目的:ClFdA是第二代抗肿瘤药物,具有显著的抗癌活性,特别是针对急性淋巴细胞白血病,并已被证明具有放射增敏活性。这项研究的目的是探索基因毒性,氯法拉滨(ClFdA)对骨髓细胞(BMC)的细胞毒性和放射增敏作用,小鼠体内的正常母细胞和白细胞。
方法:通过减少网织红细胞(RET)来确定细胞毒性,遗传毒性是通过诱导外周血中的微核网织红细胞(MN-RET)和通过单细胞凝胶电泳(SCGE)确定的白细胞中的DNA断裂诱导来确定的。通过SCGE测定白细胞和BMC中ClFdA的放射增敏能力。
结果:根据前因确定了MN-RET诱导的两种机制,这可能是由于抑制了DNA合成和G-C区的去甲基化,以及随后的染色体脆弱性。ClFdA细胞毒性导致两个连续的峰,似乎抑制MN-RET诱导的早期峰和似乎由核糖核苷酸还原酶(RR)和/或DNA合成抑制引起的第二个峰。ClFdA诱导非循环白细胞的早期DNA损伤,并在治疗后立即对白细胞进行放射增敏。ClFdA-电离辐射(IR)引起两个时间依赖性的DNA损伤事件,最近一次在80分钟后引发了DNA的重大破坏。就受损细胞的数量而言,白细胞和BMCs同样对电离辐射敏感;BMCs比白细胞对ClFdA稍微敏感,但BMC对联合治疗双重敏感。
结论:ClFdA引起非增殖白细胞的早期DNA损伤和放射敏感性,排除了参与RR和DNA聚合酶抑制的最受欢迎的假设。
OBJECTIVE: ClFdA is a second-generation antineoplastic agent that has demonstrated significant anticancer activity, particularly against acute lymphoblastic leukemia and has been shown to have radiosensitizing activity. The aim of the study was to explore the genotoxic, cytotoxic and radiosensitizing effects of clofarabine (ClFdA) on bone marrow cells (BMCs), normoblasts and leukocytes of mice in vivo.
METHODS: Cytotoxicity was determined by the reduction in reticulocytes (RET), and genotoxicity was determined by the induction of micronucleated reticulocytes (MN-RET) in the peripheral blood and by DNA break induction in leukocytes determined by single-cell gel electrophoresis (SCGE). The radiosensitizing capacity of ClFdA was determined in leukocytes and BMCs by SCGE.
RESULTS: Two mechanisms of MN-RET induction were identified according to the antecedents, that could be due to inhibition of DNA synthesis and demethylation of G-C regions, and subsequent chromosome fragility. ClFdA cytotoxicity causes two contiguous peaks, an early peak that seems to inhibit MN-RET induction and a second peak that seems to be caused by ribonucleotide reductase (RR) and/or DNA synthesis inhibitions. ClFdA induced early DNA damage in noncycling leukocytes, and also radiosensitizes leukocytes immediately after treatment. ClFdA-ionizing radiation (IR) causes two time-dependent episodes of DNA damage, the latest after 80 min triggers a major breakage of DNA. In terms of the number of damaged cells, leukocytes and BMCs are similarly sensitive to ionizing radiation; BMCs are slightly more sensitive than leukocytes to ClFdA, but BMCs are doubly sensitive to combined treatment.
CONCLUSIONS: ClFdA causes early DNA damage and radiosensitivity in non-proliferating leukocytes, which rules out the most favored hypotheses of the participation of RR and DNA polymerase inhibition.