Unique effects of Stat3 on the early phase of hematopoietic stem cell regeneration

STAT1 inhibition promotes oxidative stress to sustain leukemia stem cell maintenance

New strategy to prevent relapse and drug resistance in acute myeloid leukemia (AML) is urgently to be solved. The connection between those properties and leukemia stem cells (LSCs) in AML remains poorly understood. In this study, we demonstrate that leukemia cells with high signal transducer and activator of transcription 1 (STAT1) expression preserve quiescent properties, in contrast, leukemia cells with low STAT1 expression possess active and vulnerable apoptotic properties in AML model, highlighting the differential impact of STAT1 expression on cellular behavior in acute myeloid leukemia. STAT1 depletion damages the quiescence of LSCs and prolongs the survive of AML mice. By inhibiting STAT1 in leukemia cells, we observe a significant elevation in reactive oxygen species (ROS) levels, rendering the cells more susceptible to the detrimental effects of oxidative stress. The synergistic administration of Fludarabine, a potent STAT1 inhibitor, with conventional chemotherapy regimens, augments the efficacy of chemotherapy drugs against AML cells and the sensitivity of LSCs to chemotherapy. In a word, STAT1, as a switch, enables leukemia cells convertible in ROS high and low states. Inhibition of STAT1 enables leukemia cells more sensitive to chemotherapy, STAT1 as a new target offers a promising strategy in AML treatment.

Modulation of the JAK2-STAT3 pathway promotes expansion and maturation of human iPSCs-derived myogenic progenitor cells

Generation of in vitro induced pluripotent cells (hiPSCs)-derived skeletal muscle progenitor cells (SMPCs) holds great promise for regenerative medicine for skeletal muscle wasting diseases, as for example Duchenne Muscular Dystrophy (DMD). Multiple approaches, involving ectopic expression of key regulatory myogenic genes or small molecules cocktails, have been described by different groups to obtain SMPC towards cell-transplantation in vivo as a therapeutic approach to skeletal muscle diseases. However, hiPSCs-derived SMPC generated using transgene-free protocols are usually obtained in a low amount and resemble a more embryonal/fetal stage of differentiation. Here we demonstrate that modulation of the JAK2/STAT3 signaling pathway during an in vitro skeletal muscle differentiation protocol, increases the yield of PAX7+ and CD54+ SMPCs and drive them to a postnatal maturation stage, in both human ES and patient-derived iPSCs. Importantly, upon removal of the inhibition from the cultures, the obtained SMPCs are able to differentiate into multinucleated myotubes in vitro. These findings reveal that modulation of the JAK2/STAT3 signaling pathway is a potential therapeutic avenue to generate SMPCs in vitro with increase potential for cell-therapy approaches.

Fluacrypyrim Protects Hematopoietic Stem and Progenitor Cells against Irradiation via Apoptosis Prevention

Ionizing radiation (IR)-induced hematopoietic injury has become a global concern in the past decade. The underlying cause of this condition is a compromised hematopoietic reserve, and this kind of hematopoietic injury could result in infection or bleeding, in addition to lethal mishaps. Therefore, developing an effective treatment for this condition is imperative. Fluacrypyrim (FAPM) is a recognized effective inhibitor of STAT3, which exhibits anti-inflammation and anti-tumor effects in hematopoietic disorders. In this context, the present study aimed to determine whether FAPM could serve as a curative agent in hematopoietic-acute radiation syndrome (H-ARS) after total body irradiation (TBI). The results revealed that the peritoneally injection of FAPM could effectively promote mice survival after lethal dose irradiation. In addition, promising recovery of peripheral blood, bone marrow (BM) cell counts, hematopoietic stem cell (HSC) cellularity, BM colony-forming ability, and HSC reconstituting ability upon FAPM treatment after sublethal dose irradiation was noted. Furthermore, FAPM could reduce IR-induced apoptosis in hematopoietic stem and progenitor cells (HSPCs) both in vitro and in vivo. Specifically, FAPM could downregulate the expressions of p53-PUMA pathway target genes, such as Puma, Bax, and Noxa. These results suggested that FAPM played a protective role in IR-induced hematopoietic damage and that the possible underlying mechanism was the modulation of apoptotic activities in HSCs.

Chronic inflammation promotes cancer progression as a second hit

Acute myeloid leukemia (AML) is a malignant neoplasia of the hematopoietic system characterized by the accumulation of immature and nonfunctional leukemic blasts in the bone marrow and peripheral tissues. Mechanistically, the development of AML is explained by the "two-hit" theory, which is based on the accumulation of driver mutations that will cooperate to induce transformation. However, a significant percentage of patients with AML exhibit only one driver mutation, and thus, how leukemic transformation occurs in these cases is unclear. Accumulating evidence suggests that nongenetic factors, such as chronic inflammation, might influence AML development, and accordingly, clinical data have reported that patients with chronic inflammatory disorders have an increased risk of developing hematological malignancies. Here, using a mouse model of chronic inflammation, we demonstrate that systemic elevated levels of cytokines and chemokines and hyperactivation of the Jak/Stat3 signaling pathway may substitute "second hit" mutations and accelerate tumorigenesis. Altogether, our data highlight chronic inflammation as an additional factor in the development of AML, providing additional understanding of the mechanisms of transformation and opening new avenues for the treatment of this disease.

STAT3 protects HSCs from intrinsic interferon signaling and loss of long-term blood-forming activity

STAT3 function in hematopoietic stem and progenitor cells (HSPCs) has been difficult to discern as Stat3 deficiency in the hematopoietic system induces systemic inflammation, which can impact HSPC activity. To address this, we established mixed bone marrow (BM) chimeric mice with CreER-mediated Stat3 deletion in 20% of the hematopoietic compartment. Stat3-deficient HSPCs had impaired hematopoietic activity and failed to undergo expansion in BM in contrast to Stat3-sufficient (CreER) controls. Single-cell RNA sequencing of Lin-ckit+Sca1+ BM cells revealed altered transcriptional responses in Stat3-deficient hematopoietic stem cells (HSCs) and multipotent progenitors, including intrinsic activation of cell cycle, stress response, and interferon signaling pathways. Consistent with their deregulation, Stat3-deficient Lin-ckit+Sca1+ cells accumulated γH2AX over time. Following secondary BM transplantation, Stat3-deficient HSPCs failed to reconstitute peripheral blood effectively, indicating a severe functional defect in the HSC compartment. Our results reveal essential roles for STAT3 in HSCs and suggest the potential for using targeted synthetic lethal approaches with STAT3 inhibition to remove defective or diseased HSPCs.

Polyphyllin VII as a Potential Drug for Targeting Stemness in Hepatocellular Cancer via STAT3 Signaling

BACKGROUND

At present, the treatment of hepatocellular carcinoma (HCC) is disturbed by the treatment failure and recurrence caused by the residual liver cancer stem cells (CSCs). Therefore, drugs targeting HCC CSCs should be able to effectively eliminate HCC and prevent its recurrence. In this study, we demonstrated the effect of Polyphyllin VII (PP7) on HCC CSCs and explored their potential mechanism.

METHODS

HepG2 and Huh7 cells were used to analyze the antitumor activity of PP7 by quantifying cell growth and metastasis as well as to study the effect on stemness.

RESULTS

Our results demonstrated that PP7 promoted apoptosis and significantly inhibited proliferation and migration of both HepG2 and Huh7 cells. PP7 also inhibited tumor spheroid formation and induced significant changes in the expression of stemness markers (CD133 and OCT-4). These effects of PP7 were mediated by STAT3 signaling.

CONCLUSION

PP7 can effectively suppress tumor initiation, growth, and metastasis and inhibit stemness through regulation of STAT3 signaling pathway in liver cancer cells. Our data would add more evidence to further clarify the therapeutic effect of PP7 against HCC.

