GATA-1 blocks IL-6-induced macrophage differentiation and apoptosis through the sustained expression of cyclin D1 and Bcl-2 in a murine myeloid cell line M1

Targeting cytokine and chemokine signaling pathways for cancer therapy

Cytokines are critical in regulating immune responses and cellular behavior, playing dual roles in both normal physiology and the pathology of diseases such as cancer. These molecules, including interleukins, interferons, tumor necrosis factors, chemokines, and growth factors like TGF-β, VEGF, and EGF, can promote or inhibit tumor growth, influence the tumor microenvironment, and impact the efficacy of cancer treatments. Recent advances in targeting these pathways have shown promising therapeutic potential, offering new strategies to modulate the immune system, inhibit tumor progression, and overcome resistance to conventional therapies. In this review, we summarized the current understanding and therapeutic implications of targeting cytokine and chemokine signaling pathways in cancer. By exploring the roles of these molecules in tumor biology and the immune response, we highlighted the development of novel therapeutic agents aimed at modulating these pathways to combat cancer. The review elaborated on the dual nature of cytokines as both promoters and suppressors of tumorigenesis, depending on the context, and discussed the challenges and opportunities this presents for therapeutic intervention. We also examined the latest advancements in targeted therapies, including monoclonal antibodies, bispecific antibodies, receptor inhibitors, fusion proteins, engineered cytokine variants, and their impact on tumor growth, metastasis, and the tumor microenvironment. Additionally, we evaluated the potential of combining these targeted therapies with other treatment modalities to overcome resistance and improve patient outcomes. Besides, we also focused on the ongoing research and clinical trials that are pivotal in advancing our understanding and application of cytokine- and chemokine-targeted therapies for cancer patients.

Monocyte transcriptomic profile following EPA and DHA supplementation in men and women with low-grade chronic inflammation

BACKGROUND

Recent data indicate considerable variability in response to very long chain omega-3 fatty acid supplementation on cardiovascular disease risk. This inconsistency may be due to differential effects of EPA vs DHA and/or sex-specific responses.

METHODS

Sixteen subjects (eight men and eight women) 50-75 y and with low-grade chronic inflammation participated in a randomized controlled crossover trial comparing 3 g/d EPA, 3 g/d DHA, and placebo (3 g/d high oleic acid sunflower oil). Blood monocytes were isolated at the end of each phase for RNA-sequencing.

RESULTS

Sex dimorphism in monocyte gene expression was observed, therefore, data for men and women were analyzed separately. 1088 genes were differentially expressed in men and 997 in women (p < 0.05). In both men and women, EPA and DHA repressed genes involved in protein turnover and mitochondrial energy metabolism, relative to placebo. In men only, EPA and DHA upregulated genes related to wound healing and PPARα activation. In women only, EPA and DHA activated genes related to ER stress response. Relative to DHA, EPA resulted in lower expression of genes involved in inflammatory processes in men, and lower expression of genes involved in ER stress response in women.

CONCLUSIONS

EPA and DHA supplementation elicited both similar and differential effects on monocyte transcriptome, some of which were sex specific. The observed variability in response to EPA and DHA in men and women could in part explain the conflicting results from previous cardiovascular clinical trials using omega-3 fatty acids.

Transcriptomic Effects of Low-Dose Inorganic Arsenic Exposure on Murine Bone Marrow-Derived Macrophages

Both tissue-resident macrophages and monocytes recruited from the bone marrow that transform into tissue-resident cells play critical roles in mediating homeostasis as well as in the pathology of inflammatory diseases. Inorganic arsenic (iAs) is the most common drinking water contaminant worldwide and represents a major public health concern. Several diseases that macrophages have implicated involvement in are caused by iAs exposure, including cardiovascular disease, cancer, and increased risk of infectious disease. Therefore, understanding the effects of iAs exposure on macrophages can help us better grasp the full range of arsenic immunotoxicity and better design therapeutic targets for iAs-induced diseases particularly in exposed populations. In this study, we analyzed the transcriptome of low dose iAs-exposed male and female murine bone marrow-derived macrophages (BMDMs) with either M0, M1, or M2 stimulation. We identified differentially expressed genes by iAs in a sex- and stimulation-dependent manner and used bioinformatics tools to predict protein-protein interactions, transcriptional regulatory networks, and associated biological processes. Overall, our data suggest that M1-stimulated, especially female-derived, BMDMs are most susceptible to iAs exposure. Most notably, we observed significant downregulation of major proinflammatory transcription factors, like IRF8, and its downstream targets, as well as genes encoding proteins involved in pattern recognition and antigen presentation, such as TLR7, TLR8, and H2-D1, potentially providing causal insight regarding arsenic's role in perturbing immune responses to infectious diseases. We also observed significant downregulation of genes involved in processes crucial to coordinating a proinflammatory response including leukocyte migration, differentiation, and cytokine and chemokine production and response. Finally, we discovered that 24 X-linked genes were dysregulated in iAs-exposed female stimulation groups compared to only 3 across the iAs-exposed male stimulation groups. These findings elucidate the potential mechanisms underlying the sex-differential iAs-associated immune-related disease risk.

Heme oxygenase-1 mitigates liver injury and fibrosis via modulation of LNX1/Notch1 pathway in myeloid cells

Activation of resident macrophages (Mϕ) and hepatic stellate cells is a key event in chronic liver injury. Mice with heme oxygenase-1 (HO-1; Hmox1)-deficient Mϕ (LysM-Cre:Hmox1 ^flfl ) exhibit increased inflammation, periportal ductular reaction, and liver fibrosis following bile duct ligation (BDL)-induced liver injury and increased pericellular fibrosis in NASH model. RiboTag-based RNA-sequencing profiling of hepatic HO-1-deficient Mϕ revealed dysregulation of multiple genes involved in lipid and amino acid metabolism, regulation of oxidative stress, and extracellular matrix turnover. Among these genes, ligand of numb-protein X1 (LNX1) expression is strongly suppressed in HO-1-deficient Mϕ. Importantly, HO-1 and LNX1 were expressed by hepatic Mϕ in human biliary and nonbiliary end-stage cirrhosis. We found that Notch1 expression, a downstream target of LNX1, was increased in LysM-Cre:Hmox1 ^flfl mice. In HO-1-deficient Mϕ treated with heme, transient overexpression of LNX1 drives M2-like Mϕ polarization. In summary, we identified LNX1/Notch1 pathway as a downstream target of HO-1 in liver fibrosis.

