Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand; Center for Research and Development of Natural Products for Health, Chiang Mai University, Chiang Mai, Thailand.
Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Phytomedicine. 2017 Oct 15;34:182-190. doi: 10.1016/j.phymed.2017.08.004. Epub 2017 Aug 3.
Multidrug resistance (MDR) is a major reason for the failure of chemotherapy in the treatment of cancer patients. P-gp over-expression in MDR cancer cells is a multifactorial phenomenon with biochemical resistance mechanisms. Stemofoline (STF), isolated from Stemona bukillii, has been reported to be an MDR reversing compound.
This study investigated whether other Stemona alkaloids that had been purified from Stemonaceae plants exerted MDR modulation activity.
MTT assay was performed to determine the MDR reversing property of the alkaloids. Modulation of P-gp function by these compounds was investigated using cell cycle analysis and P-gp fluorescent substrate accumulation assays. P-gp expression was determined by Western blot analysis. We preliminarily examined the safety of these compounds in normal human fibroblasts and human peripheral blood mononuclear cells (PBMCs) using the MTT assay, and in red blood cells (human and rat) through in vitro hemolysis assays.
Three of the eight alkaloids tested, isostemofoline (ISTF), 11Z -didehydrostemofoline (11Z-DSTF) and 11E-didehydrostemofoline (11E-DSTF), enhanced the chemotherapeutic sensitivity of MDR leukemic K562/Adr cells, which overexpressed P-gp. The P-gp functional studies showed that these three alkaloids increased the accumulation of P-gp substrates, calcein-AM (C-AM) and rhodamine123 (Rho 123) in K562/Adr cells, while this effect was not seen in drug sensitive parental K562 cells. Whereas, the alkaloids did not alter P-gp expression as was determined by Western blotting analysis.
The alkaloids reversed MDR via the inhibition of P-gp function. For pharmaceutical safety testing, the alkaloids were found to be not toxic to normal human fibroblasts and PBMCs. Moreover, the effective compounds did not induce hemolysis in either human or rat erythrocytes. These compounds may be introduced as potential candidate molecules for treating cancers exhibiting P-gp-mediated MDR.
多药耐药（MDR）是癌症患者化疗失败的主要原因。MDR 癌细胞中 P-糖蛋白的过度表达是一种具有生化耐药机制的多因素现象。从百部科植物直立百部中分离得到的 Stemofoline（STF）已被报道为一种 MDR 逆转化合物。
本研究旨在探讨从百部科植物中分离得到的其他百部生物碱是否具有 MDR 调节活性。
采用 MTT 法测定生物碱的 MDR 逆转特性。通过细胞周期分析和 P-糖蛋白荧光底物积累实验研究这些化合物对 P-糖蛋白功能的调节作用。采用 Western blot 分析测定 P-糖蛋白的表达。我们初步通过 MTT 法在正常人成纤维细胞和人外周血单个核细胞（PBMCs）以及在体外溶血实验中在人（和大鼠）红细胞中检测了这些化合物的安全性。
在被测试的 8 种生物碱中，有 3 种，即异 Stemofoline（ISTF）、11Z-去氢 Stemofoline（11Z-DSTF）和 11E-去氢 Stemofoline（11E-DSTF），增强了过表达 P-糖蛋白的 MDR 白血病 K562/Adr 细胞的化疗敏感性。P-糖蛋白功能研究表明，这 3 种生物碱增加了 K562/Adr 细胞中 P-糖蛋白底物 calcein-AM（C-AM）和 rhodamine123（Rho 123）的积累，而在药物敏感的亲本 K562 细胞中则没有观察到这种作用。然而，通过 Western blot 分析发现，生物碱并没有改变 P-糖蛋白的表达。
这些生物碱通过抑制 P-糖蛋白的功能逆转了 MDR。在药物安全性测试中，这些生物碱对正常人成纤维细胞和 PBMCs 没有毒性。此外，有效化合物在人或大鼠红细胞中均不会引起溶血。这些化合物可能被引入作为治疗 P-糖蛋白介导的 MDR 癌症的潜在候选分子。