STAT3 suppression and β-cell ablation enhance α-to-β reprogramming mediated by Pdx1

As diabetes results from the absolute or relative deficiency of insulin secretion from pancreatic β cells, possible methods to efficiently generate surrogate β cells have attracted a lot of efforts. To date, insulin-producing cells have been generated from various differentiated cell types in the pancreas, such as acinar cells and α cells, by inducing defined transcription factors, such as PDX1 and MAFA, yet it is still challenging as to how surrogate β cells can be efficiently generated for establishing future regenerative therapies for diabetes. In this study, we demonstrated that the exogenous expression of PDX1 activated STAT3 in α cells in vitro, and STAT3-null PDX1-expressing α cells in vivo resulted in efficient induction of α-to-β reprogramming, accompanied by the emergence of α-cell-derived insulin-producing cells with silenced glucagon expression. Whereas β-cell ablation by alloxan administration significantly increased the number of α-cell-derived insulin-producing cells by PDX1, STAT3 suppression resulted in no further increase in β-cell neogenesis after β-cell ablation. Thus, STAT3 modulation and β-cell ablation nonadditively enhance α-to-β reprogramming induced by PDX1, which may lead to the establishment of cell therapies for curing diabetes.

Competition between hematopoietic stem and progenitor cells controls hematopoietic stem cell compartment size

Cellular competition for limiting hematopoietic factors is a physiologically regulated but poorly understood process. Here, we studied this phenomenon by hampering hematopoietic progenitor access to Leptin receptor⁺ mesenchymal stem/progenitor cells (MSPCs) and endothelial cells (ECs). We show that HSC numbers increase by 2-fold when multipotent and lineage-restricted progenitors fail to respond to CXCL12 produced by MSPCs and ECs. HSCs are qualitatively normal, and HSC expansion only occurs when early hematopoietic progenitors but not differentiated hematopoietic cells lack CXCR4. Furthermore, the MSPC and EC transcriptomic heterogeneity is stable, suggesting that it is impervious to major changes in hematopoietic progenitor interactions. Instead, HSC expansion correlates with increased availability of membrane-bound stem cell factor (mSCF) on MSPCs and ECs presumably due to reduced consumption by cKit-expressing hematopoietic progenitors. These studies suggest that an intricate homeostatic balance between HSCs and proximal hematopoietic progenitors is regulated by cell competition for limited amounts of mSCF.

Hematopoietic stem cells (HSCs) rely on a combination of paracrine signals produced by their niche, including SCF. Here the authors show that HSCs and hematopoietic progenitors compete for limited amounts of membrane-bound SCF.

Drosophila Innate Immunity Involves Multiple Signaling Pathways and Coordinated Communication Between Different Tissues

The innate immune response provides the first line of defense against invading pathogens, and immune disorders cause a variety of diseases. The fruit fly Drosophila melanogaster employs multiple innate immune reactions to resist infection. First, epithelial tissues function as physical barriers to prevent pathogen invasion. In addition, macrophage-like plasmatocytes eliminate intruders through phagocytosis, and lamellocytes encapsulate large particles, such as wasp eggs, that cannot be phagocytosed. Regarding humoral immune responses, the fat body, equivalent to the mammalian liver, secretes antimicrobial peptides into hemolymph, killing bacteria and fungi. Drosophila has been shown to be a powerful in vivo model for studying the mechanism of innate immunity and host-pathogen interactions because Drosophila and higher organisms share conserved signaling pathways and factors. Moreover, the ease with which Drosophila genetic and physiological characteristics can be manipulated prevents interference by adaptive immunity. In this review, we discuss the signaling pathways activated in Drosophila innate immunity, namely, the Toll, Imd, JNK, JAK/STAT pathways, and other factors, as well as relevant regulatory networks. We also review the mechanisms by which different tissues, including hemocytes, the fat body, the lymph gland, muscles, the gut and the brain coordinate innate immune responses. Furthermore, the latest studies in this field are outlined in this review. In summary, understanding the mechanism underlying innate immunity orchestration in Drosophila will help us better study human innate immunity-related diseases.

A novel strategy to reveal clinical advantages and molecular mechanism of aidi injection in the treatment of pancreatic cancer based on network meta-analysis and network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Pancreatic cancer is a common malignancy worldwide due to its poor prognosis and high mortality rate. It is clinically proven that the combination of chemotherapeutic drugs and Traditional Chinese Medicine injections (TCMIs) significantly improves the therapeutic effect.

AIM OF THE STUDY

To evaluate the efficacy and clinical benefits of TCMIs in combination with chemotherapy in the treatment of pancreatic cancer and to explore the mechanism of clinical advantage of Aidi injection.

METHODS

Randomized controlled trials (RCTs) were searched in databases by NMA before December 29, 2020. WinBUGS 1.4, Stata 14.0, and R 4.0.4 software were used for calculations. All results were expressed as odds ratios and 95% credible intervals. Through the network pharmacology method, the chemical components and their targets, as well as the disease targets were further analyzed. And then, biological experiments were integrated to verify the results of network pharmacology analysis. (PROSPERO ID: CRD42021283559).

RESULTS

A total of 33 RCTs with 8 TCMIs and 2011 patients were included. The results of NMA showed that Aidi injection can significantly improve the clinical efficacy (OR = 0.34, 95%CI: 0.16-0.74), and the clinical advantage was that it can significantly alleviate the leukopenia and thrombocytopenia caused by chemotherapy (OR = 5.65, 95%CI: 1.18-28.13). A total of 23 chemical compounds and 280 potential targets for Aidi injection were obtained from the online databases. Among them, there were 22 compounds, 50 targets and 211 signaling pathways closely related to leukopenia. Five genes were predicted to be core targets of ADI in alleviating leukopenia, and 2 of them (TP53 and VEGFA) were confirmed by biological experiments as regulatory targets of ADI in the treatment of PC.

CONCLUSIONS

In conclusion, TCMIs in combination with chemotherapy, can improve clinical efficacy and safety in the treatment of pancreatic cancer. However, the overall evidence base is low, and large samples with multi-center RCTs are still needed to support further research findings. Aidi injection can alleviate leukopenia mainly by intervening in oxidative stress, regulating cell proliferation and apoptosis, and regulating the inflammatory response. The combined application of NMA, network pharmacology, and biological experiments provides a reference for clinical evaluation and mechanism of action exploration of other drugs.

Inhibition of STAT3 prevents bone metastatic progression of prostate cancer in vivo

BACKGROUND

Prostate cancer (PC) metastasizes to the skeleton forming predominantly sclerotic lesions, and there is currently no cure for bone metastatic disease. The transcription factor signal transducer and activator of transcription 3 (STAT3) is implicated as a metastatic driver, but its potential as therapeutic target in bone metastasis has not been investigated. In this study, we evaluated for the first time a STAT3 inhibitor, Napabucasin, as a therapeutic option for bone metastatic PC.

METHODS

Effects of STAT3 inhibitors, Stattic and Napabucasin, on metastatic potential in PC cells were studied in vitro by assessment of migration capacity, self-renewal potential, and tumorsphere formation. For evaluation of the role of STAT3 in initial skeletal establishment of PC cells as well as in progressed castration-resistant PC (CRPC) in bone, human VCaP prostate cancer cells were inoculated in the tibia of mice which subsequently were treated with the STAT3 inhibitor Napabucasin. Bone specimens were analyzed using computed tomography (CT), immunohistochemistry, and quantitative polymerase chain reaction.

