Aberrant epigenetic regulators control expansion of human CD34+ hematopoietic stem/progenitor cells

Defined Human Leukemic CD34+ Liquid Cultures to Study HDAC/Transcriptional Repressor Complexes

Defined human primary cell model systems with growth dependence on oncogenes are highly requested to investigate tumor pathogenesis and to validate pharmacological inhibitors that specifically target oncoproteins and their executing protein complex partners. In acute myeloid leukemia (AML), transcription factors such as RUNX1 and MLL1, which are important for normal blood cell development, frequently harbor mutations including chromosomal translocations with other coding genes, resulting in tumor-promoting gain-of-function fusion proteins. These oncoproteins completely modify transcriptional programs, thereby inducing malignant cell phenotypes. A common theme of the chimeric gene products is their physical interaction with a variety of chromatin-modifying effector molecules, including histone acetyltransferases (HATs) and histone deacetylases (HDACs). These aberrant multiprotein machineries disturb gene expression and promote malignant cell growth. In this chapter, we briefly summarize the current understanding regarding AML-associated oncogene-driven human CD34+ blood progenitor cell expansion in ex vivo liquid cultures. We provide a step-by-step protocol to establish oncogene-induced human CD34+ blood progenitor cell cultures suitable to analyze the impact of transcriptional repressor/HDAC activity in these human AML cell models.

Preleukemic Hematopoietic Stem Cells in Human Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive malignancy of the bone marrow characterized by an uncontrolled proliferation of undifferentiated myeloid lineage cells. Decades of research have demonstrated that AML evolves from the sequential acquisition of genetic alterations within a single lineage of hematopoietic cells. More recently, the advent of high-throughput sequencing has enabled the identification of a premalignant phase of AML termed preleukemia. Multiple studies have demonstrated that AML can arise from the accumulation of mutations within hematopoietic stem cells (HSCs). These HSCs have been termed "preleukemic HSCs" as they represent the evolutionary ancestors of the leukemia. Through examination of the biological and clinical characteristics of these preleukemic HSCs, this review aims to shed light on some of the unexplored questions in the field. We note that some of the material discussed is speculative in nature and is presented in order to motivate future work.

The immunogenetics of Psoriasis: A comprehensive review

Psoriasis vulgaris is a common, chronic inflammatory skin disease with a complex etiology involving genetic risk factors and environmental triggers. Here we describe the many known genetic predispositions of psoriasis with respect to immune genes and their encoded pathways in psoriasis susceptibility. These genes span an array of functions that involve antigen presentation (HLA-Cw6, ERAP1, ERAP2, MICA), the IL-23 axis (IL12Bp40, IL23Ap19, IL23R, JAK2, TYK2), T-cell development and T-cells polarization (RUNX1, RUNX3, STAT3, TAGAP, IL4, IL13), innate immunity (CARD14, c-REL, TRAF3IP2, DDX58, IFIH1), and negative regulators of immune responses (TNIP1, TNFAIP3, NFKBIA, ZC3H12C, IL36RN, SOCS1). The contribution of some of these gene products to psoriatic disease has also been revealed in recent years through targeting of key immune components, such as the Th17/IL-23 axis which has been highly successful in disease treatment. However, many of the genetic findings involve immune genes with less clear roles in psoriasis pathogenesis. This is particularly the case for those genes involved in innate immunity and negative regulation of immune specific pathways. It is possible that risk alleles of these genes decrease the threshold for the initial activation of the innate immune response. This could then lead to the onslaught of the pathogenic adaptive immune response known to be active in psoriatic skin. However, precisely how these various genes affect immunobiology need to be determined and some are speculated upon in this review. These novel genetic findings also open opportunities to explore novel therapeutic targets and potentially the development of personalized medicine, as well as discover new biology of human skin disease.