Metallothioneins alter macrophage phenotype and represent novel therapeutic targets for acetaminophen-induced liver injury

Acetaminophen (APAP) intoxication is the foremost cause of drug-induced liver failure in developed countries. The only pharmacologic treatment option, N-acetylcysteine (NAC), is not effective for patients who are admitted too late and/or who have excessive liver damage, emphasizing the need for alternative treatment options. APAP intoxication results in hepatocyte death and release of danger signals, which further contribute to liver injury, in part by hepatic monocyte/macrophage infiltration and activation. Metallothionein (MT) 1 and 2 have important danger signaling functions and might represent novel therapeutic targets in APAP overdose. Therefore, we evaluated hepatic MT expression and the effect of anti-MT antibodies on the transcriptional profile of the hepatic macrophage population and liver injury following APAP overdose in mice. Hepatic MT expression was significantly induced in APAP-intoxicated mice and abundantly present in human livers. APAP intoxication in mice resulted in increased serum transaminase levels, extended necrotic regions on liver histology and induced expression of proinflammatory markers, which was significantly less pronounced in mice treated with anti-MT antibodies. Anti-MT antibody therapy attenuated proinflammatory macrophage polarization, as demonstrated by RNA sequencing analyses of isolated liver macrophages and in LPS-stimulated bone marrow-derived macrophages. Importantly, NAC and anti-MT antibodies were equally effective whereas administration of anti-MT antibody in combination with NAC exceeded the efficiency of both monotherapies in APAP-induced liver injury (AILI). We conclude that the neutralization of secreted MTs using a monoclonal antibody is a novel therapeutic strategy as mono- or add-on therapy for AILI. In addition, we provide evidence suggesting that MTs in the extracellular environment are involved in macrophage polarization.

Tumor Immune Evasion Induced by Dysregulation of Erythroid Progenitor Cells Development

Cancer cells harness normal cells to facilitate tumor growth and metastasis. Within this complex network of interactions, the establishment and maintenance of immune evasion mechanisms are crucial for cancer progression. The escape from the immune surveillance results from multiple independent mechanisms. Recent studies revealed that besides well-described myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) or regulatory T-cells (Tregs), erythroid progenitor cells (EPCs) play an important role in the regulation of immune response and tumor progression. EPCs are immature erythroid cells that differentiate into oxygen-transporting red blood cells. They expand in the extramedullary sites, including the spleen, as well as infiltrate tumors. EPCs in cancer produce reactive oxygen species (ROS), transforming growth factor β (TGF-β), interleukin-10 (IL-10) and express programmed death-ligand 1 (PD-L1) and potently suppress T-cells. Thus, EPCs regulate antitumor, antiviral, and antimicrobial immunity, leading to immune suppression. Moreover, EPCs promote tumor growth by the secretion of growth factors, including artemin. The expansion of EPCs in cancer is an effect of the dysregulation of erythropoiesis, leading to the differentiation arrest and enrichment of early-stage EPCs. Therefore, anemia treatment, targeting ineffective erythropoiesis, and the promotion of EPC differentiation are promising strategies to reduce cancer-induced immunosuppression and the tumor-promoting effects of EPCs.

Regulation of GATA1 levels in erythropoiesis

GATA1 is considered as the "master" transcription factor in erythropoiesis. It regulates at the transcriptional level all aspects of erythroid maturation and function, as revealed by gene knockout studies in mice and by genome-wide occupancies in erythroid cells. The GATA1 protein contains two zinc finger domains and an N-terminal transactivation domain. GATA1 translation results in the production of the full-length protein and of a shorter variant (GATA1s) lacking the N-terminal transactivation domain, which is functionally deficient in supporting erythropoiesis. GATA1 protein abundance is highly regulated in erythroid cells at different levels, including transcription, mRNA translation, posttranslational modifications, and protein degradation, in a differentiation-stage-specific manner. Maintaining high GATA1 protein levels is essential in the early stages of erythroid maturation, whereas downregulating GATA1 protein levels is a necessary step in terminal erythroid differentiation. The importance of maintaining proper GATA1 protein homeostasis in erythropoiesis is demonstrated by the fact that both GATA1 loss and its overexpression result in lethal anemia. Importantly, alterations in any of those GATA1 regulatory checkpoints have been recognized as an important cause of hematological disorders such as dyserythropoiesis (with or without thrombocytopenia), β-thalassemia, Diamond-Blackfan anemia, myelodysplasia, or leukemia. In this review, we provide an overview of the multilevel regulation of GATA1 protein homeostasis in erythropoiesis and of its deregulation in hematological disease.

METTL14 Inhibits Hematopoietic Stem/Progenitor Differentiation and Promotes Leukemogenesis via mRNA m6A Modification

N6-methyladenosine (m6A), the most prevalent internal modification in eukaryotic messenger RNAs (mRNAs), plays critical roles in many bioprocesses. However, its functions in normal and malignant hematopoiesis remain elusive. Here, we report that METTL14, a key component of the m6A methyltransferase complex, is highly expressed in normal hematopoietic stem/progenitor cells (HSPCs) and acute myeloid leukemia (AML) cells carrying t(11q23), t(15;17), or t(8;21) and is downregulated during myeloid differentiation. Silencing of METTL14 promotes terminal myeloid differentiation of normal HSPCs and AML cells and inhibits AML cell survival/proliferation. METTL14 is required for development and maintenance of AML and self-renewal of leukemia stem/initiation cells (LSCs/LICs). Mechanistically, METTL14 exerts its oncogenic role by regulating its mRNA targets (e.g., MYB and MYC) through m6A modification, while the protein itself is negatively regulated by SPI1. Collectively, our results reveal the SPI1-METTL14-MYB/MYC signaling axis in myelopoiesis and leukemogenesis and highlight the critical roles of METTL14 and m6A modification in normal and malignant hematopoiesis.

Interleukin-6 Signaling Pathway and Its Role in Kidney Disease: An Update

Interleukin-6 (IL-6) is a pleiotropic cytokine that not only regulates the immune and inflammatory response but also affects hematopoiesis, metabolism, and organ development. IL-6 can simultaneously elicit distinct or even contradictory physiopathological processes, which is likely discriminated by the cascades of signaling pathway, termed classic and trans-signaling. Besides playing several important physiological roles, dysregulated IL-6 has been demonstrated to underlie a number of autoimmune and inflammatory diseases, metabolic abnormalities, and malignancies. This review provides an overview of basic concept of IL-6 signaling pathway as well as the interplay between IL-6 and renal-resident cells, including podocytes, mesangial cells, endothelial cells, and tubular epithelial cells. Additionally, we summarize the roles of IL-6 in several renal diseases, such as IgA nephropathy, lupus nephritis, diabetic nephropathy, acute kidney injury, and chronic kidney disease.

TRAF3IP2 mediates atherosclerotic plaque development and vulnerability in ApoE(-/-) mice

BACKGROUND AND AIMS

Atherosclerosis is a major cause of heart attack and stroke. Inflammation plays a critical role in the development of atherosclerosis. Since the cytoplasmic adaptor molecule TRAF3IP2 (TRAF3-Interacting Protein 2) plays a causal role in various autoimmune and inflammatory diseases, we hypothesized that TRAF3IP2 mediates atherosclerotic plaque development.

