Identification of the chemokine CCL28 as a growth and survival factor for human hematopoietic stem and progenitor cells

Clinical Aspects and Significance of β-Chemokines, γ-Chemokines, and δ-Chemokines in Molecular Cancer Processes in Acute Myeloid Leukemia (AML) and Myelodysplastic Neoplasms (MDS)

BACKGROUND/OBJECTIVES

Acute myeloid leukemia (AML) is a type of leukemia with a very poor prognosis. Consequently, this neoplasm is extensively researched to discover new therapeutic strategies. One area of investigation is the study of intracellular communication and the impact of the bone marrow microenvironment on AML cells, with chemokines being a key focus. The roles of β-chemokines, γ-chemokines, and δ-chemokines in AML processes have not yet been sufficiently characterized.

METHODS

This publication summarizes all available knowledge about these chemotactic cytokines in AML and myelodysplastic neoplasm (MDS) processes and presents potential therapeutic strategies to combat the disease. The significance of β-chemokines, γ-chemokines, and δ-chemokines is detailed, including CCL2 (MCP-1), CCL3 (MIP-1α), CCL5 (RANTES), CCL23, CCL28, and CX3CL1 (fractalkine). Additionally, the importance of atypical chemokine receptors in AML is discussed, specifically ACKR1, ACKR2, ACKR4, and CCRL2.

RESULTS/CONCLUSIONS

The focus is on the effects of these chemokines on AML cells, particularly their influence on proliferation and resistance to anti-leukemic drugs. Intercellular interactions with non-AML cells, such as mesenchymal stem cells (MSC), macrophages, and regulatory T cells (Treg), are also characterized. The clinical aspects of chemokines are thoroughly explained, including their effect on overall survival and the relationship between their blood levels and AML characteristics.

A De Novo Noncoding RARB Variant Associated with Complex Microphthalmia Alters a Putative Regulatory Element

Retinoic acid receptor beta (RARB) is a transcriptional regulator crucial for coordinating retinoic acid- (RA-) mediated morphogenic movements, cell growth, and differentiation during eye development. Loss- or gain-of-function RARB coding variants have been associated with microphthalmia, coloboma, and anterior segment defects. We identified a de novo variant c.157+1895G>A located within a conserved region (CR1) in the first intron of RARB in an individual with complex microphthalmia and significant global developmental delay. Based on the phenotypic overlap, we further investigated the possible effects of the variant on mRNA splicing and/or transcriptional regulation through in silico and functional studies. In silico analysis identified the possibility of alternative splicing, suggested by one out of three (HSF, SpliceAI, and MaxEntScan) splicing prediction programs, and a strong indication of regulatory function based on publicly available DNase hypersensitivity, histone modification, chromatin folding, and ChIP-seq data sets. Consistent with the predictions of SpliceAI and MaxEntScan, in vitro minigene assays showed no effect on RARB mRNA splicing. Evaluation of CR1 for a regulatory role using luciferase reporter assays in human lens epithelial cells demonstrated a significant increase in the activity of the RARB promoter in the presence of wild-type CR1. This activity was further significantly increased in the presence of CR1 carrying the c.157+1895G>A variant, suggesting that the variant may promote RARB overexpression in human cells. Induction of RARB overexpression in human lens epithelial cells resulted in increased cell proliferation and elevated expression of FOXC1, a known downstream target of RA signaling and a transcription factor whose down- and upregulation is associated with ocular phenotypes overlapping the RARB spectrum. These results support a regulatory role for the CR1 element and suggest that the de novo c.157+1895G>A variant affecting this region may alter the proper regulation of RARB and, as a result, its downstream genes, possibly leading to abnormal development.

