Regulation of Hematopoiesis and Hematological Disease by TGF-β Family Signaling Molecules

Repression of SMAD3 by STAT3 and c-Ski induces conventional dendritic cell differentiation

A pleiotropic immunoregulatory cytokine, TGF-β, signals via the receptor-regulated SMADs: SMAD2 and SMAD3, which are constitutively expressed in normal cells. Here, we show that selective repression of SMAD3 induces cDC differentiation from the CD115+ common DC progenitor (CDP). SMAD3 was expressed in haematopoietic cells including the macrophage DC progenitor. However, SMAD3 was specifically down-regulated in CD115+ CDPs, SiglecH- pre-DCs, and cDCs, whereas SMAD2 remained constitutive. SMAD3-deficient mice showed a significant increase in cDCs, SiglecH- pre-DCs, and CD115+ CDPs compared with the littermate control. SMAD3 repressed the mRNA expression of FLT3 and the cDC-related genes: IRF4 and ID2. We found that one of the SMAD transcriptional corepressors, c-SKI, cooperated with phosphorylated STAT3 at Y705 and S727 to repress the transcription of SMAD3 to induce cDC differentiation. These data indicate that STAT3 and c-Ski induce cDC differentiation by repressing SMAD3: the repressor of the cDC-related genes during the developmental stage between the macrophage DC progenitor and CD115+ CDP.

Biology of Exfoliation of Plasma Membrane-Derived Vesicles and the Radiation Response: Historical Background, Applications in Biodosimetry and Cell-Free Therapeutics, and Quantal Mechanisms for Their Release and Function with Implications for Space Travel

This historical review of extracellular vesicles in the setting of exposure to ionizing radiation (IR) traces our understanding of how vesicles were initially examined and reported in the literature in the late 1970s (for secreted exosomes) and early 1980s (for plasma membrane-derived, exfoliated vesicles) to where we are now and where we may be headed in the next decade. An emphasis is placed on biophysical properties of extracellular vesicles, energy consumption and the role of vesiculation as an essential component of membrane turnover. The impact of intercellular signal trafficking by vesicle surface and intra-vesicular lipids, proteins, nucleic acids and metabolites is reviewed in the context of biomarkers for estimating individual radiation dose after exposure to radiation, pathogenesis of disease and development of cell-free therapeutics. Since vesicles express both growth stimulatory and inhibitory molecules, a hypothesis is proposed to consider superposition in a shared space and entanglement of molecules by energy sources that are external to human cells. Implications of this approach for travel in deep space are briefly discussed in the context of clinical disorders that have been observed after space travel.

SPAG6 regulates cell proliferation and apoptosis via TGF-β/Smad signal pathway in adult B-cell acute lymphoblastic leukemia

Adult B-cell acute lymphoblastic leukemia (B-ALL) prognosis remains unsatisfactory, and searching for new therapeutic targets is crucial for improving patient prognosis. Sperm-associated antigen 6 (SPAG6), a member of the cancer-testis antigen family, plays an important role in tumors, especially hematologic tumors; however, it is unknown whether SPAG6 plays a role in adult B-ALL. In this study, we demonstrated for the first time that SPAG6 expression was up-regulated in the bone marrow of adult B-ALL patients compared to healthy donors, and expression was significantly reduced in patients who achieved complete remission (CR) after treatment. In addition, patients with high SPAG6 expression were older (≥ 35 years; P = 0.015), had elevated white blood cell counts (WBC > 30 × 109/L; P = 0.021), and a low rate of CR (P = 0.036). We explored the SPAG6 effect on cell function by lentiviral transfection of adult B-ALL cell lines BALL-1 and NALM-6, and discovered that knocking down SPAG6 significantly inhibited cell proliferation and promoted apoptosis. We identified that SPAG6 knockdown might regulate cell proliferation and apoptosis via the transforming growth factor-β (TGF-β)/Smad signaling pathway.

TGF-β signaling in health and disease

The TGF-β regulatory system plays crucial roles in the preservation of organismal integrity. TGF-β signaling controls metazoan embryo development, tissue homeostasis, and injury repair through coordinated effects on cell proliferation, phenotypic plasticity, migration, metabolic adaptation, and immune surveillance of multiple cell types in shared ecosystems. Defects of TGF-β signaling, particularly in epithelial cells, tissue fibroblasts, and immune cells, disrupt immune tolerance, promote inflammation, underlie the pathogenesis of fibrosis and cancer, and contribute to the resistance of these diseases to treatment. Here, we review how TGF-β coordinates multicellular response programs in health and disease and how this knowledge can be leveraged to develop treatments for diseases of the TGF-β system.