METHODS

TRAF3IP2/ApoE double knockout (DKO) mice were generated by crossing TRAF3IP2(-/-) and ApoE(-/-) mice. ApoE(-/-) mice served as controls. Both DKO and control mice were fed a high-fat diet for 12 weeks. Plasma lipids were measured by ELISA, atherosclerosis by en face analysis of aorta and plaque cross-section measurements at the aortic valve region, plaque necrotic core area, collagen and smooth muscle cell (SMC) content by histomorphometry, and aortic gene expression by RT-qPCR.

RESULTS

The plasma lipoprotein profile was not altered by TRAF3IP2 gene deletion in ApoE(-/-) mice. While total aortic plaque area was decreased in DKO female, but not male mice, the plaque necrotic area was significantly decreased in DKO mice of both genders. Plaque collagen and SMC contents were increased significantly in both female and male DKO mice compared to respective controls. Aortic expression of proinflammatory cytokine (Tumor necrosis factor α, TNFα), chemokine (Chemokine (C-X-C motif) Ligand 1, CXCL1) and adhesion molecule (Vascular cell adhesion molecule 1, VCAM1; and Intercellular adhesion molecule 1, ICAM1) gene expression were decreased in both male and female DKO mice. In addition, the male DKO mice expressed markedly reduced levels of extracellular matrix (ECM)-related genes, including TIMP1 (Tissue inhibitor of metalloproteinase 1), RECK (Reversion-Inducing-Cysteine-Rich Protein with Kazal Motifs) and ADAM17 (A Disintegrin And Metalloproteinase 17).

CONCLUSIONS

TRAF3IP2 plays a causal role in atherosclerotic plaque development and vulnerability, possibly by inducing the expression of multiple proinflammatory mediators. TRAF3IP2 could be a potential therapeutic target in atherosclerotic vascular diseases.

Characterization of hematopoietic GATA transcription factor expression in mouse and human dendritic cells

Dendritic cells (DCs) are key initiators and regulators of the immune response. The development of the DC lineage and their subsets requires an orchestrated regulation of their transcriptional program. Gata1, a transcription factor expressed in several hematopoietic cell lineages, has been recently reported to be required for mouse DC development and function. In humans, GATA1 is involved in the lineage separation between monocyte-derived DCs and Langerhans cells (LC) and loss of GATA1 results in differentiation arrest at the monocyte stage. The hematopoietic GATA factors (i.e. Gata1, Gata2, Gata3) are known to regulate each other's expression and to function consecutively throughout lineage commitment (so-called GATA switch). In humans, mutations in GATA2 are causative of MonoMAC disease, a human immunodeficiency syndrome characterized by loss of DCs, monocytes, B and NK cells. However, additional data on the expression of hematopoietic GATA factors in the DC lineage is missing. In this study, we have characterized the expression of hematopoietic GATA factors in murine and human DCs and their expression dynamics upon TLR stimulation. We found that all hematopoietic GATA factors are expressed in DCs, but identified species-specific differences in the relative expression of each GATA factor, and how their expression fluctuates upon stimulation.

GATA1s induces hyperproliferation of eosinophil precursors in Down syndrome transient leukemia

Transient leukemia (TL) is evident in 5–10% of all neonates with Down syndrome (DS) and associated with N-terminal truncating GATA1-mutations (GATA1s). Here we report that TL cell clones generate abundant eosinophils in a substantial fraction of patients. Sorted eosinophils from patients with TL and eosinophilia carried the same GATA1s-mutation as sorted TL-blasts, consistent with their clonal origin. TL-blasts exhibited a genetic program characteristic of eosinophils and differentiated along the eosinophil lineage in vitro. Similarly, ectopic expression of Gata1s, but not Gata1, in wild-type CD34⁺-hematopoietic stem and progenitor cells induced hyperproliferation of eosinophil promyelocytes in vitro. While GATA1s retained the function of GATA1 to induce eosinophil genes by occupying their promoter regions, GATA1s was impaired in its ability to repress oncogenic MYC and the pro-proliferative E2F transcription network. ChIP-seq indicated reduced GATA1s occupancy at the MYC promoter. Knockdown of MYC, or the obligate E2F-cooperation partner DP1, rescued the GATA1s-induced hyperproliferative phenotype. In agreement, terminal eosinophil maturation was blocked in Gata1^Δe2 knockin mice, exclusively expressing Gata1s, leading to accumulation of eosinophil precursors in blood and bone marrow. These data suggest a direct relationship between the N-terminal truncating mutations of GATA1 and clonal eosinophilia in DS patients.

Angiotensin II induces apoptosis in intestinal epithelial cells through the AT2 receptor, GATA-6 and the Bax pathway

Angiotensin II (Ang II) has been shown to play an important role in cell apoptosis. However, the mechanisms of Ang-II-induced apoptosis in intestinal epithelial cells are not fully understood. GATA-6 is a zinc finger transcription factor expressed in the colorectal epithelium, which directs cell proliferation, differentiation and apoptosis. In the present study we investigated the underlying mechanism of which GATA-6 affects Ang-II induced apoptosis in intestinal epithelial cells. The in vitro intestinal epithelial cell apoptosis model was established by co-culturing Caco-2 cells with Ang II. Pretreatment with Angiotensin type 2 (AT2) receptor antagonist, PD123319, significantly reduced the expression of Bax and prevented the Caco-2 cells apoptosis induced by Ang II. In addition, Ang II up-regulated the expression of GATA-6. Interestingly, GATA-6 short hairpin RNA prevented Ang II-induced intestinal epithelial cells apoptosis and reduced the expression of Bax, but not Bcl-2. Taken together, the present study suggests that Angiotensin II promotes apoptosis in intestinal epithelial cells through GATA-6 and the Bax pathway in an AT2 receptor-dependent manner.

Cell signaling pathways for the regulation of GATA4 transcription factor: Implications for cell growth and apoptosis

GATA4 is a member of the GATA family of zinc finger transcription factor, which regulates gene transcription by binding to GATA elements. GATA4 was originally discovered as a regulator of cardiac development and subsequently identified as a major regulator of adult cardiac hypertrophy. GATA4 regulates gene expression of various genes, which are involved in cardiac development and cardiac hypertrophy and heart failure. In addition to the heart, GATA4 plays important roles in the reproductive system, gastrointestinal system, respiratory system and cancer. Positive and negative regulations of GATA4 therefore are important components of biologic functions. The activation of GATA4 occurs via various cell signaling events. Earlier studies have identified protein-protein interactions of GATA4 with other factors. The discovery of interactions of GATA4 with nuclear factor for activated T cells (NFAT) revealed the importance of calcium signaling in the activation of GATA4. GATA4 can also be phosphorylated by mitogen activated protein kinases and protein kinase A. Lysine modifications also occur on the GATA4 molecule including acetylation and sumoylation. Both reactive oxygen-dependent and -independent antioxidant-sensitive pathways for GATA4 activation have also been demonstrated. The GATA4 activity is also regulated by modulating the level of GATA4 expression via transcriptional as well as translational mechanisms. This work summarizes the current understanding of regulatory mechanisms for modulating GATA4 activity.

