Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Cell Biol Toxicol. 2010 Apr;26(2):117-26. doi: 10.1007/s10565-009-9122-1. Epub 2009 Apr 2.
Antifolates, such as methotrexate (MTX), are the treatment of choice for numerous cancers. MTX inhibits dihydrofolate reductase (DHFR), which is essential for cell growth and proliferation. Mammalian cells can acquire resistance to antifolate treatment through a variety of mechanisms but decreased antifolate titers due to changes in drug efflux or influx, or alternatively, the amplification of the DHFR gene are the most commonly acquired resistance mechanisms. In Drosophila, however, a resistant phenotype has only been observed to occur by mutation resulting in a MTX-resistant DHFR. It is unclear if differences in gene structure and/or genome organization between Drosophila and mammals contribute to the observed differences in acquired drug resistance. To investigate if gene structure is involved, Drosophila Dhfr cDNA was transfected into a line of CHO cells that do not express endogenous DHFR. These transgenic cells, together with wild-type CHO cells, were selected for 19 months for resistance to increasing concentrations of MTX, from 50- to 200-fold over the initial concentration. Since Drosophila Dhfr appears to have been amplified several fold in the selected transgenic mammalian cells, a difference in genome organization may contribute to the mechanism of MTX resistance.
叶酸拮抗剂，如氨甲喋呤（MTX），是众多癌症的首选治疗方法。MTX 抑制二氢叶酸还原酶（DHFR），这对细胞生长和增殖是必不可少的。哺乳动物细胞可以通过多种机制获得对抗叶酸药物的耐药性，但由于药物外排或内流的变化导致抗叶酸药物滴度降低，或者 DHFR 基因的扩增是最常获得的耐药机制。然而，在果蝇中，只有通过突变导致 MTX 耐药性 DHFR 的突变才会观察到耐药表型。目前尚不清楚果蝇和哺乳动物之间基因结构和/或基因组组织的差异是否导致了观察到的获得性药物耐药性的差异。为了研究基因结构是否参与其中，将果蝇 Dhfr cDNA 转染到不表达内源性 DHFR 的 CHO 细胞系中。这些转基因细胞与野生型 CHO 细胞一起，在 MTX 浓度从初始浓度增加 50-200 倍的情况下，经过 19 个月的选择，以获得对 MTX 的抗性。由于在选定的转基因哺乳动物细胞中果蝇 Dhfr 似乎已扩增了数倍，因此基因组组织的差异可能有助于 MTX 耐药的机制。
