Regulation of cell proliferation, apoptosis, and carcinogenesis by activin

Endothelial ActRIIA inhibition protects the cardiac microvasculature in severe viral respiratory infection

Cardiac complications, including myocardial injury and dysfunction, are common in severe viral respiratory infections (VRI) and are associated with increased mortality 1-3 . The pathophysiology of VRI-induced myocardial injury is multifactorial, but frequently involves structural damage to the heart's microvascular network that leads to subsequent myocardial ischemia and dysfunction 4-6 . Currently, there are no targeted therapies available to prevent or attenuate VRI-associated myocardial injury. Moreover, the molecular mechanisms driving the cardiac microvascular pathology in severe VRI are largely unclear. In this study, we identify increased endothelial cell (EC) activin type IIA receptor (ActRIIA) signaling as a key mediator of cardiac microvascular injury and pathologic remodeling in severe VRI. We show that genetic deletion of EC ActRIIA is sufficient to mitigate EC death and myocardial capillary loss in a murine model of severe influenza infection, which results in improved myocardial perfusion, cardiac function, and survival. We then provide proof-of-concept evidence for two novel pharmacological approaches to target EC ActRIIA pathophysiology in the treatment of VRI-induced cardiac dysfunction.

Pathological insights into activin A: Molecular underpinnings and therapeutic prospects in various diseases

Activin A (Act A) is a member of the TGFβ (transforming growth factor β) superfamily. It communicates via the Suppressor of Mothers against Decapentaplegic Homolog (SMAD2/3) proteins which govern processes such as cell proliferation, wound healing, apoptosis, and metabolism. Act A produces its action by attaching to activin receptor type IIA (ActRIIA) or activin receptor type IIB (ActRIIB). Increasing circulating Act A increases ActRII signalling, which on phosphorylation initiates the ALK4 (activin receptor-like kinase 4) type 1 receptor which further turns on the SMAD pathway and hinders cell functioning. Once triggered, this route leads to gene transcription, differentiation, apoptosis, and extracellular matrix (ECM) formation. Act A also governs the immunological and inflammatory responses of the body, as well as cell death. Moreover, Act A levels have been observed to elevate in several disorders like renal fibrosis, CKD, asthma, NAFLD, cardiovascular diseases, cancer, inflammatory conditions etc. Here, we provide an update on the recent studies relevant to the role of Act A in the modulation of various pathological disorders, giving an overview of the biology of Act A and its signalling pathways, and discuss the possibility of incorporating activin-A targeting as a novel therapeutic approach for the control of various disorders. Pathways such as SMAD signaling, in which SMAD moves to the nucleus by making a complex and leads to tissue fibrosis in CKD, STAT3, which drives renal fibroblast activity and the production of ECM, Kidney injury molecule (KIM-1) in the synthesis, deposition of ECM proteins, SERCA2a (sarcoplasmic reticulum Ca2+ ATPase) in cardiac dysfunction, and NF-κB (Nuclear factor kappa-light-chain-enhancer of activated B cells) in inflammation are involved in Act A signaling, have also been discussed.

Activin A/ACVR2A axis inhibits epithelial-to-mesenchymal transition in colon cancer by activating SMAD2

Colorectal cancer is one of the most common malignancies worldwide. Liver metastasis is the major direct cause of colorectal cancer-related deaths. Although radical resection is the most effective treatment for colorectal cancer liver metastasis, several patients are not eligible for surgery. Therefore, there is a need to develop novel treatments based on the understanding of the biological mechanisms underlying liver metastasis in colorectal cancer. This study demonstrated that activin A/ACVR2A inhibits colon cancer cell migration and invasion, as well as suppresses the epithelial-to-mesenchymal transition of mouse colon cancer cells. This finding has been further validated in animal experiments. Mechanistic studies revealed that activin A binds to Smad2 (instead of Smad3) and activates its transcription. Analysis of the paired clinical samples further confirmed that the expression levels of ACVR2A and SMAD2 were the highest in adjacent healthy tissues, followed by primary colon cancer tissues and liver metastasis tissues, suggesting that ACVR2A downregulation may promote colon cancer metastasis. Bioinformatics analysis and clinical studies demonstrated that ACVR2A downregulation was significantly associated with liver metastasis and poor disease-free and progression-free survival of patients with colon cancer. These results suggest that the activin A/ACVR2A axis promotes colon cancer metastasis by selectively activating SMAD2. Thus, targeting ACVR2A is a potential novel therapeutic strategy to prevent colon cancer metastasis.

The Role of TGF-β, Activin and Follistatin in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an immune-mediated inflammatory condition predominantly affecting the gastrointestinal (GI) tract. An increasing prevalence of IBD has been observed globally. The pathogenesis of IBD includes a complex interplay between the intestinal microbiome, diet, genetic factors and immune responses. The consequent imbalance of inflammatory mediators ultimately leads to intestinal mucosal damage and defective repair. Growth factors, given their specific roles in maintaining the homeostasis and integrity of the intestinal epithelium, are of particular interest in the setting of IBD. Furthermore, direct targeting of growth factor signalling pathways involved in the regeneration of the damaged epithelium and the regulation of inflammation could be considered as therapeutic options for individuals with IBD. Several members of the transforming growth factor (TGF)-β superfamily, particularly TGF-β, activin and follistatin, are key candidates as they exhibit various roles in inflammatory processes and contribute to maintenance and homeostasis in the GI tract. This article aimed firstly to review the events involved in the pathogenesis of IBD with particular emphasis on TGF-β, activin and follistatin and secondly to outline the potential role of therapeutic manipulation of these pathways.

Neurotensin modulation of lipopolysaccharide induced inflammation of gut-liver axis: Evaluation using neurotensin receptor agonist and antagonist

Lipopolysaccharide (LPS), a toxic component of the cell wall of Gram-negative bacteria, is a potent immune stressor. LPS-induced inflammation of the gut-liver axis is well demonstrated. Neurotensin (NTS), a tri-decapeptide present in the gastrointestinal tract, has anti-inflammatory, anti-oxidative, and growth-promoting properties. This study elucidated the efficacy of PD149163, the type I NTS receptor agonist (NTS₁) in the modulation of LPS-induced inflammation of the gut-liver axis of mice. Young-adult female mice (Age: 8 weeks; BW: 25 ± 2.5 g) were maintained in six groups (6/group); Group I as control and Group II, III & IV were exposed to LPS (1 mg/kg BW/Day; i.p.) for five days. LPS pre-exposed Group III and Group IV mice were treated with NTS₁ agonist PD149163 (100 μg/kg BW i.p.) and antagonist SR48692 (0.5 mg/kg BW i.p.) respectively for 28 days. Group V and Group VI mice were exposed to only PD149163 and only SR48692 respectively with the doses as mentioned above for 28 days. Group I and LPS-exposed Group II mice were also maintained four weeks without further treatment. Histopathology revealed LPS-induced inflammation of the gut and liver. Significant elevation of plasma TNF-α and IL-6 and serum ALT and AST reflected as biomarkers of inflammation. Oxidative stress on both organs was distinct from decreased glutathione reductase and increased lipid peroxidation. PD149163 but not SR48692 ameliorated LPS-induced inflammation in both gut and liver counteracting inflammatory responses and oxidative stress. The use of NTS agonists including PD149163 could be exploited for therapeutic intervention of inflammatory diseases including that of the gut-liver axis.