Dynamic regulation of Gata1 expression during the maturation of conventional dendritic cells

OBJECTIVES

To identify the regulatory sequences driving Gata1 expression in conventional dendritic cells (cDC).

MATERIALS AND METHODS

The number and expression levels of Gata1, Gata1-target genes and hypersensitive site (HS) 2 (the eosinophil-specific enhancer)-driven green fluorescent protein (GFP) reporter of cDCs from mice lacking HS1 (the erythroid/megakaryocytic-specific enhancer, Gata1(low) mutation) and wild-type littermates, as well as the response to lipopolysaccharide of ex vivo-generated wild-type and Gata1(low) DCs were investigated.

RESULTS

cDC maturation was associated with bell-shaped changes in Gata1 expression that peaked in cDCs precursors from blood. The Gata1(low) mutation did not affect Gata1 expression in cDC precursors and these cells expressed the HS2-driven reporter, indicating that Gata1 expression is HS2-driven in these cells. By contrast, the Gata1(low) mutation reduced Gata1 expression in mature cDCs and these cells did not express GFP, indicating that mature cDCs express Gata1 driven by HS1. In blood, the number of cDC precursors expressing CD40/CD80 was reduced in Gata1(low) mice, while CD40(pos)/CD80(pos) cDC precursors from wild-type mice expressed the HS2-GFP reporter, suggesting that Gata1 expression in these cells is both HS1- and HS2-driven. In addition, the antigen and accessory molecules presentation process induced by lipopolysaccharide in ex vivo-generated wild-type DC was associated with increased acetylated histone 4 occupancy of HS1, while ex vivo-generated Gata1(low) cDCs failed to respond to lipopolysaccharide, suggesting that HS1 activation is required for cDC maturation.

CONCLUSION

These results identify a dynamic pattern of Gata1 regulation that switches from an HS1 to an HS2-dependent phase during the maturation of cDCs associated with the antigen-presentation process in the blood.

Role of STAT3 and GATA-1 interactions in gamma-globin gene expression

OBJECTIVE

We previously demonstrated a silencing role for signal transducers and activators of transcription 3 (STAT3) in gamma-globin gene regulation in primary erythroid cells. Recently, GATA-1, a key transcription factor involved in hematopoietic cell development, was shown to directly inhibit STAT3 activity in vivo. Therefore, we completed studies to determine if interactions between these two factors influence gamma-globin gene expression.

MATERIALS AND METHODS

Chromatin immunoprecipitation assay was used to ascertain in vivo protein binding at the gamma-globin 5' untranslated region (5'UTR); protein-protein interactions were examined by coimmunoprecipitation analysis. In vitro protein-DNA binding were completed using surface plasmon resonance and electrophoretic mobility shift assay. Activity of a luciferase gamma-globin promoter reporter and levels of gamma-globin messenger RNA and fetal hemoglobin in stable K562 cell lines overexpressing STAT3 and GATA-1, were used to determine the influence of the STAT3/GATA-1 interaction on gamma-globin gene expression.

RESULTS

We observed interaction between STAT3 and GATA-1 in K562 and mouse erythroleukemia cells in vivo at the gamma-globin 5'UTR by chromatin immunoprecipitation assay. Electrophoretic mobility shift assay performed with a 41-base pair gamma-globin DNA probe (gamma41) demonstrated the presence of STAT3 and GATA-1 proteins in complexes assembled at the gamma-globin 5'UTR. A consensus STAT3 DNA probe inhibited GATA-1-binding in a concentration-dependent manner, and the converse was also true. Enforced STAT3 expression augmented its binding at the gamma-globin 5'UTR in vivo and silenced gamma-promoter-driven luciferase activity. Stable enforced STAT3 expression in K562 cells reduced endogenous gamma-globin messenger RNA level. This effect was reversed by GATA-1.

CONCLUSION

These data provide evidence that GATA-1 can reverse STAT3-mediated gamma-globin gene silencing in erythroid cells.

GATA4 is a direct transcriptional activator of cyclin D2 and Cdk4 and is required for cardiomyocyte proliferation in anterior heart field-derived myocardium

The anterior heart field (AHF) comprises a population of mesodermal progenitor cells that are added to the nascent linear heart to give rise to the majority of the right ventricle, interventricular septum, and outflow tract in mammals and birds. The zinc finger transcription factor GATA4 functions as an integral member of the cardiac transcription factor network in the derivatives of the AHF. In addition to its role in cardiac differentiation, GATA4 is also required for cardiomyocyte replication, although the transcriptional targets of GATA4 required for proliferation have not been previously identified. In the present study, we disrupted Gata4 function exclusively in the AHF and its derivatives. Gata4 AHF knockout mice die by embryonic day 13.5 and exhibit hypoplasia of the right ventricular myocardium and interventricular septum and display profound ventricular septal defects. Loss of Gata4 function in the AHF results in decreased myocyte proliferation in the right ventricle, and we identified numerous cell cycle genes that are dependent on Gata4 by microarray analysis. We show that GATA4 is required for cyclin D2, cyclin A2, and Cdk4 expression in the right ventricle and that the Cyclin D2 and Cdk4 promoters are bound and activated by GATA4 via multiple consensus GATA binding sites in each gene's proximal promoter. These findings establish Cyclin D2 and Cdk4 as direct transcriptional targets of GATA4 and support a model in which GATA4 controls cardiomyocyte proliferation by coordinately regulating numerous cell cycle genes.

Gata1 regulates dendritic-cell development and survival

Dendritic cells are key initiators and regulators of the immune response. Dendritic cell commitment and function require orchestrated regulation of transcription. Gata1 is a transcription factor expressed in several hematopoietic lineages. However, Gata1 function has not been explored in the monocytic or dendritic cell compartment. Here, we show that Gata1 is expressed in myeloid and plasmacytoid dendritic cells and that Gata1 ablation affects the survival of dendritic cells. Furthermore, lipopolysaccharide (LPS) stimulation of dendritic cells prompts Gata1 up-regulation, which is accompanied by increased levels of BclX and Ifng. Our findings show that Gata1 is a transcriptional regulator of dendritic cell differentiation and suggest that Gata1 is involved in the dendritic cell and macrophage lineage separation.

