Immunity, Inflammation and Disease Laboratory, USA.
Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, USA.
Biochim Biophys Acta Gen Subj. 2018 Dec;1862(12):2806-2814. doi: 10.1016/j.bbagen.2018.08.021. Epub 2018 Sep 1.
Development of resistance to chemotherapy drugs is a significant problem in treating human malignancies in the clinic. Overexpression of drug efflux proteins, including P-170 glycoprotein (P-gp), an ATP-dependent efflux protein, is one of the main mechanisms responsible for multi-drug resistance (MDR). Because our previous studies have shown that nitric oxide (NO) or its related species inhibit the ATPase activities of topoisomerase II, we hypothesized that NO should also inhibit the ATPase activity of P-gp and increase drug accumulation in MDR cells, causing a reversal of drug resistance.
Cytotoxicity and cellular accumulation studies showed that NO significantly inhibited the ATPase activity of P-gp in isolated membranes and in NCI/ADR-RES tumor cells, causing an increase in drug accumulation and reversals of adriamycin and taxol resistance in the MDR cells. While NO had no effects on topoisomerase II-induced, adriamycin-dependent DNA cleavage complex formation, it significantly inhibited adriamycin-induced DNA double-strand breaks. Electron spin resonance studies showed an increase in adriamycin-dependent hydroxyl radical formation in the presence of an NO-donor.
The reversal of drug resistance is due to inhibition of the ATPase activity by NO, resulting in enhancement of the drug accumulation in the MDR cells. Furthermore, DNA damage was not responsible for this reversal of adriamycin resistance. However, formation of adriamycin-dependent toxic free radical species and subsequent cellular damage may be responsible for the increased cytotoxicity of adriamycin by NO in NCI/ADR-RES cells.
Appropriately designed NO donors would be ideal for the treatment of P-gp-overexpressing tumors in the clinic.
在临床上，化疗药物耐药性的发展是治疗人类恶性肿瘤的一个重大问题。药物外排蛋白的过度表达，包括 P-170 糖蛋白（P-gp），一种 ATP 依赖性外排蛋白，是导致多药耐药（MDR）的主要机制之一。因为我们之前的研究表明，一氧化氮（NO）或其相关物质抑制拓扑异构酶 II 的 ATP 酶活性，所以我们假设 NO 也应该抑制 P-gp 的 ATP 酶活性，增加 MDR 细胞中的药物积累，从而逆转耐药性。
细胞毒性和细胞内积聚研究表明，NO 显著抑制了分离膜中和 NCI/ADR-RES 肿瘤细胞中 P-gp 的 ATP 酶活性，导致药物积聚增加，并逆转了 MDR 细胞对阿霉素和紫杉醇的耐药性。虽然 NO 对拓扑异构酶 II 诱导的、阿霉素依赖性 DNA 切割复合物的形成没有影响，但它显著抑制了阿霉素诱导的 DNA 双链断裂。电子自旋共振研究表明，在存在 NO 供体的情况下，阿霉素依赖性羟自由基的形成增加。
耐药性的逆转是由于 NO 抑制了 ATP 酶的活性，导致 MDR 细胞中药物积累增加。此外，DNA 损伤不是这种阿霉素耐药性逆转的原因。然而，阿霉素依赖性有毒自由基的形成和随后的细胞损伤可能是导致 NCI/ADR-RES 细胞中 NO 增加阿霉素细胞毒性的原因。
适当设计的 NO 供体将是治疗临床上 P-gp 过表达肿瘤的理想选择。