Genetic analysis of activin/inhibin β subunits in zebrafish development and reproduction

Activin and inhibin are both dimeric proteins sharing the same β subunits that belong to the TGF-β superfamily. They are well known for stimulating and inhibiting pituitary FSH secretion, respectively, in mammals. In addition, activin also acts as a mesoderm-inducing factor in frogs. However, their functions in development and reproduction of other species are poorly defined. In this study, we disrupted all three activin/inhibin β subunits (βAa, inhbaa; βAb, inhbab; and βB, inhbb) in zebrafish using CRISPR/Cas9. The loss of βAa/b but not βB led to a high mortality rate in the post-hatching stage. Surprisingly, the expression of fshb but not lhb in the pituitary increased in the female βA mutant together with aromatase (cyp19a1a) in the ovary. The single mutant of βAa/b showed normal folliculogenesis in young females; however, their double mutant (inhbaa-/-;inhbab-/-) showed delayed follicle activation, granulosa cell hypertrophy, stromal cell accumulation and tissue fibrosis. The ovary of inhbaa-/- deteriorated progressively after 180 dpf with reduced fecundity and the folliculogenesis ceased completely around 540 dpf. In addition, tumor- or cyst-like tissues started to appear in the inhbaa-/- ovary after about one year. In contrast to females, activin βAa/b mutant males showed normal spermatogenesis and fertility. As for activin βB subunit, the inhbb-/- mutant exhibited normal folliculogenesis, spermatogenesis and fertility in both sexes; however, the fecundity of mutant females decreased dramatically at 270 dpf with accumulation of early follicles. In summary, the activin-inhibin system plays an indispensable role in fish reproduction, in particular folliculogenesis and ovarian homeostasis.

TAK1 inhibition increases proliferation and differentiation of chick retinal cells

The factors necessary for the differentiation of cell types within the retina are incompletely understood. The transforming growth factor beta (TGF-β) superfamily, including TGF-β1 and 2, the bone morphogenetic proteins, and the activins have all been implicated in differentiation; however, the mechanisms by which these factors affect differentiation are only partially understood. The studies herein focus on a potential role for transforming growth factor β-activated kinase 1 (TAK1), a hub kinase that lies at the intersection of multiple signaling pathways, in the differentiation of cell types within the chick retina. Previous studies have focused predominantly on the role this kinase plays in the inflammation process and axonal growth. TAK1 is downstream of multiple signaling pathways that are critical to development of the central nervous system, including transforming growth factor β (TGFβ), bone morphogenetic proteins (BMPs), and activins. The present study indicates that activated TAK1 is found throughout the developing retina; however, it is localized at higher levels in dividing and differentiating cells. Further, ex ovo retinal studies using TAK1 inhibitor 5Z-7-oxozeaenol increased both progenitor and differentiating cell populations, accompanied by a substantial increase in proliferation and a smaller increase in cell death. These results indicate a unique role for TAK1 in differentiating and proliferating retinal cells.

Optimization of 3D islet-like cluster derived from human pluripotent stem cells: an efficient in vitro differentiation protocol

Development of an optimized protocol to produce sufficient functional human insulin-producing islet-like cluster is important as a potential therapeutic strategy for diabetes as well as in vitro studies. Here, we described a stepwise protocol for differentiation of the human induced pluripotent stem cell line (R1-hiPSC1) into the islet-like cluster using several growth factors and small molecules. Therefore, various differentiation steps have been adopted to maximize mimicking of developmental processes in order to form functional islet like cluster. The differentiation protocol enables us to generate 3D islet-like clusters with highly viable cells, which are insulin producer and glucose responsive. Transcriptome analysis of transcription factors and functional genes revealed high coordination between gene expressions and resembling to those reported during natural development of islet cell. This coordination was further confirmed by hierarchical clustering of genes during differentiation. Furthermore, the islet-like clusters were enriched with insulin producing cells and formed glucose responsiveness behavior upon stimulation with glucose. Our protocol provides a robust platform and well-behaved model for additional developmental studies and shed light our clusters as a good candidate for in vitro model. Further studies are needed to assess the hormonal content of this cluster as well as transplantation into the animal model.

5-Demethylnobiletin Inhibits Cell Proliferation, Downregulates ID1 Expression, Modulates the NF-κB/TNF-α Pathway and Exerts Antileukemic Effects in AML Cells

Acute myeloid leukemia (AML) is characterized by the dysregulation of hematopoietic cell proliferation, resulting in the accumulation of immature myeloid cells in bone marrow. 5-Demethylnobiletin (5-demethyl NOB), a citrus 5-hydroxylated polymethoxyflavone, has been reported to exhibit various bioactivities, such as antioxidant, anti-inflammatory and anticancer properties. In this study, we investigated the antileukemic effects of 5-demethyl NOB and its underlying molecular mechanisms in human AML cells. We found that 5-demethyl NOB (20−80 μM) significantly reduced human leukemia cell viability, and the following trend of effectiveness was observed: THP-1 ≈ U-937 > HEL > HL-60 > K562 cells. 5-Demethyl NOB (20 and 40 μM) modulated the cell cycle through the regulation of p21, cyclin E1 and cyclin A1 expression and induced S phase arrest. 5-Demethyl NOB also promoted leukemia cell apoptosis and differentiation. Microarray-based transcriptome, Gene Ontology (GO) and Gene Set Enrichment Analysis (GSEA) of differentially expressed genes (DEGs) analysis showed that the expression of inhibitor of differentiation/DNA binding 1 (ID1), a gene associated with the GO biological process (BP) cell population proliferation (GO: 0008283), was most strongly suppressed by 5-demethyl NOB (40 μM) in THP-1 cells. We further demonstrated that 5-demethyl NOB-induced ID1 reduction was associated with the inhibition of leukemia cell growth. Moreover, DEGs involved in the hallmark gene set NF-κB/TNF-α signaling pathway were markedly enriched and downregulated by 5-demethyl NOB. Finally, we demonstrated that 5-demethyl NOB (20 and 40 μM), combined with cytarabine, synergistically reduced THP-1 and U-937 cell viability. Our current findings support that 5-demethyl NOB dramatically suppresses leukemia cell proliferation and may serve as a potential phytochemical for human AML chemotherapy.

Activin A Promotes Osteoblastic Differentiation of Human Preosteoblasts through the ALK1-Smad1/5/9 Pathway

Activin A, a member of transforming growth factor-β superfamily, is involved in the regulation of cellular differentiation and promotes tissue healing. Previously, we reported that expression of activin A was upregulated around the damaged periodontal tissue including periodontal ligament (PDL) tissue and alveolar bone, and activin A promoted PDL-related gene expression of human PDL cells (HPDLCs). However, little is known about the biological function of activin A in alveolar bone. Thus, this study analyzed activin A-induced biological functions in preosteoblasts (Saos2 cells). Activin A promoted osteoblastic differentiation of Saos2 cells. Activin receptor-like kinase (ALK) 1, an activin type I receptor, was more strongly expressed in Saos2 cells than in HPDLCs, and knockdown of ALK1 inhibited activin A-induced osteoblastic differentiation of Saos2 cells. Expression of ALK1 was upregulated in alveolar bone around damaged periodontal tissue when compared with a nondamaged site. Furthermore, activin A promoted phosphorylation of Smad1/5/9 during osteoblastic differentiation of Saos2 cells and knockdown of ALK1 inhibited activin A-induced phosphorylation of Smad1/5/9 in Saos2 cells. Collectively, these findings suggest that activin A promotes osteoblastic differentiation of preosteoblasts through the ALK1-Smad1/5/9 pathway and could be used as a therapeutic product for the healing of alveolar bone as well as PDL tissue.

Clinical relevance of circulating activin A and follistatin in small cell lung cancer

OBJECTIVES

Circulating levels of activin A (ActA) and follistatin (FST) have been investigated in various disorders including malignancies. However, to date, their diagnostic and prognostic relevance is largely unknown in small cell lung cancer (SCLC). Our aim was to evaluate circulating ActA and FST levels as potential biomarkers in this devastating disease.

METHODS

Seventy-nine Caucasian SCLC patients and 67 age- and sex-matched healthy volunteers were included in this study. Circulating ActA and FST concentrations were measured by ELISA and correlated with clinicopathological parameters and long-term outcomes.

