Development of molcular target therapy for.... telomerase

端粒酶复合物负责端粒的维持，代表了一个有希望的肿瘤治疗靶点。利用人类端粒酶的显性阴性形式进行的遗传实验表明，端粒酶抑制可导致端粒缩短，随后是增殖停止和细胞凋亡导致的死亡（Tauchi等人）。中国癌症杂志，8；3341年,2002年)。最近，我们已经证明用端粒抑素（SOT-095）治疗可重复性地抑制BCR-ABL阳性白血病细胞系OM9的端粒酶活性；22和K562，导致端粒缩短。端粒抑素抑制端粒酶活性破坏端粒维持，最终导致端粒功能障碍。在1 μM下，端米抑素完全抑制K562细胞的镀效率，但对正常骨髓CD34阳性细胞BFU-Es和CFU-GMs集落形成的影响较小。在端米司他汀处理的K562细胞中也观察到对伊马替尼和化疗药物的化学敏感性增强。此外，端米司汀联合伊马替尼更有效地抑制原发性人慢性粒细胞白血病细胞的造血集落形成。最后，端粒抑素诱导了ATM和Chk2的激活，随后增加了p21^<CIP1>和p27^<KIP1>的表达。Telomestatin还激活MKX3/6和p38MAP激酶，并通过caspase-3级联诱导细胞凋亡。这些结果表明，端粒抑素诱导的端粒功能障碍激活了atm依赖性DNA损伤反应和MKK3/6-p38MAP激酶级联。我们得出结论，端粒酶抑制剂联合使用伊马替尼和其他化疗药物可能对治疗人类白血病非常有用。

The telomerase complex is responsible for telomere maintenance and represents a promising neoplasia therapeutic target. Genetic experiments using a dominant-negative form of human telomerase have demonstrated that telomerase inhibition can result in telomere shortening followed by proliferation arrest and cell death by apoptosis (Tauchi et al. Chin Cancer Res, 8; 3341, 2002).Recently, we have demonstrated that treatment with telomestatin (SOT-095) reproducibly inhibited telomerase activity in the BCR-ABL positive leukemic cell lines OM9;22 and K562, resulting in telomere shortening. Inhibition of telomerase activity by telomestatin disrupts telomere maintenance and ultimately results in telomere dysfunction. Telomestatin completely suppressed the plating efficiency of K562 cells at 1 μM, however, telomestatin had less effects on BFU-Es and CFU-GMs colony formation from normal bone marrow CD34 positive cells. Enhanced chemosensitivity toward imatinib and chemotherapeutic agents was also observed in telomestatin-treated K562 cells. Further, the combination of telomestatin plus imatinib more effectively inhibited hematopoietic colony formation by primary human chronic myelogenous leukemia cells. Last, telomestatin induced the activation of ATM and Chk2, and subsequently increased the expression of p21^<CIP1> and p27^<KIP1>. Telomestatin also activated MKX3/6 and p38MAP kinae and induced apoptosis by caspase-3 cascades. These results demonstrate that telomere dysfunction induced by telomestatin activates the ATM-dependent DNA damage response and MKK3/6-p38MAP kinase cascade. We conclude that telomerase inhibitors combined use of imatinib and other chemotherapeutic agents may be very useful for the treatment of human leukemia.