Deregulated KLF4 Expression in Myeloid Leukemias Alters Cell Proliferation and Differentiation through MicroRNA and Gene Targets

Abstract

bAcute myeloid leukemia (AML) is characterized by increased proliferation and blocked differentiation of hematopoietic progenitors mediated, in part, by altered myeloid transcription factor expression. Decreased Krüppel-like factor 4 (KLF4) expression has been observed in AML, but how decreased KLF4 contributes to AML pathogenesis is largely unknown. We demonstrate decreased KLF4 expression in AML patient samples with various cytogenetic aberrations, confirm that KLF4 overexpression promotes myeloid differentiation and inhibits cell proliferation in AML cell lines, and identify new targets of KLF4. We have demonstrated that microRNA 150 (miR-150) expression is decreased in AML and that reintroducing miR-150 expression induces myeloid differentiation and inhibits proliferation of AML cells. We show that KLF family DNA binding sites are necessary for miR-150 promoter activity and that KLF2 or KLF4 overexpression induces miR-150 expression. miR-150 silencing, alone or in combination with silencing of CDKN1A, a well-described KLF4 target, did not fully reverse KLF4-mediated effects. Gene expression profiling and validation identified putative KLF4-regulated genes, including decreased MYC and downstream MYC-regulated gene expression in KLF4-overexpressing cells. Our findings indicate that decreased KLF4 expression mediates antileukemic effects through regulation of gene and microRNA networks, containing miR-150, CDKN1A, and MYC, and provide mechanistic support for therapeutic strategies increasing KLF4 expression.A cute myeloid leukemia (AML) is characterized by increased self-renewal of leukemia stem or progenitor cells and a failure of differentiation to mature myeloid cells. Normal hematopoietic cell differentiation and proliferation are regulated by the expression and interaction of specific transcription factors (1, 2), which are altered in AML (3-5). Elucidation of the genomic landscape of AML has further highlighted that alterations in myeloid transcription factors play a significant role in leukemogenesis (4). Recent attention has focused on the role of aberrant expression of the Krüppel-like factor (KLF) family of transcription factors in cancer (5). This family includes 17 different isoforms that bind to GCrich regions of DNA via three zinc finger domains and regulate the transcriptional activity of target genes by using two glutaminerich transactivation domains (5). KLF4 regulates differentiation of epidermal and vascular smooth muscle cells (6, 7), as well as cellular reprogramming to induce pluripotent stem cells (8). In normal hematopoiesis, KLF2 and KLF4 regulate myeloid differentiation and KLF4 expression induces CDKN1A (p21), which contributes to cell cycle arrest (9-13). In T-cell acute lymphoblastic leukemia (T-ALL) (14) and B-cell lymphomas, KLF4 has been described as a tumor suppressor regulating proliferation, apoptosis, and differentiation (15). A recent study showed that the homeobox transcription factor CDX2 represses KLF4 in myeloid leukemia cells (16). The investigators also observed that C...

Novel tumor-suppressor function of KLF4 in pediatric T-cell acute lymphoblastic leukemia

“…In addition, a recent study using single-cell RNA sequencing revealed high KLF4 expression during the acceleration of chronic lymphocytic leukemia (CLL) that reoccurs at relapse (24). In myeloid leukemias, low KLF4 levels were associated with altered differentiation via deregulation of gene and microRNA networks (25) and KLF4 expression inversely correlated with HDAC1 activity (26). Inducible expression of KLF4 in Jurkat cell lines and primary T-ALL cells induced apoptosis via the BCL2/BCLXL pathway (27).…”

Loss of quiescence and self-renewal capacity of hematopoietic stem cell in an in vitro leukemic niche

“…It has been shown that Ezh2 is required for proper B and T cell development [47] suggesting that lower Ezh2 expression would affect differentiation of both lymphocyte subpopulations, similar to the observed effect in leukemia patients. Interestingly, Ezh2 inactivation has been also observed in leukemia [48] and Klf4 may function as a tumor suppressor gene in leukemia [49]. The third gene that we observed differentially expressed in these in vitro systems was c-Kit, the SCF receptor.…”

Identification of Acute Myeloid Leukemia Bone Marrow Circulating MicroRNAs

“…Recent work revealed that miR-145, which is known to be downregulated by cisplatin in cisplatin-resistant ovarian cancer cells, also represses PD-L1 gene expression and induces T cell apoptosis in vitro [ 52 ]. It is known that the level of miR-150 is decreased in the plasma and blast cells of AML patients at diagnosis and that reintroducing miR-150 expression induces myeloid differentiation and inhibits the proliferation of AML cells [ 18 , 53 ]. Xi et al developed a novel targeted therapeutic strategy using FLT3L-guided miR-150-based nanoparticles to treat FLT3-overexpressing AML in an animal model with high efficacy and minimal side effects [ 54 ].…”