The maternal hormone in the male brain: Sexually dimorphic distribution of prolactin signalling in the mouse brain

Research of the central actions of prolactin is highly focused on females, but this hormone has also documented roles in male physiology and behaviour. Here, we provide the first description of the pattern of prolactin-derived signalling in the male mouse brain, employing the immunostaining of phosphorylated signal transducer and activator of transcription 5 (pSTAT5) after exogenous prolactin administration. Next, we explore possible sexually dimorphic differences by comparing pSTAT5 immunoreactivity in prolactin-supplemented males and females. We also assess the role of testosterone in the regulation of central prolactin signalling in males by comparing intact with castrated prolactin-supplemented males. Prolactin-supplemented males displayed a widespread pattern of pSTAT5 immunoreactivity, restricted to brain centres showing expression of the prolactin receptor. Immunoreactivity for pSTAT5 was present in several nuclei of the preoptic, anterior and tuberal hypothalamus, as well as in the septofimbrial nucleus or posterodorsal medial amygdala of the telencephalon. Conversely, non-supplemented control males were virtually devoid of pSTAT5-immunoreactivity, suggesting that central prolactin actions in males are limited to situations concurrent with substantial hypophyseal prolactin release (e.g. stress or mating). Furthermore, comparison of prolactin-supplemented males and females revealed a significant, female-biased sexual dimorphism, supporting the view that prolactin has a preeminent role in female physiology and behaviour. Finally, in males, castration significantly reduced pSTAT5 immunoreactivity in some structures, including the paraventricular and ventromedial hypothalamic nuclei and the septofimbrial region, thus indicating a region-specific regulatory role of testosterone over central prolactin signalling.

Growth hormone activated STAT5 is required for induction of beige fat in vivo

OBJECTIVE

The anti-obesity actions of growth hormone (GH) led us to investigate if GH signaling is able to regulate beige/brite fat development of white adipose tissue (WAT).

METHODS

We studied WAT in GHR-391 mice engineered to be unable to activate STAT5 in response to GH, in mice with adipose specific deletion of GHR, in GHR-/- mice and in bGH transgenic mice. QPCR, immunoblots and immunohistochemistry were used to characterize WAT. The in vivo effects of β-3 adrenergic activation with CL-316,243 and that of FGF21 infusion were also studied.

RESULTS

GHR-391 mice had lower surface temperature than WT, with deficiency in β-oxidation and beiging transcripts including Ucp1. Oxidative phosphorylation complex subunit proteins were decreased dramatically in GHR-391 inguinal white adipose tissue (iWAT), but increased in bGH iWAT, as were proteins for beige/brown markers. In accord with its lack of β-3 adrenergic receptors, iWAT of GHR-391 mice did not beige in response to administration of the β-3 specific agonist CL-316,243 in contrast to WT mice. GHR-391 mice are deficient in FGF21, but unlike WT, infusion of the purified protein was without effect on extent of beiging. Finally, fat-specific deletion of the GHR replicated the loss of beiging associated transcripts.

CONCLUSION

In addition to promoting lipolysis, our study suggests that GH is able to promote formation of beige adipose tissue through activation of STAT5 and induction of Adrb3. This sensitizes WAT to adrenergic input, and may contribute to the anti-obesity actions of GH.

Identification of an Essential Cytoplasmic Region of Interleukin-7 Receptor α Subunit in B-Cell Development

Interleukin-7 (IL-7) is essential for lymphocyte development. To identify the functional subdomains in the cytoplasmic tail of the IL-7 receptor (IL-7R) α chain, here, we constructed a series of IL-7Rα deletion mutants. We found that IL-7Rα-deficient hematopoietic progenitor cells (HPCs) gave rise to B cells both in vitro and in vivo when a wild-type (WT) IL-7Rα chain was introduced; however, no B cells were observed under the same conditions from IL-7Rα-deficient HPCs with introduction of the exogenous IL-7Rα subunit, which lacked the amino acid region at positions 414⁻441 (d414⁻441 mutant). Signal transducer and activator of transcription 5 (STAT5) was phosphorylated in cells with the d414⁻441 mutant, similar to that in WT cells, in response to IL-7 stimulation. In contrast, more truncated STAT5 (tSTAT5) was generated in cells with the d414⁻441 mutant than in WT cells. Additionally, the introduction of exogenous tSTAT5 blocked B lymphopoiesis but not myeloid cell development from WT HPCs in vivo. These results suggested that amino acids 414⁻441 in the IL-7Rα chain formed a critical subdomain necessary for the supportive roles of IL-7 in B-cell development.