RESULTS

Plasma ActA and FST concentrations were significantly elevated in SCLC patients when compared to healthy volunteers (p < 0.0001). Furthermore, extensive-stage SCLC patients had significantly higher circulating ActA levels than those with limited-stage disease (p = 0.0179). Circulating FST concentration was not associated with disease stage (p = 0.6859). Notably, patients with high (≥548.8 pg/ml) plasma ActA concentration exhibited significantly worse median overall survival (OS) compared to those with low (<548.8 pg/ml) ActA levels (p = 0.0009). Moreover, Cox regression analysis adjusted for clinicopathological parameters revealed that high ActA concentration is an independent predictor of shorter OS (HR: 1.932; p = 0.023). No significant differences in OS have been observed with regards to plasma FST levels (p = 0.1218).

CONCLUSION

Blood ActA levels are elevated and correlate with disease stage in SCLC patients. Measurement of circulating ActA levels might help in the estimation of prognosis in patients with SCLC.

The Role of TGF-β Signaling Pathways in Cancer and Its Potential as a Therapeutic Target

The transforming growth factor-β (TGF-β) signaling pathway mediates various biological functions, and its dysregulation is closely related to the occurrence of malignant tumors. However, the role of TGF-β signaling in tumorigenesis and development is complex and contradictory. On the one hand, TGF-β signaling can exert antitumor effects by inhibiting proliferation or inducing apoptosis of cancer cells. On the other hand, TGF-β signaling may mediate oncogene effects by promoting metastasis, angiogenesis, and immune escape. This review summarizes the recent findings on molecular mechanisms of TGF-β signaling. Specifically, this review evaluates TGF-β's therapeutic potential as a target by the following perspectives: ligands, receptors, and downstream signaling. We hope this review can trigger new ideas to improve the current clinical strategies to treat tumors related to the TGF-β signaling pathway.

Dual Roles of the Activin Signaling Pathway in Pancreatic Cancer

Activin, a member of the TGF-β superfamily, is involved in many physiological processes, such as embryonic development and follicle development, as well as in multiple human diseases including cancer. Genetic mutations in the activin signaling pathway have been reported in many cancer types, indicating that activin signaling plays a critical role in tumorigenesis. Recent evidence reveals that activin signaling may function as a tumor-suppressor in tumor initiation, and a promoter in the later progression and metastasis of tumors. This article reviews many aspects of activin, including the signaling cascade of activin, activin-related proteins, and its role in tumorigenesis, particularly in pancreatic cancer development. The mechanisms regulating its dual roles in tumorigenesis remain to be elucidated. Further understanding of the activin signaling pathway may identify potential therapeutic targets for human cancers and other diseases.

Differentiation of Cells Isolated from Afterbirth Tissues into Hepatocyte-Like Cells and Their Potential Clinical Application in Liver Regeneration

Toxic, viral and surgical injuries can pose medical indications for liver transplantation. The number of patients waiting for a liver transplant still increases, but the number of organ donors is insufficient. Hepatocyte transplantation was suggested as a promising alternative to liver transplantation, however, this method has some significant limitations. Currently, afterbirth tissues seem to be an interesting source of cells for the regenerative medicine, because of their unique biological and immunological properties. It has been proven in experimental animal models, that the native stem cells, and to a greater extent, hepatocyte-like cells derived from them and transplanted, can accelerate regenerative processes and restore organ functioning. The effective protocol for obtaining functional mature hepatocytes in vitro is still not defined, but some studies resulted in obtaining functionally active hepatocyte-like cells. In this review, we focused on human stem cells isolated from placenta and umbilical cord, as potent precursors of hepatocyte-like cells for regenerative medicine. We summarized the results of preclinical and clinical studies dealing with the introduction of epithelial and mesenchymal stem cells of the afterbirth origin to the liver failure therapy. It was concluded that the use of native afterbirth epithelial and mesenchymal cells in the treatment of liver failure could support liver function and regeneration. This effect would be enhanced by the use of hepatocyte-like cells obtained from placental and/or umbilical stem cells.

A polymorphism in the cachexia-associated gene INHBA predicts efficacy of regorafenib in patients with refractory metastatic colorectal cancer

Activin/myostatin signaling has a critical role not only in cachexia but also in tumor angiogenesis. Cachexia is a frequent complication among patients with advanced cancer and heavily pretreated patients. We aimed to evaluate the prognostic significance of cachexia-associated genetic variants in refractory metastatic colorectal cancer (mCRC) patients treated with regorafenib. Associations between twelve single nucleotide polymorphisms in 8 genes (INHBA, MSTN, ALK4, TGFBR1, ALK7, ACVR2B, SMAD2, FOXO3) and clinical outcome were evaluated in mCRC patients of three cohorts: a discovery cohort of 150 patients receiving regorafenib, a validation cohort of 80 patients receiving regorafenib and a control cohort of 128 receiving TAS-102. In the discovery cohort, patients with any G variant in FOXO3 rs12212067 had a significantly lower response rate (P = 0.031) and overall survival (OS) than those with a T/T in univariate analysis (4.5 vs. 7.6 months, hazard ratio [HR] = 1.63, 95% confidence interval [CI] = 1.09-2.46, P = 0.012). Among female patients, those with any G variant in INHBA rs2237432 had a significantly longer OS than those with an A/A in both univariate (7.6 vs. 4.3 months, HR = 0.57, 95%CI = 0.34-0.95, P = 0.021) and multivariable (HR = 0.53, 95%CI = 0.29-0.94, adjusted P = 0.031) analysis. This association was confirmed in female patients of the validation cohort, though without statistical significance (P = 0.059). Conversely, female patients with any G allele in the control group receiving TAS-102 did not show a longer OS. This was the first study evaluating the associations between polymorphisms in cachexia-associated genes and outcomes in refractory mCRC patients treated with regorafenib. Further studies should be conducted to confirm these associations.

Automated Hypothesis Generation to Identify Signals Relevant in the Development of Mammalian Cell and Tissue Bioprocesses, With Validation in a Retinal Culture System

We have developed an accessible software tool (receptoR) to predict potentially active signaling pathways in one or more cell type(s) of interest from publicly available transcriptome data. As proof-of-concept, we applied it to mouse photoreceptors, yielding the previously untested hypothesis that activin signaling pathways are active in these cells. Expression of the type 2 activin receptor (Acvr2a) was experimentally confirmed by both RT-qPCR and immunochemistry, and activation of this signaling pathway with recombinant activin A significantly enhanced the survival of magnetically sorted photoreceptors in culture. Taken together, we demonstrate that our approach can be easily used to mine publicly available transcriptome data and generate hypotheses around receptor expression that can be used to identify novel signaling pathways in specific cell types of interest. We anticipate that receptoR (available at https://www.ucalgary.ca/ungrinlab/receptoR) will enable more efficient use of limited research resources.

Optimization of activin-A: a breakthrough in differentiation of human induced pluripotent stem cell into definitive endoderm

The first step in differentiation of pluripotent stem cell toward endoderm-derived cell/organ is differentiation to definitive endoderm (DE) which is the central issue in developmental biology. Based on several evidences, we hypothesized that activin-A optimization as well as replacement of fetal bovine serum (FBS) with knockout serum replacement (KSR) is important for differentiation of induced pluripotent stem cell (iPSC) line into DE. Therefore, a stepwise differentiation protocol was applied on R1-hiPSC1 cell line. At first, activin-A concentration (30, 50, 70 and 100 ng/ml) was optimized. Then, substitution of FBS with KSR was evaluated across four treatment groups. The amount of differentiation of iPSC toward DE was determined by quantitative gene expression analyses of pluripotency (NANOG and OCT4), definitive endoderm (SOX17 and FOXA2) and endoderm-derived organs (PDX1, NEUROG3, and PAX6). Based on gene expression analyses, the more decrease in concentrations of activin-A can increase the differentiation of iPSC into DE, therefore, 30 ng/ml activin-A was chosen as the best concentration for the differentiation of R1-hiPSC1 line toward endoderm-derived organ. Moreover, complete replacement of FBS with gradually increased KSR improved the differentiation of iPSC toward DE. For this reason, the addition of 0% KSR at day 1, 0.2% at day 2 and 2% for the next 3 days was the best optimal protocol of the differentiation of iPSC toward DE. Overall, our results demonstrate that optimization of activin-A is important for differentiation of iPSC line. Furthermore, the replacement of FBS with KSR can improve the efficiency of iPSC differentiation toward DE.

