Potential therapeutic implications of targeting miR-150 in acute myeloid leukemia

描述（由申请人提供）：急性髓性白血病（AML）是一种遗传多样性的造血恶性肿瘤，对治疗有不同的反应。大约10%的aml参与混合谱系白血病（MLL）基因的染色体重排，有超过60个融合伙伴。MLL重排的关键特征是产生由5‘ MLL和3’配对基因序列组成的嵌合转录物（80%涉及AML中的AF9， AF6, AF10， ELL或ENL）。mll相关性白血病预后较差。一组重要的癌基因，包括同源盒A （HOXA）基因、MEIS1、FLT3、MYB和MYC，在mll相关白血病中经常上调，并在携带mll重排的白血病干细胞（LSCs）的自我更新中发挥关键作用。然而，临床上尚未开发出有效靶向这些基因的有意义的治疗方法。因此，迫切需要更好地了解mll相关白血病发病机制的分子机制，并在此基础上开发有效的治疗策略。MicroRNAs （miRNA）是一类小的非编码rna，在转录后基因调控中起重要作用。最近，我们报道了miR-150在大多数AML病例中显著下调，其抑制对mml - af9介导的细胞转化和白血病发生至关重要；miR-150通过直接靶向FLT3/MYB和间接靶向MYC/LIN28/HOXA9/MEIS1信号通路，在MLL-fusion/MYC/LIN28 / miR-150 / FLT3/MYB/HOXA9/MEIS1信号通路中作为关键的肿瘤抑制基因守门人（Jiang X.，等）。《癌症细胞》，2012)。假设：miR-150对于mll重排的aml的发展和维持以及相关LSCs的自我更新都是必需的。因此，miR-150表达/功能的恢复具有显著的临床应用潜力，可用于治疗目前治疗耐药的这类疾病

DESCRIPTION (provided by applicant): Acute myeloid leukemia (AML) is a heterogeneous group of genetically diverse hematopoietic malignancies with variable responses to treatment. Around 10% of AMLs are involved in chromosomal rearrangements of the mixed lineage leukemia (MLL) gene with over 60 fusion partners. The critical feature of MLL-rearrangements is the generation of a chimeric transcript consisting of 5' MLL and 3' sequences of a partner gene (80% involving AF9, AF6, AF10, ELL or ENL in AML). The prognosis of MLL-associated leukemia is poor. A group of important oncogenes, including homeobox A (HOXA) genes, MEIS1, FLT3, MYB, and MYC, are frequently up-regulated in MLL-associated leukemias, and play a key role in the self-renewal of leukemia stem cells (LSCs) carrying MLL-rearrangements. However, clinically significant therapies have not been developed to effectively target these genes yet. Thus, better understanding of the molecular mechanisms underlying the pathogenesis of MLL-associated leukemia, and the development of effective therapeutic strategies based on such understanding, are urgently needed. MicroRNAs (miRNA) are a class of small, non- coding RNAs that play important roles in post-transcriptional gene regulation. Very recently, we reported that miR-150 is significantly down-regulated in most AML cases, and its repression is critical for MLL-AF9-mediated cell transformation and leukemogenesis; miR-150 functions as a pivotal tumor-suppressor gatekeeper in the MLL-fusion/MYC/LIN28⊣miR-150⊣FLT3/MYB/HOXA9/MEIS1 signaling circuit, through targeting FLT3/MYB directly and MYC/LIN28/HOXA9/MEIS1 indirectly (Jiang X., et al. Cancer Cell. 2012). Hypothesis: miR-150 is required for both development and maintenance of MLL-rearranged AMLs and for the self-renewal of the relevant LSCs. Therefore, the restoration of miR-150 expression/function holds significant potential to be clinically applicable to treat this type of presently therapy-resistant disease. Specific Aims: 1) To determine whether repression of miR-150 is required for both development and maintenance of MLL-rearranged AMLs; 2) To determine whether repression of miR-150 is required for the self- renewal of LSCs of MLL-rearranged AMLs; and 3) To determine whether restoration of the expression/function of miR-150 (delivered by nanoparticles) is an effective new strategy for treating MLL-rearranged AMLs. Study Design: 1) We will use mouse bone marrow transplantation (BMT) models to determine whether ectopic expression of miR-150 can significantly inhibit both development and maintenance of all five major sub- types of MLL-rearranged AMLs (i.e., MLL-AF9, -AF6, -AF10, -ELL and -ENL). 2) We will conduct both competitive repopulation and limiting dilution assays to determine whether ectopic expression of miR-150 can significantly inhibit the self-renewal of relevant LSCs. 3) We will develop novel targeted nanoparticles based on FLT3L (FLT3 ligand)-directed dendrimers complexed with miR-150 oligos, followed by assessment of their specificity and efficacy in targeting/treating MLL-rearranged AMLs both in vitro and in vivo.