BackgroundAcute myeloid leukaemia (AML) is characterised by the halt in maturation of myeloid progenitor cells, combined with uncontrolled proliferation and abnormal survival, leading to the accumulation of immature blasts. In many subtypes of AML the underlying causative genetic insults are not fully described. MicroRNAs are known to be dysregulated during oncogenesis. Overexpression of miR-155 is associated with some cancers, including haematological malignancies, and it has been postulated that miR-155 has an oncogenic role. This study investigated the effects of modulating miR-155 expression in human AML cells, and its mechanism of action.ResultsAnalysis of miR-155 expression patterns in AML patients found that Fms-like tyrosine kinase 3 (FLT3)-wildtype AML has the same expression level as normal bone marrow, with increased expression restricted to AML with the FLT3-ITD mutation. Induction of apoptosis by cytarabine arabinoside or myelomonocytic differentiation by 1,23-dihydroxyvitaminD3 in FLT3-wildtype AML cells led to upregulated miR-155 expression. Knockdown of miR-155 by locked nucleic acid antisense oligonucleotides in the FLT3-wildtype AML cells conferred resistance to cytarabine arabinoside induced apoptosis and suppressed the ability of cells to differentiate.Ectopic expression of miR-155 in FLT3-wildtype AML cells led to a significant gain of myelomonocytic markers (CD11b, CD14 and CD15), increase in apoptosis (AnnexinV binding), decrease in cell growth and clonogenic capacity.In silico target prediction identified a number of putative miR-155 target genes, and the expression changes of key transcription regulators of myeloid differentiation and apoptosis (MEIS1, GF1, cMYC, JARID2, cJUN, FOS, CTNNB1 and TRIB2) were confirmed by PCR. Assessment of expression of apoptosis-related proteins demonstrated a marked increase in cleaved caspase-3 expression confirming activation of the apoptosis cascade.ConclusionsThis study provides evidence for an anti-leukaemic role for miR-155 in human FLT3-wildtype AML, by inducing cell apoptosis and myelomonocytic differentiation, which is in contrast to its previously hypothesized role as an oncogene. This highlights the complexity of gene regulation by microRNAs that may have tumour repressor or oncogenic effects depending on disease context or tissue type.

Krüppel-like factor 3 (Klf3) is a member of the Klf family of transcription factors. Klfs are widely expressed and have diverse roles in development and differentiation. In this study, we examine the function of Klf3 in B cell development by studying B lymphopoiesis in a Klf3 knockout mouse model. We show that B cell differentiation is significantly impaired in the bone marrow, spleen, and peritoneal cavity of Klf3 null mice and confirm that the defects are cell autonomous. In the bone marrow, there is a reduction in immature B cells, whereas recirculating mature cells are noticeably increased. Immunohistology of the spleen reveals a poorly structured marginal zone (MZ) that may in part be caused by deregulation of adhesion molecules on MZ B cells. In the peritoneal cavity, there are significant defects in B1 B cell development. We also report that the loss of Klf3 in MZ B cells is associated with reduced BCR signaling strength and an impaired ability to respond to LPS stimulation. Finally, we show increased expression of a number of Klf genes in Klf3 null B cells, suggesting that a Klf regulatory network may exist in B cells.

IntroductionSp/Krüppel-like factors (KLFs) encompass more than 20 transcription factors in mice or humans. All KLFs share a characteristic DNA-binding domain at their C-terminus consisting of 3 Krüppel-like zinc-finger domains. One subset of KLFs, containing the PXDLS/T motive, recruits the C-terminal binding protein 2 general transcriptional repressor (CtBP2). 1 Apart from this motive, no consensus sequences are found in the N-terminal domain of KLFs. For KLF3 an interaction with four and a half LIM domains 3 protein (FHL3) has been demonstrated. 2 KLFs are involved in differentiation, proliferation, or trafficking of cells in various tissues. 3 They are differentially expressed in lymphocytes, including T cells. Here, KLF2 and few other KLFs have been studied extensively. [4][5][6][7][8] To date, little is known about the role of KLFs in B-cell development.Before colonizing secondary lymphoid organs, such as spleen or lymph nodes, B cells differentiate from hematopoietic precursors in the bone marrow. After the developmental processes there, most of the immature/transitional B cells that are IgM hi CD24 hi IgD lo CD93 hi (AA4.1, 493) CD21/35 Ϫ CD23 Ϫ migrate via the blood to the spleen where they complete their maturation. During splenic maturation, they down-modulate CD93, gain CD21/35 and CD23 expression, and, finally, appear as mature follicular or marginal zone (MZ) B cells, together referred to as B2 cells. Mature follicular and MZ B cells differentially express several cell surface markers: follicular B cells are CD21/35 ϩ CD23 ϩ CD1d lo , whereas MZ B cells are CD21/35 hi CD23 Ϫ CD1d hi ; both express IgM and IgD, but to different levels (IgM lo IgD hi and IgM hi IgD lo for follicular and MZ B cells, respectively). 9 Another lineage of B cells, the B1 subset, localizes predominantly to the peritoneum. These derive mostly from fetal hematopoietic stem cells, as opposed to adult bone marrow stem cells, and require the spleen for maturation. In the spleen, follicular and MZ B cells are localized differently: naive follicular B cells constitute the white pulp follicles that enwrap the T cell-rich periarteriolar zone, surrounding the central ateriole. Branching off the central ateriole, small vessels end openly into the marginal sinus at the white pulp and red pulp interface. This zone is termed "marginal zone" and contains resident macrophages, dendritic cells, and MZ B cells. Here, blood-borne pathogens and microbial products come by contact with the immune systems' tissue first. Thought of as a first line of defense, MZ B cells can initiate rapid T cellindependent antibody responses. 10 Thus, the function of MZ B cells is dependent on their proper localization.Whereas integrins mediate their adhesion, 11,12 chemoattractant molecules define where MZ B cells home to. They are attracted by sphingosine-1-phospate (S1P), with the highest concentration *F.F., J.K., and S.S. contributed equally to this study.The online version of this article contains a data supplement.The publication costs of this article were ...

Basal insulin therapy can improve glycemic control in people with type 2 diabetes. However, timely initiation, optimal titration, and proper adherence to prescribed basal insulin regimens are necessary to achieve optimal glycemic control. Even so, glycemic control may remain suboptimal in a significant proportion of patients. Unique circumstances in Asia (eg, limited resources, management of diabetes primarily in nonspecialist settings, and patient populations that are predominantly less educated) coupled with the limitations of current basal insulin options (eg, risk of hypoglycemia and dosing time inflexibility) amplify the challenge of optimal basal insulin therapy in Asia. Significant progress has been made with long-acting insulin analogs (insulin glargine 100 units/mL and insulin detemir), which provide longer coverage and less risk of hypoglycemia over intermediate-acting insulin (Neutral Protamine Hagedorn insulin). Furthermore, recent clinical evidence suggests that newer long-acting insulin analogs, new insulin glargine 300 units/mL and insulin degludec, may address some of the unmet needs of current basal insulin options in terms of risk of hypoglycemia and dosing time inflexibility. Nevertheless, more can be done to overcome barriers to basal insulin therapy in Asia, through educating both patients and physicians, developing better patient support models, and improving accessibility to long-acting insulin analogs. In this study, we highlight the unique challenges associated with basal insulin therapy in Asia and, where possible, propose strategies to address the unmet needs by drawing on clinical experiences and perspectives in Asia.