Basic Science Division, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America.
PLoS One. 2012;7(6):e40342. doi: 10.1371/journal.pone.0040342. Epub 2012 Jun 29.
Bendamustine (BDM) is an active chemotherapeutic agent approved in the U. S. for treating chronic lymphocytic leukemia and non-Hodgkin lymphoma. Its chemical structure suggests it may have alkylator and anti-metabolite activities; however the precise mechanism of action is not well understood. Here we report the concentration-dependent effects of BDM on cell cycle, DNA damage, checkpoint response and cell death in HeLa cells. Low concentrations of BDM transiently arrested cells in G2, while a 4-fold higher concentration arrested cells in S phase. DNA damage at 50, but not 200 µM, was efficiently repaired after 48 h treatment, suggesting a difference in DNA repair efficiency at the two concentrations. Indeed, perturbing base-excision repair sensitized cells to lower concentrations of BDM. Timelapse studies of the checkpoint response to BDM showed that inhibiting Chk1 caused both the S- and G2-arrested cells to prematurely enter mitosis. However, whereas the cells arrested in G2 (low dose BDM) entered mitosis, segregated their chromosomes and divided normally, the S-phase arrested cells (high dose BDM) exhibited a highly aberrant mitosis, whereby EM images showed highly fragmented chromosomes. The vast majority of these cells died without ever exiting mitosis. Inhibiting the Chk1-dependent DNA damage checkpoint accelerated the time of killing by BDM. Our studies suggest that BDM may affect different biological processes depending on drug concentration. Sensitizing cells to killing by BDM can be achieved by inhibiting base-excision repair or disrupting the DNA damage checkpoint pathway.
苯达莫司汀（BDM）是一种在美国被批准用于治疗慢性淋巴细胞白血病和非霍奇金淋巴瘤的活性化疗药物。其化学结构表明它可能具有烷化剂和抗代谢物活性；然而，其确切的作用机制尚不清楚。在这里，我们报告了 BDM 对 HeLa 细胞细胞周期、DNA 损伤、检查点反应和细胞死亡的浓度依赖性影响。低浓度的 BDM 会使细胞短暂地停滞在 G2 期，而高 4 倍的浓度则会使细胞停滞在 S 期。在 50 µM 而非 200 µM 时，BDM 处理 48 小时后能有效地修复 DNA 损伤，这表明在这两种浓度下，DNA 修复效率存在差异。事实上，干扰碱基切除修复会使细胞对低浓度的 BDM 更加敏感。对 BDM 检查点反应的延时研究表明，抑制 Chk1 会导致 S 期和 G2 期阻滞的细胞过早进入有丝分裂。然而，在 G2 期（低剂量 BDM）被阻滞的细胞进入有丝分裂，其染色体分离并正常分裂，而在 S 期（高剂量 BDM）被阻滞的细胞则表现出高度异常的有丝分裂，电镜图像显示染色体高度碎片化。这些细胞中的绝大多数在没有离开有丝分裂的情况下死亡。抑制 Chk1 依赖性 DNA 损伤检查点会加速 BDM 的杀伤时间。我们的研究表明，BDM 可能会根据药物浓度影响不同的生物学过程。通过抑制碱基切除修复或破坏 DNA 损伤检查点途径，可以使细胞对 BDM 的杀伤更加敏感。