Two-day-treatment of Activin-A leads to transient change in SV-HFO osteoblast gene expression and reduction in matrix mineralization

Activins regulate bone formation by controlling osteoclasts and osteoblasts. We investigated Activin‐A mechanism of action on human osteoblast mineralization, RNA and microRNA (miRNA) expression profile. A single 2‐day treatment of Activin‐A at Day 5 of osteoblast differentiation significantly reduced matrix mineralization. Activin A‐treated osteoblasts responded with transient change in gene expression, in a 2‐wave‐fashion. The 38 genes differentially regulated during the first wave (within 8 hr after Activin A start) were involved in transcription regulation. In the second wave (1–2 days after Activin A start), 65 genes were differentially regulated and related to extracellular matrix. Differentially expressed genes in both waves were associated to transforming growth factor beta signaling. We identified which microRNAs modulating osteoblast differentiation were regulated by Activin‐A. In summary, 2‐day treatment with Activin‐A in premineralization period of osteoblast cultures influenced miRNAs, gene transcription, and reduced matrix mineralization. Modulation of Activin A signaling might be useful to control bone quality for therapeutic purposes.

An autocrine ActivinB mechanism drives TGFβ/Activin signaling in Group 3 medulloblastoma

Medulloblastoma (MB) is a pediatric tumor of the cerebellum divided into four groups. Group 3 is of bad prognosis and remains poorly characterized. While the current treatment involving surgery, radiotherapy, and chemotherapy often fails, no alternative therapy is yet available. Few recurrent genomic alterations that can be therapeutically targeted have been identified. Amplifications of receptors of the TGFβ/Activin pathway occur at very low frequency in Group 3 MB. However, neither their functional relevance nor activation of the downstream signaling pathway has been studied. We showed that this pathway is activated in Group 3 MB with some samples showing a very strong activation. Beside genetic alterations, we demonstrated that an ActivinB autocrine stimulation is responsible for pathway activation in a subset of Group 3 MB characterized by high PMEPA1 levels. Importantly, Galunisertib, a kinase inhibitor of the cognate receptors currently tested in clinical trials for Glioblastoma patients, showed efficacy on orthotopically grafted MB‐PDX. Our data demonstrate that the TGFβ/Activin pathway is active in a subset of Group 3 MB and can be therapeutically targeted.

Upregulation of interleukin-8 and activin A induces osteoclastogenesis in ameloblastoma

Ameloblastoma is a common odontogenic benign tumor located in the jaws and is characterized by severe local bone destruction. The current study aimed to investigate the effect of interactions between tumor cells and bone marrow stromal cells (BMSCs) on osteoclast formation in ameloblastoma. The impact of ameloblastoma/BMSC interactions on cytokine production, gene expression and osteoclastogenesis was examined using an immortalized ameloblastoma cell line that the authors' previously established. The results demonstrated that interactions between ameloblastoma cells and BMSCs increased interleukin (IL)‑8 and activin A secretion by BMSCs. IL‑8 expression in BMSCs was modulated by tumor‑derived tumor necrosis factor‑α and IL‑8 contributed to osteoclast formation not only directly but also by stimulating receptor activator of NF‑κB ligand (RANKL) expression in BMSCs. Activin A secretion in BMSCs was stimulated by ameloblastoma cells via cell‑to‑cell‑mediated activation of c‑Jun N‑terminal kinase activation, acting as a cofactor of RANKL to induce osteoclast formation and function. The present study highlights the critical role of communication between BMSCs and ameloblastoma cells in bone resorption in ameloblastoma.

Activin A in Mammalian Physiology

Activins are dimeric glycoproteins belonging to the transforming growth factor beta superfamily and resulting from the assembly of two beta subunits, which may also be combined with alpha subunits to form inhibins. Activins were discovered in 1986 following the isolation of inhibins from porcine follicular fluid, and were characterized as ovarian hormones that stimulate follicle stimulating hormone (FSH) release by the pituitary gland. In particular, activin A was shown to be the isoform of greater physiological importance in humans. The current understanding of activin A surpasses the reproductive system and allows its classification as a hormone, a growth factor, and a cytokine. In more than 30 yr of intense research, activin A was localized in female and male reproductive organs but also in other organs and systems as diverse as the brain, liver, lung, bone, and gut. Moreover, its roles include embryonic differentiation, trophoblast invasion of the uterine wall in early pregnancy, and fetal/neonate brain protection in hypoxic conditions. It is now recognized that activin A overexpression may be either cytostatic or mitogenic, depending on the cell type, with important implications for tumor biology. Activin A also regulates bone formation and regeneration, enhances joint inflammation in rheumatoid arthritis, and triggers pathogenic mechanisms in the respiratory system. In this 30-yr review, we analyze the evidence for physiological roles of activin A and the potential use of activin agonists and antagonists as therapeutic agents.

TGF-β signaling in cancer

Signals from the transforming growth factor-β (TGF-β) superfamily mediate a broad spectrum of cellular processes and are deregulated in many diseases, including cancer. TGF-β signaling has dual roles in tumorigenesis. In the early phase of tumorigenesis, TGF-β has tumor suppressive functions, primarily through cell cycle arrest and apoptosis. However, in the late stage of cancer, TGF-β acts as a driver of tumor progression and metastasis by increasing tumor cell invasiveness and migration and promoting chemo-resistance. Here, we briefly review the mechanisms and functions of TGF-β signaling during tumor progression and discuss the therapeutic potentials of targeting the TGF-β pathway in cancer.

Biophysics of Tumor Microenvironment and Cancer Metastasis - A Mini Review

The role of tumor microenvironment in cancer progression is gaining significant attention. It is realized that cancer cells and the corresponding stroma co-evolve with time. Cancer cells recruit and transform the stromal cells, which in turn remodel the extra cellular matrix of the stroma. This complex interaction between the stroma and the cancer cells results in a dynamic feed-forward/feed-back loop with biochemical and biophysical cues that assist metastatic transition of the cancer cells. Although biochemistry has long been studied for the understanding of cancer progression, biophysical signaling is emerging as a critical paradigm determining cancer metastasis. In this mini review, we discuss the role of one of the biophysical cues, mostly the mechanical stiffness of tumor microenvironment, in cancer progression and its clinical implications.

Parkinson's disease-associated protein Parkin: an unusual player in cancer

The mutation of the Parkin gene is a cause of familial Parkinson’s disease. A growing body of evidence suggests that Parkin also functions as a tumor suppressor. Parkin is an ubiquitin E3 ligase, and plays important roles in a variety of cellular processes implicated in tumorigenesis, including cell cycle, cell proliferation, apoptosis, metastasis, mitophagy and metabolic reprogramming. Here we review the role and mechanism of Parkin in cancer.

