Development of molcular target therapy for.... telomerase

端粒酶复合物负责端粒的维持，是一个有前途的肿瘤治疗靶点。使用显性阴性形式的人端粒酶的遗传实验已经证明端粒酶抑制可以导致端粒缩短，随后增殖停滞和细胞凋亡死亡（Tauchi等，Chin Cancer Res，8; 3341，2002）。最近，我们已经证明用端粒抑素（SOT-095）处理可重复地抑制BCR-ABL阳性白血病细胞系OM 9; 22和K562，导致端粒缩短。端粒酶抑制素抑制端粒酶活性，破坏端粒的维持，最终导致端粒功能障碍。在1 μM浓度下，端粒酶抑制素完全抑制K562细胞的贴板率，但对正常骨髓CD 34阳性细胞的BFU-Es和CFU-GM集落形成的影响较小。在端粒酶抑制素处理的K562细胞中也观察到对伊马替尼和化疗药物的化疗敏感性增强。此外，端粒酶抑制素加伊马替尼的组合更有效地抑制原代人慢性髓性白血病细胞的造血集落形成。最后，端粒酶抑制素诱导ATM和Chk 2的活化，随后增加p21^<CIP1>和p27^的表达<KIP1>。端粒酶抑制素还激活MKX 3/6和p38 MAP激酶，并通过caspase-3级联反应诱导细胞凋亡。这些结果表明，端粒功能障碍诱导的端粒酶抑制素激活ATM依赖的DNA损伤反应和MKK 3/6-p38 MAP激酶级联反应。端粒酶抑制剂联合伊马替尼及其他化疗药物治疗白血病可能是一种有效的方法。

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.