Cooperative Enhancer Activation by TLX1 and STAT5 Drives Development of NUP214-ABL1/TLX1-Positive T Cell Acute Lymphoblastic Leukemia

The NUP214-ABL1 fusion is a constitutively activated tyrosine kinase that is significantly associated with overexpression of the TLX1 and TLX3 transcription factors in T cell acute lymphoblastic leukemia (T-ALL). Here we show that NUP214-ABL1 cooperates with TLX1 in driving T-ALL development using a transgenic mouse model and human T-ALL cells. Using integrated ChIP-sequencing, ATAC-sequencing, and RNA-sequencing data, we demonstrate that TLX1 and STAT5, the downstream effector of NUP214-ABL1, co-bind poised enhancer regions, and cooperatively activate the expression of key proto-oncogenes such as MYC and BCL2. Inhibition of STAT5, downregulation of TLX1 or MYC, or interference with enhancer function through BET-inhibitor treatment leads to reduction of target gene expression and induction of leukemia cell death.

GH directly stimulates UCP3 expression

OBJECTIVE

We evaluated the direct action of GH signaling in energy homeostasis in myocytes.

DESIGN

We investigated the GH-induced expression of UCP3 in human embryonic kidney 293 cells, human H-EMC-SS chondrosarcoma cells, murine C2C12 skeletal muscle myoblasts, and rat L6 skeletal muscle cells, as well as its direct effect on the GHR/JAK/STAT5 pathway using a combination of a reporter assay, real-time quantitative polymerase chain reaction, and western blotting.

RESULTS

We demonstrated that the regulation of energy metabolism by GH involves UCP3 via activated STAT5, a signal transducer downstream of GH. UCP3 expression increased with STAT5 in a dose-dependent manner and was higher than that of UCP2. We confirmed the functional STAT5 binding site consensus sequences at -861 and -507 bp in the UCP3 promoter region.

CONCLUSION

The results suggest that GH stimulates UCP3 directly and that UCP2 and that UCP3 participate in the signal transduction pathway that functions downstream of the GHR/JAK/STAT.

Roles of germline JAK2 activation mutation JAK2 V625F in the pathology of myeloproliferative neoplasms

Janus tyrosine kinase 2 (JAK2) mediates downstream signaling of cytokine receptors in all hematological lineages, constitutively active somatic JAK2 mutations play key roles in the pathology of myeloproliferative neoplasms (MPNs). Recently, germline JAK2 mutations are also associated with triple-negative MPNs. A novel germline mutation JAK2 V625F is reported to be involved in a subset of MPNs patients. However, the pathogenesis of this mutation caused MPN is still unclear. In this study, the homology models of JAK2 V625F showed that the newly formed interaction between F625 and Y613 disrupted the JAK2 JH1-JH2 domain interactions was responsible for its activation, when F625 and Y613 interaction was disrupted, its activity significantly decreased. While, when this interaction was repaired whether by forming hydrogen bond or salt bond, it would cause JAK2 activation. Biochemical studies also demonstrated that JAK2 V625F mutation led to JAK2-STAT5 pathway activation and promoted the proliferation of BaF3 cells. Thus, our results herein provide clues to understand the mechanism JAK2 V625F mutation caused MPNs and give information for the development of JAK2 mutation specific inhibitors.

DKK2 imparts tumor immunity evasion through β-catenin-independent suppression of cytotoxic immune-cell activation

Immunotherapy offers new options for cancer treatment, but efficacy varies across cancer types. Colorectal cancers (CRCs) are largely refractory to immune-checkpoint blockade, which suggests the presence of yet uncharacterized immune-suppressive mechanisms. Here we report that the loss of adenomatosis polyposis coli (APC) in intestinal tumor cells or of the tumor suppressor PTEN in melanoma cells upregulates the expression of Dickkopf-related protein 2 (DKK2), which, together with its receptor LRP5, provides an unconventional mechanism for tumor immune evasion. DKK2 secreted by tumor cells acts on cytotoxic lymphocytes, inhibiting STAT5 signaling by impeding STAT5 nuclear localization via LRP5, but independently of LRP6 and the Wnt-β-catenin pathway. Genetic or antibody-mediated ablation of DKK2 activates natural killer (NK) cells and CD8+ T cells in tumors, impedes tumor progression, and enhances the effects of PD-1 blockade. Thus, we have identified a previously unknown tumor immune-suppressive mechanism and immunotherapeutic targets particularly relevant for CRCs and a subset of melanomas.

Arginine reverses growth hormone resistance through the inhibition of toll-like receptor 4-mediated inflammatory pathway

OBJECTIVE

Growth hormone stimulates growth by increasing insulin-like growth factor 1 expression and secretion. In the presence of insufficient nutrients, GH increases, whereas IGF-1 expression becomes severely suppressed, leading to GH resistance. This study aimed to explore the effect of arginine (Arg) on GH resistance during malnutrition and to describe its underlying mechanism.

