Department of Pharmaceutics, Key Lab of State Natural Medicine, China Pharmaceutical University, Nanjing 210009, PR China.
Mol Pharm. 2013 Jun 3;10(6):2479-89. doi: 10.1021/mp4001266. Epub 2013 May 20.
Refractory leukemia remains the most common therapeutic problem in clinical treatment of leukemia. The key therapy of refractory leukemia is to kill, thoroughly, the minimal residual disease and leukemia stem cells in the highly vascularized red marrow areas. In this study, two new conjugates, alendronate-polyethylene glycol (100) monostearate and folate-polyethylene glycol (100) monostearate, were synthesized to develop a multistep targeting nanostructured lipid carriers by enhancing drug transport to the high bone turnover areas adjacent to the red marrow and targeting the minimal residual disease and leukemia stem cells. This dual targeting system demonstrated a great binding affinity to hydroxyapatite, a model component of bone minerals, and higher cell uptake (in the form of carriers but not drug) and cytotoxicity in the K562 cell line, a leukemia cell line with overexpressed folate receptors, were observed in vitro compared to unmodified carriers, especially when the cells were pretreated and the receptors were up-regulated by all-trans retinoic acid. The comodel test of K562 cells and HA showed that this dual targeting system could desorb from bone surface and be taken up by leukemia cells. For the in vivo study, this dual targeting system exhibited a significant increase in plasma half-life and could specifically accumulate in the bone tissue of rats or mice after intravenous injection. Ex vivo imaging of mice femurs and confocal laser scanning microscope imaging of mice femur slices further confirmed that this dual targeting system could favorably deposit to the osteoblast-enriched areas of high bone turnover in regions of trabecular bone surrounded by red marrow. In vivo antitumor activity in K562/BALB/c-nu leukemia mice showed that the treatment of this dual targeting system significantly reduced the white blood cell (WBC) number in peripheral blood and bone marrow to the normal level. In conclusion, this dual targeting system could precisely target to the regions where the minimal residual disease and leukemia stem cells are located and then be specifically uptaken in large amounts, which is a valuable target for refractory leukemia therapy.
难治性白血病仍然是白血病临床治疗中最常见的治疗难题。难治性白血病的关键治疗方法是彻底杀死高度血管化的红骨髓区域中的微小残留疾病和白血病干细胞。在这项研究中，我们合成了两种新的缀合物，阿仑膦酸钠-聚乙二醇（100）单硬脂酸酯和叶酸-聚乙二醇（100）单硬脂酸酯，通过增强药物向靠近红骨髓的高骨转换区域的输送，并靶向微小残留疾病和白血病干细胞，开发了一种多步靶向纳米结构脂质载体。这种双靶向系统对羟基磷灰石（骨矿物质的一种模型成分）具有很强的结合亲和力，并且与未修饰的载体相比，在体外观察到对 K562 细胞系（一种过度表达叶酸受体的白血病细胞系）的细胞摄取（以载体的形式而不是药物）和细胞毒性更高，尤其是当细胞用全反式视黄酸预处理并上调受体时。K562 细胞和 HA 的共模型测试表明，这种双靶向系统可以从骨表面解吸并被白血病细胞摄取。在体内研究中，这种双靶向系统表现出显著增加的血浆半衰期，并可以在静脉注射后特异性地积聚在大鼠或小鼠的骨组织中。对小鼠股骨的体外成像和对小鼠股骨切片的共聚焦激光扫描显微镜成像进一步证实，这种双靶向系统可以有利地沉积到富含成骨细胞的高骨转换区域，这些区域位于由红骨髓包围的小梁骨周围。在 K562/BALB/c-nu 白血病小鼠中的体内抗肿瘤活性研究表明，该双靶向系统的治疗显著降低了外周血和骨髓中的白细胞（WBC）数量至正常水平。总之，这种双靶向系统可以精确地靶向微小残留疾病和白血病干细胞所在的区域，然后大量特异性摄取，这是难治性白血病治疗的一个有价值的靶点。