Imatinib as a potential antiresorptive therapy for bone disease

Osteoclasts (OCs) are large multinucleated cells derived from progenitor cells of the monocyte-macrophage lineage. Signal transduction via the macrophage–colony-stimulating factor (M-CSF) receptor, c-fms, is essential for OC formation. Since we have previously demonstrated inhibition of c-fms by imatinib, we examined the effect of imatinib on OC formation and activity. OC formation was not affected by concentrations of 1.0 μM imatinib and lower, but was reduced by 75% at 3.0 μM imatinib. In contrast, both the area of resorption and the number of resorption lacunae were reduced by 80% at 0.3 μM imatinib, and no resorption was observed at concentrations above 3.0 μM. A dose-dependent decrease in receptor activator of nuclear factor κB (RANK) expression was observed in OCs when cultured in the presence of imatinib, providing a mechanism for the decrease in OC function. In vivo analysis of the effect of imatinib on OC activity in adult mice following 8 weeks of imatinib treatment also demonstrated a decrease in OC activity. These results suggest that imatinib may have therapeutic value as an antiosteolytic agent in diseases such as osteoporosis, metastatic bone disease, and multiple myeloma.

Characterization of the differential expression of uncoupling protein 2 and ROS production in differentiated mouse macrophage-cells (Mm1) and the progenitor cells (M1)

The expression status of mitochondrial uncoupling protein 2 (UCP2) was investigated in undifferentiated mouse myeloid leukemia (M1) and its differentiated macrophage-like cells (Mm1). Mm1 cells have a high ability of phagocytosis along with significantly high levels of reactive oxygen species (ROS) production, UCP2 protein and manganese superoxide dismutase (Mn-SOD), in contrast to undifferentiated leukemia cells (M1). Mm1 cells expressed 10-fold more UCP2 protein compared with undifferentiated M1 cells, although the UCP2 mRNA levels in both cell types were similar. The higher expression of UCP2 in the Mm1 cells suggests a regulatory role of UCP2 in the ROS production. Furthermore, the transfection of UCP2-GFP-expression vector in Mm1 cells dissipated the mitochondrial membrane potential and reduced ROS production, which was shown by their direct visualization using MitoTracker Red CM-H2Xros. The macrophage gp91phox protein, a membrane catalytic component of the NADPH oxidase complex, was at a similar level in both of UCP2-GFP expressed and non-expressed Mm1 cells. These results suggest that the UCP2 protein of the undifferentiated cell is regulated at a quite low level and the higher UCP2 protein of the differentiated macrophages involves with the regulation of ROS production.

MAPK-mediated phosphorylation of GATA-1 promotes Bcl-XL expression and cell survival

In the interleukin 3-dependent hematopoietic cell line Ba/F3, inhibition of mitogen-activated protein kinase, a member of the MAPK/c-Jun N-terminal kinase/stress-activated protein kinase kinase family that plays an important role in cell growth and death control, rapidly leads to severe apoptosis. However, most of the antiapoptotic substrates of MAPK remain to be identified. Here we report that, upon interleukin-3 stimulation of Ba/F3 cells, the transcription factor GATA-1 is strongly phosphorylated at residue serine 26 by a MAPK-dependent pathway. Phosphorylation of GATA-1 increases GATA-1-mediated transcription of the E4bp4 survival gene without significantly changing the DNA-binding affinity of GATA-1. Further characterization of GATA-1 phosphorylation site mutants revealed that the antiapoptotic function of GATA-1 is strongly dependent upon its phosphorylation at the Ser-26 position and is probably mediated through its up-regulation of Bcl-X(L) expression. Taken together, our data demonstrate that MAPK-dependent GATA-1 phosphorylation is important for its transactivation of the E4bp4 gene, Bcl-X(L) expression and cell survival. Therefore, GATA-1 may represent a novel MAPK substrate that plays an essential role in a cytokine-mediated antiapoptotic response.

Morphogenesis of the right ventricle requires myocardial expression of Gata4

Mutations in developmental regulatory genes have been found to be responsible for some cases of congenital heart defects. One such regulatory gene is Gata4, a zinc finger transcription factor. In order to circumvent the early embryonic lethality of Gata4-null embryos and to investigate the role of myocardial Gata4 expression in cardiac development, we used Cre/loxP technology to conditionally delete Gata4 in the myocardium of mice at an early and a late time point in cardiac morphogenesis. Early deletion of Gata4 by Nkx2-5Cre resulted in hearts with striking myocardial thinning, absence of mesenchymal cells within the endocardial cushions, and selective hypoplasia of the RV. RV hypoplasia was associated with downregulation of Hand2, a transcription factor previously shown to regulate formation of the RV. Cardiomyocyte proliferation was reduced, with a greater degree of reduction in the RV than in the LV. Late deletion of Gata4 by Cre recombinase driven by the alpha myosin heavy chain promoter did not selectively affect RV development or generation of endocardial cushion mesenchyme but did result in marked myocardial thinning with decreased cardiomyocyte proliferation, as well as double-outlet RV. Our results demonstrate a general role of myocardial Gata4 in regulating cardiomyocyte proliferation and a specific, stage-dependent role in regulating the morphogenesis of the RV and the atrioventricular canal.

GATA4 is a dosage-sensitive regulator of cardiac morphogenesis

Normal heart development is orchestrated by a set of highly conserved transcription factors that includes GATA4, Nkx2-5, and Tbx5. Heterozygous mutation of each of these genes causes congenital heart disease in humans. In mouse models, haploinsufficiency for Nkx2-5 or Tbx5 resulted in an increased incidence of structural heart disease, confirming that normal heart development is sensitive to small changes in expression levels of Nkx2-5 and Tbx5. However, mice haploinsufficient for GATA4 have not been reported to have cardiac abnormalities. We generated two new GATA4 alleles, GATA4(H) and GATA4(flox). GATA4(flox/flox) embryos expressed 50% less GATA4 protein in the heart and survived normally. In contrast, GATA4(H/H) embryos expressed 70% less GATA4 protein in the heart and died between days 13.5 and 16.5 of gestation. These embryos had common atrioventricular canal (CAVC), double outlet right ventricle (DORV), hypoplastic ventricular myocardium, and normal coronary vasculature. Myocardial hypoplasia was associated with diminished cardiomyocyte proliferation. Hemodynamic measurements demonstrated that these embryos had normal systolic function, severe diastolic dysfunction, and atrioventricular regurgitation. Surprisingly, expression levels of the putative GATA4 target genes ANF, BNP, MEF2C, Nkx2-5, cyclin D2, and BMP4 were unchanged in mutant hearts, suggesting that GATA4 is not a dose-limiting regulator of the expression of these genes during later stages of embryonic cardiac development. These data demonstrate that multiple aspects of embryonic cardiac morphogenesis and function are exquisitely sensitive to small changes in GATA4 expression levels.

