Yoon Kyong-Ah, Ku Ja-Lok, Yang Jung Ok, Park Jae-Gahb
Laboratory of Cell Biology, Cancer Research Institute, Seoul National University College of Medicine, Chongno-gu, Seoul 110-744, Korea.
Int J Mol Med. 2003 Mar;11(3):343-8.
As telomeres play a role in protecting DNA, there is the possibility that telomerase activity is involved with cellular response to DNA-damaging agents. This study was designed to investigate the association between telomerase and the doxorubicin altered cell cycle in drug resistant gastric carcinoma cell lines. Three doxorubicin resistant gastric carcinoma cell lines and their parent cell lines (SNU-1, SNU-16 and SNU-620) were incubated with doxorubicin at the final concentration induced resistance and ten times final concentration for 24 h. Telomerase activity and hTERT mRNA expression were lowered by doxorubicin treatment in parent cell lines, but in drug resistant cell lines, telomerase activity and hTERT mRNA expression were not repressed by doxorubicin treatment. Bcl-2 protein expression, which is known to regulate telomerase activity, did not change in doxorubicin resistant cell lines but decreased in parent cell lines by doxorubicin treatment. Cell cycle analysis revealed that the parent cell lines had an increased fraction of cells in G2/M phase after doxorubicin treatment and doxorubicin resistant cell lines had maintained fractions in G0/G1 phase. Doxorubicin treatment did not alter cyclin B or cdc2 protein level, which is known as the essential component of G2/M transition. G2/M arrest in the parent cell lines was associated with an increase in inhibitory phosphorylation of Tyr15 on cdc2. In summary, the parent cell lines showed G2/M arrest and a reduction of telomerase activity after doxorubicin treatment. In contrast, reduced telomerase activity, Bcl-2 expression and G2/M arrest after doxorubicin treatment did not appear in resistant cell lines. Therefore, relative resistance to doxorubicin may be related to high levels of bcl-2 or intact cell cycle and consequently high telomerase activity.
由于端粒在保护DNA方面发挥作用，端粒酶活性有可能参与细胞对DNA损伤剂的反应。本研究旨在探讨端粒酶与多柔比星改变耐药胃癌细胞系细胞周期之间的关联。将三种多柔比星耐药胃癌细胞系及其亲本细胞系（SNU-1、SNU-16和SNU-620）与多柔比星以诱导耐药的终浓度和终浓度的十倍进行孵育24小时。多柔比星处理使亲本细胞系中的端粒酶活性和hTERT mRNA表达降低，但在耐药细胞系中，多柔比星处理并未抑制端粒酶活性和hTERT mRNA表达。已知调节端粒酶活性的Bcl-2蛋白表达在多柔比星耐药细胞系中未发生变化，但在亲本细胞系中经多柔比星处理后降低。细胞周期分析显示，多柔比星处理后亲本细胞系中G2/M期细胞比例增加，而多柔比星耐药细胞系维持在G0/G1期的比例。多柔比星处理未改变细胞周期蛋白B或cdc2蛋白水平，已知这两种蛋白是G2/M期转换的关键成分。亲本细胞系中的G2/M期阻滞与cdc2上Tyr15抑制性磷酸化增加有关。总之，多柔比星处理后亲本细胞系表现出G2/M期阻滞和端粒酶活性降低。相比之下，多柔比星处理后耐药细胞系未出现端粒酶活性降低、Bcl-2表达降低和G2/M期阻滞。因此，对多柔比星的相对耐药性可能与高水平的bcl-2或完整的细胞周期以及因此而产生的高端粒酶活性有关。