Predictive nonlinear modeling of malignant myelopoiesis and tyrosine kinase inhibitor therapy

Chronic myeloid leukemia (CML) is a blood cancer characterized by dysregulated production of maturing myeloid cells driven by the product of the Philadelphia chromosome, the BCR-ABL1 tyrosine kinase. Tyrosine kinase inhibitors (TKIs) have proved effective in treating CML, but there is still a cohort of patients who do not respond to TKI therapy even in the absence of mutations in the BCR-ABL1 kinase domain that mediate drug resistance. To discover novel strategies to improve TKI therapy in CML, we developed a nonlinear mathematical model of CML hematopoiesis that incorporates feedback control and lineage branching. Cell-cell interactions were constrained using an automated model selection method together with previous observations and new in vivo data from a chimeric BCR-ABL1 transgenic mouse model of CML. The resulting quantitative model captures the dynamics of normal and CML cells at various stages of the disease and exhibits variable responses to TKI treatment, consistent with those of CML patients. The model predicts that an increase in the proportion of CML stem cells in the bone marrow would decrease the tendency of the disease to respond to TKI therapy, in concordance with clinical data and confirmed experimentally in mice. The model further suggests that, under our assumed similarities between normal and leukemic cells, a key predictor of refractory response to TKI treatment is an increased maximum probability of self-renewal of normal hematopoietic stem cells. We use these insights to develop a clinical prognostic criterion to predict the efficacy of TKI treatment and design strategies to improve treatment response. The model predicts that stimulating the differentiation of leukemic stem cells while applying TKI therapy can significantly improve treatment outcomes.

Imatinib blocks tyrosine phosphorylation of Smad4 and restores TGF-β growth-suppressive signaling in BCR-ABL1-positive leukemia

Loss of TGF-β-mediated growth suppression is a major contributor to the development of cancers, best exemplified by loss-of-function mutations in genes encoding components of the TGF-β signaling pathway in colorectal and pancreatic cancers. Alternatively, gain-of-function oncogene mutations can also disrupt antiproliferative TGF-β signaling. However, the molecular mechanisms underlying oncogene-induced modulation of TGF-β signaling have not been extensively investigated. Here, we show that the oncogenic BCR-ABL1 of chronic myelogenous leukemia (CML) and the cellular ABL1 tyrosine kinases phosphorylate and inactivate Smad4 to block antiproliferative TGF-β signaling. Mechanistically, phosphorylation of Smad4 at Tyr195, Tyr301, and Tyr322 in the linker region interferes with its binding to the transcription co-activator p300/CBP, thereby blocking the ability of Smad4 to activate the expression of cyclin-dependent kinase (CDK) inhibitors and induce cell cycle arrest. In contrast, the inhibition of BCR-ABL1 kinase with Imatinib prevented Smad4 tyrosine phosphorylation and re-sensitized CML cells to TGF-β-induced antiproliferative and pro-apoptotic responses. Furthermore, expression of phosphorylation-site-mutated Y195F/Y301F/Y322F mutant of Smad4 in Smad4-null CML cells enhanced antiproliferative responses to TGF-β, whereas the phosphorylation-mimicking Y195E/Y301E/Y322E mutant interfered with TGF-β signaling and enhanced the in vivo growth of CML cells. These findings demonstrate the direct role of BCR-ABL1 tyrosine kinase in suppressing TGF-β signaling in CML and explain how Imatinib-targeted therapy restored beneficial TGF-β anti-growth responses.

The role of erythrocytes and erythroid progenitor cells in tumors

In the current research context of precision treatment of malignant tumors, the advantages of immunotherapy are unmatched by conventional antitumor therapy, which can prolong progression-free survival and overall survival. The search for new targets and novel combination therapies can improve the efficacy of immunotherapy and reduce adverse effects. Since current research targets for immunotherapy mainly focus on lymphocytes, little research has been done on erythrocytes. Nucleated erythroid precursor stem cells have been discovered to play an essential role in tumor progression. Researchers are exploring new targets and therapeutic approaches for immunotherapy from the perspective of erythroid progenitor cells (EPCs). Recent studies have shown that different subtypes of EPCs have specific surface markers and distinct biological roles in tumor immunity. CD45⁺ EPCs are potent myeloid-derived suppressor cell-like immunosuppressants that reduce the patient's antitumor immune response. CD45^- EPCs promote tumor invasion and metastasis by secreting artemin. A specific type of EPC also promotes angiogenesis and provides radiation protection. Therefore, EPCs may be involved in tumor growth, infiltration, and metastasis. It may also be an important cause of anti-angiogenesis and immunotherapy resistance. This review summarizes recent research advances in erythropoiesis, EPC features, and their impacts and processes on tumors.