METHODS

C57BL/6J mice were injected intraperitoneally with Arg for 1h or subjected to caloric restriction with Arg supplement in drinking water for 18days. HepG2 cells were exposed to different Arg concentrations for 24h. Signaling pathway agonists/inhibitors, siRNA, and overexpression plasmids were used to investigate the underlying molecular mechanism. Liver-specific toll-like receptor (TLR4) knockout mice were utilized to clarify the role of TLR4 in Arg-induced IGF-I expression and secretion.

RESULTS

Arg inhibited the TLR4 downstream pathway by binding to TLR4 and consequently activated Janus kinase 2/signal transducer and activator of transcription 5 signaling pathway. As a result, IGF-1 transcription and secretion increased. Arg activity was absent in liver-specific TLR4 knockout mice and was greatly suppressed in liver with overexpressed TLR4, suggesting that hepatic TLR4 was required and sufficient to induce GH resistance. By contrast, the mammalian target of rapamycin pathway was unnecessary for Arg activity. Arg not only significantly increased IGF-1 expression and secretion under acute fasting and chronic CR conditions but also attenuated body weight loss.

CONCLUSIONS

Our results demonstrate a previously unappreciated pathway involving Arg that reverses GH resistance and alleviates malnutrition-induced growth restriction through the inhibition of TLR4-mediated inflammatory pathway.

MRTF-A mediated FN and ICAM-1 expression in AGEs-induced rat glomerular mesangial cells via activating STAT5

Advanced glycation end products (AGEs), formed at an accelerated rate under diabetes, play a role in inflammation and fibrosis in mesangial areas in diabetic nephropathy (DN). However, the transcriptional modulator that mediates the cellular response to AGEs remains largely obscure. Our goal was to determine whether myocardin-related transcription factor (MRTF)-A, a key protein involved in the transcriptional regulation of smooth muscle cell phenotype, was responsible for the glomerular mesangial cells (GMCs) injury by AGEs, and, if so, how MRTF-A promoted mesangial dysfunction initiated by AGEs. In this study, MRTF-A was activated by AGEs in terms of protein expression and nuclear translocation in rat GMCs. MRTF-A overexpression synergistically enhanced the induction of FN and ICAM-1 by AGEs. In contract, depletion of MRTF-A abrogated the pathogenic program triggered by AGEs. Then, by interfering with MRTF-A, STAT1, STAT3 and STAT5 nuclear translocation were observed and we screened out STAT5, which was decreased obviously when MRTF-A depleted. Further investigation showed that MRTF-A interacted with STAT5 and promoted its nuclear accumulation and transcriptional activity. Therefore, our present findings suggested a role of MRTF-A in AGEs-induced GMCs injury, and further revealed that the underlying molecular mechanism was related to activating the nuclear factor STAT5.

Ginsenoside Rg3 ameliorated HFD-induced hepatic steatosis through downregulation of STAT5-PPARγ

Healthy expansion of adipose tissue maintains metabolic homeostasis by storing excess chemical energy in increased fat mass. The STAT5-PPAR gamma pathway reportedly regulates adipocyte differentiation, lipid metabolism and adipogenesis. Ginsenoside Rg3 is one of the diverse groups of steroidal saponins, the major active components of ginseng, which have demonstrated pharmacological properties. In this study, we evaluated the therapeutic effects of ginsenoside Rg3 under pathological conditions in vitro and in vivo We examined the effects of ginsenoside Rg3 on glucose level, insulin sensitivity and lipogenesis in high-fat diet-fed C57BL/6 mice. Ginsenoside Rg3 was also applied to the pre-adipocyte cell line 3T3-L1 to assess the impact on lipogenesis. Ginsenoside Rg3 reduced epididymal white adipose tissue (eWAT) size and hepatic steatosis, and the amount of triglycerides (TGs) in both eWAT and liver. Similar to the murine model, Rg3-treated 3T3-L1 cells showed a reduction in lipid accumulation and amount of total TGs. Ginsenoside Rg3 regulates the expression of PPAR gamma though STAT5 in vitro and in vivo According to our results, lipid metabolism-related genes were downregulated in the high-fat mice and 3T3-L1 cell line. Rg3 shows potential for the amelioration of obesity-induced pathology, acting though STAT5-PPAR gamma to facilitate the healthy functioning of adipose tissue. This is the first report of evidence that obesity-induced insulin resistance and lipotoxicity can be treated with ginsenoside Rg3, which acts though the STAT5-PPAR gamma pathway in vivo and in vitro.

