Wani M A, Snapka R M
Department of Radiology, Ohio State University 43210.
Cancer Invest. 1990;8(6):587-93. doi: 10.3109/07357909009018925.
Methotrexate-resistant R500 cells slowly lose amplified dihydrofolate reductase (dhrf) genes with biphasic kinetics when grown in the absence of methotrexate. Both phases of gene loss were markedly accelerated by subcytotoxic drug treatments. R500 cells were passed in low concentrations of cytotoxic drugs (inhibitors of ribonucleotide reductase, type I and type II topoisomerases, and polyamine synthesis). At each passage, relative dhfr gene copy number was determined by slot blot analysis. All of these drugs were able to induce rapid loss of dhfr gene dosage in the R500 cell population. The ability of these treatments to cause the rapid emergence of a cell population with substantially reduced dhfr gene dosage indicates that either the amplified genes or those cells with the highest levels of gene amplification are selectively targeted by low-level cytotoxic stress. The complex kinetics of amplified gene loss are suggestive of differential targeting of resistant cell subpopulations.
在无甲氨蝶呤的情况下培养时，对甲氨蝶呤耐药的R500细胞会以双相动力学缓慢丢失扩增的二氢叶酸还原酶（dhrf）基因。亚细胞毒性药物处理显著加速了基因丢失的两个阶段。将R500细胞传代于低浓度的细胞毒性药物（核糖核苷酸还原酶抑制剂、I型和II型拓扑异构酶抑制剂以及多胺合成抑制剂）中。在每次传代时，通过狭缝印迹分析确定相对dhfr基因拷贝数。所有这些药物都能够在R500细胞群体中诱导dhfr基因剂量的快速丢失。这些处理导致基因剂量大幅降低的细胞群体快速出现的能力表明，扩增基因或基因扩增水平最高的那些细胞被低水平细胞毒性应激选择性靶向。扩增基因丢失的复杂动力学提示耐药细胞亚群存在差异靶向。