New insight into GARP striking role in cancer progression: application for cancer therapy

T regulatory cells play a crucial role in antitumor immunity suppression. Glycoprotein-A repetitions predominant (GARP), transmembrane cell surface marker, is mostly expressed on Tregs and mediates intracellular organization of transforming growth factor-beta (TGF-β). The physiological role of GARP is immune system homeostasis, while it may cause tumor development by upregulating TGF-β secretion. Despite the vast application of anti- programmed cell death protein-1 (PD-1)/programmed death-ligand 1 (PD-L1) and anti-cytotoxic T-lymphocyte Antigen-4 (CTLA-4) antibodies in immunotherapy, anti-GARP antibodies have the advantage of better response in patients who has resistance to anti-PD-1/PD-L1. Furthermore, simultaneous administration of anti-GARP antibody and anti-PD-1/PD-L1 antibody is much more effective than anti-PD-1/PD-L1 alone. It is worth mentioning that the GARP-mTGF-β complex is more potent than secretory TGF-β to induce T helper 17 cells differentiation in HIV + patients. On the other hand, TGF-β is an effective cytokine in cancer development, and some microRNAs could control its secretion by regulating GARP. In the present review, some information is provided about the undeniable role of GARP in cancer progression and its probable importance as a novel prognostic biomarker. Anti-GARP antibodies are also suggested for cancer immunotherapy.

Directional capacity of human mesenchymal stem cells to support hematopoietic stem cell proliferation in vitro

OBJECTIVES

Hematopoietic stem cells (HSCs) reside in a specialised microenvironment in the bone marrow, which is majorly composed of mesenchymal stem cells (MSCs) and its' derivatives. This study aimed to investigate the regulatory role of MSCs to decipher the cellular and humoral communications on HSCs' proliferation, self-renewal, and differentiation at the transcriptomic level.

MATERIALS AND METHODS

Microarray assay was employed to analyse the gene expression profile of HSCs that imparted by MSCs during co-culture.

RESULTS

The proliferation of human umbilical cord blood-derived HSCs (hUC-HSCs) markedly propagated when MSCs were used as the feeder layer, without disturbing the undifferentiated state of HSCs, and reduced the cell death of HSCs. Upon co-culture with MSCs, the global microarray analysis of HSCs disclosed 712 differentially expressed genes (DEGs) (561 up-regulated and 151 down-regulated). The dysregulations of various transcripts were enriched for cellular functions such as cell cycle (including CCND1), apoptosis (including TNF), and genes related to signalling pathways governing self-renewal, as well as WNT5A from the Wnt signalling pathway, MAPK, Hedgehog, FGF2 from FGF, Jak-STAT, and PITX2 from the TGF-β signalling pathway. To concur this, real-time quantitative PCR (RT-qPCR) was utilised for corroborating the microarray results from five of the most dysregulated genes.

CONCLUSION

This study elucidates the underlying mechanisms of the mitogenic influences of MSCs on the propagation of HSCs. The exploitation of such mechanisms provides a potential means for achieving larger quantities of HSCs in vitro, thus obviating the need for manipulating their differentiation potential for clinical application.

In the spotlight: the role of TGFβ signalling in haematopoietic stem and progenitor cell emergence

Haematopoietic stem and progenitor cells (HSPCs) sustain haematopoiesis by generating precise numbers of mature blood cells throughout the lifetime of an individual. In vertebrates, HSPCs arise during embryonic development from a specialised endothelial cell population, the haemogenic endothelium (HE). Signalling by the Transforming Growth Factor β (TGFβ) pathway is key to regulate haematopoiesis in the adult bone marrow, but evidence for a role in the formation of HSPCs has only recently started to emerge. In this review, we examine recent work in various model systems that demonstrate a key role for TGFβ signalling in HSPC emergence from the HE. The current evidence underpins two seemingly contradictory views of TGFβ function: as a negative regulator of HSPCs by limiting haematopoietic output from HE, and as a positive regulator, by programming the HE towards the haematopoietic fate. Understanding how to modulate the requirement for TGFβ signalling in HSC emergence may have critical implications for the generation of these cells in vitro for therapeutic use.

