Laboratory of Bioanalysis, Department of Pharmaceutical Chemistry, Drug Analysis and Radiopharmacy, Medical University of Lodz, ul. Muszyńskiego 1, 90-151 Lodz, Poland.
School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland.
Int J Mol Sci. 2021 Jul 20;22(14):7727. doi: 10.3390/ijms22147727.
Efflux transporters, namely ATP-binding cassette (ABC), are one of the primary reasons for cancer chemoresistance and the clinical failure of chemotherapy. Ganciclovir (GCV) is an antiviral agent used in herpes simplex virus thymidine kinase (HSV-TK) gene therapy. In this therapy, HSV-TK gene is delivered together with GCV into cancer cells to activate the phosphorylation process of GCV to active GCV-triphosphate, a DNA polymerase inhibitor. However, GCV interacts with efflux transporters that are responsible for the resistance of HSV-TK/GCV therapy. In the present study, it was explored whether GCV and its more lipophilic derivative () could inhibit effluxing of another chemotherapeutic, methotrexate (MTX), out of the human breast cancer cells. Firstly, it was found that the combination of GCV and MTX was more hemocompatible than the corresponding combination with compound . Secondly, both GCV and compound enhanced the cellular accumulation of MTX in MCF-7 cells, the MTX exposure being 13-21 times greater compared to the MTX uptake alone. Subsequently, this also reduced the number of viable cells (41-56%) and increased the number of late apoptotic cells (46-55%). Moreover, both GCV and compound were found to interact with breast cancer resistant protein (BCRP) more effectively than multidrug-resistant proteins (MRPs) in these cells. Since the expression of BCRP was higher in MCF-7 cells than in MDA-MB-231 cells, and the cellular uptake of GCV and compound was smaller but increased in the presence of BCRP-selective inhibitor (Fumitremorgin C) in MCF-7 cells, we concluded that the improved apoptotic effects of higher MTX exposure were raised mainly from the inhibition of BCRP-mediated efflux of MTX. However, the effects of GCV and its derivatives on MTX metabolism and the quantitative expression of MTX metabolizing enzymes in various cancer cells need to be studied more thoroughly in the future.
外排转运蛋白，即三磷酸腺苷结合盒（ABC），是癌症化疗耐药和化疗临床失败的主要原因之一。更昔洛韦（GCV）是一种用于单纯疱疹病毒胸苷激酶（HSV-TK）基因治疗的抗病毒药物。在这种治疗中，HSV-TK 基因与 GCV 一起递送到癌细胞中，以激活 GCV 的磷酸化过程，将 GCV 转化为活性 GCV-三磷酸，一种 DNA 聚合酶抑制剂。然而，GCV 与负责 HSV-TK/GCV 治疗耐药的外排转运蛋白相互作用。在本研究中，研究了 GCV 及其更亲脂的衍生物（）是否可以抑制另一种化疗药物甲氨蝶呤（MTX）从人乳腺癌细胞中外排。首先，发现 GCV 与 MTX 的组合比相应的与化合物的组合更具血液相容性。其次，GCV 和化合物都增强了 MCF-7 细胞中甲氨蝶呤的细胞内积累，与单独使用甲氨蝶呤相比，MTX 的暴露量增加了 13-21 倍。随后，这也减少了存活细胞的数量（41-56%）并增加了晚期凋亡细胞的数量（46-55%）。此外，在这些细胞中，GCV 和化合物都被发现比多药耐药蛋白（MRPs）更有效地与乳腺癌耐药蛋白（BCRP）相互作用。由于 BCRP 在 MCF-7 细胞中的表达高于 MDA-MB-231 细胞，并且在 MCF-7 细胞中存在 BCRP 选择性抑制剂（Fumitremorgin C）时，GCV 和化合物的细胞摄取较小但增加，我们得出结论，更高 MTX 暴露的改善凋亡作用主要是由于抑制了 BCRP 介导的 MTX 外排。然而，GCV 及其衍生物对各种癌细胞中甲氨蝶呤代谢和甲氨蝶呤代谢酶的定量表达的影响需要在未来更深入地研究。