4-Methylcatechol stimulates apoptosis and reduces insulin secretion by decreasing betacellulin and inhibin beta-A in INS-1 beta-cells

Insulinoma INS-1 cell line is a pancreatic beta cell tumor which is characterized with high insulin content and secretion in response to increasing glucose levels. 4-Methylcatechol (4-MC) is a metabolite of quercetin, which is known as a potential drug for inhibition of tumorigenesis. The aim of this study was to determine the applying doses of 4-methylcatechol (4-MC) for triggening cell death and decreasing the cell function of rat insulinoma INS-1 beta cells. The rate of apoptosis and the amount of insulin in the cell and the secretions were determined by the ELISA method. Betacellulin (BTC) and inhibin beta-A amounts in both the cell and the glucose induced secretion were investigated by Western blotting. Furthermore, BTC, Inhibin beta-A, Ins1, Ins2, and GLUT2 gene expression levels were determined by the by the real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) method. We noted a significant decrease in cell viability, while an increase in apoptotic cell death by 4-MC treatment. It caused a decrease in the secretion of BTC, expressions of both BTC and inhibin beta-A. We showed a decrease in the expressions of Ins1 and GLUT2, while there is no alteration in the level of insulin protein. Insulin secretion levels increased in INS-1 cells given 4-MC by basal glucose concentration while they did not response to high concentration of glucose, which indicates that 4-MC disrupts the functionality of INS-1 cells. These results revealed that 4-MC induces apoptosis and decreases insulin secretion by reducing BTC and inhibin beta-A in insulinoma INS-1 cells. Thus, 4-MC may be offered as a potential molecule for treatment of insulinoma.

Testes-specific protease 50 promotes cell proliferation via inhibiting activin signaling

Testes-specific protease 50 (TSP50), a novelly identified oncogene, has the capacity to induce cell proliferation, cell invasion and tumor growth. Further studies indicated that CAGA-luc (an activin-responsive reporter construct) reporter activity could be significantly suppressed by TSP50 overexpression, implying that the activin signaling may participate in TSP50-mediated cell proliferation. Here, we reported that TSP50 had an inhibitory effect on activin signaling. Mechanistic studies revealed that TSP50 could interact with ActRIIA, inhibit activin typeIreceptor (ActRIB) phosphorylation, repress Smad2/3 nuclear accumulation and finally promote cell proliferation by reducing the expression of activin signal target gene p27. Additionally, we found that ActRIB activation could reverse TSP50-mediated cell proliferation and tumor growth. Furthermore, analysis of human breast cancer specimens by immunohistochemistry indicated that TSP50 expression was negatively related to p-Smad2/3 and p27 protein levels. Most importantly, breast cancer diagnosis-related indicators such as tumor size, tumor grade, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER-2) levels, were correlated well with TSP50/p-Samd2/3 and TSP50/p27 expression status. Thus, our studies revealed a novel regulatory mechanism underlying TSP50-induced cell proliferation and provided a new favorable intervention target for the treatment of breast cancer.

Endothelial transcription factor KLF2 negatively regulates liver regeneration via induction of activin A

Endothelial cells (ECs) not only are important for oxygen delivery but also act as a paracrine source for signals that determine the balance between tissue regeneration and fibrosis. Here we show that genetic inactivation of flow-induced transcription factor Krüppel-like factor 2 (KLF2) in ECs results in reduced liver damage and augmentation of hepatocyte proliferation after chronic liver injury by treatment with carbon tetrachloride (CCl₄). Serum levels of GLDH3 and ALT were significantly reduced in CCl₄-treated EC-specific KLF2-deficient mice. In contrast, transgenic overexpression of KLF2 in liver sinusoidal ECs reduced hepatocyte proliferation. KLF2 induced activin A expression and secretion from endothelial cells in vitro and in vivo, which inhibited hepatocyte proliferation. However, loss or gain of KLF2 expression did not change capillary density and liver fibrosis, but significantly affected hepatocyte proliferation. Taken together, the data demonstrate that KLF2 induces an antiproliferative secretome, including activin A, which attenuates liver regeneration.

Activin A regulates microRNAs and gene expression in LNCaP cells

BACKGROUND

Prostate cancer (PCa) is an increasing health issue worldwide. For patients with advanced castration-resistant PCa (CRPC) treatment options are limited and overall survival is relatively short. Paired with this, non-invasive diagnostic options are yet to be established. Activins are members of the TGF-β superfamily and have been linked to prostate physiology. For instance, activin A is an inhibitor of growth in the prostate. A novel class of non-coding RNA, microRNAs (miRNAs) have been intrinsically linked to a range of cellular processes and carcinogenesis. No studies have investigated the impact of activin A on miRNA expression in PCa cell lines. Hence, the objective of this study was to determine the effect of activin A on miRNA expression and downstream target genes in PCa.

METHODS

Activin-sensitive (LNCaP) and insensitive (PC3) prostate cells were treated with 50 ng/ml of activin A for 72 hr. To examine miRNA expression following treatment, SYBR RT-qPCR miRNA arrays were used in conjunction with TaqMan RT-qPCR. MiRPath-TarBase analysis was conducted using the miRNAs that were significantly altered following activin A treatment of LNCaP cells to highlight enriched target genes within biological pathways. Highlighted target genes were assessed using pathway-focused TGF-β and cell cycle SYBR RT-qPCR arrays.

RESULTS

Activin A treatment altered nine miRNAs in LNCaP cells: miR-222-3p, miR-15b-5p, miR-93-5p, miR-18a-5p, and let-7i-5p were significantly decreased, while miR-30a/30d-5p, let-7c, and miR-196b-5p were significantly increased versus media control. In PC3 cells five miRNAs were altered: miR-130a-3p, miR-7-5p, and miR-140-3p were significantly decreased while miR-191-5p and miR-26a-5p were significantly increased versus media control. MiRPath-TarBase analysis highlighted that the miRNAs significantly altered in LNCaP cells targeted genes contained in activin A-related KEGG pathways. Furthermore, when LNCaP cells were treated with activin A the expression of the targeted genes was the inverse of the expression of activin A-mediated miRNAs.

CONCLUSIONS

This study demonstrated the ability of activin A to modulate miRNA expression in PCa cell lines and suggests a correlative relationship between miRNA expression and downstream target genes in LNCaP cells. This study provides impetus for further studies into activin A and miRNAs in PCa. Prostate 76:951-963, 2016. © 2016 Wiley Periodicals, Inc.

Molecular Pathways: Cachexia Signaling-A Targeted Approach to Cancer Treatment

Cancer cachexia is a multifactorial syndrome characterized by an ongoing loss of skeletal muscle mass, which negatively affects quality of life and portends a poor prognosis. Numerous molecular substrates and mechanisms underlie the dysregulation of skeletal muscle synthesis and degradation observed in cancer cachexia, including proinflammatory cytokines (TNFα, IL1, and IL6), and the NF-κB, IGF1/AKT/mTOR, and myostatin/activin-SMAD pathways. Recent preclinical and clinical studies have demonstrated that anti-cachexia drugs (such as MABp1 and soluble receptor antagonist of myostatin/activin) not only prevent muscle wasting but also may prolong overall survival. In this review, we focus on the significance of cachexia signaling in patients with cancer and highlight promising drugs targeting tumor cachexia in clinical development. Clin Cancer Res; 22(16); 3999-4004. ©2016 AACR.

Transforming Growth Factor-β Family Ligands Can Function as Antagonists by Competing for Type II Receptor Binding

Transforming growth factor-β (TGF-β) family ligands are pleiotropic cytokines. Their physiological activities are not determined by a simple coupling of stimulus and response, but depend critically on context, i.e. the interplay of receptors, ligands, and regulators that form the TGF-β signal transduction system of a cell or tissue. How these different components combine to regulate signaling activities remains poorly understood. Here, we describe a ligand-mediated mechanism of signaling regulation. Based on the observation that the type II TGF-β family receptors ActRIIA, ActRIIB, and BMPRII interact with a large group of overlapping ligands at overlapping epitopes, we hypothesized high affinity ligands compete with low affinity ligands for receptor binding and signaling. We show activin A and other high affinity ligands directly inhibited signaling by the low affinity ligands BMP-2, BMP-7, and BMP-9. We demonstrate activin A functions as a competitive inhibitor that blocks the ligand binding epitope on type II receptors. We propose binding competition and signaling antagonism are integral functions of the TGF-β signal transduction system. These functions could help explain how activin A modulates physiological signaling during extraordinary cellular responses, such as injury and wound healing, and how activin A could elicit disease phenotypes such as cancer-related muscle wasting and fibrosis.