RESULTS

The small molecule STAT3 inhibitors Stattic and Napabucasin both effectively impaired metastatic potential of PC cells in vitro. Furthermore, treatment with Napabucasin prevented metastatic establishment in tibial bones in vivo and thereby also the tumor-induced sclerotic bone response seen in vehicle-treated VCaP xenografts. In addition, treatment with Napabucasin of established bone CRPC significantly decreased both tumor burden and tumor-induced trabecular bone volume compared with effects seen in vehicle-treated animals. Anti-mitotic effects were confirmed by decreased Ki67 staining in Napabucasin-treated xenografts compared with vehicle-treated xenografts. Alterations of gene expression in the femoral bone marrow (BM) niche toward the maintenance of hematopoietic stem cells and the myeloid lineage were demonstrated by quantitative real-time polymerase chain reaction and were further reflected by a substantial increase in the number of erythrocytes in BM of Napabucasin-treated mice. Furthermore, a unique pattern of STAT3 phosphorylation in osteoblasts/stromal cells surrounding the areas of tumor cells was demonstrated immunohistochemically in bone xenograft models using several different PC cell lines.

CONCLUSION

Inhibition of STAT3 activity disrupts the bone metastatic niche and targets both the skeletal establishment of PC and advanced bone metastatic CRPC in mice, suggesting STAT3 as a candidate for molecular targeted therapies of skeletal metastatic disease.

JAK-STAT in Early Hematopoiesis and Leukemia

Hematopoietic stem cells (HSCs) produce all the terminally differentiated blood cells and are controlled by extracellular signals from the microenvironment, the bone marrow (BM) niche, as well as intrinsic cell signals. Intrinsic signals include the tightly controlled action of signaling pathways, as the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. Activation of JAK-STAT leads to phosphorylation of members of the STAT family to regulate proliferation, survival, and self-renewal of HSCs. Mutations in components of the JAK-STAT pathway are linked with defects in HSCs and hematologic malignancies. Accumulating mutations in HSCs and aging contribute to leukemia transformation. Here an overview of hematopoiesis, and the role of the JAK-STAT pathway in HSCs and in the promotion of leukemic transformation is presented. Therapeutic targeting of JAK-STAT and clinical implications of the existing research findings are also discussed.

Cell signaling pathways as molecular targets to eliminate AML stem cells

Acute myeloid leukemia (AML) remains the most lethal of leukemias and a small population of cells called leukemic stem cells (LSCs) has been associated with disease relapses. Some cell signaling pathways play an important role in AML survival, proliferation and self-renewal properties and are abnormally activated or suppressed in LSCs. This includes the NF-κB, Wnt/β-catenin, Hedgehog, Notch, EGFR, JAK/STAT, PI3K/AKT/mTOR, TGF/SMAD and PPAR pathways. This review aimed to discuss these pathways as molecular targets for eliminating AML LSCs. Herein, inhibitors/activators of these pathways were summarized as a potential new anti-AML therapy capable of eliminating LSCs to guide future researches. The clinical use of cell signaling pathways data can be useful to enhance the anti-AML therapy.

Gynecologic cancers and non-coding RNAs: Epigenetic regulators with emerging roles

Gynecologic cancers involve the female genital organs, such as the vulva, vagina, cervix, endometrium, ovaries, and fallopian tubes. The occurrence and frequency of gynecologic cancer depends on personal lifestyle, history of exposure to viruses or carcinogens, genetics, body shape, and geographical habitat. For a long time, research into the molecular biology of cancer was broadly restricted to protein-coding genes. Recently it has been realized that non-coding RNAs (ncRNA), including long noncoding RNAs (LncRNAs), microRNAs, circular RNAs and piRNAs (PIWI-interacting RNAs), can all play a role in the regulation of cellular function within gynecological cancer. It is now known that ncRNAs are able to play dual roles, i.e. can exert both oncogenic or tumor suppressive functions in gynecological cancer. Moreover, several clinical trials are underway looking at the biomarker and therapeutic roles of ncRNAs. These efforts may provide a new horizon for the diagnosis and treatment of gynecological cancer. Herein, we summarize some of the ncRNAs that have been shown to be important in gynecological cancers.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

MDH1-mediated malate-aspartate NADH shuttle maintains the activity levels of fetal liver hematopoietic stem cells

The connections between energy metabolism and stemness of hematopoietic stem cells (HSCs) at different developmental stages remain largely unknown. We generated a transgenic mouse line for the genetically encoded NADH/NAD+ sensor (SoNar) and demonstrate that there are 3 distinct fetal liver hematopoietic cell populations according to the ratios of SoNar fluorescence. SoNar-low cells had an enhanced level of mitochondrial respiration but a glycolytic level similar to that of SoNar-high cells. Interestingly, 10% of SoNar-low cells were enriched for 65% of total immunophenotypic fetal liver HSCs (FL-HSCs) and contained approximately fivefold more functional HSCs than their SoNar-high counterparts. SoNar was able to monitor sensitively the dynamic changes of energy metabolism in HSCs both in vitro and in vivo. Mechanistically, STAT3 transactivated MDH1 to sustain the malate-aspartate NADH shuttle activity and HSC self-renewal and differentiation. We reveal an unexpected metabolic program of FL-HSCs and provide a powerful genetic tool for metabolic studies of HSCs or other types of stem cells.

The stem-like Stat3-responsive cells of zebrafish intestine are Wnt/β-catenin dependent

The transcription factor Stat3 is required for proliferation and pluripotency of embryonic stem cells; we have prepared and characterized fluorescent Stat3-reporter zebrafish based on repeats of minimal responsive elements. These transgenic lines mimic in vivo Stat3 expression patterns and are responsive to exogenous Stat3; notably, fluorescence is inhibited by both stat3 knockout and IL6/Jak/STAT inhibitors. At larval stages, Stat3 reporter activity correlates with proliferating regions of the brain, haematopoietic tissue and intestine. In the adult gut, the reporter is active in sparse proliferating cells, located at the base of intestinal folds, expressing the stemness marker sox9b and having the morphology of mammalian crypt base columnar cells; noteworthy, zebrafish stat3 mutants show defects in intestinal folding. Stat3 reporter activity in the gut is abolished with mutation of T cell factor 4 (Tcf7l2), the intestinal mediator of Wnt/β-catenin-dependent transcription. The Wnt/β-catenin dependence of Stat3 activity in the gut is confirmed by abrupt expansion of Stat3-positive cells in intestinal adenomas of apc heterozygotes. Our findings indicate that Jak/Stat3 signalling is needed for intestinal stem cell maintenance and possibly crucial in controlling Wnt/β-catenin-dependent colorectal cancer cell proliferation.

Summary: Using a fluorescent reporter for Stat3 activity, we have identified the stem cells of zebrafish intestine and characterized their Wnt requirements and responsiveness.

The influence of fibroblast growth factor 2 on the senescence of human adipose-derived mesenchymal stem cells during long-term culture

Adipose-derived mesenchymal stem cells (ASCs) exhibit great potential in regenerative medicine, and in vitro expansion is frequently necessary to obtain a sufficient number of ASCs for clinical use. Fibroblast growth factor 2 (FGF2) is a common supplement in the ASC culture medium to enhance cell proliferation. To achieve clinical applicability of ASC-based products, prolonged culture of ASCs is sometimes required to obtain sufficient quantity of ASCs. However, the effect of FGF2 on ASCs during prolonged culture has not been previously determined. In this study, ASCs were subjected to prolonged in vitro culture with or without FGF2. FGF2 maintained the small cell morphology and expedited proliferation kinetics in early ASC passages. After prolonged in vitro expansion, FGF2-treated ASCs exhibited increased cell size, arrested cell proliferation, and increased cellular senescence relative to the control ASCs. We observed an upregulation of FGFR1c and enhanced expression of downstream STAT3 in the initial passages of FGF2-treated ASCs. The application of an FGFR1 or STAT3 inhibitor effectively blocked the enhanced proliferation of ASCs induced by FGF2 treatment. FGFR1c upregulation and enhanced STAT3 expression were lost in the later passages of FGF2-treated ASCs, suggesting that the continuous stimulation of FGF2 becomes ineffective because of the refractory downstream FGFR1 and the STAT3 signaling pathway. In addition, no evidence of tumorigenicity was noted in vitro and in vivo after prolonged expansion of FGF2-cultured ASCs. Our data indicate that ASCs have evolved a STAT3-dependent response to continuous FGF2 stimulation which promotes the initial expansion but limits their long-term proliferation.