CD63 acts as a functional marker in maintaining hematopoietic stem cell quiescence through supporting TGFβ signaling in mice

Hematopoietic stem cell (HSC) fate is tightly controlled by various regulators, whereas the underlying mechanism has not been fully uncovered due to the high heterogeneity of these populations. In this study, we identify tetraspanin CD63 as a novel functional marker of HSCs in mice. We show that CD63 is unevenly expressed on the cell surface in HSC populations. Importantly, HSCs with high CD63 expression (CD63^hi) are more quiescent and have more robust self-renewal and myeloid differentiation abilities than those with negative/low CD63 expression (CD63^-/lo). On the other hand, using CD63 knockout mice, we find that loss of CD63 leads to reduced HSC numbers in the bone marrow. In addition, CD63-deficient HSCs exhibit impaired quiescence and long-term repopulating capacity, accompanied by increased sensitivity to irradiation and 5-fluorouracil treatment. Further investigations demonstrate that CD63 is required to sustain TGFβ signaling activity through its interaction with TGFβ receptors I and II, thereby playing an important role in regulating the quiescence of HSCs. Collectively, our data not only reveal a previously unrecognized role of CD63 but also provide us with new insights into HSC heterogeneity.

Granulocytes Negatively Regulate Secretion of Transforming Growth Factor β1 by Bone Marrow Mononuclear Cells via Secretion of Erythropoietin Receptors in the Milieu

In my previous study, I demonstrated that bone marrow-derived mononuclear cells (BM MNCs) secrete copious amounts of Transforming Growth Factor β1 (TGFβ1) in response to erythropoietin (EPO). In this study, I investigated the principal cell type involved in the process. I found that a large percentage of various marrow cells, but not their mature counterparts present in the peripheral blood, express EPO-receptors (EPO-R). Cell depletion experiments showed that depletion of Glycophorin positive erythroblasts and CD41⁺ megakaryocytes - the prime suspects - did not affect the EPO-mediated TGFβ1 secretion by the BM MNCs. However, individual depletion of CD2⁺ T lymphocytes, CD14⁺ monocyte/macrophages, and CD19⁺ B cells affected the TGFβ1 secretion by EPO-primed MNCs: depletion of CD2⁺ cells had the most striking effect. Unexpectedly, and most interestingly, depletion of CD15⁺ granulocytes led to a significant increase in the TGFβ1 secretion by both naïve and EPO-primed BM MNCs, suggesting that these cells negatively regulate the process. Mechanistically, I show that the CD15⁺ cells exert this regulatory effect via secretion of both full-length and soluble EPO-R in the milieu. Overall my results, for the first time, unravel an in-built regulatory mechanism prevailing in the BM microenvironment that regulates the secretion of TGFβ1 by controlling EPO-EPO-R interaction.My data could be relevant in understanding the pathophysiology of several conditions associated with deregulated production of TGFβ1 in the marrow compartment.

Heterotopic ossification in mice overexpressing Bmp2 in Tie2+ lineages

Bone morphogenetic protein (Bmp) signaling is critical for organismal development and homeostasis. To elucidate Bmp2 function in the vascular/hematopoietic lineages we generated a new transgenic mouse line in which ectopic Bmp2 expression is controlled by the Tie2 promoter. Tie2CRE/+;Bmp2tg/tg mice develop aortic valve dysfunction postnatally, accompanied by pre-calcific lesion formation in valve leaflets. Remarkably, Tie2CRE/+;Bmp2tg/tg mice develop extensive soft tissue bone formation typical of acquired forms of heterotopic ossification (HO) and genetic bone disorders, such as Fibrodysplasia Ossificans Progressiva (FOP). Ectopic ossification in Tie2CRE/+;Bmp2tg/tg transgenic animals is accompanied by increased bone marrow hematopoietic, fibroblast and osteoblast precursors and circulating pro-inflammatory cells. Transplanting wild-type bone marrow hematopoietic stem cells into lethally irradiated Tie2CRE/+;Bmp2tg/tg mice significantly delays HO onset but does not prevent it. Moreover, transplanting Bmp2-transgenic bone marrow into wild-type recipients does not result in HO, but hematopoietic progenitors contribute to inflammation and ectopic bone marrow colonization rather than to endochondral ossification. Conversely, aberrant Bmp2 signaling activity is associated with fibroblast accumulation, skeletal muscle fiber damage, and expansion of a Tie2+ fibro-adipogenic precursor cell population, suggesting that ectopic bone derives from a skeletal muscle resident osteoprogenitor cell origin. Thus, Tie2CRE/+;Bmp2tg/tg mice recapitulate HO pathophysiology, and might represent a useful model to investigate therapies seeking to mitigate disorders associated with aberrant extra-skeletal bone formation.

