Tauchi Tetsuzo, Nakajima Akihiro, Sashida Goro, Shimamoto Takashi, Ohyashiki Junko H, Abe Kenji, Yamamoto Kohtaro, Ohyashiki Kazuma
First Department of Internal Medicine, Tokyo Medical University, Tokyo, 160-0023, Japan.
Clin Cancer Res. 2002 Nov;8(11):3341-7.
Telomerase is a ribonucleoprotein enzyme that maintains protective structures at the ends of eukaryotic chromosomes. Earlier findings have supported an association between progressive telomere shortening in the chronic phase of chronic myelogenous leukemia and the up-regulation of telomerase activity occurring late in the evolution of the disease. We examined the impact of telomerase inhibition by dominant negative-human telomerase reverse transcriptase (DN-hTERT) on the biological features of BCR-ABL-transformed cells.
We introduced vectors encoding DN-hTERT, wild-type (WT)-hTERT, or a control vector expressing only a drug-resistant marker into Philadelphia chromosome-positive K562 cells and OM9;22 cells and assessed the biological effect of telomerase inhibition on cellular immortality.
Ectopic expression of DN-hTERT resulted in complete inhibition of telomerase activity and reduction of telomere length. The entire population of telomerase-inhibited K562 cells exhibited cytoplasmic blebbling and chromatin condensation, features of apoptosis. In contrast, K562 cells expressing WT-hTERT, which differ from the mutants by only two amino acids, exhibited normal morphology. The evidence of apoptosis in the telomerase-inhibited cells was determined by flow cytometric analysis with APO2.7 monoclonal antibody. We also observed enhanced induction of apoptosis by imatinib seen in DN-hTERT-expressing K562 cells, as compared with WT-hTERT-expressing cells.
These results demonstrate that disruption of telomere maintenance limits the cellular life span of leukemia cells and show that the combined use of imatinib and telomere maintenance inhibition may be effective in the treatment of BCR-ABL-positive leukemia.
端粒酶是一种核糖核蛋白酶，可维持真核染色体末端的保护结构。早期研究结果支持慢性粒细胞白血病慢性期端粒进行性缩短与疾病进展后期端粒酶活性上调之间存在关联。我们研究了显性负性人端粒酶逆转录酶（DN-hTERT）抑制端粒酶对BCR-ABL转化细胞生物学特性的影响。
我们将编码DN-hTERT、野生型（WT）-hTERT或仅表达耐药标记的对照载体导入费城染色体阳性的K562细胞和OM9;22细胞，并评估端粒酶抑制对细胞永生化的生物学效应。
DN-hTERT的异位表达导致端粒酶活性完全抑制和端粒长度缩短。端粒酶抑制的K562细胞全部表现出细胞质起泡和染色质浓缩，即凋亡特征。相比之下，仅两个氨基酸不同的表达WT-hTERT的K562细胞形态正常。通过用APO2.7单克隆抗体进行流式细胞术分析确定了端粒酶抑制细胞中的凋亡证据。我们还观察到，与表达WT-hTERT的细胞相比，表达DN-hTERT的K562细胞中伊马替尼诱导的凋亡增强。
这些结果表明，端粒维持的破坏限制了白血病细胞的细胞寿命，并表明伊马替尼与端粒维持抑制联合使用可能对治疗BCR-ABL阳性白血病有效。