Pharmacological Inhibition of Oncogenic STAT3 and STAT5 Signaling in Hematopoietic Cancers

Signal Transducer and Activator of Transcription (STAT) 3 and 5 are important effectors of cellular transformation, and aberrant STAT3 and STAT5 signaling have been demonstrated in hematopoietic cancers. STAT3 and STAT5 are common targets for different tyrosine kinase oncogenes (TKOs). In addition, STAT3 and STAT5 proteins were shown to contain activating mutations in some rare but aggressive leukemias/lymphomas. Both proteins also contribute to drug resistance in hematopoietic malignancies and are now well recognized as major targets in cancer treatment. The development of inhibitors targeting STAT3 and STAT5 has been the subject of intense investigations during the last decade. This review summarizes the current knowledge of oncogenic STAT3 and STAT5 functions in hematopoietic cancers as well as advances in preclinical and clinical development of pharmacological inhibitors.

JMJD1B Demethylates H4R3me2s and H3K9me2 to Facilitate Gene Expression for Development of Hematopoietic Stem and Progenitor Cells

The arginine methylation status of histones dynamically changes during many cellular processes, including hematopoietic stem/progenitor cell (HSPC) development. The arginine methyltransferases and the readers that transduce the histone codes have been defined. However, whether arginine demethylation actively occurs in cells and what enzyme demethylates the methylarginine residues during various cellular processes are unknown. We report that JMJD1B, previously identified as a lysine demethylase for H3K9me2, mediates arginine demethylation of H4R3me2s and its intermediate, H4R3me1. We show that demethylation of H4R3me2s and H3K9me2s in promoter regions is correlated with active gene expression. Furthermore, knockout of JMJD1B blocks demethylation of H4R3me2s and/or H3K9me2 at distinct clusters of genes and impairs the activation of genes important for HSPC differentiation and development. Consequently, JMJD1B^−/− mice show defects in hematopoiesis. Altogether, our study demonstrates that demethylase-mediated active arginine demethylation process exists in eukaryotes and that JMJD1B demethylates both H4R3me2s and H3K9me2 for epigenetic programming during hematopoiesis.

Protecting intestinal epithelial cells against deoxynivalenol and E. coli damage by recombinant porcine IL-22

Pigs suffer enteritis induced by pathogenic bacteria infection and toxins in the moldy feed, which cause intestinal epithelial damage and diarrhea through the whole breeding cycle. Interleukin-22 (IL-22) plays a critical role in maintaining intestinal mucosal barrier function through repairing intestinal epithelial damage. However, little was known about the effects of IL-22 against apoptosis caused by toxins and infection of intestinal pathogens in the intestinal epithelium, especially in pigs. In this study, we had successfully used prokaryotic expression system to produce recombinant porcine interleukin-22. Meanwhile, purified rIL-22 could activate STAT3 signal pathway and have been demonstrated to be safe to IPEC-J2 cells by increasing E-cadherin expression, without proinflammatory cytokines changes. Furthermore, rIL-22 reversed apoptosis induced by deoxynivalenol (DON) and played a vital part in repairing the intestinal injury. We also found that rIL-22 stimulated epithelial cells to secrete pBD-1 against enterotoxigenic E. coli (ETEC) K88 infection, as well as alleviating apoptosis ratio. This study provided a theoretical basis for curing intestinal inflammation caused by ETEC infection and epithelial apoptosis induced by DON with rIL-22 in pigs.

Eltrombopag maintains human hematopoietic stem and progenitor cells under inflammatory conditions mediated by IFN-γ

The proinflammatory cytokine interferon-γ (IFN-γ) has been implicated in human hematopoietic stem and progenitor cell (HSPC) depletion in immune-mediated bone marrow failure syndromes. We show that IFN-γ specifically prevents full engagement of thrombopoietin (TPO), a primary positive regulator of HSPC survival, to its receptor (c-MPL) via steric occlusion of the low-affinity binding site, contributing to perturbation of TPO-induced signaling pathways and decreased survival of human HSPCs. Eltrombopag, a synthetic small molecule mimetic of TPO that interacts with c-MPL at a position distinct from the extracellular binding site of TPO, bypasses this inhibition, providing an explanation for its clinical activity in bone marrow failure, despite already elevated endogenous TPO levels. Thus, IFN-γ-mediated perturbation of TPO:c-MPL complex formation and the resulting inhibition of a critical pathway of growth factor cell signaling may represent a general mechanism by which IFN-γ impairs the function of human HSPCs. This understanding could have broad therapeutic implications for various disorders of chronic inflammation.

Long Noncoding RNA FEZF1-AS1 Promotes Proliferation and Inhibits Apoptosis in Ovarian Cancer by Activation of JAK-STAT3 Pathway

BACKGROUND Long noncoding RNAs (lncRNAs) have been acknowledged as important regulators in human cancers, including ovarian cancer. Several reports identified lncRNA FEZF1-AS1 as an oncogene in gastric cancer, colorectal carcinoma, and non-small cell lung cancer (NSCLC). However, the function of FEZF1-AS1 in ovarian cancer remains largely unknown. This study was aimed to investigate the role of FEZF1-AS1 in ovarian cancer. MATERIAL AND METHODS FEZF1-AS1 expression levels in pairs of ovarian cancer tissues and adjacent normal tissues were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Kaplan-Meier curve analysis was used to determine the correlation between FEZF1-AS1 expression and prognosis in ovarian cancer patients. The effects of FEZF1-AS1 knockdown on ovarian cancer cell proliferation, cell-cycle, and apoptosis were analyzed by Cell Counting Kit-8 (CCK8) and Fluorescence activated Cell Sorting (FACS) assays. Western blot was utilized to assess the effect of FEZF1-AS1 on the activation of JAK-STAT3 pathway. RESULTS FEZF1-AS1 was overexpressed in ovarian cancer tissues compared to adjacent normal tissues. Consistently, FEZF1-AS1 expression was also upregulated in ovarian cancer cell lines compared with normal cell line. Furthermore, higher expression of FEZF1-AS1 in ovarian cancer patients contributed to poorer prognosis. FEZF1-AS1 knockdown significantly suppressed the proliferation and promoted apoptosis in ovarian cancer cells. In mechanism, FEZF1-AS1 regulated activation of JAK-STAT3 signaling pathway by modulating STAT3 phosphorylation. Knockdown of FEZF1-AS1 significantly impaired the phosphorylation of STAT3. CONCLUSIONS Our study demonstrated that FEZF1-AS1 exerted an oncogenic role in ovarian cancer via modulating JAK-STAT3 pathway.

The Use of Normal Stem Cells and Cancer Stem Cells for Potential Anti-Cancer Therapeutic Strategy

BACKGROUND

Despite recent advance in conventional cancer therapies including surgery, radiotherapy, chemotherapy, and immunotherapy to reduce tumor size, unfortunately cancer mortality and metastatic cancer incidence remain high. Along with a deeper understanding of stem cell biology, cancer stem cell (CSC) is important in targeted cancer therapy. Herein, we review representative patents using not only normal stem cells as therapeutics themselves or delivery vehicles, but also CSCs as targets for anti-cancer strategy.