Ascending the PEAK1 toward targeting TGFβ during cancer progression: Recent advances and future perspectives

Cancer is the second leading cause of death in the United States. Mortality in patients with solid, epithelial-derived tumors strongly correlates with disease stage and the systemic metastatic load. In such cancers, notable morphological and molecular changes have been attributed to cells as they pass through a continuum of epithelial-mesenchymal transition (EMT) states and many of these changes are essential for metastasis. While cancer metastasis is a complex cascade that is regulated by cell-autonomous and microenvironmental influences, it is well-accepted that understanding and controlling metastatic disease is a viable method for increasing patient survival. In the past 5 years, the novel non-receptor tyrosine kinase PEAK1 has surfaced as a central regulator of tumor progression and metastasis in the context of solid, epithelial cancers. Here, we review this literature with a special focus on our recent work demonstrating that PEAK1 mediates non-canonical pro-tumorigenic TGFβ signaling and is an intracellular control point between tumor cells and their extracellular microenvironment. We conclude with a brief discussion of potential applications derived from our current understanding of PEAK1 biology.

Circulating microRNAs as Potential Biomarkers of Endothelial Dysfunction in Obese Children

BACKGROUND

Cardiovascular disease (CVD) is a complex disease with multifactorial etiology. The presence of endothelial dysfunction constitutes an early risk factor for CVD in children. Circulating microRNAs (miRNAs) are small noncoding RNAs that regulate gene expression and represent a novel class of biomarkers and therapeutic targets; therefore, we examined whether the presence of endothelial dysfunction is associated with differential expression of plasma miRNAs in otherwise healthy children.

METHODS

A total of 70 children (aged 5-10 years) were recruited and classified into two groups (normal endothelial function [NEF] and endothelial dysfunction). Time to peak postocclusive reperfusion (Tmax) was considered as the indicator of either normal endothelial function (NEF; Tmax < 45 s) or endothelial dysfunction (Tmax ≥ 45 s). Lipid profiles, high-sensitivity C-reactive protein, fasting glucose, and insulin were assayed using enzyme-linked immunosorbent assay. miRNAs isolated from plasma were assayed with a custom human CVD array, followed by quantitative polymerase chain reaction verification of candidates. In addition, bioinformatics approaches including combinatorial target prediction algorithms and gene ontology were applied.

RESULTS

Three miRNAs that have been previously linked to cardiomyopathy, hsa-miR-125a-5p, hsa-miR-342-3p, and hsa-miR-365b-3p, were identified as potential biomarkers of children with endothelial dysfunction. The miRNA predicted gene targets revealed 31 common targets among all three putative candidate biomarker miRNAs and encompass three biologic pathways, including transforming growth factor-β signaling, cytokine-cytokine receptor interactions, and activin receptor-like kinase in cardiac myocytes.

CONCLUSIONS

Plasma miRNAs may be useful as potential screening tools for the presence of endothelial dysfunction in children and may reveal endothelial dysfunction-relevant target genes.

Activin and TGFβ use diverging mitogenic signaling in advanced colon cancer

Background

Understanding cell signaling pathways that contribute to metastatic colon cancer is critical to risk stratification in the era of personalized therapeutics. Here, we dissect the unique involvement of mitogenic pathways in a TGFβ or activin-induced metastatic phenotype of colon cancer.

Method

Mitogenic signaling/growth factor receptor status and p21 localization were correlated in primary colon cancers and intestinal tumors from either AOM/DSS treated ACVR2A (activin receptor 2) −/− or wild type mice. Colon cancer cell lines (+/− SMAD4) were interrogated for ligand-induced PI3K and MEK/ERK pathway activation and downstream protein/phospho-isoform expression/association after knockdown and pharmacologic inhibition of pathway members. EMT was assessed using epithelial/mesenchymal markers and migration assays.

Results

In primary colon cancers, loss of nuclear p21 correlated with upstream activation of activin/PI3K while nuclear p21 expression was associated with TGFβ/MEK/ERK pathway activation. Activin, but not TGFβ, led to PI3K activation via interaction of ACVR1B and p85 independent of SMAD4, resulting in p21 downregulation. In contrast, TGFβ increased p21 via MEK/ERK pathway through a SMAD4-dependent mechanism. While activin induced EMT via PI3K, TGFβ induced EMT via MEK/ERK activation. In vivo, loss of ACVR2A resulted in loss of pAkt, consistent with activin-dependent PI3K signaling.

Conclusion

Although activin and TGFβ share growth suppressive SMAD signaling in colon cancer, they diverge in their SMAD4-independent pro-migratory signaling utilizing distinct mitogenic signaling pathways that affect EMT. p21 localization in colon cancer may determine a dominant activin versus TGFβ ligand signaling phenotype warranting further validation as a therapeutic biomarker prior to targeting TGFβ family receptors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0456-4) contains supplementary material, which is available to authorized users.

Activin-A signaling promotes epithelial-mesenchymal transition, invasion, and metastatic growth of breast cancer

Background:

Activins belong to the transforming growth factor-β (TGF-β) superfamily of cytokines. Although the role of TGF-β in cancer progression has been highly advocated, the role of activin signaling in cancer is not well known. However, overexpression of activin-A has been observed in several cancers.

Aims:

The gene expression profile indicated higher expression of Activin-A in breast tumors. Hence the aim of this study was to evaluate the status and role of Activin signaling pathway in these tumors.

Methods:

Microarray analysis was performed to reveal gene expression changes in breast tumors. The results were validated by quantitative PCR and immunohistochemical analysis in two independent sets of normal and tumor samples. Further, correlation of activin expression with survival and distant metastasis was performed to evaluate its possible role in tumor progression. We used recombinant activin-A, inhibitors, overexpression, and knockdown strategies both in vitro and in vivo, to understand the mechanism underlying the protumorigenic role of this signaling pathway.

Results:

We report that activin-A signaling is hyperactivated in breast cancers as indicated by higher activin-A, phosphoSMAD2, and phosphoSMAD3 levels in advanced breast cancers. Bone morphogenetic proteins and molecules involved in this signaling pathway were downregulated, suggesting its suppression in breast cancers. Activin-A expression correlates inversely with survival and metastasis in advanced breast cancers. Further, activin-A promotes anchorage-independent growth, epithelial–mesenchymal transition, invasion, angiogenesis, and stemness of breast cancer cells. We show that activin-A-induced phenotype is mediated by SMAD signaling pathway. In addition, activin-A expression affects the tumor-forming ability and metastatic colonization of cancer cells in nude mice.

Conclusions:

These results suggest that activin-A has a critical role in breast cancer progression and, hence, targeting this pathway can be a valuable strategy in treating breast cancer patients.

Longitudinal analysis of maternal serum Follistatin concentration in normal pregnancy and preeclampsia

OBJECTIVE

Follistatin (FST) is a regulator of the biological activity of activin A (Act A), binding and blocking it, which could contribute to the modulation of its pro-inflammatory activity during pregnancy. We sought to investigate, in this nested case-control study, FST serum levels during normal pregnancy and correlate it with the FST profile in preeclamptic pregnant women, normal pregnant women followed 3 months postpartum and eumenorrheic nonpregnant women throughout the menstrual cycle.

SUBJECTS AND METHODS

Follistatin serum levels determined by ELISA, biochemical and anthropometric variables were measured in normal pregnant (n = 28) and preeclamptic (n = 20) women during three periods of gestation. In addition, FST serum levels were measured in a subset of normal pregnant women (n = 13) followed 3 months postpartum and in eumenorrheic nonpregnant women (n = 20) during the follicular and luteal phases of the menstrual cycle.