An interactive resource of molecular signalling in the developing human haematopoietic stem cell niche

The emergence of definitive human haematopoietic stem cells (HSCs) from Carnegie Stage (CS) 14 to CS17 in the aorta-gonad-mesonephros (AGM) region is a tightly regulated process. Previously, we conducted spatial transcriptomic analysis of the human AGM region at the end of this period (CS16/CS17) and identified secreted factors involved in HSC development. Here, we extend our analysis to investigate the progression of dorso-ventral polarised signalling around the dorsal aorta over the entire period of HSC emergence. Our results reveal a dramatic increase in ventral signalling complexity from the CS13-CS14 transition, coinciding with the first appearance of definitive HSCs. We further observe stage-specific changes in signalling up to CS17, which may underpin the step-wise maturation of HSCs described in the mouse model. The data-rich resource is also presented in an online interface enabling in silico analysis of molecular interactions between spatially defined domains of the AGM region. This resource will be of particular interest for researchers studying mechanisms underlying human HSC development as well as those developing in vitro methods for the generation of clinically relevant HSCs from pluripotent stem cells.

Antibody-mediated depletion of CCR10+EphA3+ cells ameliorates fibrosis in IPF

Idiopathic pulmonary fibrosis (IPF) is characterized by aberrant repair that diminishes lung function via mechanisms that remain poorly understood. CC chemokine receptor (CCR10) and its ligand CCL28 were both elevated in IPF compared with normal donors. CCR10 was highly expressed by various cells from IPF lungs, most notably stage-specific embryonic antigen-4-positive mesenchymal progenitor cells (MPCs). In vitro, CCL28 promoted the proliferation of CCR10+ MPCs while CRISPR/Cas9-mediated targeting of CCR10 resulted in the death of MPCs. Following the intravenous injection of various cells from IPF lungs into immunodeficient (NOD/SCID-γ, NSG) mice, human CCR10+ cells initiated and maintained fibrosis in NSG mice. Eph receptor A3 (EphA3) was among the highest expressed receptor tyrosine kinases detected on IPF CCR10+ cells. Ifabotuzumab-targeted killing of EphA3+ cells significantly reduced the numbers of CCR10+ cells and ameliorated pulmonary fibrosis in humanized NSG mice. Thus, human CCR10+ cells promote pulmonary fibrosis, and EphA3 mAb-directed elimination of these cells inhibits lung fibrosis.

Early growth response 1 regulates hematopoietic support and proliferation in human primary bone marrow stromal cells

Human bone marrow stromal cells (BMSC) are key elements of the hematopoietic environment and they play a central role in bone and bone marrow physiology. However, how key stromal cell functions are regulated is largely unknown. We analyzed the role of the immediate early response transcription factor EGR1 as key stromal cell regulator and found that EGR1 was highly expressed in prospectively-isolated primary BMSC, down-regulated upon culture, and low in non-colony-forming CD45^neg stromal cells. Furthermore, EGR1 expression was lower in proliferative regenerating adult and fetal primary cells compared to adult steady-state BMSC. Overexpression of EGR1 in stromal cells induced potent hematopoietic stroma support as indicated by an increased production of transplantable CD34⁺CD90⁺ hematopoietic stem cells in expansion co-cultures. The improvement in bone marrow stroma support function was mediated by increased expression of hematopoietic supporting genes, such as VCAM1 and CCL28. Furthermore, EGR1 overexpression markedly decreased stromal cell proliferation whereas EGR1 knockdown caused the opposite effects. These findings thus show that EGR1 is a key stromal transcription factor with a dual role in regulating proliferation and hematopoietic stroma support function that is controlling a genetic program to co-ordinate the specific functions of BMSC in their different biological contexts.

CCR10/CCL27 crosstalk contributes to failure of proteasome-inhibitors in multiple myeloma

The bone marrow microenvironment plays a decisive role in multiple myeloma progression and drug resistance. Chemokines are soluble mediators of cell migration, proliferation and survival and essentially modulate tumor progression and drug resistance. Here we investigated bone marrow-derived chemokines of naive and therapy-refractory myeloma patients and discovered that high levels of the chemokine CCL27, known so far for its role in skin inflammatory processes, correlated with worse overall survival of the patients. In addition, chemokine levels were significantly higher in samples from patients who became refractory to bortezomib at first line treatment compared to resistance at later treatment lines.

