In a previous study, however, shRNA-mediated knockdown in purified human CD34+ HSPCs resulted in reduced myeloid colony formation and impaired in vivo engraftment . transformation that was induced by MLL-AF9one of the most common MLL-r oncoproteins found in patients. In addition, the underlying transcriptional and epigenetic mechanisms were explored using chromatin immunoprecipitation (ChIP) sequencing (ChIP-Seq), mRNA microarray, qRT-PCR, histone modification, co-immunoprecipitation (co-IP), cell cycle, and apoptosis assays. The effects of SALL4 loss on normal hematopoiesis in mice were also investigated. Results In vitro and in vivo studies revealed that SALL4 expression is critically required for MLL-AF9-induced leukemic transformation and disease progression in mice. Loss of SALL4 in MLL-AF9-transformed cells induced apoptosis and ALK-IN-1 (Brigatinib analog, AP26113 analog) cell cycle arrest at G1. ChIP-Seq assay identified that Sall4 binds to key MLL-AF9 target genes and important MLL-r or non-MLL-r leukemia-related genes. ChIP-PCR ALK-IN-1 (Brigatinib analog, AP26113 analog) assays indicated that SALL4 affects the levels of the histone modification markers H3K79me2/3 and H3K4me3 at MLL-AF9 target gene promoters by physically interacting with DOT1-like histone H3K79 methyltransferase (DOT1l) and LSD1/KDM1A, and thereby regulates transcript expression. Surprisingly, normal could be one of a few genes that bridge the unique properties of stem cells and malignancies. Although downregulated or absent in most adult tissues, abnormal SALL4 expression has been detected in various human tumors and leukemias which include acute myeloid leukemia (AML), B-acute lymphoblastic leukemia, and chronic myeloid leukemia (for a review, see ALK-IN-1 (Brigatinib analog, AP26113 analog) Ref. Rabbit polyclonal to PLA2G12B ). Moreover, SALL4 expression was enriched in the side population (SP) of tumor cells, implicating its roles in cancer initiation and drug resistance . In human AMLs, SALL4 knockdown caused massive cellular apoptosis and great cell growth arrest , while overexpression of SALL4 largely blocked myeloid differentiation and apoptosis that was induced by all-trans retinoic acid (ATRA) . In animal studies, transgenic mice overexpressing SALL4 (the -B isoform) developed myelodysplastic syndrome (MDS) and AML features, and their BM HSPCs displayed increased serial replating potential  which rapidly induced leukemia in secondarily transplanted mice, indicating the presence of leukemia-initiating cells (LICs). It is becoming clear that the SALL4 regulatory functions are associated with a variety of chromatin-modifying factors which include DNA methyltransferases (DNMT-1, DNMT-3A, DNMT-3B, DNMT-3L) , the nucleosome remodeling and deacetylase (NuRD) complex components HDAC1 /HDAC2 , the histone demethylase LSD1/ KDM1A , and others . SALL4 appears to selectively recruit these epi-factors to define target genes that control hematopoietic self-renewal, differentiation, and apoptosis, and thus affect their expression levels and control proper cell growth. For example, in NB4 AML cells transduced with lentiviral-SALL4 , there was an overall increased percentage of DNA methylation at various CpG sites of the tumor suppression gene promoter and promoter itself. In cultured mouse Lin-Sca-1+ c-kit + (LSK) HSPCs, lentiviral SALL4 overexpression or Cre-induced gene deletion significantly affected LSD1 binding and drastically altered H3K4me3 levels at promoters of differentiation genes promoter were substantially increased . The SALL4-mediated H3K4me3 modification is likely due to the SALL4-mixed lineage leukemia (MLL) interaction, which also induced increased H3K4me3 and H3K79me3 at promoter . In a separate functional study, a SALL4-specific 12-amino acid peptide interfering its interaction with epi-factors (such as HDAC1/2) induced leukemia death but caused no cytotoxic effects in normal HSPCs in culture nor impaired in vivo engraftment . Recently, the SALL4 functions have been further linked with the MLL/HOXA9 pathway. SALL4 was demonstrated to interact with MLL protein, and the two factors occupy the same promoter regions in hematopoietic cells . Of note, MLL-fusion proteins (MFPs) caused by frequent chromatin rearrangements are potent inducers of oncogenic transformation, and their expression has been considered the main oncogenic driving force in ?10% of human AML patients . Remarkably, MLL-r leukemias display constant genomic stability, with very few gains or losses of chromosomal regions, ALK-IN-1 (Brigatinib analog, AP26113 analog) but rely heavily on epigenetic dysregulation. In murine MLL-AF9one of the most common MFPs with poor outcomesAML model studies,.