Departments of Hematology and Medical Oncology and Cell Biology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, Georgia, USA.
PLoS One. 2012;7(12):e52662. doi: 10.1371/journal.pone.0052662. Epub 2012 Dec 21.
Arsenic trioxide (ATO) has been tested in relapsed/refractory multiple myeloma with limited success. In order to better understand drug mechanism and resistance pathways in myeloma we generated an ATO-resistant cell line, 8226/S-ATOR05, with an IC50 that is 2-3-fold higher than control cell lines and significantly higher than clinically achievable concentrations. Interestingly we found two parallel pathways governing resistance to ATO in 8226/S-ATOR05, and the relevance of these pathways appears to be linked to the concentration of ATO used. We found changes in the expression of Bcl-2 family proteins Bfl-1 and Noxa as well as an increase in cellular glutathione (GSH) levels. At low, clinically achievable concentrations, resistance was primarily associated with an increase in expression of the anti-apoptotic protein Bfl-1 and a decrease in expression of the pro-apoptotic protein Noxa. However, as the concentration of ATO increased, elevated levels of intracellular GSH in 8226/S-ATOR05 became the primary mechanism of ATO resistance. Removal of arsenic selection resulted in a loss of the resistance phenotype, with cells becoming sensitive to high concentrations of ATO within 7 days following drug removal, indicating changes associated with high level resistance (elevated GSH) are dependent upon the presence of arsenic. Conversely, not until 50 days without arsenic did cells once again become sensitive to clinically relevant doses of ATO, coinciding with a decrease in the expression of Bfl-1. In addition we found cross-resistance to melphalan and doxorubicin in 8226/S-ATOR05, suggesting ATO-resistance pathways may also be involved in resistance to other chemotherapeutic agents used in the treatment of multiple myeloma.
三氧化二砷（ATO）在复发性/难治性多发性骨髓瘤中的应用已取得一定成效。为了更好地理解骨髓瘤中的药物作用机制和耐药途径，我们构建了 ATO 耐药细胞系 8226/S-ATOR05，其 IC50 是对照细胞系的 2-3 倍，明显高于临床可达到的浓度。有趣的是，我们发现了两条平行的途径来调控 8226/S-ATOR05 对 ATO 的耐药性，而且这些途径的相关性似乎与 ATO 的浓度有关。我们发现 Bcl-2 家族蛋白 Bfl-1 和 Noxa 的表达发生了变化，细胞内谷胱甘肽（GSH）水平也升高了。在低浓度、临床可达到的浓度下，耐药性主要与抗凋亡蛋白 Bfl-1 的表达增加和促凋亡蛋白 Noxa 的表达减少有关。然而，随着 ATO 浓度的增加，8226/S-ATOR05 中细胞内 GSH 水平的升高成为 ATO 耐药的主要机制。去除砷选择导致耐药表型的丧失，在药物去除后 7 天内，细胞对高浓度 ATO 变得敏感，表明与高水平耐药（升高的 GSH）相关的变化依赖于砷的存在。相反，只有在 50 天没有砷的情况下，细胞才再次对临床相关剂量的 ATO 敏感，同时 Bfl-1 的表达下降。此外，我们还发现 8226/S-ATOR05 对美法仑和阿霉素存在交叉耐药性，这表明 ATO 耐药途径也可能参与对多发性骨髓瘤治疗中使用的其他化疗药物的耐药性。