Effects of growth hormone on uncoupling protein 1 in white adipose tissues in obese mice

OBJECTIVE

The transition of white adipocytes to beige cells (a phenomenon referred to as browning or beigeing) during obesity has been previously reported. Our study aimed to examine the mechanisms through which obesity induced by a high fat diet (HFD) affects uncoupling protein 1 (UCP1) expression via signal transduction and activator of transcription 5 (STAT5s).

DESIGN

Seven-week-old male C57BL/6J mice were fed a normal or HFD for 11weeks. Body weight, white adipose tissue weight, and blood lipid and glucose levels were measured. To unveil the molecular mechanisms of UCP1 expression in adipose tissue, we performed further studying 3T3-L1 cells using qRT-PCR. We also measured UCP1 promoter activity in the TSA201 cell line using a dual luciferase assay. In addition, we analyzed the predicted consensus sequences for STAT5 binding in the UCP1 promoter region.

RESULTS

Mice fed an HFD had higher body weight and intra-abdominal adipose tissues weight and a higher expression of UCP1, GH receptor (GHR), STATs, suppressors of cytokine signaling (SOCSs), and cytokine-inducible SH2-containing protein (CISH) compared to control mice. In 3T3-L1 cell studies, GH induced phosphorylation of the STAT5, SOCSs, CISH and UCP1 expressions. UCP1 promoter activity was associated with constitutively active STAT5 in a dose-dependent manner. We confirmed functional STAT5 binding sites at -425, -279, and -178bp of the UCP1 promoter.

CONCLUSION

We suggest that endogenous GH induces UCP1 expression in adipose tissue via STAT5.

Next generation sequencing-based mutation screening of 86 patients with idiopathic short stature

Although mutations in ACAN, FGFR3, NPR2, and SHOX typically lead to skeletal dysplasia, and mutations in GHRHR, GH1, GHR, STAT5B, IGF1, IGFALS, and IGF1R usually underlie hormonal defects of the growth hormone (GH)-insulin-like growth factor 1 (IGF1) axis, such mutations have also been identified in patients with idiopathic short stature (ISS). Of these, SHOX abnormalities are known to account for a certain percentage of ISS cases, whereas the frequency of mutations in the other 10 genes in ISS cohorts remains unknown. Here, we performed next-generation sequencing-based mutation screening of the 10 genes in 86 unrelated Japanese ISS patients without SHOX abnormalities. We searched for rare protein-altering variants. The functional significance of the identified variants was assessed by in silico analyses. Consequently, we identified 18 heterozygous rare variants in 19 patients, including four probable damaging variants in ACAN, six pathogenicity-unknown variants in FGFR3, GHRHR, GHR, and IGFALS, and eight possible benign variants. Pathogenic variants in NPR2, GH1, and IGF1 were absent from our cohort. Unlike previously reported patients with ACAN mutations, our four patients with ACAN variants manifested non-specific short stature with age-appropriate or mildly delayed bone ages, and had parents of normal stature. These results indicate that ACAN mutations can underlie ISS without characteristic skeletal features, and that such mutations are possibly associated with de novo occurrence or low penetrance. In addition, our data imply that mutations in FGFR3, NPR2, and GH-IGF1 axis genes play only limited roles in the etiology of ISS.

Immunoexpression analysis of selected JAK/STAT pathway molecules in patients with non- small-cell lung cancer

INTRODUCTION    Signal transducer and activator of transcription (STAT) proteins are critically involved in tumorigenesis in various cancers, including lung cancer. OBJECTIVES    The aim of the study was to analyze the immunoexpression levels of 3 STAT proteins: STAT3, STAT5, and STAT6 in their phosphorylated forms (pSTATs), STAT inhibitors PIAS3 and SOCS3, and additionally cyclooxygenase 2 (COX‑2), as potential diagnostic and prognostic markers in lung cancer. PATIENTS AND METHODS    The study included 71 patients diagnosed with non- small-cell lung cancer (NSCLC). The immunoexpression levels of the proteins were assessed in lung tissue samples, using an enzyme‑linked immunosorbent assay. Tumors were staged using the postoperative TNM classification. RESULTS    All studied STATs were overexpressed in 54% to 55% of NSCLC specimens. Significantly higher STAT3 and STAT6 immunoexpression levels were observed in squamous cell carcinoma. Significant differences between NSCLC samples and controls were found for STAT5. Significantly higher STAT5 levels were observed in pT2 tumors. The COX‑2 overexpression was observed in 55% of NSCLC specimens and was significantly higher in T2 tumors. STAT inhibitors were underexpressed in 56% to 58% of NSCLC specimens. The PIAS3 immunoexpression was significantly lower in non-squamous cell carcinoma. The SOCS3 level was significantly lower in smaller tumors (pT1). Negative correlations between STAT5 and PIAS3 levels, as well as between STAT6 and SOCS levels, and a positive correlation between STAT5 and COX-2 levels were observed. CONCLUSIONS    The deregulated expression of the studied pSTATs and their inhibitors may be involved in the development and progression of lung cancer. The observed differences between the histotypes suggest the potential usefulness of STAT proteins as diagnostic markers. Our results may contribute to the search for targets in lung cancer therapy.