Up-regulation of miR-155 potentiates CD34+ CML stem/progenitor cells to escape from the growth-inhibitory effects of TGF-ß1 and BMP signaling

microRNAs (miRNAs or miRs) play key roles in different stages of chronic myeloid leukemia (CML) pathogenesis. The present study aimed to demonstrate whether miR-155 enables CD34⁺ CML cells to escape from the growth-inhibitory effects of TGF-β1 and bone morphogenetic protein (BMP) signaling. Among differentially expressed miRNAs in CD34⁺ CML cells, miR-155 was highly up-regulated. QRT-PCR revealed an inverse correlation between miR-155 and two key members of the TGF-β pathway-TGF-βR2 and SMAD5. Results showed that SMAD5 is not only up-regulated through BMPs treatment, but recombinant TGF-β1 can also induce SMAD5 in CML cells. We also demonstrated that TGF-β1-mediated phosphorylation of SMAD1/5 was abolished by pre-treatment with the blocking TGF-βR2 antibody, suggesting a possible involvement of TGF-βR2. Additionally, overexpression of miR-155 significantly promoted the proliferation rate of CD34⁺ CML cells. Results showed that siRNA-mediated knockdown of SMAD5 had a promoting effect on CD34⁺ CML cell proliferation, suggesting that SMAD5 knock-down recapitulates the proliferative effects of miR-155. Importantly, TGF-β1 and BMP2/4 treatment had inhibitory effects on cell proliferation; however, miR-155 overexpression enabled CD34⁺ CML cells to evade the anti-proliferative effects of TGF-β1 and BMPs. Consistently, down-regulation of miR-155 augmented the promoting effects of TGF-β1 and BMP signaling on inducing apoptosis in CD34⁺ CML stem cells. Our findings demonstrated that targeting of SMAD5 and TGF-βR2 links miR-155 to TGF-β signaling in CML. Overexpression of miR-155 enables CD34⁺ CML cells to evade growth-inhibitory effects of the TGF-β1 and BMP signaling, providing new perspectives for miR-155 as a therapeutic target for CML.

ceRNA Network Regulation of TGF-β, WNT, FOXO, Hedgehog Pathways in the Pharynx of Ciona robusta

The transforming growth factor-β (TGF-β) family of cytokines performs a multifunctional signaling, which is integrated and coordinated in a signaling network that involves other pathways, such as Wintless, Forkhead box-O (FOXO) and Hedgehog and regulates pivotal functions related to cell fate in all tissues. In the hematopoietic system, TGF-β signaling controls a wide spectrum of biological processes, from immune system homeostasis to the quiescence and self-renewal of hematopoietic stem cells (HSCs). Recently an important role in post-transcription regulation has been attributed to two type of ncRNAs: microRNAs and pseudogenes. Ciona robusta, due to its philogenetic position close to vertebrates, is an excellent model to investigate mechanisms of post-transcriptional regulation evolutionarily highly conserved in immune homeostasis. The combined use of NGS and bioinformatic analyses suggests that in the pharynx, the hematopoietic organ of Ciona robusta, the Tgf-β, Wnt, Hedgehog and FoxO pathways are involved in tissue homeostasis, as they are in human. Furthermore, ceRNA network interactions and 3'UTR elements analyses of Tgf-β, Wnt, Hedgehog and FoxO pathways genes suggest that different miRNAs conserved (cin-let-7d, cin-mir-92c, cin-mir-153), species-specific (cin-mir-4187, cin-mir-4011a, cin-mir-4056, cin-mir-4150, cin-mir-4189, cin-mir-4053, cin-mir-4016, cin-mir-4075), pseudogenes (ENSCING00000011392, ENSCING00000018651, ENSCING00000007698) and mRNA 3'UTR elements are involved in post-transcriptional regulation in an integrated way in C. robusta.