In vitro as well as in an in vivo model we could show that CCL27 triggers bortezomib-resistance of myeloma cells. This effect was strictly dependent on the expression of the respective receptor, CCR10, on stroma cells and involved the modulation of IL-10 expression, activation of myeloma survival pathways, and modulation of proteasomal activity. Drug resistance could be totally reversed by blocking CCR10 by siRNA as well as blocking IL-10 and its receptor.

From our data we suggest that blocking the CCR10/CCL27/IL-10 myeloma-stroma crosstalk is a novel therapeutic target that could be especially relevant in early refractory myeloma patients.

Interleukin 4 induces apoptosis of acute myeloid leukemia cells in a Stat6-dependent manner

Cytokines provide signals that regulate immature normal and acute myeloid leukemia (AML) cells in the bone marrow microenvironment. We here identify interleukin 4 (IL4) as a selective inhibitor of AML cell growth and survival in a cytokine screen using fluorescently labeled AML cells. RNA-sequencing of the AML cells revealed an IL4-induced upregulation of Stat6 target genes and enrichment of apoptosis-related gene expression signatures. Consistent with these findings, we found that IL4 stimulation of AML cells induced Stat6 phosphorylation and that disruption of Stat6 using CRISPR/Cas9-genetic engineering rendered cells partially resistant to IL4-induced apoptosis. To evaluate whether IL4 inhibits AML cells in vivo, we expressed IL4 ectopically in AML cells transplanted into mice and also injected IL4 into leukemic mice; both strategies resulted in the suppression of the leukemia cell burden and increased survival. Notably, IL4 exposure caused reduced growth and survival of primary AML CD34⁺CD38^- patient cells from several genetic subtypes of AML, whereas normal stem and progenitor cells were less affected. The IL4-induced apoptosis of AML cells was linked to Caspase-3 activation. Our results demonstrate that IL4 selectively induces apoptosis of AML cells in a Stat6-dependent manner-findings that may translate into new therapeutic opportunities in AML.

CCL28 promotes breast cancer growth and metastasis through MAPK-mediated cellular anti-apoptosis and pro-metastasis

Breast cancer is one of the most commonly diagnosed cancers worldwide and the second leading cause of cancer-related deaths among females. CCL28 (mucosa-associated epithelial chemokine, MEC), a CC subfamily chemokine, has been well studied in the process of inflammation, and recently increasing evidence indicates that CCL28 is related to tumor progression. However, little is known concerning its function in breast cancer. In the present study, we generated a CCL28-overexpressing breast cancer cell line MDA-MB-231HM/CCL28 from parental MDA-MB-231HM cells. We found that overexpression of CCL28 promoted cell proliferation and tumor formation, and also enhanced migration, invasion and metastasis both in vitro and in vivo. Mechanistic studies revealed that CCL28 mediated intracellular activation of the mitogen-activated protein kinase (MAPK) signaling pathway to promote breast cancer cell proliferation and metastasis by upregulating anti-apoptotic protein Bcl-2 and suppressing cell adhesion protein β-catenin. However, overexpression of CCL28 did not influence the expression of metastasis-related protein matrix metalloproteinase MMP2 and MMP9 and VEGF. Tissue sample analysis from animal models also indicated that overexpression of CCL28 was associated with enhanced pERK expression and reduced β-catenin expression in breast carcinomas. Thus, our results show for the first time that CCL28 contributes to breast cancer progression through the ERK/MAPK-mediated anti-apoptotic and metastatic signaling pathway. Antagonists of CCL28 and the MAPK signaling pathway may be used synergistically to treat breast cancer patients.

