Background: Acute myeloid leukemia (AML) is a common disease with over 70% of patients cannot be cured. Thus, it is urgent to develop effective new therapies. The TET (TET1/2/3) proteins are a family of methylcytosine dioxygenases involving DNA demethylation. In contrast to the tumor-suppressor roles of TET genes reported previously, we found that TET1 is significantly up-regulated and functions as a critical oncogene in MLL-rearranged AMLs (Huang et al. PNAS, 2013). We have recently found that TET1 is also up- regulated in AMLs carrying t(8;21), in which TET1 likely also plays an essential oncogenic role. Moreover, we have identified NSC-370284 as a lead small-molecule compound that selectively represses TET1 signaling and effectively inhibits growth of AML cells with a high level of endogenous TET1 expression. Hypothesis: TET1 plays a critical oncogenic role in the pathogenesis of not only MLL-rearranged AMLs but also t(8;21) AMLs, and targeting TET1 signaling by selective small-molecule compound(s) represents an effective novel therapeutic strategy to treat these AMLs. Specific Aims: 1) To determine the definitive role of TET1 in both development and maintenance of t(8;21) AMLs, and identify critical target genes of TET1 in t(8;21) AMLs; 2) To decipher the molecular mechanism by which the lead compound (NSC-370284) inhibits TET1 signaling and exhibits an anti-leukemia activity; and 3) To develop novel therapies targeting TET1 signaling to treat MLL-rearranged AMLs and t(8;21) AMLs. Study Design: 1) First, to determine the role of TET1 in both development and maintenance of the major subtypes of t(8;21) AMLs, we will conduct both primary and secondary mouse bone marrow transplantation (BMT) assays using wild-type and Tet1 knockout mouse models together with retrovirally induced major subtypes of t(8;21) AML models. Second, to identify critical target genes of TET1 in t(8;21) AML, ChIP-Seq, 5hmC-Seq and RNA-Seq will be conducted. 2) Our preliminary data suggests that NSC-370284 likely targets SATA5 directly and thereby inhibits TET1 transcription. Here we will conduct a series of structural-functional studies, biochemical and pharmaceutical assays, and gene transcriptional regulation assays to determine whether STAT5 is a critical direct target of NSC-370284 and also a direct upstream regulator of TET1. Meanwhile, we will also conduct a series of assays to identify other potential direct targets of NSC-370284. 3) We will first assess pharmacokinetics (PK), pharmacodynamics (PD), maximum tolerated dose (MTD) and toxicity profile of NSC-370284 in vivo. We will then employ a series of preclinical animal models to evaluate the therapeutic efficacy and potential of NSC-370284, alone and especially together with other therapeutic agent(s), in treating both MLL-rearranged AMLs and t(8;21) AMLs in vivo. Thereafter, we will further optimize 370284 by chemical modifications to improve the potency, selectivity, and/or pharmacokinetic parameters. The anti-leukemia effects of a set of top derivatives will be evaluated in vivo.