Targeted Liposomal Doxorubicin Delivery to Leukemia

描述（由申请人提供）：靶向药物递送具有改善治疗剂的功效同时减少其副作用的潜力。 叶酸受体β（FRB）是一种细胞表面标记物，约70%的急性髓系白血病（AML）选择性表达FRB。在FR-β阳性KG-1和原代AML细胞中，全反式维甲酸（ATRA）可特异性诱导FR-β表达增加，而不诱导细胞分化或生长抑制。叶酸是FR-β的高亲和力配体（Kd约为1 nM）。 重要的是，已发现由正常造血细胞表达的FR-β是无功能的，而由KG-1 AML细胞和FR-β转染的CHO细胞表达的受体介导叶酸包被的脂质体的选择性摄取和细胞毒性。 ATRA可诱导FR-β表达上调，进一步增加叶酸脂质体阿霉素（f-L-Dox）在KG-1细胞中的摄取和细胞毒性。 此外，在FR阳性鼠L1210 JF和人KG-1 AML腹水肿瘤模型中，f-L-DOX表现出比非靶向脂质体DOX（LDox）更大的治疗功效。在KG-1移植小鼠中，ATRA进一步增强了由于用f-L-Dox治疗而增加的存活率。 FR靶向的脂质体Dox递送也已显示在对游离Dox表现出抗性的FR阳性肿瘤细胞中绕过P-糖蛋白介导的药物流出。 该项目的目的是评估f-L-Dox联合ATRA诱导FR-β上调治疗AML的效果，这是一个基于选择性靶向FR阳性肿瘤细胞的概念。 具体目标是：1.评价全反式维甲酸（ATRA）对急性髓系白血病细胞FR-β表达的影响。2. 为了评价脂质体制剂和FR-β水平作为f-L-Dox与AML细胞的结合和体外细胞毒性的因素，以及脂质体的药代动力学特性;还将研究膳食叶酸的影响。3. 评估单独或与ATRA组合的f-L-Dox针对AML母细胞、克隆生成祖细胞（CFU）和原始AML干细胞（SL-Ic）的选择性细胞毒性;和4. 目的评价f-L-Dox单独或联合ATRA治疗小鼠白血病模型的体内疗效。 该项目将导致开发一种新的治疗策略，该策略基于靶向药物递送至肿瘤细胞和上调细胞靶点的组合，用于治疗化疗难治性AML。

DESCRIPTION (provided by applicant): Targeted drug delivery has the potential to improve the efficacy of a therapeutic agent while reducing its side effects. Folate receptor type-beta (FRB) is a cell surface marker selectively expressed by approximately70 percent of acute myeloid leukemias (AMLs). Increased FR-beta expression can be specifically induced by all trans retinoic acid (ATRA) in FR-beta-positive KG-1 and primary AML cells, without inducing cellular differentiation or growth inhibition. Folic acid is a high affinity ligand for FR-beta (Kd approximately 1 nM). Importantly, FR-beta expressed by normal hematopoietic cells has been found to be non-functional, whereas the receptor expressed by KG-1 AML cells and FR-beta-transfected CHO cells mediates selective uptake and cytotoxicity of folate-coated liposomes. Both uptake and cytotoxicity of folate coated liposome doxorubicin (f-L-Dox) in KG-1 cells were further increased by ATRA, which induced FR-beta upregulation. Moreover, f-L-DOX exhibited greater therapeutic efficacy than non-targeted liposomal DOX (LDox) in FR positive murine L1210JF and human KG-1 AML ascitic tumor models. Increased survival due to treatment with f-L-Dox was further enhanced by ATRA in the KG-1 engrafted mice. FR-targeted liposomal Dox delivery has also been shown to bypass the P-glycoprotein-mediated drug efflux in FR positive tumor cells exhibiting resistance to free Dox. The objective of this project is to evaluate f-L-Dox, combined with ATRA-induction of FR-beta upregulation, for the treatment of AML, a concept based on the selective targeting of the FR positive tumor cells. The specific aims are: 1. To evaluate the effect of ATRA on FR-beta expression by AML cells in vivo. 2. To evaluate liposome formulation and FR-beta level as factors in the binding and in vitro cytotoxicity of f-L-Dox to AML cells, as well as the pharmacokinetic properties of the liposomes; the effect of dietary folate will also be studied. 3. To evaluate the selective cytotoxicity of f-L-Dox, alone or combined with ATRA, against AML blast cells, clonogenic progenitor cells (CFUs), and primitive AML stem cells (SL-Ics); and 4. To evaluate the in vivo therapeutic efficacy of f-L-Dox alone or combined with ATRA in murine leukemia models. This project should lead to the development of a novel therapeutic strategy based on the combination of targeted drug delivery to tumor cells and upregulation of the cellular target for the treatment of chemotherapy refractory AMLs.