Myeloid Leukemia Factor 1 inhibits erythropoietin-induced differentiation, cell cycle exit and p27Kip1 accumulation

Myeloid leukemia factor 1 (MLF1) is a novel oncoprotein involved in translocations associated with acute myeloid leukemia (AML), especially erythroleukemias. In this study, we demonstrate that ectopic expression of Mlf1 prevented J2E erythroleukemic cells from undergoing biological and morphological maturation in response to erythropoietin (Epo). We show that Mlf1 inhibited Epo-induced cell cycle exit and suppressed a rise in the cell cycle inhibitor p27(Kip1). Unlike differentiating J2E cells, Mlf1-expressing cells did not downregulate Cul1 and Skp2, components of the ubiquitin E3 ligase complex SCF(Skp2) involved in the proteasomal degradation of p27(Kip1). In contrast, Mlf1 did not interfere with increases in p27(Kip1) and terminal differentiation initiated by thyroid hormone withdrawal from erythroid cells, or cytokine-stimulated maturation of myeloid cells. These data demonstrate that Mlf1 interferes with an Epo-responsive pathway involving p27(Kip1) accumulation, which inhibits cell cycle arrest essential for erythroid terminal differentiation.

Essential role of GATA-4 in cell survival and drug-induced cardiotoxicity

In recent years, significant progress has been made in understanding cardiomyocyte differentiation. However, little is known about the regulation of myocyte survival despite the fact that myocyte apoptosis is a leading cause of heart failure. Here we report that transcription factor GATA-4 is a survival factor for differentiated, postnatal cardiomyocytes and an upstream activator of the antiapoptotic gene Bcl-X. An early event in the cardiotoxic effect of the antitumor drug doxorubicin is GATA-4 depletion, which in turn causes cardiomyocyte apoptosis. Mouse heterozygotes for a null Gata4 allele have enhanced susceptibility to doxorubicin cardiotoxicity. Genetic or pharmacologic enhancement of GATA-4 prevents cardiomyocyte apoptosis and drug-induced cardiotoxicity. The results indicate that GATA-4 is an antiapoptotic factor required for the adaptive stress response of the adult heart. Modulation of survival/apoptosis genes by tissue-specific transcription factors may be a general paradigm that can be exploited effectively for cell-specific regulation of apoptosis in disease states.

Regulation of cardiac myocyte apoptosis by the GATA-4 transcription factor

Apoptosis of cardiac muscle cells plays important roles in the development of various heart diseases including myocardial infarction and anthracycline-induced cardiomyopathy. Understanding the regulatory mechanisms of cardiac myocyte apoptosis and survival is important for establishing therapeutic strategies against heart disease. Our recent experiments demonstrate that the GATA-4 transcription factor not only mediates cardiac hypertrophy, but also regulates apoptosis and survival of adult cardiac muscle cells. Apoptosis induced by anthracyclines is associated with decreased expression of GATA-4, while the restoration of GATA-4 levels via ectopic expression attenuated the apoptosis. Survival factors of cardiac myocytes such as hepatocyte growth factor and endothelin-1 activate GATA-4, and this signal transduction mechanism at least in part serves to protect the heart against oxidative stress.

Growth factor signaling for cardioprotection against oxidative stress-induced apoptosis

The heart is subjected to oxidative stress during various clinical situations, such as ischemia-reperfusion injury and anthracycline chemotherapy. The loss of cardiac myocytes is the major problem in heart failure; thus, it is important to protect cardiac myocytes against cell death. Various growth factors, including insulin like growth factor, hepatocyte growth factor, endothelin-1, fibroblast growth factor, and transforming growth factor, have been shown to protect the heart against oxidative stress. The mechanism of growth factor-mediated cardioprotection may involve the attenuation of cardiac myocyte apoptosis. The present article summarizes the current knowledge on the molecular mechanisms of growth factor-mediated antiapoptotic signaling in cardiac myocytes. Insulin-like growth factor-1 activates phosphatidylinositol 3' -kinase and extracellular signal-regulated kinase pathways. Recent data showed that GATA-4 might be an important mediator of cardiac myocyte survival by endothelin-1 and hepatocyte growth factor. These growth factors, as well as mediators of growth factor-signaling, may be useful in therapeutic strategies against oxidative stress-induced cardiac injury.

GATA-1-mediated proliferation arrest during erythroid maturation

Transcription factor GATA-1 is essential for erythroid and megakaryocytic maturation. GATA-1 mutations are associated with hematopoietic precursor proliferation and leukemogenesis, suggesting a role in cell cycle control. While numerous GATA-1 target genes specifying mature hematopoietic phenotypes have been identified, how GATA-1 regulates proliferation remains unknown. We used a complementation assay based on synchronous inducible rescue of GATA-1(-) erythroblasts to show that GATA-1 promotes both erythroid maturation and G(1) cell cycle arrest. Molecular studies combined with microarray transcriptome analysis revealed an extensive GATA-1-regulated program of cell cycle control in which numerous growth inhibitors were upregulated and mitogenic genes were repressed. GATA-1 inhibited expression of cyclin-dependent kinase (Cdk) 6 and cyclin D2 and induced the Cdk inhibitors p18(INK4C) and p27(Kip1) with associated inactivation of all G(1) Cdks. These effects were dependent on GATA-1-mediated repression of the c-myc (Myc) proto-oncogene. GATA-1 inhibited Myc expression within 3 h, and chromatin immunoprecipitation studies indicated that GATA-1 occupies the Myc promoter in vivo, suggesting a direct mechanism for gene repression. Surprisingly, enforced expression of Myc prevented GATA-1-induced cell cycle arrest but had minimal effects on erythroid maturation. Our results illustrate how GATA-1, a lineage-determining transcription factor, coordinates proliferation arrest with cellular maturation through distinct, interrelated genetic programs.

Activation of GATA-4 by serotonin in pulmonary artery smooth muscle cells

Serotonin (5-hydroxytryptamine (5-HT)) is a mitogen of pulmonary artery smooth muscle cells (PASMC) and plays an important role in the development of pulmonary hypertension. Signal transduction initiated by 5-HT involves serotonin transporter-dependent generation of reactive oxygen species and activation of the MEK-ERK pathway. However, the downstream transcriptional regulatory components have not been identified. In systemic smooth muscle cells, GATA-6 has been shown to regulate mitogenesis by driving cells into a quiescent state, and the down-regulation of GATA-6 induces mitogenesis. Thus, the present study tested the hypothesis that 5-HT induces mitogenesis of PASMC by down-regulating GATA-6. Quiescent bovine PASMC were treated with 5-HT, and the binding activity of nuclear extracts toward GATA DNA sequence was monitored. Surprisingly, PASMC express GATA-4, and 5-HT up-regulates the GATA DNA binding activity. Pretreatment of cells with inhibitors of serotonin transporter, reactive oxygen species, and MEK blocks GATA-4 activation by 5-HT. GATA-4 is not activated when the ERK phosphorylation site is mutated, indicating that 5-HT phosphorylates GATA-4 via the MEK/ERK pathway. GATA up-regulation is also induced by other mitogens of PASMC such as endothelin-1 and platelet-derived growth factor. Dominant negative mutants of GATA-4 suppress cyclin D2 expression and cell growth, indicating that GATA-4 activation regulates PASMC proliferation. Thus, GATA-4 mediates 5-HT-induced growth of PASMC and may be an important therapeutic target for the prevention of pulmonary hypertension.

