Department of Molecular-Targeting Cancer Prevention, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Cancer Sci. 2010 Mar;101(3):728-34. doi: 10.1111/j.1349-7006.2009.01449.x. Epub 2009 Nov 27.
Methotrexate (MTX) has been used to treat various hematological malignancies. Since MTX prevents tumor cells from proliferating by inhibiting dihydrofolate reductase (DHFR), DHFR expression is a key determinant of resistance to MTX in malignant hematological tumor cells. The antiproliferative effect of MTX was significantly enhanced by the knockdown of DHFR expression by siRNA in Jurkat cells. Therefore, a novel strategy down-regulating DHFR expression seems promising for enhancing sensitivity to MTX. We found that SU9516, a cyclin-dependent kinase inhibitor, reduced the expression of both DHFR mRNA and protein. Moreover, we found that DHFR promoter activity was attenuated by SU9516 dependent on the E2F site. Finally, pretreatment with SU9516 significantly enhanced sensitivity to MTX in a colony formation assay. We conclude that a combination of cyclin-dependent kinase inhibitors and MTX may be useful for overcoming resistance to MTX.
甲氨蝶呤(MTX)已被用于治疗各种血液系统恶性肿瘤。由于 MTX 通过抑制二氢叶酸还原酶(DHFR)来阻止肿瘤细胞增殖,因此 DHFR 的表达是恶性血液肿瘤细胞对 MTX 产生耐药性的关键决定因素。在 Jurkat 细胞中,通过 siRNA 敲低 DHFR 表达可显著增强 MTX 的抗增殖作用。因此,下调 DHFR 表达的新策略似乎有望提高对 MTX 的敏感性。我们发现,细胞周期蛋白依赖性激酶抑制剂 SU9516 可降低 DHFR mRNA 和蛋白的表达。此外,我们发现,DHFR 启动子活性可被 SU9516 依赖 E2F 位点减弱。最后,SU9516 的预处理可显著增强 MTX 在集落形成试验中的敏感性。我们得出结论,细胞周期蛋白依赖性激酶抑制剂与 MTX 的联合应用可能有助于克服 MTX 的耐药性。