METHODS

Relevant patent literatures published between 2005 and 2017 are discussed to present developmental status and experimental results on using normal stem cells and CSCs for cancer therapy and explore potential future directions in this field.

RESULTS

Stem cells have been considered as important element of regenerative therapy by promoting tissue regeneration. Particularly, there is a growing trend to use stem cells as a target drug-delivery system to reduce undesirable side effects in non-target tissues. Noteworthy, studies on CSC-specific markers for distinguishing CSCs from normal stem cells and mature cancer cells have been conducted as a selective anti-cancer therapy with few side effects. Many researchers have also reported the development of various substances with anticancer effects by targeting CSCs from cancer tissues.

CONCLUSION

There has been a continuing increase in the number of studies on therapeutic stem cells and CSC-specific markers for selective diagnosis and therapy of cancer. This review focuses on the current status in the use of normal stem cells and CSCs for targeted cancer therapy. Future direction is also proposed.

Designing Motif-Engineered Receptors To Elucidate Signaling Molecules Important for Proliferation of Hematopoietic Stem Cells

The understanding of signaling events is critical for attaining long-term expansion of hematopoietic stem cells ex vivo. In this study, we aim to analyze the contribution of multiple signaling molecules in proliferation of hematopoietic stem cells. To this end, we design a bottom-up engineered receptor with multiple tyrosine motifs, which can recruit multiple signaling molecules of interest. This is followed by a top-down approach, where one of the multiple tyrosine motifs in the bottom-up engineered receptor is functionally knocked out by tyrosine-to-phenylalanine mutation. The combination of these two approaches demonstrates the importance of Shc in cooperation with STAT3 or STAT5 in the proliferation of hematopoietic stem cells. The platform developed herein may be applied for analyzing other cells and/or other cell fate regulation systems.

The Drosophila lymph gland is an ideal model for studying hematopoiesis

Hematopoiesis in Drosophila melanogaster occurs throughout the entire life cycle, from the embryo to adulthood. The healthy lymph gland, as a hematopoietic organ during the larval stage, can give rise to two mature types of hemocytes, plasmatocytes and crystal cells, which persist into the pupal and adult stages. Homeostasis of the lymph gland is tightly controlled by a series of conserved factors and signaling pathways, which also play key roles in mammalian hematopoiesis. Thus, revealing the hematopoietic mechanisms in Drosophila will advance our understanding of hematopoietic stem cells and their niche as well as leukemia in mammals. In addition, the lymph gland employs a battery of strategies to produce lamellocytes, another type of mature hemocyte, to fight against parasitic wasp eggs, making the lymph gland an important immunological organ. In this review, the developmental process of the lymph gland and the regulatory networks of hematopoiesis are summarized. Moreover, we outline the current knowledge and novel insight into homeostasis of the lymph gland.

Scorpion Venom Causes Upregulation of p53 and Downregulation of Bcl-xL and BID Protein Expression by Modulating Signaling Proteins Erk1/2 and STAT3, and DNA Damage in Breast and Colorectal Cancer Cell Lines

Scorpion venoms efficiently block the normal neurotransmitter signaling pathway by prejudicing the ion channel operating mechanism in the body system. Besides its negative effect, venoms also possess some beneficial qualities for humans. They have also been shown to exhibit anticancer properties in various cancer types. This unique property of the venom as an anticancer agent is mainly a result of its role in initiating apoptosis and inhibiting several signaling cascade mechanisms that promote cancer cell proliferation and growth. In this study, we examine the effect of venom on phenotypic changes as well as changes at the molecular levels in colorectal and breast cancer cell lines. A dramatic decrease in cell invasion was observed in both cancer cell lines on venom treatment. Additionally, there was decrease in IL-6, RhoC, Erk1/2, and STAT3 in venom-treated cell lines, providing strong evidence of its anticancer properties. Furthermore, decrease in the expression of antiapoptotic proteins and also upregulation of proapoptotic ones by these lines were observed on venom treatment. Moreover, a vivid picture of DNA damage was also detected on venom treatment. In conclusion, scorpion venom possesses significant potential as an anticancer agent against colorectal and breast cancer cell lines.

STAT3, stem cells, cancer stem cells and p63

Signal Transducer and Activator of Transcription 3 (STAT3) is a transcription factor with many important functions in the biology of normal and transformed cells. Its regulation is highly complex as it is involved in signaling pathways in many different cell types and under a wide variety of conditions. Besides other functions, STAT3 is an important regulator of normal stem cells and cancer stem cells. p63 which is a member of the p53 protein family is also involved in these functions and is both physically and functionally connected with STAT3. This review summarizes STAT3 function and regulation, its role in stem cell and cancer stem cell properties and highlights recent reports about its relationship to p63.

Genetic rescue of lineage-balanced blood cell production reveals a crucial role for STAT3 antiinflammatory activity in hematopoiesis

Blood cell formation must be appropriately maintained throughout life to provide robust immune function, hemostasis, and oxygen delivery to tissues, and to prevent disorders that result from over- or underproduction of critical lineages. Persistent inflammation deregulates hematopoiesis by damaging hematopoietic stem and progenitor cells (HSPCs), leading to elevated myeloid cell output and eventual bone marrow failure. Nonetheless, antiinflammatory mechanisms that protect the hematopoietic system are understudied. The transcriptional regulator STAT3 has myriad roles in HSPC-derived populations and nonhematopoietic tissues, including a potent antiinflammatory function in differentiated myeloid cells. STAT3 antiinflammatory activity is facilitated by STAT3-mediated transcriptional repression of Ube2n, which encodes the E2 ubiquitin-conjugating enzyme Ubc13 involved in proinflammatory signaling. Here we demonstrate a crucial role for STAT3 antiinflammatory activity in preservation of HSPCs and lineage-balanced hematopoiesis. Conditional Stat3 removal from the hematopoietic system led to depletion of the bone marrow lineage- Sca-1+ c-Kit+ CD150+ CD48- HSPC subset (LSK CD150+ CD48- cells), myeloid-skewed hematopoiesis, and accrual of DNA damage in HSPCs. These responses were accompanied by intrinsic transcriptional alterations in HSPCs, including deregulation of inflammatory, survival and developmental pathways. Concomitant Ube2n/Ubc13 deletion from Stat3-deficient hematopoietic cells enabled lineage-balanced hematopoiesis, mitigated depletion of bone marrow LSK CD150+ CD48- cells, alleviated HSPC DNA damage, and corrected a majority of aberrant transcriptional responses. These results indicate an intrinsic protective role for STAT3 in the hematopoietic system, and suggest that this is mediated by STAT3-dependent restraint of excessive proinflammatory signaling via Ubc13 modulation.

STAT3 inhibition as a therapeutic strategy for leukemia

Leukemia is characterized by selective overgrowth of malignant hematopoietic stem cells (HSC's) that interfere with HSC differentiation. Cytoreductive chemotherapy can kill rapidly dividing cancerous cells but cannot eradicate the malignant HSC pool leading to relapses. Leukemic stem cells have several dysregulated pathways and the Janus kinases (JAKs) and signal transducer and activator of transcription (STAT) pathway are prominent among them. STAT3 is an important transcription factor that regulates cell growth, proliferation, and inhibits apoptosis. High STAT3 expression in leukemia has been associated with an increased risk for relapse and decreased overall survival. Multiple strategies for interfering with STAT3 activity in leukemic cells include inhibition of STAT3 phosphorylation, interfering with STAT3 interactions, preventing nuclear transfer, inhibiting transcription and causing interference in STAT: DNA binding. A better understanding of key interactions and upstream mediators of STAT3 activity will help facilitate the development of effective cancer therapies and may result in durable remissions.

