a ribonucleoprotein complex that includes the telomerase RNA component (hTR), telomerase associated protein (TP1) and the telomerase catalytic subunit (hTERT). Telomerase has been shown in stem cells and found to be activated in tumor tissues and immortalized cells. We wanted to test whether the expression of the telomerase complex subunits correlate with the enzyme activity in human thyroid tissue. Hence, we determined the expression of hTERT, hTR and TP1 mRNA by RT-PCR and compared the results to telomerase activity as detected by the telomeric repeat amplification protocol (TRAP) assay. Fifteen benign goiters (G), 11 follicular carcinomas (FTC) including 2 oncocytic follicular carcinomas (also called Hurthle cell carcinoma, oFTC), 12 papillary carcinomas (PTC) including 3 microcarcinomas (mPTC), and 12 undifferentiated anaplastic thyroid carcinomas (UTC) were investigated. Experienced pathologists performed histological and pTNM classification in each specimen. RT-PCR analysis revealed that TP1 was ubiquitously expressed in all G and carcinomas. hTR was expressed in 4 out of 15 G, in 2 out of 3 mPTC, in 5 out of 9 PTC, in 5 out of 9 FTC, in all oFTC and in 9 out of 12 UTC samples. Regarding all carcinomas, no statistically significant correlation was observed between hTR-expression and tumor stage, lymph node or distant metastasis. hTERT-expression was associated with malignancy and tumor stage. All mPTC and 13 out of 15 G did not express hTERT, whereas all samples of pT3-4 tumor stage of FTC, PTC, UTC and all oFTC were positive for hTERT. No telomerase activity could be detected in G. Telomerase activity in carcinoma was only measurable in tissues that expressed the catalytic subunit hTERT. Our data indicate that telomerase activity is up-regulated in neoplastic cells. In contrast to TP1 and hTR, hTERT and telomerase activity may be of help in identifying invasive tumors and may be additional markers for classification of benign goiter and malignant thyroid carcinoma.     

Detection of telomerase RNA in the plasma of patients with breast cancer, malignant melanoma or thyroid cancer

The crucial step in cellular immortalisation seems to be the activation of telomerase, the enzyme that synthesizes telomere repeat ending sequences. Since the telomerase activity has been detected in almost all types of cancer tissue it has been proposed as new reliable tumor marker. This study was conducted to evaluate the significance of appearance of circulating RNA for telomerase subunits hTR and hTERT in the plasma of cancer patients. Seven healthy volunteers, 25 primary breast cancer patients (stage I-III), 29 patients with advanced malignant melanoma (stage III-IV), and 4 patients with advanced thyroid cancer (stage III-IV) were included in the study. The total RNA was extracted from plasma samples, reverse transcribed to cDNAs, and specific cDNAs for hTR and hTERT were amplified by semi-nested PCR. In healthy volunteers, the control GAPDH was positive in all, hTR was positive in 3 cases, and hTERT was negative in all 7 tested cases. Among 25 breast cancer patients, hTR was positive in 23, and hTERT in 12 patients. Two cases, that were hTR and hTERT negative, were at the same time negative also for GAPDH. Of the 29 patients with malignant melanoma, 24 were positive for hTR, and 17 for hTERT. Again, the 5 patients that were negative for hTR and hTERT, were negative also for the control GAPDH. In all plasma samples from thyroid cancer patients, hTR and hTERT were positive. In conclusion, the RT-PCR followed by semi-nested PCR is a highly sensitive method for detection of circulating RNA in the plasma. Among the telomerase subunits, only hTERT could serve as an unspecific tumor marker in the plasma of cancer patients.     

上皮性卵巢癌hTERT表达及端粒酶活性的研究

目的探讨人端粒酶反转录酶(hTERT)表达及端粒酶活性与卵巢癌发生、发展的关系,评价其可否作为卵巢癌的肿瘤标志物及预后指标.方法应用RT-PCR及端粒重复扩增方法对43例上皮性卵巢癌、11例良性卵巢肿瘤和卵巢正常组织以及4例交界性卵巢肿瘤共69份标本进行hTERTmRNA及端粒酶活性检测.结果hTERT表达及端粒酶活性率在卵巢癌中分别为83.7%(36/43)及76.7%(33/43),良性肿瘤中均为9%(1/11),在正常卵巢组织和交界性卵巢肿瘤中阴性,其差异在卵巢癌与良性肿瘤及正常组织间均有显著性(P值分别为0.0004及0.0001).hTERT及端粒酶阳性率在某些预后因素如肿瘤类型、组织学分级、临床分期及肿瘤转移之间的差异皆无显著性.结论卵巢癌中存在高频率的hTERT表达及端粒酶激活,表明hTERT作为端粒酶的催化亚基,在肿瘤细胞端粒酶的激活中起关键作用.hTERT表达及端粒酶活性可望作为有价值的肿瘤标志物而用于卵巢癌的早期诊断,但其预后价值尚有待于进一步研究.