Kyo S, Kanaya T, Takakura M, Tanaka M, Inoue M
Department of Obstetrics and Gynecology, School of Medicine, Kanazawa University, Ishikawa, Japan.
Int J Cancer. 1999 Jan 5;80(1):60-3. doi: 10.1002/(sici)1097-0215(19990105)80:1<60::aid-ijc12>3.0.co;2-e.
Telomerase activation is thought to be essential for cellular immortality and oncogenesis. It is observed in most malignant tumors but not in most normal somatic tissues. Normal human endometrium is, however, known to express significant telomerase activity in a menstrual phase-dependent manner. The 3 major subunits composing telomerase have been identified. Using normal and malignant endometrial tissues, we studied how these components are involved in telomerase activation. A total of 23 endometrial cancers and 32 normal human endometria in various menstrual phases as well as cell lines derived from endometrial cancer were examined for the expression of each telomerase subunit using RT-PCR analysis. Telomerase activity in each sample was determined by the TRAP assay, and the correlation between subunit expression and telomerase activity was examined. RT-PCR analysis revealed that telomerase RNA (hTR) and telomerase-associated protein (TP1) mRNA were constitutively expressed in both normal and malignant endometrial tissues. Expression of human telomerase reverse transcriptase (hTERT) mRNA was observed in most endometrial cancers, while that in normal endometrium depended on the phases of menstrual cycles. Proliferative phase normal endometria expressed hTERT mRNA, while secretory phase endometria did not. There was a strong association between telomerase activity and hTERT expression but not TP1 or hTR expression in both normal and tumor tissues. Five telomerase-positive endometrial cancer cell lines expressed each of the telomerase subunits including hTERT, while 2 telomerase-negative normal primary fibroblast cells expressed TP1 mRNA and hTR, but not hTERT mRNA. Our findings suggest that hTERT is a rate-limiting determinant of enzymatic activity of human telomerase. Since some normal tissues with high regenerative potential can express hTERT, special attention should be paid to the clinical use of hTERT inhibitors as anti-cancer drugs.
端粒酶激活被认为是细胞永生化和肿瘤发生所必需的。在大多数恶性肿瘤中可观察到端粒酶激活，但在大多数正常体细胞组织中则不然。然而，已知正常人类子宫内膜会以月经周期依赖的方式表达显著的端粒酶活性。构成端粒酶的3个主要亚基已被鉴定出来。我们使用正常和恶性子宫内膜组织，研究了这些组分如何参与端粒酶激活。采用逆转录聚合酶链反应（RT-PCR）分析，对23例子宫内膜癌、32例处于不同月经周期的正常人类子宫内膜以及源自子宫内膜癌的细胞系进行检测，以分析每个端粒酶亚基的表达情况。通过端粒重复序列扩增法（TRAP）检测每个样本中的端粒酶活性，并研究亚基表达与端粒酶活性之间的相关性。RT-PCR分析显示，端粒酶RNA（hTR）和端粒酶相关蛋白（TP1）mRNA在正常和恶性子宫内膜组织中均持续表达。人类端粒酶逆转录酶（hTERT）mRNA在大多数子宫内膜癌中表达，而在正常子宫内膜中的表达则取决于月经周期阶段。增殖期正常子宫内膜表达hTERT mRNA，而分泌期子宫内膜则不表达。在正常和肿瘤组织中，端粒酶活性与hTERT表达之间存在强关联，但与TP1或hTR表达无关。5个端粒酶阳性的子宫内膜癌细胞系表达包括hTERT在内的每个端粒酶亚基，而2个端粒酶阴性的正常原代成纤维细胞表达TP1 mRNA和hTR，但不表达hTERT mRNA。我们的研究结果表明，hTERT是人类端粒酶酶活性的限速决定因素。由于一些具有高再生潜能的正常组织可以表达hTERT，因此在将hTERT抑制剂用作抗癌药物的临床应用中应特别注意。