NRF2 Activation Impairs Quiescence and Bone Marrow Reconstitution Capacity of Hematopoietic Stem Cells

Tissue stem cells are maintained in quiescence under physiological conditions but proliferate and differentiate to replenish mature cells under stressed conditions. The KEAP1-NRF2 system plays an essential role in stress response and cytoprotection against redox disturbance. To clarify the role of the KEAP1-NRF2 system in tissue stem cells, we focused on hematopoiesis in this study and used Keap1-deficient mice to examine the effects of persistent activation of NRF2 on long-term hematopoietic stem cells (LT-HSCs). We found that persistent activation of NRF2 due to Keap1 deficiency did not change the number of LT-HSCs but reduced their quiescence in steady-state hematopoiesis. During hematopoietic regeneration after bone marrow (BM) transplantation, persistent activation of NRF2 reduced the BM reconstitution capacity of LT-HSCs, suggesting that NRF2 reduces the quiescence of LT-HSCs and promotes their differentiation, leading to eventual exhaustion. Transient activation of NRF2 by an electrophilic reagent also promotes the entry of LT-HSCs into the cell cycle. Taken together, our findings show that NRF2 drives the cell cycle entry and differentiation of LT-HSCs at the expense of their quiescence and maintenance, an effect that appears to be beneficial for prompt recovery from blood loss. We propose that the appropriate control of NRF2 activity by KEAP1 is essential for maintaining HSCs and guarantees their stress-induced regenerative response.

The STAT3-miRNA-92-Wnt Signaling Pathway Regulates Spheroid Formation and Malignant Progression in Ovarian Cancer

Ovarian cancer spheroids constitute a metastatic niche for transcoelomic spread that also engenders drug resistance. Spheroid-forming cells express active STAT3 signaling and display stem cell-like properties that may contribute to ovarian tumor progression. In this study, we show that STAT3 is hyperactivated in ovarian cancer spheroids and that STAT3 disruption in this setting is sufficient to relieve chemoresistance. In an NSG murine model of human ovarian cancer, STAT3 signaling regulated spheroid formation and self-renewal properties, whereas STAT3 attenuation reduced tumorigenicity. Mechanistic investigations revealed that Wnt signaling was required for STAT3-mediated spheroid formation. Notably, the Wnt antagonist DKK1 was the most strikingly upregulated gene in response to STAT3 attenuation in ovarian cancer cells. STAT3 signaling maintained stemness and interconnected Wnt/β-catenin signaling via the miR-92a/DKK1-regulatory pathways. Targeting STAT3 in combination with paclitaxel synergistically reduced peritoneal seeding and prolonged survival in a murine model of intraperitoneal ovarian cancer. Overall, our findings define a STAT3-miR-92a-DKK1 pathway in the generation of cancer stem-like cells in ovarian tumors, with potential therapeutic applications in blocking their progression. Cancer Res; 77(8); 1955-67. ©2017 AACR.

Heterogeneous Niche Activity of Ex-Vivo Expanded MSCs as Factor for Variable Outcomes in Hematopoietic Recovery

Ex-vivo expanded mesenchymal stromal cells (MSCs) are increasingly used for paracrine support of hematopoietic stem cell (HSC) regeneration, but inconsistent outcomes have hindered ongoing clinical trials. Here, we show that significant heterogeneity in the niche activity of MSCs is created during their culture in various serum-supplemented media. The MSCs cultured under stimulatory or non-stimulatory culture conditions exhibited differences in colony forming unit-fibroblast contents, expression levels of cross-talk molecules (Jagged-1 and CXCL-12) and their support for HSC self-renewal. Accordingly, the enhancing effects of MSCs on hematopoietic engraftment were only visible when HSCs were co-transplanted with MSCs under stimulatory conditions. Of note, these differences in MSCs and their effects on HSCs were readily reversed by switching the cultures, indicating that the difference in niche activity can be caused by distinct functional state, rather than by clonal heterogeneity. Supporting the findings, transcriptomic analysis showed distinct upstream signaling pathways such as inhibition of P53 and activation of ER-stress response gene ATF4 for MSCs under stimulatory conditions. Taken together, our study shows that the niche activity of MSCs can vary rapidly by the extrinsic cues during culture causing variable outcomes in hematopoietic recoveries, and point to the possibility that MSCs can be pre-screened for more predictable efficacy in various cell therapy trials.

Transient Tcf3 Gene Repression by TALE-Transcription Factor Targeting

Transplantation of hematopoietic stem and progenitor cells (HSCs) i.e., self-renewing cells that retain multipotentiality, is now a widely performed therapy for many hematopoietic diseases. However, these cells are present in low number and are subject to replicative senescence after extraction; thus, the acquisition of sufficient numbers of cells for transplantation requires donors able to provide repetitive blood samples and/or methods of expanding cell numbers without disturbing cell multipotentiality. Previous studies have shown that HSCs maintain their multipotentiality and self-renewal activity if TCF3 transcription function is blocked under B cell differentiating conditions. Taking advantage of this finding to devise a new approach to HSC expansion in vitro, we constructed an episomal expression vector that specifically targets and transiently represses the TCF3 gene. This consisted of a vector encoding a transcription activator-like effector (TALE) fused to a Krüppel-associated box (KRAB) repressor. We showed that this TALE-KRAB vector repressed expression of an exogenous reporter gene in HEK293 and COS-7 cell lines and, more importantly, efficiently repressed endogenous TCF3 in a human B lymphoma cell line. These findings suggest that this vector can be used to maintain multipotentiality in HSC being subjected to a long-term expansion regimen prior to transplantation.

Loss of p300 accelerates MDS-associated leukemogenesis

The role that changes in DNA methylation and histone modifications have in human malignancies is poorly understood. p300 and CREB-binding protein (CBP), two distinct but highly homologous lysine acetyltransferases, are mutated in several cancers, suggesting their role as tumor suppressors. In the current study, we found that deletion of p300, but not CBP, markedly accelerated the leukemogenesis ofNup98-HoxD13 (NHD13) transgenic mice, an animal model that phenotypically copies human myelodysplastic syndrome (MDS). p300 deletion restored the ability of NHD13 expressing hematopoietic stem and progenitor cells (HSPCs) to self-renew in vitro, and to expand in vivo, with an increase in stem cell symmetric self-renewal divisions and a decrease in apoptosis. Furthermore, loss of p300, but not CBP, promoted cytokine signaling, including enhanced activation of the MAPK and JAK/STAT pathways in the HSPC compartment. Altogether, our data indicate that p300 has a pivotal role in blocking the transformation of MDS to acute myeloid leukemia, a role distinct from that of CBP.

Protein kinase CK2 regulates AKT, NF-κB and STAT3 activation, stem cell viability and proliferation in acute myeloid leukemia

Protein kinase CK2 sustains acute myeloid leukemia cell growth, but its role in leukemia stem cells is largely unknown. Here, we discovered that the CK2 catalytic α and regulatory β subunits are consistently expressed in leukemia stem cells isolated from acute myeloid leukemia patients and cell lines. CK2 inactivation with the selective inhibitor CX-4945 or RNA interference induced an accumulation of leukemia stem cells in the late S-G2-M phases of the cell cycle and triggered late-onset apoptosis. As a result, leukemia stem cells displayed an increased sensitivity to the chemotherapeutic agent doxorubicin. From a molecular standpoint, CK2 blockade was associated with a downmodulation of the stem cell-regulating protein BMI-1 and a marked impairment of AKT, nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) activation, whereas FOXO3a nuclear activity was induced. Notably, combined CK2 and either NF-κB or STAT3 inhibition resulted in a superior cytotoxic effect on leukemia stem cells. This study suggests that CK2 blockade could be a rational approach to minimize the persistence of residual leukemia cells.

