Multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transport proteins remains a major problem in the chemotherapeutic treatment of cancer and might be overcome by inhibition of the transporter. Because of the lack of understanding, the complex mechanisms involved in the transport process, in particular for breast cancer resistance protein (BCRP/ABCG2), there is a persistent need for studies of inhibitors of ABCG2. In this study, we investigated a systematic series of 4-substituted-2-pyridylquinazolines in terms of their inhibitory potency as well as selectivity toward ABCG2. For comparison, the quinazoline scaffold was reduced to the significantly smaller 4-methylpyrimidine basic structure. Furthermore, the cytotoxicity and the ability to reverse MDR was tested with the chemotherapeutic agents SN-38 and mitoxantrone (MX). Interaction of the compounds with ABCG2 was investigated by a colorimetric ATPase assay. Enzyme kinetic studies were carried out with Hoechst 33342 as fluorescent dye and substrate of ABCG2 to elucidate the compounds binding modes.

中文翻译：

---

4-苯胺基-2-吡啶基喹唑啉和-嘧啶类药物是乳腺癌抗性蛋白（ABCG2）的高效无毒抑制剂

由ATP结合盒（ABC）转运蛋白介导的多药耐药性（MDR）仍然是癌症化学治疗中的主要问题，可以通过抑制转运蛋白来克服。由于缺乏了解，特别是对于乳腺癌抗性蛋白（BCRP / ABCG2），转运过程中涉及的复杂机制，一直需要研究ABCG2抑制剂。在这项研究中，我们研究了系统的一系列4-取代的-2-吡啶基喹唑啉，它们具有抑制力以及对ABCG2的选择性。为了比较，将喹唑啉支架还原为明显更小的4-甲基嘧啶基本结构。此外，用化学治疗剂SN-38和米托蒽醌（MX）测试了细胞毒性和逆转MDR的能力。通过比色ATP酶测定法研究了化合物与ABCG2的相互作用。以Hoechst 33342作为荧光染料和ABCG2的底物进行酶动力学研究，以阐明化合物的结合模式。