Cancer non-stem cells as a potent regulator of tumor microenvironment: a lesson from chronic myeloid leukemia

A limited subset of human leukemia cells has a self-renewal capacity and can propagate leukemia upon their transplantation into animals, and therefore, are named as leukemia stem cells, in the early 1990’s. Subsequently, cell subpopulations with similar characteristics were detected in various kinds of solid cancers and were denoted as cancer stem cells. Cancer stem cells are presently presumed to be crucially involved in malignant progression of solid cancer: chemoresitance, radioresistance, immune evasion, and metastasis. On the contrary, less attention has been paid to cancer non-stem cell population, which comprise most cancer cells in cancer tissues, due to the lack of suitable markers to discriminate cancer non-stem cells from cancer stem cells. Chronic myeloid leukemia stem cells generate a larger number of morphologically distinct non-stem cells. Moreover, accumulating evidence indicates that poor prognosis is associated with the increases in these non-stem cells including basophils and megakaryocytes. We will discuss the potential roles of cancer non-stem cells in fostering tumor microenvironment, by illustrating the roles of chronic myeloid leukemia non-stem cells including basophils and megakaryocytes in the pathogenesis of chronic myeloid leukemia, a typical malignant disorder arising from leukemic stem cells.

Variation in genes implicated in B-cell development and antibody production affects susceptibility to pemphigus

Pemphigus foliaceus (PF) is an autoimmune blistering skin disease characterized by the presence of pathogenic autoantibodies against desmoglein 1, a component of intercellular desmosome junctions. PF occurs sporadically across the globe and is endemic in some Brazilian regions. Because PF is a B-cell-mediated disease, we aimed to study the impact of variants within genes encoding molecules involved in the different steps of B-cell development and antibody production on the susceptibility of endemic PF. We analysed 3,336 single nucleotide polymorphisms (SNPs) from 167 candidate genes genotyped with Illumina microarray in a cohort of 227 PF patients and 193 controls. After quality control and exclusion of non-informative and redundant SNPs, 607 variants in 149 genes remained in the logistic regression analysis, in which sex and ancestry were included as covariates. Our results revealed 10 SNPs within or nearby 11 genes that were associated with susceptibility to endemic PF (OR >1.56; p < 0.005): rs6657275*G (TGFB2); rs1818545*A (RAG1/RAG2/IFTAP);rs10781530*A (PAXX), rs10870140*G and rs10781522*A (TRAF2); rs535068*A (TNFRSF1B); rs324011*A (STAT6);rs6432018*C (YWHAQ); rs17149161*C (YWHAG); and rs2070729*C (IRF1). Interestingly, these SNPs have been previously associated with differential gene expression, mostly in peripheral blood, in publicly available databases. For the first time, we show that polymorphisms in genes involved in B-cell development and antibody production confer differential susceptibility to endemic PF, and therefore are candidates for possible functional studies to understand immunoglobulin gene rearrangement and its impact on diseases.

Expansion of senescent megakaryocyte-lineage cells maintains CML cell leukemogenesis

BCR-ABL, an oncogenic fusion gene, plays a central role in the pathogenesis of chronic myeloid leukemia (CML). Oncogenic signaling induces oncogene-induced senescence and senescence-associated secretory phenotype (SASP), which is characterized by enhanced production of various cytokines. BCR-ABL gene transduction confers senescent phenotype in vitro; however, the in vivo relevance of senescence has not been explored in this context. Transplantation of BCR-ABL-expressing hematopoietic stem/progenitor cells caused CML in mice with an increase in bone marrow BCR-ABL+CD41+CD150+ leukemic megakaryocyte-lineage (MgkL) cells, which exhibited enhanced senescence-associated β-galactosidase staining and increased expression of p16 and p21, key molecules that are crucially involved in senescence. Moreover, knockout of p16 and p21 genes reduced both BCR-ABL-induced abnormal megakaryopoiesis and the maintenance of CML cell leukemogenic capacity, as evidenced by attenuated leukemogenic capacity at secondary transplantation. The expression of transforming growth factor-β1 (TGF-β1), a representative SASP molecule, was enhanced in the leukemic MgkL cells, and TGF-β1 inhibition attenuated CML cell leukemogenic capacity both in vitro and in vivo. Furthermore, BCR-ABL-expressing MgkL cells displayed enhanced autophagic activity, and autophagy inhibition reduced bone marrow MgkL cell number and prolonged the survival of CML mice, which had transiently received the tyrosine kinase inhibitor, imatinib, earlier. Thus, BCR-ABL induced the expansion of senescent leukemic MgkL cells, which supported CML leukemogenesis by providing TGF-β1.

