Holm B, Jensen P B, Sehested M, Hansen H H
Department of Oncology, Rigshospitalet, Copenhagen, Denmark.
Cancer Chemother Pharmacol. 1994;34(6):503-8. doi: 10.1007/BF00685662.
A number of clinically important drugs such as the epipodophyllotoxins etoposide (VP-16) and teniposide (VM-26), the anthracycline daunorubicin and doxorubicin (Adriamycin), and the aminoacridine amsacrine exert their cytotoxic action by stabilizing the cleavable complex formed between DNA and the nuclear enzyme topoisomerase II. We have previously demonstrated in several in vitro assays that the anthracycline aclarubicin (aclacinomycin A) inhibits cleavable-complex formation and thus antagonizes the action of drugs such as VP-16 and daunorubicin. The present study was performed to validate these in vitro data in an in vivo model. At nontoxic doses of 6 and 9 mg/kg, aclarubicin yielded a marked increase in the survival of non-tumor-bearing mice given high doses of VP-16 (80-90 mg/kg) in six separate experiments. In therapy experiments on mice inoculated with Ehrlich ascites tumor cells, aclarubicin given at 6 mg/kg roughly halved the increase in median life span induced by VP-16 at doses ranging from 22 to 33 mg/kg. An attempt to determine a more favorable combination of VP-16 and aclarubicin by increasing VP-16 doses failed, as the two drugs were always less effective than VP-16 alone. The way in which VP-16-induced DNA strand breaks lead to cell death remains unknown. However, VP-16 has been reported to cause apoptosis (programmed cell death) in several cell lines. To ascertain whether the protection given by aclarubicin could have a disruptive effect on the apoptotic process, we used the small intestine as an in vivo model. Whereas VP-16-induced apoptosis in crypt stem cells was detectable at a dose as low as 1.25 mg/kg, aclarubicin given at up to 20 mg/kg did not cause apoptosis. Indeed, aclarubicin caused a statistically significant reduction in the number of cells rendered apoptotic by VP-16. The present study thus confirms the previous in vitro experiments and indicates the value of including an in vivo model in a preclinical evaluation of drug combinations.
许多具有临床重要性的药物，如表鬼臼毒素依托泊苷（VP - 16）和替尼泊苷（VM - 26）、蒽环类药物柔红霉素和多柔比星（阿霉素）以及氨基吖啶安吖啶，通过稳定DNA与核酶拓扑异构酶II形成的可裂解复合物来发挥其细胞毒性作用。我们之前在多个体外试验中证明，蒽环类药物阿克拉霉素（阿克拉胞苷A）抑制可裂解复合物的形成，从而拮抗VP - 16和柔红霉素等药物的作用。本研究旨在在体内模型中验证这些体外数据。在六个独立实验中，以6和9 mg/kg的无毒剂量给予阿克拉霉素，可使接受高剂量VP - 16（80 - 90 mg/kg）的无瘤小鼠的存活率显著提高。在接种艾氏腹水瘤细胞的小鼠的治疗实验中，以6 mg/kg给予阿克拉霉素，大致使VP - 16在22至33 mg/kg剂量下诱导的中位寿命增加减半。通过增加VP - 16剂量来确定VP - 16和阿克拉霉素更有利组合的尝试失败了，因为这两种药物总是比单独使用VP - 16效果更差。VP - 16诱导的DNA链断裂导致细胞死亡的方式仍然未知。然而，据报道VP - 16在几种细胞系中可导致凋亡（程序性细胞死亡）。为了确定阿克拉霉素提供的保护是否会对凋亡过程产生破坏作用，我们使用小肠作为体内模型。虽然在低至1.25 mg/kg的剂量下就能检测到VP - 16诱导的隐窝干细胞凋亡，但给予高达20 mg/kg的阿克拉霉素不会导致凋亡。事实上，阿克拉霉素使VP - 16诱导凋亡的细胞数量在统计学上显著减少。本研究因此证实了先前的体外实验，并表明在药物组合的临床前评估中纳入体内模型的价值。