Hypoxia-induced CCL28 promotes recruitment of regulatory T cells and tumor growth in liver cancer

Tumor cells craft microenvironment to overcome growth disadvantages and adjust to escape the immunosurveillance during tumorigenesis and metastasis. The evolving adaption to the changing microenvironment is exemplified by the development of strategies to deal with hypoxia resulted from fast proliferation of the tumor cells. In this study, we found that hypoxia hepatocellular carcinoma (HCC) cells recruited Regulatory T cells (Tregs) and expressed more Chemokine (C-C motif) ligand 28 (CCL28). Deletion of CCL28 inhibited Treg recruitment. Furthermore, overexpression of CCL28 promoted tumor growth and Treg infiltration in vivo. Enhanced angiogenesis and VEGF expression was also observed. Moreover, inhibition of HIF1α reversed hypoxia-induced CCL28 upregulation. Taken together, our results demonstrate that HCC recruits Tregs to promote angiogenesis under hypoxic condition by upregulating CCL28 expression. These findings establish a link between Tregs and hypoxia in HCC growth and may provide a new potential therapeutic target for treating HCC.

Large Scale Gene Expression Meta-Analysis Reveals Tissue-Specific, Sex-Biased Gene Expression in Humans

The severity and prevalence of many diseases are known to differ between the sexes. Organ specific sex-biased gene expression may underpin these and other sexually dimorphic traits. To further our understanding of sex differences in transcriptional regulation, we performed meta-analyses of sex biased gene expression in multiple human tissues. We analyzed 22 publicly available human gene expression microarray data sets including over 2500 samples from 15 different tissues and 9 different organs. Briefly, by using an inverse-variance method we determined the effect size difference of gene expression between males and females. We found the greatest sex differences in gene expression in the brain, specifically in the anterior cingulate cortex, (1818 genes), followed by the heart (375 genes), kidney (224 genes), colon (218 genes), and thyroid (163 genes). More interestingly, we found different parts of the brain with varying numbers and identity of sex-biased genes, indicating that specific cortical regions may influence sexually dimorphic traits. The majority of sex-biased genes in other tissues such as the bladder, liver, lungs, and pancreas were on the sex chromosomes or involved in sex hormone production. On average in each tissue, 32% of autosomal genes that were expressed in a sex-biased fashion contained androgen or estrogen hormone response elements. Interestingly, across all tissues, we found approximately two-thirds of autosomal genes that were sex-biased were not under direct influence of sex hormones. To our knowledge this is the largest analysis of sex-biased gene expression in human tissues to date. We identified many sex-biased genes that were not under the direct influence of sex chromosome genes or sex hormones. These may provide targets for future development of sex-specific treatments for diseases.

Genome-wide placental DNA methylation analysis of severely growth-discordant monochorionic twins reveals novel epigenetic targets for intrauterine growth restriction

BACKGROUND

Intrauterine growth restriction (IUGR), which refers to reduced fetal growth in the context of placental insufficiency, is etiologically heterogeneous. IUGR is associated not only with perinatal morbidity and mortality but also with adult-onset disorders, such as cardiovascular disease and diabetes, posing a major health burden. Placental epigenetic dysregulation has been proposed as one mechanism that causes IUGR; however, the spectrum of epigenetic pathophysiological mechanisms leading to IUGR remains to be elucidated. Monozygotic monochorionic twins are particularly affected by IUGR, in the setting of severe discordant growth. Because monozygotic twins have the same genotype at conception and a shared maternal environment, they provide an ideal model system for studying epigenetic dysregulation of the placenta.

RESULTS

We compared genome-wide placental DNA methylation patterns of severely growth-discordant twins to identify novel candidate genes for IUGR. Snap-frozen placental samples for eight severely growth-discordant monozygotic monochorionic twin pairs were obtained at delivery from each twin. A high-resolution DNA methylation array platform was used to identify methylation differences between IUGR and normal twins. Our analysis revealed differentially methylated regions in the promoters of eight genes: DECR1, ZNF300, DNAJA4, CCL28, LEPR, HSPA1A/L, GSTO1, and GNE. The largest methylation differences between the two groups were in the promoters of DECR1 and ZNF300. The significance of these group differences was independently validated by bisulfite pyrosequencing, implicating aberrations in fatty acid beta oxidation and transcriptional regulation, respectively. Further analysis of the array data identified methylation changes most prominently affecting the Wnt and cadherin pathways in the IUGR cohort.