JAK/STAT pathway directed therapy of T-cell leukemia/lymphoma: Inspired by functional and structural genomics

Abnormal activation of the γc cytokine JAK/STAT signaling pathway assessed by STAT3 or STAT5b phosphorylation was present in a proportion of many T-cell malignancies. Activating mutations of STAT3/STAT5b and JAK1/3 were present in some but not in all cases with constitutive signaling pathway activation. Using shRNA analysis pSTAT malignant T-cell lines were addicted to JAKs/STATs whether they were mutated or not. Activating JAK/STAT mutations were not sufficient to support leukemic cell proliferation but only augmented upstream pathway signals. Functional cytokine receptors were required for pSTAT expression. Combining a JAK1/2 inhibitor with a Bcl-xL inhibitor navitoclax provided additive/synergistic activity with IL-2 dependent ATLL cell lines and in a mouse model of human IL-2 dependent ATLL. The insight that disorders of the γc/JAK/STAT system are pervasive suggests approaches including those that target gamma cytokines, their receptors or that use JAK kinase inhibitors may be of value in multicomponent therapy for T-cell malignancies.

The complex roles of STAT3 and STAT5 in maintaining redox balance: Lessons from STAT-mediated xCT expression in cancer cells

STAT3 and STAT5 mediate diverse cellular processes, transcriptionally regulating gene expression and interacting with cytoplasmic proteins. Their canonical activity is stimulated by cytokines/growth factors through JAK-STAT signaling. As targets of oncogenes with intrinsic tyrosine kinase activity, STAT3 and STAT5 become constitutively active in hematologic neoplasms and solid tumors, promoting cell proliferation and survival and modulating redox homeostasis. This review summarizes reactive oxygen species (ROS)-regulated STAT activation and how STATs influence ROS production. ROS-induced effects on post-translational modifications are presented, and STAT3/5-mediated regulation of xCT, a redox-sensitive target up-regulated in numerous cancers, is discussed with regard to transcriptional cross-talk.

Crosstalk between STAT5 activation and PI3K/AKT functions in normal and transformed mammary epithelial cells

Janus kinases (JAKs) and signal transducers and activators of transcription (STATs) have been shown to function downstream of several peptide hormones and cytokines that are required for postnatal development and secretory function of the mammary gland. As part of an extended network, these signal transducers can engage in crosstalk with other pathways to facilitate synergistic, and sometimes antagonistic, actions of different growth factors. Specifically, signaling through the JAK2/STAT5 cascade has been demonstrated to be indispensable for the specification, proliferation, differentiation, and survival of secretory mammary epithelial cells. Following a concise description of major cellular programs in mammary gland development and the role of growth factors that rely on JAK/STAT signaling to orchestrate these programs, this review highlights the significance of active STAT5 and its crosstalk with the PI3 kinase and AKT1 for mediating the proliferation of alveolar progenitors and survival of their functionally differentiated descendants in the mammary gland. Based on its ability to provide self-sufficiency in growth signals that are also capable of overriding intrinsic cell death programs, persistently active STAT5 can serve as a potent oncoprotein that contributes to the genesis of breast cancer. Recent experimental evidence demonstrated that, similar to normal developmental programs, oncogenic functions of STAT5 rely on molecular crosstalk with PI3K/AKT signaling for the initiation, and in some instances the progression, of breast cancer. The multitude by which STATs can interact with individual mediators of the PI3K/AKT signaling cascade may provide novel avenues for targeting signaling nodes within molecular networks that are crucial for the survival of cancer cells.