RESULTS

Follistatin serum levels in the eumenorrheic nonpregnant and postpartum group were significantly lower when compared to levels throughout gestation (P < 0·01). Serum FST levels increased in each period of pregnancy analysed, being significantly higher towards the end of gestation (P < 0·01). FST levels were lower in late pregnancy in preeclamptic women compared to normal pregnant women (P < 0·05). Finally, FST levels were higher in the luteal phase when compared with the follicular phase of the menstrual cycle (P < 0·05).

CONCLUSIONS

These analyses would permit the consideration that changes in FST levels during pregnancy contribute to the control of the Act A system.

Noggin inhibits hypoxia-induced proliferation by targeting store-operated calcium entry and transient receptor potential cation channels

Abnormally elevated bone morphogenetic protein 4 (BMP4) expression and mediated signaling play a critical role in the pathogenesis of chronic hypoxia-induced pulmonary hypertension (CHPH). In this study, we investigated the expression level and functional significance of four reported naturally occurring BMP4 antagonists, noggin, follistatin, gremlin1, and matrix gla protein (MGP), in the lung and distal pulmonary arterial smooth muscle cell (PASMC). A 21-day chronic hypoxic (10% O2) exposure rat model was utilized, which has been previously shown to successfully establish experimental CHPH. Among the four antagonists, noggin, but not the other three, was selectively downregulated by hypoxic exposure in both the lung tissue and PASMC, in correlation with markedly elevated BMP4 expression, suggesting that the loss of noggin might account for the hypoxia-triggered BMP4 signaling transduction. Then, by using treatment of extrogenous recombinant noggin protein, we further found that noggin significantly normalized 1) BMP4-induced phosphorylation of cellular p38 and ERK1/2; 2) BMP4-induced phosphorylation of cellular JAK2 and STAT3; 3) hypoxia-induced PASMC proliferation; 4) hypoxia-induced store-operated calcium entry (SOCE), and 5) hypoxia-increased expression of transient receptor potential cation channels (TRPC1 and TRPC6) in PASMC. In combination, these data strongly indicated that the hypoxia-suppressed noggin accounts, at least partially, for hypoxia-induced excessive PASMC proliferation, while restoration of noggin may be an effective way to inhibit cell proliferation by suppressing SOCE and TRPC expression.

Activin/Nodal signalling in stem cells

Activin/Nodal growth factors control a broad range of biological processes, including early cell fate decisions, organogenesis and adult tissue homeostasis. Here, we provide an overview of the mechanisms by which the Activin/Nodal signalling pathway governs stem cell function in these different stages of development. We describe recent findings that associate Activin/Nodal signalling to pathological conditions, focusing on cancer stem cells in tumorigenesis and its potential as a target for therapies. Moreover, we will discuss future directions and questions that currently remain unanswered on the role of Activin/Nodal signalling in stem cell self-renewal, differentiation and proliferation.

Regulation and actions of activin A and follistatin in myocardial ischaemia-reperfusion injury

Activin A, a member of the transforming growth factor-β superfamily, is stimulated early in inflammation via the Toll-like receptor (TLR) 4 signalling pathway, which is also activated in myocardial ischaemia-reperfusion. Neutralising activin A by treatment with the activin-binding protein, follistatin, reduces inflammation and mortality in several disease models. This study assesses the regulation of activin A and follistatin in a murine myocardial ischaemia-reperfusion model and determines whether exogenous follistatin treatment is protective against injury. Myocardial activin A and follistatin protein levels were elevated following 30 min of ischaemia and 2h of reperfusion in wild-type mice. Activin A, but not follistatin, gene expression was also up-regulated. Serum activin A did not change significantly, but serum follistatin decreased. These responses to ischaemia-reperfusion were absent in TLR4(-/-) mice. Pre-treatment with follistatin significantly reduced ischaemia-reperfusion induced myocardial infarction. In mouse neonatal cardiomyocyte cultures, activin A exacerbated, while follistatin reduced, cellular injury after 3h of hypoxia and 2h of re-oxygenation. Neither activin A nor follistatin affected hypoxia-reoxygenation induced reactive oxygen species production by these cells. However, activin A reduced cardiomyocyte mitochondrial membrane potential, and follistatin treatment ameliorated the effect of hypoxia-reoxygenation on cardiomyocyte mitochondrial membrane potential. Taken together, these data indicate that myocardial ischaemia-reperfusion, through activation of TLR4 signalling, stimulates local production of activin A, which damages cardiomyocytes independently of increased reactive oxygen species. Blocking activin action by exogenous follistatin reduces this damage.

Role of activin-A and myostatin and their signaling pathway in human myometrial and leiomyoma cell function

CONTEXT

Uterine leiomyomas are highly prevalent benign tumors of premenopausal women and the most common indication for hysterectomy. However, the exact etiology of this tumor is not fully understood.

OBJECTIVE

The objective of the study was to evaluate the role of activin-A and myostatin and their signaling pathways in human myometrial and leiomyoma cells.

DESIGN

This was a laboratory study.

SETTING

Myometrial and leiomyoma cells (primary and cell lines) were cultured in vitro.

PATIENTS

The study included premenopausal women who were admitted to the hospital for myomectomy or hysterectomy.

INTERVENTIONS

Primary myometrial and leiomyoma cells and/or cell lines were treated with activin-A (4 nM) and myostatin (4 nM) for different days of interval (to measure proliferation rate) or 30 minutes (to measure signaling molecules) or 48 hours to measure proliferating markers, extracellular matrix mRNA, and/or protein expression by real-time PCR, Western blot, and/or immunocytochemistry.

RESULTS

We found that activin-A and myostatin significantly reduce cell proliferation in primary myometrial cells but not in leiomyoma cells as measured by a CyQUANT cell proliferation assay kit. Reduced expression of proliferating cell nuclear antigen and Ki-67 were also observed in myometrial cells in response to activin-A and myostatin treatment. Activin-A also significantly increased mRNA expression of fibronectin, collagen1A1, and versican in primary leiomyoma cells. Finally, we found that activin-A and myostatin activate Smad-2/3 signaling but do not affect ERK or p38 signaling in both myometrial and leiomyoma cells.

CONCLUSIONS

This study results suggest that activin-A and myostatin can exert antiproliferative and/or fibrotic effects on these cell types via Smad-2/3 signaling.

Follistatin and activins in polycystic ovary syndrome: relationship to metabolic and hormonal markers

OBJECTIVE

Polycystic ovary syndrome (PCOS) is common and has reproductive and metabolic manifestations. Activin A and follistatin levels remain controversial and activin B levels are unstudied in PCOS. The aim of this study was to evaluate activin A, activin B and follistatin levels and to examine their associations with metabolic status in overweight and obese women with and without PCOS.

MATERIALS AND METHODS

Cross-sectional study assessing overweight and obese, premenopausal women with PCOS (n=51, n=26 National Institutes of Health (NIH) and n=25 non-NIH) and without PCOS (n=25 controls). Outcomes included activin A, activin B, follistatin and activin A/follistatin ratio and the association of the activins and follistatin with metabolic variables.

RESULTS

Activin A, activin B and activin A/follistatin ratio were not significantly different and follistatin was elevated for PCOS versus controls (P=0.01) independent of age or BMI. Follistatin levels were significantly different across the PCOS phenotypes (p=0.05), however this was a non-significant trend (after correction for age and BMI) for women with NIH PCOS or non-NIH PCOS to have elevated levels in comparison to controls. Activin A was most strongly predicted by low density lipoprotein/high density lipoprotein (r(2)=0.192, p<0.001), follistatin by triglycerides and highly sensitive C-reactive protein (r(2)=0.340, p<0.001) and the activin A/follistatin ratio by insulin area under the curve and mean arterial pressure (r(2)=0.289, p<0.001).