CONCLUSIONS

Our results suggest that IUGR in monozygotic twins is associated with impairments in lipid metabolism and transcriptional regulation as well as cadherin and Wnt signaling. We show that monozygotic monochorionic twins discordant for growth provide a useful model to study one type of the epigenetic placental dysregulation that drives IUGR.

A Subset of Patients with Acute Myeloid Leukemia Has Leukemia Cells Characterized by Chemokine Responsiveness and Altered Expression of Transcriptional as well as Angiogenic Regulators

Acute myeloid leukemia (AML) is an aggressive and heterogeneous bone marrow malignancy, the only curative treatment being intensive chemotherapy eventually in combination with allogeneic stem cell transplantation. Both the AML and their neighboring stromal cells show constitutive chemokine release, but chemokines seem to function as regulators of AML cell proliferation only for a subset of patients. Chemokine targeting is therefore considered not only for immunosuppression in allotransplanted patients but also as a possible antileukemic strategy in combination with intensive chemotherapy or as part of disease-stabilizing treatment at least for the subset of patients with chemokine-responsive AML cells. In this study, we characterized more in detail the leukemia cell phenotype of the chemokine-responsive patients. We investigated primary AML cells derived from 79 unselected patients. Standardized in vitro suspension cultures were used to investigate AML cell proliferation, and global gene expression profiles were compared for chemokine responders and non-responders identified through the proliferation assays. CCL28-induced growth modulation was used as marker of chemokine responsiveness, and 38 patients were then classified as chemokine-responsive. The effects of exogenous CCL28 (growth inhibition/enhancement/no effect) thus differed among patients and was also dependent on the presence of exogenous hematopoietic growth factors as well as constitutive AML cell cytokine release. The effect of CCR1 inhibition in the presence of chemokine-secreting mesenchymal stem cells also differed among patients. Chemokine-responsive AML cells showed altered expression of genes important for (i) epigenetic transcriptional regulation, particularly lysine acetylation; (ii) helicase activity, especially DExD/H RNA helicases; and (iii) angioregulatory proteins important for integrin binding. Thus, chemokine responsiveness is part of a complex AML cell phenotype with regard to extracellular communication and transcriptional regulation. Chemokine targeting in chemokine-responsive patients may thereby alter AML cell trafficking and increase their susceptibility toward antileukemic treatment, e.g., conventional chemotherapy or targeting of other phenotypic characteristics of the chemokine-responsive cells.

Bovine CCL28 Mediates Chemotaxis via CCR10 and Demonstrates Direct Antimicrobial Activity against Mastitis Causing Bacteria

In addition to the well characterized function of chemokines in mediating the homing and accumulation of leukocytes to tissues, some chemokines also exhibit potent antimicrobial activity. Little is known of the potential role of chemokines in bovine mammary gland health and disease. The chemokine CCL28 has previously been shown to play a key role in the homing and accumulation of IgA antibody secreting cells to the lactating murine mammary gland. CCL28 has also been shown to act as an antimicrobial peptide with activity demonstrated against a wide range of pathogens including bacteria, fungi and protozoans. Here we describe the cloning and function of bovine CCL28 and document the concentration of this chemokine in bovine milk. Bovine CCL28 was shown to mediate cellular chemotaxis via the CCR10 chemokine receptor and exhibited antimicrobial activity against a variety of bovine mastitis causing organisms. The concentration of bovine CCL28 in milk was found to be highly correlated with the lactation cycle. Highest concentrations of CCL28 were observed soon after parturition, with levels decreasing over time. These results suggest a potential role for CCL28 in the prevention/resolution of bovine mastitis.

The Genetic Landscape of Hematopoietic Stem Cell Frequency in Mice

Prior efforts to identify regulators of hematopoietic stem cell physiology have relied mainly on candidate gene approaches with genetically modified mice. Here we used a genome-wide association study (GWAS) strategy with the hybrid mouse diversity panel to identify the genetic determinants of hematopoietic stem/progenitor cell (HSPC) frequency. Among 108 strains, we observed ∼120- to 300-fold variation in three HSPC populations. A GWAS analysis identified several loci that were significantly associated with HSPC frequency, including a locus on chromosome 5 harboring the homeodomain-only protein gene (Hopx). Hopx previously had been implicated in cardiac development but was not known to influence HSPC biology. Analysis of the HSPC pool in Hopx^−/− mice demonstrated significantly reduced cell frequencies and impaired engraftment in competitive repopulation assays, thus providing functional validation of this positional candidate gene. These results demonstrate the power of GWAS in mice to identify genetic determinants of the hematopoietic system.

