Ihnat M A, Lariviere J P, Warren A J, La Ronde N, Blaxall J R, Pierre K M, Turpie B W, Hamilton J W
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755-3835, USA.
Clin Cancer Res. 1997 Aug;3(8):1339-46.
Overexpression of the trans-membrane drug efflux pump P-glycoprotein is one of the major mechanisms by which cancer cells develop multidrug resistance. We demonstrated previously that noncytotoxic doses of various genotoxic chemicals, particularly DNA cross-linking agents, preferentially altered expression of inducible genes. These effects occurred principally at the transcriptional level and were closely correlated temporally with DNA damage. Because the mdr1 gene coding for P-glycoprotein has been reported to be highly inducible, we were interested in the effects of genotoxic cancer chemotherapy agents on its expression. We report that the DNA cross-linking agent mitomycin C significantly suppressed mRNA and protein expression of P-glycoprotein and decreased the rate of drug efflux. Mitomycin C pretreatment also significantly increased the sensitivity of cancer cells to subsequent killing by the P-glycoprotein substrate doxorubicin, decreasing the ED50 by 5- to 10-fold. Suppression of P-glycoprotein expression was also observed with subtoxic doses of the DNA cross-linking agents cisplatin, BMS181174, and chromium(VI). These effects occurred in both human and rodent cell lines; in cell lines derived from colon, breast, leukemia, neuroblastoma, and hepatoma tumors; and under both monolayer and "spheroid" culture conditions. These results suggest the basis for novel clinical cancer chemotherapy regimens aimed at drug-resistant tumors, in which a sub-chemotherapeutic dose of a DNA cross-linking agent is used to modulate the multidrug resistance phenotype prior to treatment with a second cytotoxic agent.
跨膜药物外排泵P-糖蛋白的过表达是癌细胞产生多药耐药性的主要机制之一。我们之前证明，各种基因毒性化学物质的非细胞毒性剂量，尤其是DNA交联剂，优先改变诱导基因的表达。这些效应主要发生在转录水平，并且在时间上与DNA损伤密切相关。由于编码P-糖蛋白的mdr1基因据报道具有高度可诱导性，我们对基因毒性癌症化疗药物对其表达的影响感兴趣。我们报告说，DNA交联剂丝裂霉素C显著抑制P-糖蛋白的mRNA和蛋白质表达，并降低药物外排率。丝裂霉素C预处理还显著增加了癌细胞对随后P-糖蛋白底物阿霉素杀伤的敏感性，使半数有效剂量降低了5至10倍。用DNA交联剂顺铂、BMS181174和六价铬的亚毒性剂量也观察到了P-糖蛋白表达的抑制。这些效应在人和啮齿动物细胞系中均有发生；在源自结肠、乳腺、白血病、神经母细胞瘤和肝癌肿瘤的细胞系中；以及在单层和“球体”培养条件下。这些结果为针对耐药肿瘤的新型临床癌症化疗方案提供了依据，其中在使用第二种细胞毒性药物治疗之前，使用亚化疗剂量的DNA交联剂来调节多药耐药表型。