Transforming growth factor-β boosts the functionality of human bone marrow-derived mesenchymal stromal cells

Transforming growth factor β1 (TGFβ1) is a negative regulator of hematopoiesis, and yet, it is frequently found at the active sites of hematopoiesis. Here, we show for the first time that bone marrow-derived mononuclear cells (BM MNCs) secrete TGFβ1 in response to erythropoietin (EPO). We further show that human bone marrow-derived mesenchymal stromal cells (BMSCs) briefly exposed to the conditioned medium of EPO-primed MNCs, or purified TGFβ1, gain significantly increased hematopoiesis-supportive ability. Mechanistically, we show that this phenomenon involves TGFβ1-mediated activation of nitric oxide (NO) signalling pathway in the BMSCs. The data suggest that EPO-MNC-TGFβ1 could be one of the regulatory axes operative in the bone marrow microenvironment involved in maintaining the functionality of the resident BMSCs.

MLLT10 in benign and malignant hematopoiesis

Non-random chromosomal translocations involving the putative transcription factor Mixed Lineage Leukemia Translocated to 10 (MLLT10, also known as AF10) are commonly observed in both acute myeloid and lymphoid leukemias and are indicative of a poor prognosis. Despite the well-described actions of oncogenic MLLT10 fusion proteins, the role of wild-type MLLT10 in hematopoiesis is not well characterized. The protein structure and several interacting partners have been described and provide indications as to the potential functions of MLLT10. This review examines these aspects of MLLT10, contextualizing its function in benign and malignant hematopoiesis.

Therapeutic discovery for marrow failure with MDS predisposition using pluripotent stem cells

Monosomy 7 or deletion of 7q (del(7q)) are common clonal cytogenetic abnormalities associated with high grade myelodysplastic syndrome (MDS) arising in inherited and acquired bone marrow failure. Current non-transplant approaches to treat marrow failure may be complicated by stimulation of clonal outgrowth. To study the biological consequences of del(7q) within the context of a failing marrow, we generated induced pluripotent stem cells (iPSCs) derived from patients with Shwachman Diamond Syndrome (SDS), a bone marrow failure disorder with MDS predisposition, and genomically engineered a 7q deletion. The TGFβ pathway was the top differentially regulated pathway in transcriptomic analysis of SDS versus SDSdel(7q) iPSCs. SMAD2 phosphorylation was increased in SDS relative to wild type cells consistent with hyperactivation of the TGFbeta pathway in SDS. Phospho-SMAD2 levels were reduced following 7q deletion in SDS cells and increased upon restoration of 7q diploidy. Inhibition of the TGFbeta pathway rescued hematopoiesis in SDS-iPSCs and in bone marrow hematopoietic cells from SDS patients while it had no impact on the SDSdel(7q) cells. These results identified a potential targetable vulnerability to improve hematopoiesis in an MDS-predisposition syndrome, and highlight the importance of the germline context of somatic alterations to inform precision medicine approaches to therapy.

Parallels between hematopoietic stem cell and prostate cancer disseminated tumor cell regulation

The bone marrow is the primary site of hematopoiesis and the home for hematopoietic stem cells (HSCs) in adult mammals. Prostate cancer commonly metastasizes to the bone and forms bone metastases in almost all patients who die of the disease. Prostate cancer bone metastases are thought to develop after rare bone marrow disseminated tumor cells (DTCs) escape a dormant state and reactivate. Prostate cancer DTCs and normal HSCs have been shown to compete for residence in the bone marrow and share many of same regulatory mechanisms for survival, proliferation and homing. In this review, we highlight these parallels in order to help our readers use the literature in HSC and DTC biology to inform their research and generate hypotheses in both fields.