•

Genetic variation across mouse strains influences hematopoietic stem cell frequency

•

This variation can be exploited for genome-wide association studies

•

Hopx is a regulator of hematopoietic stem/progenitor cell function

•

This approach can be used to identify genetic determinants of other stem cell systems

Progress and challenges in generating functional hematopoietic stem/progenitor cells from human pluripotent stem cells

The generation of hematopoietic stem cells (HSCs) from human pluripotent stem cells (hPSCs) in vitro holds great potential for providing alternative sources of donor cells for clinical HSC transplantation. However, the low efficiency of current protocols for generating blood lineages and the dysfunction identified in hPSC-derived hematopoietic cells limit their use for full hematopoietic reconstitution in clinics. This review outlines the current understanding of in vitro hematopoietic differentiation from hPSCs, emphasizes the intrinsic and extrinsic molecular mechanisms that are attributed to the aberrant phenotype and function in hPSC-derived hematopoietic cells, pinpoints the current challenges to develop the truly functional HSCs from hPSCs for clinical applications and explores their potential solutions.

Plasma CC-chemokine ligand 28 level is correlated with hematopoietic stem cells in human cord blood

BACKGROUND

CC-chemokine ligand 28 (CCL28) was previously identified as a novel growth factor in vitro for hematopoietic stem cells (HSCs) from cord blood (CB). However, there is no report on the relationship between CCL28 and HSCs in a human body.

STUDY DESIGN AND METHODS

To reveal the effect of CCL28 on hematopoietic cells in human CB at birth, we measured CCL28 in frozen CB plasma, which was preserved as a reference sample for cryopreserved CB units for HSC transplantation. We also evaluated the correlation of CCL28 level with CB components.

RESULTS

A total of 81 cryopreserved nonconforming CB units for transplantation were selected. The level of CCL28 was 2540 ± 377 pg/mL. The CCL28 levels correlated with the number of CD34+ cells (r = 0.222, p = 0.047) and white blood cells (r = 0.254, p = 0.022) in the CB units. The CCL28 levels also correlated with hemoglobin levels (r = 0.221, p = 0.048) in fresh CB.

CONCLUSION

This finding of positive correlation between CCL28 level and CD34+ cell numbers in vivo, together with the previous report that CCL28 influences the proliferation of hematopoietic cells in CB in vitro, may give a clue for better understanding the variability in HSC content in CB that is cryopreserved for HSC transplantation.

Humanized mice as a model to study human hematopoietic stem cell transplantation

Hematopoietic stem cell (HSC) transplantation has the potential to treat a variety of human diseases, including genetic deficiencies, immune disorders, and to restore immunity following cancer treatment. However, there are several obstacles that prevent effective HSC transplantation in humans. These include finding a matched donor, having a sufficient number of cells for the transplant, and the potency of the cells in the transplant. Ethical issues prevent effective research in humans that could provide insight into ways to overcome these obstacles. Highly immunodeficient mice can be transplanted with human HSCs and this process is accompanied by HSC homing to the murine bone marrow. This is followed by stem cell expansion, multilineage hematopoiesis, long-term engraftment, and functional human antibody and cellular immune responses. As such, humanized mice serve as a model for human HSC transplantation. A variety of conditions have been analyzed for their impact on HSC transplantation to produce humanized mice, including the type and source of cells used in the transplant, the number of cells transplanted, the expansion of cells with various protocols, and the route of introduction of cells into the mouse. In this review, we summarize what has been learned about HSC transplantation using humanized mice as a recipient model and we comment on how these models may be useful to future preclinical research to determine more effective ways to expand HSCs and to determine their repopulating potential in vivo.