Endogenous transmembrane protein UT2 inhibits pSTAT3 and suppresses hematological malignancy

Regulation of STAT3 activation is critical for normal and malignant hematopoietic cell proliferation. Here, we have reported that the endogenous transmembrane protein upstream-of-mTORC2 (UT2) negatively regulates activation of STAT3. Specifically, we determined that UT2 interacts directly with GP130 and inhibits phosphorylation of STAT3 on tyrosine 705 (STAT3Y705). This reduces cytokine signaling including IL6 that is implicated in multiple myeloma and other hematopoietic malignancies. Modulation of UT2 resulted in inverse effects on animal survival in myeloma models. Samples from multiple myeloma patients also revealed a decreased copy number of UT2 and decreased expression of UT2 in genomic and transcriptomic analyses, respectively. Together, these studies identify a transmembrane protein that functions to negatively regulate cytokine signaling through GP130 and pSTAT3Y705 and is molecularly and mechanistically distinct from the suppressors of cytokine signaling (SOCS) family of genes. Moreover, this work provides evidence that perturbations of this activation-dampening molecule participate in hematologic malignancies and may serve as a key determinant of multiple myeloma pathophysiology. UT2 is a negative regulator shared across STAT3 and mTORC2 signaling cascades, functioning as a tumor suppressor in hematologic malignancies driven by those pathways.

Ciliary neurotrophic factor promotes the activation of corneal epithelial stem/progenitor cells and accelerates corneal epithelial wound healing

Ciliary neurotrophic factor (CNTF), a well-known neuroprotective cytokine, has been found to play an important role in neurogenesis and functional regulations of neural stem cells. As one of the most innervated tissue, however, the role of CNTF in cornea epithelium remains unclear. This study was to explore the roles and mechanisms of CNTF in the activation of corneal epithelial stem/progenitor cells and wound healing of both normal and diabetic mouse corneal epithelium. In mice subjecting to mechanical removal of corneal epithelium, the corneal epithelial stem/progenitor cell activation and wound healing were promoted by exogenous CNTF application, while delayed by CNTF neutralizing antibody. In cultured corneal epithelial stem/progenitor cells, CNTF enhanced the colony-forming efficiency, stimulated the mitogenic proliferation, and upregulated the expression levels of corneal epithelial stem/progenitor cell-associated transcription factors. Furthermore, the promotion of CNTF on the corneal epithelial stem/progenitor cell activation and wound healing was mediated by the activation of STAT3. Moreover, in diabetic mice, the content of CNTF in corneal epithelium decreased significantly when compared with that of normal mice, and the supplement of CNTF promoted the diabetic corneal epithelial wound healing, accompanied with the advanced activation of corneal epithelial stem/progenitor cells and the regeneration of corneal nerve fibers. Thus, the capability of expanding corneal epithelial stem/progenitor cells and promoting corneal epithelial wound healing and nerve regeneration indicates the potential application of CNTF in ameliorating limbal stem cell deficiency and treating diabetic keratopathy.

Tissue transglutaminase-interleukin-6 axis facilitates peritoneal tumor spreading and metastasis of human ovarian cancer cells

Inflammation has recently been implicated in cancer formation and progression. As tissue transglutaminase (TG2) has been associated with both inflammatory signaling and tumor cell behavior, we propose that TG2 may be an important link inducing interleukin-6 (IL-6)-mediated cancer cell aggressiveness, including cancer stem cell-like characteristics and distant hematogenous metastasis. We evaluated the effect of differential TG2 and IL-6 expression on in vivo distant metastasis of human ovarian cancer cells. IL-6 production in human ovarian cancer cells was dependent on their TG2 expression levels. The size and efficiency of tumor sphere formation were correlated with TG2 expression levels and were dependent on TG2-mediated IL-6 secretion in human ovarian cancer cells. Primary tumor growth and propagation in the peritoneum and distant hematogenous metastasis into the liver and lung were also dependent on TG2 and downstream IL-6 expression levels in human ovarian cancer cells. In this report, we provide evidence that TG2 is an important link in IL-6-mediated tumor cell aggressiveness, and that TG2 and downstream IL-6 could be important mediators of distant hematogenous metastasis of human ovarian cancer cells. Intervention specific to TG2 and/or downstream IL-6 in ovarian cancer cells could provide a promising means to control tumor metastasis.

Insulin-InsR signaling drives multipotent progenitor differentiation toward lymphoid lineages

Xia et al. report that insulin receptor signaling is required for lymphoid lineage specification in early lymphopoiesis via modulation of Ikaros expression. Disrupted insulin signaling generates more myeloid cells and fewer lymphoid cells, resulting in a skewed myeloid/lymphoid ratio in diabetic mice.

The lineage commitment of HSCs generates balanced myeloid and lymphoid populations in hematopoiesis. However, the underlying mechanisms that control this process remain largely unknown. Here, we show that insulin–insulin receptor (InsR) signaling is required for lineage commitment of multipotent progenitors (MPPs). Deletion of Insr in murine bone marrow causes skewed differentiation of MPPs to myeloid cells. mTOR acts as a downstream effector that modulates MPP differentiation. mTOR activates Stat3 by phosphorylation at serine 727 under insulin stimulation, which binds to the promoter of Ikaros, leading to its transcription priming. Our findings reveal that the insulin–InsR signaling drives MPP differentiation into lymphoid lineages in early lymphopoiesis, which is essential for maintaining a balanced immune system for an individual organism.

STAT3 signaling is activated preferentially in tumor-initiating cells in claudin-low models of human breast cancer

In breast cancer, a subset of tumor-initiating cells (TIC) or "cancer stem cells" are thought to be responsible for tumor maintenance, treatment resistance, and disease recurrence. While current breast cancer stem cell markers (e.g., CD44(high) /CD24(low/neg) , ALDH positive) have allowed enrichment for such cells, they are not universally expressed and may actually identify distinct TIC subpopulations in the same tumor. Thus, additional markers of functional stem cells are needed. The STAT3 pathway is a critical regulator of the function of normal stem cells, and evidence is accumulating for its important role in breast cancer stem cells. However, due to the lack of a method for separating live cells based on their level of STAT3 activity, it remains unknown whether STAT3 functions in the cancer stem cells themselves, or in surrounding niche cells, or in both. To approach this question, we constructed a series of lentiviral fluorescent (enhanced green fluorescent protein, EGFP) reporters that enabled flow cytometric enrichment of cells differing in STAT3-mediated transcriptional activity, as well as in vivo/in situ localization of STAT3 responsive cells. Using in vivo claudin-low cell line xenograft models of human breast cancer, we found that STAT3 signaling reporter activity (EGFP(+) ) is associated with a subpopulation of cancer cells enriched for mammosphere-forming efficiency, as well as TIC function in limiting dilution transplantation assays compared to negative or unsorted populations. Our results support STAT3 signaling activity as another functional marker for human breast cancer stem cells thus making it an attractive therapeutic target for stem-cell-directed therapy in some breast cancer subtypes.

