Waxman S, Scher B M, Hellinger N, Scher W
Rochell Belfer Chemotherapy Foundation Laboratory, Department of Medicine, Mount Sinai Medical Center, New York, New York 10029.
Cancer Res. 1990 Jul 1;50(13):3878-87.
The effects of 5-fluorouracil (5-FUra), in combination with various differentiation inducers on the growth and differentiation of mouse erythroleukemia (MEL) cells were investigated. The cells were first treated with 5-FUra, washed, and then treated with various concentrations of differentiation inducers: hexamethylene bisacetamide (HMBA), dimethyl sulfoxide (DMSO), and N-methylformamide. Pretreatment with 5-FUra, shown here to be a weak inducer of MEL cell differentiation, enhanced the subsequent HMBA induction of differentiation. The three inducers of differentiation markedly inhibited cell growth and increased cell death in a dose- and time-dependent manner if given immediately after cells were exposed to 5-FUra. In contrast, 5-FUra at similar concentrations inhibited cell growth, but only slightly increased cell death, while inducers without 5-FUra had little effect on cell growth or viability. When placed in fresh drug-free medium for 6 days following drug treatments, the cells completely recovered from the growth inhibition of 5-FUra as a single agent, whereas in cells previously treated with only HMBA there was a inhibition of cell growth without loss of viability. In contrast, a profound and prolonged growth inhibition with 98% cell death occurred in cells previously treated with 5-FUra followed by HMBA. The enhancement of 5-FUra cytotoxicity appeared to be directly related to the degree of differentiation and to biochemical events that occur during the commitment to terminal cell division induced by N-methylformamide, DMSO, or HMBA. An increase in Okazaki fragments was found in MEL cells treated with HMBA or DMSO when committed to terminal cell division. DNA breaks also follow 5-FUra treatment (A. Yoshioka et al., J. Biol. Chem., 262: 8235-8241, 1987) and may be the events that lead to cell death. The marked increase in cell death resulting from 5-FUra/HMBA treatment may be, at least partly, a consequence of increased DNA breaks due to 5-FUra followed by inhibition of DNA repair which is known to occur following the HMBA or DMSO induction of differentiation and commitment to terminal cell division. This combined sequential cytotoxic-differentiation therapy resulting in synergistic cytotoxicity and differentiation may be the basis of a new approach to cancer therapy and may aid in reducing the amounts of chemotherapeutic agents required for effective treatment, while maintaining or even increasing their therapeutic effects.
研究了5-氟尿嘧啶（5-FUra）与各种分化诱导剂联合使用对小鼠红白血病（MEL）细胞生长和分化的影响。细胞先用5-FUra处理，洗涤后，再用不同浓度的分化诱导剂处理：六甲撑双乙酰胺（HMBA）、二甲基亚砜（DMSO）和N-甲基甲酰胺。此处显示5-FUra是MEL细胞分化的弱诱导剂，其预处理增强了随后HMBA诱导的分化。如果在细胞暴露于5-FUra后立即给予这三种分化诱导剂，则它们会以剂量和时间依赖性方式显著抑制细胞生长并增加细胞死亡。相比之下，类似浓度的5-FUra抑制细胞生长，但仅略微增加细胞死亡，而没有5-FUra的诱导剂对细胞生长或活力几乎没有影响。在药物处理后置于新鲜无药培养基中6天，细胞作为单一药物完全从5-FUra的生长抑制中恢复，而在仅用HMBA预处理的细胞中存在细胞生长抑制但无活力丧失。相比之下，先前用5-FUra然后用HMBA处理的细胞发生了深刻且持久的生长抑制，细胞死亡率达98%。5-FUra细胞毒性的增强似乎与分化程度以及在由N-甲基甲酰胺、DMSO或HMBA诱导的终末细胞分裂过程中发生的生化事件直接相关。在用HMBA或DMSO处理并进入终末细胞分裂的MEL细胞中发现冈崎片段增加。5-FUra处理后也会出现DNA断裂（A. Yoshioka等人，《生物化学杂志》，262: 8235 - 8241, 1987），这可能是导致细胞死亡的事件。5-FUra/HMBA处理导致的细胞死亡显著增加可能至少部分是由于5-FUra导致DNA断裂增加，随后HMBA或DMSO诱导分化并进入终末细胞分裂后已知会发生DNA修复抑制。这种联合的序贯细胞毒性 - 分化疗法导致协同细胞毒性和分化，可能是癌症治疗新方法的基础，并且可能有助于减少有效治疗所需的化疗药物量，同时维持甚至提高其治疗效果。