Hepatocyte growth factor induces GATA-4 phosphorylation and cell survival in cardiac muscle cells

Hepatocyte growth factor (HGF) is released in response to myocardial infarction and may play a role in regulating cardiac remodeling. Recently, HGF was found to inhibit the apoptosis of cardiac muscle cells. Because GATA-4 can induce cell survival, the effects of HGF on GATA-4 activity were investigated. Treatment of HL-1 cells or primary adult rat cardiac myocytes with HGF, at concentrations that can be detected in the human serum after myocardial infarction, rapidly enhances GATA-4 DNA-binding activity. The enhanced DNA-binding activity is associated with the phosphorylation of GATA-4. HGF-induced phosphorylation and activation of GATA-4 is abolished by MEK inhibitors or the mutation of the ERK phosphorylation site (S105A), suggesting that HGF activates GATA-4 via MEK-ERK pathway-dependent phosphorylation. HGF enhances the expression of anti-apoptotic Bcl-x(L), and this is blocked by dominant negative mutants of MEK or GATA-4. Forced expression of wild-type GATA-4, but not the GATA-4 mutant (S105A) increases the expression of Bcl-x(L). Furthermore, expression of the GATA-4 mutant (S105A) suppresses HGF-mediated protection of cells against daunorubicin-induced apoptosis. These results demonstrate that HGF protects cardiac muscle cells against apoptosis via a signaling pathway involving MEK/ERK-dependent phosphorylation of GATA-4.

Anthracycline-induced suppression of GATA-4 transcription factor: implication in the regulation of cardiac myocyte apoptosis

Anthracyclines are effective cancer chemotherapeutic agents but can induce serious cardiotoxicity. Understanding the mechanism of cardiac damage by these agents will help in development of better therapeutic strategies against cancer. The GATA-4 transcription factor is an important regulator of cardiac muscle cells. The present study demonstrates that anthracyclines can down-regulate GATA-4 activity. Treatment of HL-1 cardiac muscle cells or isolated adult rat ventricular myocytes with anthracyclines such as daunorubicin and doxorubicin decreased the level of GATA-4 DNA-binding activity. The mechanism of decreased GATA-4 activity acts at the level of the GATA-4 gene, because anthracyclines caused significantly decreased levels of GATA-4 protein and mRNA. The rate of decline in GATA-4 transcript levels in the presence of actinomycin D was unaltered by anthracyclines, indicating that these agents may affect directly GATA-4 gene transcription. To determine whether decreased GATA-4 levels are functionally related to cardiac muscle cell death that can be induced by anthracyclines, the ability of ectopic GATA factors to rescue anthracycline-induced apoptosis was tested. Adenovirus-mediated expression of either GATA-4 or GATA-6 was sufficient to attenuate the incidence of apoptosis. Furthermore, suppression of GATA-4 DNA-binding activity by a dominant negative mutant of GATA-4 induced the apoptosis. These results suggest that the mechanism of anthracycline-induced cardiotoxicity may involve the down-regulation of GATA-4 and the induction of apoptosis.

Induction of immunoglobulin G1, interleukin-6 and interleukin-10 by Taenia crassiceps metacestode carbohydrates

T helper type 2 (Th2) -polarized immune responses are characteristically dominant in helminth infections. Two murine models that show a Th1 to Th2 polarization with infection progression are those of Schistosoma mansoni and Taenia crassiceps. In both, an early Th1 response is replaced by a late Th2 response. We report that the nucleic acid-, protein- and lipid-free carbohydrate fraction of T. crassiceps metacestodes (denoted T-CHO) possesses Th2-like immunomodulatory activity. Immunization of two strains of rats (Dark Agouti and Albino Oxford) and BALB/c mice with chicken albumin in the presence of T-CHO resulted in selective enhancement of immunoglobulin G1 (IgG1) antibodies, considered to be associated with Th2 responses in both rats and mice. Interleukin-6 (IL-6) followed by IL-10 were the dominant cytokines detected in in vitro cultures of mouse spleen cells stimulated with T-CHO. IL-4 and IL-5 were not detected in these culture supernates. Furthermore, Taenia carbohydrates were mitogenic to spleen cells, activated serine phosphorylation of proteins and up-regulated the expression of the anti-apoptotic protein, Bcl-2. When mouse spleen cells were cultured in the presence of Taenia carbohydrates, a concentration-dependent down-regulation of IL-2 and an overlapping up-regulation of IL-6 secretion were seen.

STAT3 down-regulates the expression of cyclin D during liver development

As the expression of cyclin D1 is induced during liver regeneration and also in hepatic tumor cells, cyclin D1 is likely to play an important role in the proliferation and transformation of hepatocytes. However, the role of cyclin D1 in liver development remains unknown. Here we show that the expression of D-type cyclins including cyclin D1, D2, and D3 is down-regulated along with liver development. In addition, oncostatin M (OSM), an interleukin-6 family cytokine, down-regulated the expression of cyclin D1 and D2 in a primary culture of fetal hepatocytes in which OSM induces hepatic differentiation. Ectopic expression of receptor mutants defective in the activation of either STAT3 or SHP-2/Ras indicated that the down-regulation of D1 and D2 cyclins by OSM was mediated by STAT3 but not by SHP-2/Ras. Consistently, expression of dominant negative STAT3 but not Ras relieved OSM-induced suppression of cyclin D expression. Activation of STAT3 in fetal hepatocytes of transgenic mice expressing the STAT3-estrogen receptor fusion protein by 4-hydroxytamoxifen resulted in the suppression of cyclin D1 and D2 expression. These results indicate that STAT3 activation is necessary and sufficient for down-regulation of D1 and D2 cyclins in fetal hepatocytes. Furthermore, STAT3-C, a constitutively active form of STAT3, suppressed transcription of the cyclin D1 promoter in fetal hepatocytes, whereas it activated the transcription in hepatic tumor cells, huH7 and HepG2. Thus, STAT3-mediated down-regulation of cyclin D expression is rather specific to fetal hepatocytes that are undergoing maturation processes including a reduction of their proliferation potential.