Direct targets of pSTAT5 signalling in erythropoiesis

Erythropoietin (EPO) acts through the dimeric erythropoietin receptor to stimulate proliferation, survival, differentiation and enucleation of erythroid progenitor cells. We undertook two complimentary approaches to find EPO-dependent pSTAT5 target genes in murine erythroid cells: RNA-seq of newly transcribed (4sU-labelled) RNA, and ChIP-seq for pSTAT5 30 minutes after EPO stimulation. We found 302 pSTAT5-occupied sites: ~15% of these reside in promoters while the rest reside within intronic enhancers or intergenic regions, some >100kb from the nearest TSS. The majority of pSTAT5 peaks contain a central palindromic GAS element, TTCYXRGAA. There was significant enrichment for GATA motifs and CACCC-box motifs within the neighbourhood of pSTAT5-bound peaks, and GATA1 and/or KLF1 co-occupancy at many sites. Using 4sU-RNA-seq we determined the EPO-induced transcriptome and validated differentially expressed genes using dynamic CAGE data and qRT-PCR. We identified known direct pSTAT5 target genes such as Bcl2l1, Pim1 and Cish, and many new targets likely to be involved in driving erythroid cell differentiation including those involved in mRNA splicing (Rbm25), epigenetic regulation (Suv420h2), and EpoR turnover (Clint1/EpsinR). Some of these new EpoR-JAK2-pSTAT5 target genes could be used as biomarkers for monitoring disease activity in polycythaemia vera, and for monitoring responses to JAK inhibitors.

Molecular interactions of EphA4, growth hormone receptor, Janus kinase 2, and signal transducer and activator of transcription 5B

We previously reported that EphA4, a member of the Eph family of receptor tyrosine kinases, is an important modulator of growth hormone (GH) signaling, leading to augmented synthesis of insulin-like growth factor 1 (IGF1) for postnatal body growth. In the present study, we report the molecular interactions of EphA4, GH receptor (GHR), Janus kinase 2 (JAK2), and signal transducer and activator of transcription 5B (STAT5B). EphA4 binds to GHR at both its extracellular and intracellular domains and phosphorylates GHR when stimulated with a ligand. The cytoplasmic domain of EphA4 binds to the carboxy-terminus of JAK2 in contrast to the known binding of GHR to the amino-terminus. STAT5B binds to the amino-terminal kinase domain of EphA4. Ligand-activated EphA4 and JAK2 phosphorylate each other and STAT5B, but JAK2 does not appear to phosphorylate EphA4-bound STAT5B. Ligand-activated EphA4 induces the nuclear translocation of STAT5B in a JAK2-independent manner. GHR expression is required for the activation of STAT5B signaling, even via the JAK2-independent pathway. Various ephrins that have affinity for EphA4 induce STAT5B phosphorylation. These findings suggest the molecular mechanisms by which ephrin/EphA4 signaling enhances the canonical GH-IGF1 axis.

Investigating critical genes and gene interaction networks that mediate cyclophosphamide sensitivity in chronic myelogenous leukemia

Drug resistance is an obstacle in the treatment of chronic myelogenous leukemia (CML), and is a common reason for treatment failure or disease progression. However, the underlying mechanisms of cyclophosphamide resistance remain poorly defined. In the present study, microarray data concerning cyclophosphamide‑sensitive and ‑resistant chronic myelogenous leukemia cell lines were analyzed. A total of 258 differentially‑expressed genes (DEGs) were identified between these two groups, from which 139 DEGs were upregulated and 119 were downregulated. Several candidate genes that were associated with cyclophosphamide resistance were also identified. These DEGs were subsequently classified using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis. A total of 487 biological processes and 17 KEGG pathways were revealed to be enriched. Furthermore, an interaction network was established to identify the core genes that regulated cyclophosphamide resistance. Signal transducer and activator of transcription 5A (STAT5A), FYN proto‑oncogene, Src family tyrosine kinase and spleen associated tyrosine kinase were revealed to be the hub genes in multiple enriched biological processes and signaling pathways, indicating that these were involved in mediating cyclophosphamide sensitivity in CML cells. The expression levels of 5 DEGs were also confirmed in two human CML cell lines (K‑562 and KU812) by reverse transcription‑quantitative polymerase chain reaction. Furthermore, selective knockdown of STAT5A and S100 calcium binding protein A4 (S100A4) recovered cyclophosphamide sensitivity in K‑562 cells, suggesting their involvement in drug resistance. The present study identified several potential genes and pathways contributing to cyclophosphamide resistance, and confirmed the involvement of STAT5A and S100A4 in drug resistance. These results enable improved understanding of the mechanisms underlying drug resistance in CML cells.

