Development of molcular target therapy for.... telomerase

端粒酶复合体负责端粒的维持，是肿瘤治疗的一个有前景的靶点。使用显性-阴性形式的人类端粒酶的遗传学实验已经证明，端粒酶抑制可以导致端粒缩短，继而导致增殖停滞和细胞凋亡(Tauchi等人。最近，我们已经证明，端粒酶抑制素(SOT-095)可重复抑制bcr-abl阳性白血病细胞系OM9；22和K562的端粒酶活性，导致端粒缩短。端粒酶活性的抑制会破坏端粒的维持，最终导致端粒功能障碍。端粒酶抑素在1μM时可完全抑制K562细胞的集落形成，但对正常骨髓CD34阳性细胞集落形成的影响较小。端粒酶抑素处理的K562细胞对伊马替尼和化疗药物的敏感性也增强。此外，联合应用端粒酶抑素和伊马替尼能更有效地抑制原代人类慢性粒细胞白血病细胞的造血祖细胞集落形成。端粒酶抑制素诱导ATM和Chk2活化，进而上调p21^&lt；CIP1&gt；和p27^&lt；KIP1&gt；的表达。Telomestatin还激活MKX3/6和p38MAP激动子，并通过caspase-3级联途径诱导细胞凋亡。这些结果表明，端粒酶抑制素诱导的端粒功能障碍激活了ATM依赖的DNA损伤反应和MKK3/6-p38MAP激酶级联反应。我们的结论是，端粒酶抑制剂与伊马替尼等化疗药物联合使用可能对人类白血病的治疗非常有用。

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.