TGFβ Superfamily Members as Regulators of B Cell Development and Function-Implications for Autoimmunity

The TGFβ superfamily is composed of more than 33 growth and differentiation factors, including TGFβ1, β2, β3, BMPs, GDFs, nodal-related proteins, and activins. These members usually exert pleiotropic actions on several tissues and control multiple cellular processes, such as cell growth, cell survival, cell migration, cell fate specification, and differentiation, both during embryonic development and postnatal life. Although the effects of these factors on immune responses were elucidated long ago, most studies have been focused on the actions of TGFβs on T cells, as major regulators of adaptive immunity. In this review, we discuss new findings about the involvement of TGFβ superfamily members in the control of B cell development and function. Moreover, the potential contribution of TGFβ signaling to control B cell-mediated autoimmune diseases and its utility in the design of new therapies are also discussed.

Bone morphogenetic protein receptor signal transduction in human disease

Bone morphogenetic proteins (BMPs) are secreted cytokines that were initially discovered on the basis of their ability to induce bone. Several decades of research have now established that these proteins function in a large variety of physiopathological processes. There are about 15 BMP family members, which signal via three transmembrane type II receptors and four transmembrane type I receptors. Mechanistically, BMP binding leads to phosphorylation of the type I receptor by the type II receptor. This activated heteromeric complex triggers intracellular signaling that is initiated by phosphorylation of receptor‐regulated SMAD1, 5, and 8 (also termed R‐SMADs). Activated R‐SMADs form heteromeric complexes with SMAD4, which engage in specific transcriptional responses. There is convergence along the signaling pathway and, besides the canonical SMAD pathway, BMP‐receptor activation can also induce non‐SMAD signaling. Each step in the pathway is fine‐tuned by positive and negative regulation and crosstalk with other signaling pathways. For example, ligand bioavailability for the receptor can be regulated by ligand‐binding proteins that sequester the ligand from interacting with receptors. Accessory co‐receptors, also known as BMP type III receptors, lack intrinsic enzymatic activity but enhance BMP signaling by presenting ligands to receptors. In this review, we discuss the role of BMP receptor signaling and how corruption of this pathway contributes to cardiovascular and musculoskeletal diseases and cancer. We describe pharmacological tools to interrogate the function of BMP receptor signaling in specific biological processes and focus on how these agents can be used as drugs to inhibit or activate the function of the receptor, thereby normalizing dysregulated BMP signaling. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Expression of myostatin in human hematopoietic cells unveils novel autocrine/paracrine actions for the hormone

Myostatin is a member of the transforming growth factor β (TGFβ) superfamily that has a well-established role as a mediator of muscle growth and development. However, myostatin is now emerging as a pleiotropic hormone with multiple actions in the regulation of the metabolism as well as several aspects of both cardiac and smooth muscle cells physiology. In addition, myostatin is also expressed in several nonmuscular cells where its physiological role remains to be elucidated in most cases. In this report, we have shown that both myostatin and its receptor system are expressed in blood cells and in hematopoietic cell lines. Furthermore, myostatin treatment promotes differentiation of both HL60 and K562 cells through a mechanism that involves activation of extracellular signal-regulated kinases 1/2 and p38-mitogen-activated protein kinase, thus leading to the possibility that myostatin may be a paracrine/autocrine factor involved in the control of haematopoiesis. In addition, the presence of myostatin expression in immune cells could envisage a novel role for the hormone in the pathogenesis of inflammatory diseases.

Intracellular and extracellular TGF-β signaling in cancer: some recent topics

Transforming growth factor (TGF)-β regulates a wide variety of cellular responses, including cell growth arrest, apoptosis, cell differentiation, motility, invasion, extracellular matrix production, tissue fibrosis, angiogenesis, and immune function. Although tumor-suppressive roles of TGF-β have been extensively studied and well-characterized in many cancers, especially at early stages, accumulating evidence has revealed the critical roles of TGF-β as a pro-tumorigenic factor in various types of cancer. This review will focus on recent findings regarding epithelial-mesenchymal transition (EMT) induced by TGF-β, in relation to crosstalk with some other signaling pathways, and the roles of TGF-β in lung and pancreatic cancers, in which TGF-β has been shown to be involved in cancer progression. Recent findings also strongly suggested that targeting TGF-β signaling using specific inhibitors may be useful for the treatment of some cancers. TGF-β plays a pivotal role in the differentiation and function of regulatory T cells (Tregs). TGF-β is produced as latent high molecular weight complexes, and the latent TGF-β complex expressed on the surface of Tregs contains glycoprotein A repetitions predominant (GARP, also known as leucine-rich repeat containing 32 or LRRC32). Inhibition of the TGF-β activities through regulation of the latent TGF-β complex activation will be discussed.