The transcriptional STAT3 is a potential target, whereas transcriptional STAT5A/5B/6 are new biomarkers for prognosis in human breast carcinoma

Signal Transducer and Activators of Transcription (STAT) is a set of transcription factors, involved in diverse cellular functions. Evidences from cell lines, mouse models and human tissues implicate these transcription factors in the oncogenesis of breast cancer. However, the diverse expression patterns and prognostic values of 7 STATs remain to be elucidated. In the current study, we mined the transcriptional and survival data of STATs in patients with breast carcinoma (BC) through ONCOMINE, bc-GenExMiner, Kaplan-Meier Plotter and cBioPortal. It was found that STAT1/2 were up-regulated, whereas STAT3/4/5A/5B were down-regulated in BC patients compared with the normal tissues. The expressions of STAT5A/5B/6 were correlated with decreased levels of histological differentiation. In survival analyses through the Kaplan-Meier plotter database, high transcription levels of STAT2/4/5A/5B/6 were associated with better relapse-free survival (RFS) in all BC patients. Conversely, high STAT3 predicted shorter RFS in BC patients, suggesting that STAT3 is potential targets for precision therapy to BC patients. These data also provided STAT5A/5B/6 as new biomarker for BC prognosis.

Phosphorylated STAT5 directly facilitates parvovirus B19 DNA replication in human erythroid progenitors through interaction with the MCM complex

Productive infection of human parvovirus B19 (B19V) exhibits high tropism for burst forming unit erythroid (BFU-E) and colony forming unit erythroid (CFU-E) progenitor cells in human bone marrow and fetal liver. This exclusive restriction of the virus replication to human erythroid progenitor cells is partly due to the intracellular factors that are essential for viral DNA replication, including erythropoietin signaling. Efficient B19V replication also requires hypoxic conditions, which upregulate the signal transducer and activator of transcription 5 (STAT5) pathway, and phosphorylated STAT5 is essential for virus replication. In this study, our results revealed direct involvement of STAT5 in B19V DNA replication. Consensus STAT5-binding elements were identified adjacent to the NS1-binding element within the minimal origins of viral DNA replication in the B19V genome. Phosphorylated STAT5 specifically interacted with viral DNA replication origins both in vivo and in vitro, and was actively recruited within the viral DNA replication centers. Notably, STAT5 interacted with minichromosome maintenance (MCM) complex, suggesting that STAT5 directly facilitates viral DNA replication by recruiting the helicase complex of the cellular DNA replication machinery to viral DNA replication centers. The FDA-approved drug pimozide dephosphorylates STAT5, and it inhibited B19V replication in ex vivo expanded human erythroid progenitors. Our results demonstrated that pimozide could be a promising antiviral drug for treatment of B19V-related diseases.

Human parvovirus B19 (B19V) infection can cause severe hematological disorders, a direct consequence of the death of infected human erythroid progenitor cells (EPCs) of the bone marrow and fetal liver. B19V replicates autonomously in human EPCs, and the erythropoietin (EPO) and EPO-receptor (EPO-R) signaling is required for productive B19V replication. The Janus kinase 2 (JAK2)-signal transducer and activator of transcription 5 (STAT5) signaling plays a key role in B19V replication. Here, we identify that phosphorylated STAT5 directly interacts with B19V replication origins and with minichromosome maintenance (MCM) complex in human EPCs, and that it functions as a scaffold protein to bring MCM to the viral replication origins and thus plays a key role in B19V DNA replication. Importantly, pimozide, a STAT5 phosphorylation-specific inhibitor and an FDA-approved drug, abolishes B19V replication in ex vivo expanded human EPCs; therefore, pimozide has the potential to be used as an antiviral drug for treatment of B19V-caused hematological disorders.

CUZD1 is a critical mediator of the JAK/STAT5 signaling pathway that controls mammary gland development during pregnancy

In the mammary gland, genetic circuits controlled by estrogen, progesterone, and prolactin, act in concert with pathways regulated by members of the epidermal growth factor family to orchestrate growth and morphogenesis during puberty, pregnancy and lactation. However, the precise mechanisms underlying the crosstalk between the hormonal and growth factor pathways remain poorly understood. We have identified the CUB and zona pellucida-like domain-containing protein 1 (CUZD1), expressed in mammary ductal and alveolar epithelium, as a novel mediator of mammary gland proliferation and differentiation during pregnancy and lactation. Cuzd1-null mice exhibited a striking impairment in mammary ductal branching and alveolar development during pregnancy, resulting in a subsequent defect in lactation. Gene expression profiling of mammary epithelium revealed that CUZD1 regulates the expression of a subset of the EGF family growth factors, epiregulin, neuregulin-1, and epigen, which act in an autocrine fashion to activate ErbB1 and ErbB4 receptors. Proteomic studies further revealed that CUZD1 interacts with a complex containing JAK1/JAK2 and STAT5, downstream transducers of prolactin signaling in the mammary gland. In the absence of CUZD1, STAT5 phosphorylation in the mammary epithelium during alveologenesis was abolished. Conversely, elevated expression of Cuzd1 in mammary epithelial cells stimulated prolactin-induced phosphorylation and nuclear translocation of STAT5. Chromatin immunoprecipitation confirmed co-occupancy of phosphorylated STAT5 and CUZD1 in the regulatory regions of epiregulin, a potential regulator of epithelial proliferation, and whey acidic protein, a marker of epithelial differentiation. Collectively, these findings suggest that CUZD1 plays a critical role in prolactin-induced JAK/STAT5 signaling that controls the expression of key STAT5 target genes involved in mammary epithelial proliferation and differentiation during alveolar development.