CONCLUSIONS

Follistatin is elevated and activins A and B are not different between PCOS and controls. Follistatin and activin A are related to metabolic parameters in women with and without PCOS. Follistatin may potentially act as a marker of or be involved in the pathophysiology of both reproductive and metabolic features of PCOS.

The inhibin-βC subunit is down-regulated, while inhibin-βE is up-regulated by interferon-β1a in Ishikawa carcinoma cell line

INTRODUCTION

Inhibins are important regulators of the female reproductive system. Recently, two new inhibin-subunits βC and βE have been described, although, their function is still quite unclear. Interestingly, there is an association between interferon and TGF-β expression. Therefore, the aim of this study was to determine expression changes of inhibin-βC and -βE subunits in endometrial Ishikawa carcinoma cell line after stimulation with interferon-β1a.

MATERIALS AND METHODS

The Ishikawa cell line was cultured until confluence was observed (after 2 days). After adding interferon-β1a (1,000 IE/ml), Ishikawa cells were analyzed for inhibin-βC and -βE subunits by RT-PCR. The fibroblast cell line BJ6 served as negative control. Experiments were performed in triplicates.

RESULTS

The endometrial adenocarcinoma cell line Ishikawa synthesized the inhibin- βC and -βE subunits. The fibroblast cells BJ6 did not demonstrate an inhibin -βC and -βE mRNA expression, while inhibin-βC subunit is down-regulated and inhibin-βE is up-regulated in Ishikawa carcinoma cell line after stimulation with interferon-β1a in Ishikawa.

DISCUSSION

We demonstrated for the first time a functional relationship between interferon and the novel inhibin-βC and -βE subunits. It might be possible that interferon exerts a possible apoptotic function through the βE-subunit, while, by down-regulating the βC isoform, cell proliferation is inhibited. However, the precise function of the novel βC- and βE-subunits are still not known in human endometrial tissue and a possible association with interferon is still unclear and warrants further research.

Activin/BMP2 chimeric ligands direct adipose-derived stem cells to chondrogenic differentiation

Human adipose derived stem cells (hASCs) can be easily isolated and their plasticity has been well characterized. Several TGF-β superfamily ligands can direct hASCs towards chondrocytes. However, these ligands are difficult to purify and expensive. We have developed a library of Activin/BMP2 chimeric ligands (AB2 ligands) by systematically mixing their sequence segments and have tested their chondrogenic potential in hASCs. Cells cultured in monolayer or in a pellet culture system were incubated with a chemically defined medium supplemented with the chimeric ligands for 4 or 6 weeks and showed higher expression levels of type II collagen, aggrecan, and Sox9 mRNAs when compared with control and non-treated cells. Moreover, toluidine blue, alcian blue, and Masson's trichrome staining was markedly increased in treated cells, both in cell pellet and monolayer assays. In addition, immunohistochemical staining for detection of type I collagen, type II collagen, and Sox 9 demonstrated the acquisition of a chondrogenic phenotype in both culture systems. We present here an inexpensive and robust protocol for differentiation of hASCs towards chondrocytes in a reproducible and highly efficient manner. The AB2 ligands employed are easily produced and have properties that may become useful in cell therapy.

Evaluation of cyclin-dependent kinase-like 1 expression in breast cancer tissues and its regulation in cancer cell growth

Cyclin-dependent kinase-like 1 (CDKL1) is a member of cell division control protein 2 (CDC2)-related serine-threonine protein kinase family, and it is likely to occur in malignant tumors, plays an important impact on the progress. This study aimed to evaluate the expression of CDKL1 in breast cancer and regulation in cancer cell growth. In the work, the CDKL1 mRNA level in fresh biopsy tissues from 186 breast cancer patients, with 98 benign tissues as negative control, and CDKL1 protein in 30 paraffin-embedded tissues from primary breast cancer patients were detected by the real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay and immunohistochemical staining, respectively. The roles of CDKL1 in cell growth were analyzed with CDKL1 short hairpin RNA (shRNA) inhibitor-transfected cells. CDKL1 was overexpressed in breast cancer patients and had a positive detection efficiency of 77% (144/186), which showed statistically significant difference compared with estrogen receptor (ER), progesterone receptor (PR), P53, vascular endothelial growth factor (VEGF), and E-cadherin (E-cad) (p<0.05). Inhibiting CDKL1 function with shRNA, MCF-7 cells exhibited obvious accumulation at the G2/M phase and increased sensitivity to cell cycle chemotherapeutic drugs. The results suggested that the CDKL1 gene could be a potential tumor marker for diagnosis and a gene target for therapy.

Activin A stimulates AKR1C3 expression and growth in human prostate cancer

Local androgen synthesis in prostate cancer (PC) may contribute to the development of castration-resistant PC (CRPC), but pathways controlling intratumoral steroidogenic enzyme expression in PC are unknown. We investigated the effects of activin, a factor involved in the regulation of PC growth and steroidogenic enzyme expression in other steroidogenic tissues, on intratumoral steroidogenesis in PC. Activin A effects and regulation of the activin-signaling pathway molecules were studied in the PC cell lines LNCaP, VCaP, and PC-3 and in 13 individual PC xenograft models. Also, expression levels of inhibin βA- and βB-subunits (INHBA and INHBB) and of the activin antagonist follistatin were quantitated in patient PC tissues. Activin A induced the expression and enzyme activity of 17β-hydroxysteroid dehydrogenase enzyme AKR1C3 in LNCaP and VCaP cells. Inhibition of endogenous activin A action in the PC-3 cell line decreased AKR1C3 levels and consequently testosterone synthesis. In return, androgens suppressed INHBA expression in both VCaP cells and the PC xenograft models. The antiproliferative effects of activin A were opposed by physiological concentrations of androstenedione in LNCaP cells. In patient PC tissues, expression levels of INHBA were increased in CRPC samples and correlated with AKR1C3 levels. Moreover, a high ratio of activin subunits to follistatin was associated with a worse metastasis-free survival in patients. In conclusion, activin A is controlled by androgens in PC models and regulates local androgen production. Activin A thus seems to mediate (residual) intratumoral androgen levels and could form a novel therapeutic target in CRPC.

Activins and activin antagonists in the prostate and prostate cancer

Activins are members of the TGF-β super-family. There are 4 mammalian activin subunits (β(A), β(B), β(C) and β(E)) that combine to form functional proteins. The role of activin A (β(A)β(A)) is well characterized and known to be a potent growth and differentiation factor. Two of the activin subunits (β(C) and β(E)) were discovered more recently and little is known about their biological functions. In this review the evidence that activin-β(C) is a significant regulator of activin A bioactivity is presented and discussed. It is concluded that activin-β(C), like other antagonists of activin A, is an important growth regulator in prostate health and disease.

Effects of activin and TGFβ on p21 in colon cancer

Activin and TGFβ share SMAD signaling and colon cancers can inactivate either pathway alone or simultaneously. The differential effects of activin and TGFβ signaling in colon cancer have not been previously dissected. A key downstream target of TGFβ signaling is the cdk2 inhibitor p21 (p21^cip1/waf1). Here, we evaluate activin-specific effects on p21 regulation and resulting functions. We find that TGFβ is a more potent inducer of growth suppression, while activin is a more potent inducer of apoptosis. Further, growth suppression and apoptosis by both ligands are dependent on SMAD4. However, activin downregulates p21 protein in a SMAD4-independent fashion in conjunction with increased ubiquitination and proteasomal degradation to enhance migration, while TGFβ upregulates p21 in a SMAD4-dependent fashion to affect growth arrest. Activin-induced growth suppression and cell death are dependent on p21, while activin-induced migration is counteracted by p21. Further, primary colon cancers show differential p21 expression consistent with their ACVR2/TGFBR2 receptor status. In summary, we report p21 as a differentially affected activin/TGFβ target and mediator of ligand-specific functions in colon cancer, which may be exploited for future risk stratification and therapeutic intervention.