GATA factors are essential for transcription of the survival gene E4bp4 and the viability response of interleukin-3 in Ba/F3 hematopoietic cells

E4bp4, a member of the basic region/leucine zipper transcription factor superfamily, is up-regulated by the interleukin-3 (IL-3) signaling pathway and plays an important role in the anti-apoptotic response of IL-3. In this study, we demonstrated that E4bp4 is regulated by IL-3 mainly at the transcriptional level. Promoter analysis revealed that a GATA motif downstream of a major transcription initiation site is essential for E4bp4 expression in the IL-3-dependent Ba/F3 cell line. Gel shift assays demonstrated that both GATA-1 and GATA-2 proteins bind to the E4bp4 GATA site in vitro, and the chromatin immunoprecipitation assay further confirmed the in vivo binding of GATA-1 to the E4bp4 promoter. Overexpression of GATA-1 alone transactivates the E4bp4 reporter, whereas transactivation of the E4bp4 reporter by GATA-2 is dependent on the stimulation of IL-3. Last, we demonstrated that alteration of GATA-1 binding to the GATA site by stably overexpressing GATA-1 or a GATA-1 mutant containing only the DNA-binding domain not only modulates the expression of the E4bp4 gene but also influences apoptosis induced by IL-3 removal. Taken together, our results suggest that the GATA factors play an important role in transducing the survival signal of IL-3, and one of their cellular targets is E4bp4.

Molecular control of megakaryopoiesis and thrombopoiesis

Megakaryopoiesis and subsequent thrombopoiesis occur through complex biologic steps: megakaryocyte precursors that developed from hematopoietic stem cells initially proliferate, then differentiate into mature polyploid megakaryocytes, and finally release platelets. Although a number of growth factors can augment megakaryopoiesis in vitro, thrombopoietin is a physiologic and the most potent regulator of megakaryopoiesis in vitro and in vivo. Thrombopoietin induces the growth of megakaryocyte precursors through activation of multiple signaling cascades, including Ras/mitogen-activated protein kinase (MAPK), signal transducers and activators of transcription 5 (STAT5), phosphatidylinositol 3-kinase (PI3-K)/Akt, and protein kinase C, whereas it induces megakaryocytic maturation primarily through the Ras/MAPK pathway. During the maturation step, megakaryocytes undergo polyploidization characterized by repeated rounds of DNA replication without concomitant cell division. During these rounds of replication, cytokinesis is neglected because of the down-regulated expression of AIM-1, and DNA replication occurs through the increased expression of D-type cyclins. As for transcriptional regulation during megakaryopoiesis, GATA-1 plays a central role in the lineage commitment of hematopoietic stem cells toward erythroid/megakaryocytic lineage and subsequent maturation. p45 NF-E2 is essential for platelet release from terminally differentiated megakaryocytes. At present, mutations of GATA-1, AML1, and HOXA11 genes have been found in hereditary diseases accompanying thrombocytopenia among humans.

Cytokine control of developmental programs in normal hematopoiesis and leukemia

The establishment of a system for in vitro clonal development of hematopoietic cells made it possible to discover the cytokines that regulate hematopoiesis. These cytokines include colony stimulating factors and others, which interact in a network, and there is a cytokine cascade which couples growth and differentiation. A network allows considerable flexibility and a ready amplification of response to a particular stimulus. A network may also be necessary to stabilize the whole system. Cells called hematopoietic stem cells (HSC) can repopulate all hematopoietic lineages in lethally irradiated hosts, and under appropriate conditions give rise to neuronal, muscle, and epithelial cells. Granulocyte colony stimulating factor induces migration of both HSC and in vitro colony forming cells from the bone marrow to peripheral blood. Granulocyte colony stimulating factor is also used clinically to repair irradiation and chemotherapy associated suppression of normal hematopoiesis in cancer patients, and to stimulate normal granulocyte development in patients with infantile congenital agranulocytosis. It is suggested that there may also be appropriate conditions under which in vitro colony forming cells have a wider differentiation potential similar to that shown by HSC. An essential part of the developmental program is cytokine suppression of apoptosis by changing the balance in expression of apoptosis inducing and suppressing genes. Decreasing the level of cytokines that suppress therapeutic induction of apoptosis in malignant cells can improve cancer therapy. Cytokines and some other compounds can reprogram abnormal developmental programs in leukemia, so that the leukemic cells differentiate to mature non dividing cells, and this can also be used for therapy. There is considerable plasticity in the developmental programs of normal and malignant cells.

Molecular cloning and characterization of the human p19(INK4d) gene promoter

p19(INK4d), a member of the INK4 family of cyclin-dependent kinase (CDK) inhibitors, negatively regulates the cyclin D-CDK4/6 complexes, which promote G1/S transition by phosphorylating the retinoblastoma tumor-suppressor gene product. To investigate the mechanism of transcriptional regulation of the p19(INK4d) gene, we characterized the 5'-flanking region of the human p19(INK4d) gene. The cap-site hunting method revealed that the transcription starts at -16 nucleotide (nt) upstream of the initiation codon. The 5'-flanking region of the human p19(INK4d) gene was ligated to a luciferase reporter gene and possessed functional promoter activity. Luciferase assay with a series of truncated 5'-flanking regions indicated that the region from -81 to -2 nt could drive the transcription of the p19(INK4d) gene. Several Sp1 and activating protein 2 binding sites are located within the region from -81 to -2 nt. Mutation of the second Sp1 binding site from -33 to -25 nt decreased the promoter activity. Collectively, it was demonstrated that the human p19(INK4d) gene is under the control of TATA-less promoter and the Sp1 binding site is involved in the transcription.

Transcriptional regulation of hemopoiesis

The regulation of blood cell formation, or hemopoiesis, is central to the replenishment of mature effector cells of innate and acquired immune responses. These cells fulfil specific roles in the host defense against invading pathogens, and in the maintenance of homeostasis. The development of hemopoietic cells is under stringent control from extracellular and intracellular stimuli that result in the activation of specific downstream signaling cascades. Ultimately, all signal transduction pathways converge at the level of gene expression where positive and negative modulators of transcription interact to delineate the pattern of gene expression and the overall cellular hemopoietic response. Transcription factors, therefore, represent a nodal point of hemopoietic control through the integration of the various signaling pathways and subsequent modulation of the transcriptional machinery. Transcription factors can act both positively and negatively to regulate the expression of a wide range of hemopoiesis-relevant genes including growth factors and their receptors, other transcription factors, as well as various molecules important for the function of developing cells. The expression of these genes is dependent on the complex interactions between transcription factors, co-regulatory molecules, and specific binding sequences on the DNA. Recent advances in various vertebrate and invertebrate systems emphasize the importance of transcription factors for hemopoiesis control and the evolutionary conservation of several of such mechanisms. In this review we outline some of the key issues frequently identified in studies of the transcriptional regulation of hemopoietic gene expression. In teleosts, we expect that the characterization of several of these transcription factors and their regulatory mechanisms will complement recent advances in a number of fish systems where identification of cytokine and other hemopoiesis-relevant factors are currently under investigation.