In the mammary gland, genetic circuits controlled by the hormones, estrogen, progesterone and prolactin, act in concert with pathways regulated by members of the epidermal growth factor family to orchestrate growth and morphogenesis during puberty, pregnancy and lactation. We have identified CUZD1 as a novel mediator of prolactin signaling in the steroid hormone-primed mouse mammary gland during pregnancy and lactation. Cuzd1-null mice exhibited a striking impairment in ductal branching and alveolar development during pregnancy, resulting in a subsequent defect in lactation. Administration of prolactin failed to induce proliferation of the mammary epithelium in Cuzd1-null mice. Protein binding studies revealed that CUZD1 interacts with downstream transducers of prolactin signaling, JAK1/JAK2 and STAT5. Additionally, elevated expression of Cuzd1 in mammary epithelial cells stimulated phosphorylation and nuclear translocation of STAT5. CUZD1, therefore, is a critical mediator of prolactin that controls mammary alveolar development.

Nitro-oleic acid regulates growth factor-induced differentiation of bone marrow-derived macrophages

Many diseases accompanied by chronic inflammation are connected with dysregulated activation of macrophage subpopulations. Recently, we reported that nitro-fatty acids (NO₂-FAs), products of metabolic and inflammatory reactions of nitric oxide and nitrite, modulate macrophage and other immune cell functions. Bone marrow cell suspensions were isolated from mice and supplemented with macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) in combination with NO₂-OA for different times. RAW 264.7 macrophages were used for short-term (1-5min) experiments. We discovered that NO₂-OA reduces cell numbers, cell colony formation, and proliferation of macrophages differentiated with colony-stimulating factors (CSFs), all in the absence of toxicity. In a case of GM-CSF-induced bone marrow-derived macrophages (BMMs), NO₂-OA acts via downregulation of signal transducer and activator of transcription 5 and extracellular signal-regulated kinase (ERK) activation. In the case of M-CSF-induced BMMs, NO₂-OA decreases activation of M-CSFR and activation of related PI3K and ERK. Additionally, NO₂-OA also attenuates activation of BMMs. In aggregate, we demonstrate that NO₂-OA regulates the process of macrophage differentiation and that NO₂-FAs represent a promising therapeutic tool in the treatment of inflammatory pathologies linked with increased accumulation of macrophages in inflamed tissues.

Adipocyte STAT5 deficiency promotes adiposity and impairs lipid mobilisation in mice

AIMS/HYPOTHESIS

Dysfunction of lipid metabolism in white adipose tissue can substantially interfere with health and quality of life, for example in obesity and associated metabolic diseases. Therefore, it is important to characterise pathways that regulate lipid handling in adipocytes and determine how they affect metabolic homeostasis. Components of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway are involved in adipocyte physiology and pathophysiology. However, the exact physiological importance of the STAT family member STAT5 in white adipose tissue is yet to be determined. Here, we aimed to delineate adipocyte STAT5 functions in the context of lipid metabolism in white adipose tissue.

METHODS

We generated an adipocyte specific knockout of Stat5 in mice using the Adipoq-Cre recombinase transgene followed by in vivo and in vitro biochemical and molecular studies.

RESULTS

Adipocyte-specific deletion of Stat5 resulted in increased adiposity, while insulin resistance and gluconeogenic capacity was decreased, indicating that glucose metabolism can be improved by interfering with adipose STAT5 function. Basal lipolysis and fasting-induced lipid mobilisation were diminished upon STAT5 deficiency, which coincided with reduced levels of the rate-limiting lipase of triacylglycerol hydrolysis, adipose triglyceride lipase (ATGL, encoded by Pnpla2) and its coactivator comparative gene identification 58 (CGI-58). In a mechanistic analysis, we identified a functional STAT5 response element within the Pnpla2 promoter, indicating that Pnpla2 is transcriptionally regulated by STAT5.

CONCLUSIONS/INTERPRETATION

Our findings reveal an essential role for STAT5 in maintaining lipid homeostasis in white adipose tissue and provide a rationale for future studies into the potential of STAT5 manipulation to improve outcomes in metabolic diseases.