Catalase inhibits ionizing radiation-induced apoptosis in hematopoietic stem and progenitor cells

Hematologic toxicity is a major cause of mortality in radiation emergency scenarios and a primary side effect concern in patients undergoing chemo-radiotherapy. Therefore, there is a critical need for the development of novel and more effective approaches to manage this side effect. Catalase is a potent antioxidant enzyme that coverts hydrogen peroxide into hydrogen and water. In this study, we evaluated the efficacy of catalase as a protectant against ionizing radiation (IR)-induced toxicity in hematopoietic stem and progenitor cells (HSPCs). The results revealed that catalase treatment markedly inhibits IR-induced apoptosis in murine hematopoietic stem cells and hematopoietic progenitor cells. Subsequent colony-forming cell and cobble-stone area-forming cell assays showed that catalase-treated HSPCs can not only survive irradiation-induced apoptosis but also have higher clonogenic capacity, compared with vehicle-treated cells. Moreover, transplantation of catalase-treated irradiated HSPCs results in high levels of multi-lineage and long-term engraftments, whereas vehicle-treated irradiated HSPCs exhibit very limited hematopoiesis reconstituting capacity. Mechanistically, catalase treatment attenuates IR-induced DNA double-strand breaks and inhibits reactive oxygen species. Unexpectedly, we found that the radioprotective effect of catalase is associated with activation of the signal transducer and activator of transcription 3 (STAT3) signaling pathway and pharmacological inhibition of STAT3 abolishes the protective activity of catalase, suggesting that catalase may protect HSPCs against IR-induced toxicity via promoting STAT3 activation. Collectively, these results demonstrate a previously unrecognized mechanism by which catalase inhibits IR-induced DNA damage and apoptosis in HSPCs.

Molecular integration of HoxB4 and STAT3 for self-renewal of hematopoietic stem cells: a model of molecular convergence for stemness

The upregulation of HoxB4 promotes self-renewal of hematopoietic stem cells (HSCs) without overriding the normal stem cell pool size. A similar enhancement of HSC self-renewal occurs when signal transducer and activator of transcription 3 (STAT3) is activated in HSCs. In this study, to gain insight into the functional organization of individual transcription factors (TFs) that have similar effects on HSCs, we investigated the molecular interplay between HoxB4 and STAT3 in the regulation of HSC self-renewal. We found that while STAT3-C or HoxB4 similarly enhanced the in vitro self-renewal and in vivo repopulating activities of HSCs, simultaneous transduction of both TFs did not have additive effects, indicating their functional redundancy in HSCs. In addition, activation of STAT3 did not cause changes in the expression levels of HoxB4. In contrast, the inhibition of STAT3 activity in HoxB4-overexpressing hematopoietic cells significantly abrogated the enhancing effects of HoxB4, and the upregulation of HoxB4 caused a ligand-independent Tyr-phosphorylation of STAT3. Microarray analysis revealed a significant overlap of the transcriptomes regulated by STAT3 and HoxB4 in undifferentiated hematopoietic cells. Moreover, a gene set enrichment analysis showed significant overlap in the candidate TFs that can recapitulate the transcriptional changes induced by HoxB4 or STAT3. Interestingly, among these common TFs were the pluripotency-related genes Oct-4 and Nanog. These results indicate that tissue-specific TFs regulating HSC self-renewal are functionally organized to play an equivalent role in transcription and provide insights into the functional convergence of multiple entries of TFs toward a conserved transcription program for the stem cell state.

STAT3 as a possible therapeutic target in human malignancies: lessons from acute myeloid leukemia

STAT3 is important for transcriptional regulation in human acute myeloid leukemia (AML). STAT3 has thousands of potential DNA binding sites but usually shows cell type specific binding preferences to a limited number of these. Furthermore, AML is a very heterogeneous disease, and studies of the prognostic impact of STAT3 in human AML have also given conflicting results. A more detailed characterization of STAT3 functions and the expression of various isoforms in human AML will therefore be required before it is possible to design clinical studies of STAT3 inhibitors in this disease, and it will be especially important to investigate whether the functions of STAT3 differ between patients. Several other malignancies also show extensive biological heterogeneity, and the present discussion and the suggested scientific approaches may thus be relevant for other cancer patients.

Priming with ligands secreted by human stromal progenitor cells promotes grafts of cardiac stem/progenitor cells after myocardial infarction

Transplantation of culture-expanded adult stem/progenitor cells often results in poor cellular engraftment, survival, and migration into sites of tissue injury. Mesenchymal cells including fibroblasts and stromal cells secrete factors that protect injured tissues, promote tissue repair, and support many types of stem/progenitor cells in culture. We hypothesized that secreted factors in conditioned medium (CdM) from adult bone marrow-derived multipotent stromal cells (MSCs) could be used to prime adult cardiac stem/progenitor cells (CSCs/CPCs) and improve graft success after myocardial infarction (MI). Incubation of adult rat CPCs in CdM from human MSCs isolated by plastic adherence or by magnetic sorting against CD271 (a.k.a., p75 low-affinity nerve growth factor receptor; p75MSCs) induced phosphorylation of STAT3 and Akt in CPCs, supporting their proliferation under normoxic conditions and survival under hypoxic conditions (1% oxygen). Priming CSCs with 30× p75MSC CdM for 30 minutes prior to transplantation into subepicardial tissue 1 day after MI markedly increased engraftment compared with vehicle priming. Screening CdM with neutralizing/blocking antibodies identified connective tissue growth factor (CTGF) and Insulin as key factors in p75MSC CdM that protected CPCs. Human CTGF peptide (CTGF-D4) and Insulin synergistically promoted CPC survival during hypoxia in culture. Similar to CdM priming, priming of CSCs with CTGF-D4 and Insulin for 30 minutes prior to transplantation promoted robust engraftment, survival, and migration of CSC derivatives at 1 week and 1 month after MI. Our results indicate that short-term priming of human CSCs with CTGF-D4 and Insulin may improve graft success and cardiac regeneration in patients with MI.

Comments on the mechanisms of action of radiation protective agents: basis components and their polyvalence

Purpose

These comments suggest a division of radiation protective agents on the grounds of their mechanism of action that increase the radio resistance of an organism.

Conclusion

Given below is the division of radiation protective agents on the basis of their mechanism of action into 3 groups: 1) Radiation protective agents, with the implementation of radiation protective action taking place at the cellular level in the course of rapidly proceeding radiation-chemical reactions. At the same time, when the ionizing radiation energy is absorbed, these agents partially neutralize the “oxygen effect” as a radiobiological phenomenon, especially in the radiolysis of DNA; 2) Radiation protective agents that exert their effect at the system level by accelerating the post-radiation recovery of radiosensitive tissues through activation of a number of pro-inflammatory signaling pathways and an increase in the secretion of hematopoietic growth factors, including their use as mitigators in the early period after irradiation prior to the clinical development of acute radiation syndrome (ARS). 3) Radiomodulators including drugs and nutritional supplements that can elevate the resistance of the organism to adverse environmental factors, including exposure to ionization by means of modulating the gene expression through a hormetic effect of small doses of stressors and a “substrate” maintenance of adaptive changes, resulting in an increased antioxidant protection of the organism. Radiation protective agents having polyvalence in implementation of their action may simultaneously induce radioprotective effect by various routes with a prevalence of basis mechanisms of the action.

STAT transcription factors in normal and cancer stem cells

Signal transducer and activator of transcription proteins (STATs) play vital roles in the regulation of cellular proliferation and survival in normal hematopoietic cells, including hematopoietic stem cells. However, aberrant activation of STATs is commonly observed in a number of hematologic malignancies, and recent studies indicate that targeting of STATs may have therapeutic benefit in these diseases. Additional studies have provided greater understanding of the cells responsible for leukemia initiation, referred to as leukemia stem cells. Emerging evidence indicates that STATs are important in maintaining leukemia stem cells and represent a promising target for eradication of this dangerous cell population. Here we summarize what is known about normal hematopoietic stem cells and the origin of leukemic stem cells. We further describe the roles of STAT proteins in these cell populations, as well as current progress toward the development of novel agents and strategies for targeting the STAT proteins.