Mitogen-activated Protein Kinase/extracellular Regulated Protein Kinase Research Articles

In vitro reconstitution of epigenetic reprogramming in the human germ line.

Epigenetic reprogramming resets parental epigenetic memories and differentiates primordial germ cells (PGCs) into mitotic pro-spermatogonia or oogonia, ensuring sexually dimorphic germ-cell development for totipotency 1. In vitro reconstitution of epigenetic reprogramming in humans remains a fundamental challenge. Here, we establish a robust strategy for inducing epigenetic reprogramming and differentiation of pluripotent stem cell (PSC)-derived human PGC-like cells (hPGCLCs) into mitotic pro-spermatogonia or oogonia, coupled with their extensive amplification (~>1010-fold). Strikingly, bone morphogenetic protein (BMP) signalling is a key driver of these processes: BMP-driven hPGCLC differentiation involves an attenuation of the mitogen-activated protein kinase/extracellular-regulated kinase (MAPK/ERK) pathway and both de novo and maintenance DNA methyltransferase (DNMT) activities, likely promoting replication-coupled, passive DNA demethylation. On the other hand, hPGCLCs deficient in tens-eleven translocation (TET) 1, an active DNA demethylase abundant in human germ cells 2,3, differentiate into extraembryonic cells, including amnion, with de-repression of key genes bearing bivalent promoters; these cells fail to fully activate genes vital for spermatogenesis and oogenesis, with their promoters remaining methylated. Our study elucidates the framework of epigenetic reprogramming in humans, making afundamental advance in human biology, and through the generation of abundant mitotic pro-spermatogonia and oogonia-like cells, represents a milestone for human in vitro gametogenesis (IVG) research and its potential translation into reproductive medicine.

Ran GTPase and Its Importance in Cellular Signaling and Malignant Phenotype

Ran is a member of the Ras superfamily of proteins, which primarily regulates nucleocytoplasmic trafficking and mediates mitosis by regulating spindle formation and nuclear envelope (NE) reassembly. Therefore, Ran is an integral cell fate determinant. It has been demonstrated that aberrant Ran expression in cancer is a result of upstream dysregulation of the expression of various factors, such as osteopontin (OPN), and aberrant activation of various signaling pathways, including the extracellular-regulated kinase/mitogen-activated protein kinase (ERK/MEK) and phosphatidylinositol 3-kinase/Protein kinase B (PI3K/Akt) pathways. In vitro, Ran overexpression has severe effects on the cell phenotype, altering proliferation, adhesion, colony density, and invasion. Therefore, Ran overexpression has been identified in numerous types of cancer and has been shown to correlate with tumor grade and the degree of metastasis present in various cancers. The increased malignancy and invasiveness have been attributed to multiple mechanisms. Increased dependence on Ran for spindle formation and mitosis is a consequence of the upregulation of these pathways and the ensuing overexpression of Ran, which increases cellular dependence on Ran for survival. This increases the sensitivity of cells to changes in Ran concentration, with ablation being associated with aneuploidy, cell cycle arrest, and ultimately, cell death. It has also been demonstrated that Ran dysregulation influences nucleocytoplasmic transport, leading to transcription factor misallocation. Consequently, patients with tumors that overexpress Ran have been shown to have a higher malignancy rate and a shorter survival time compared to their counterparts.

Gallic Acid Induces Neural Stem Cell Differentiation into Neurons and Proliferation through the MAPK/ERK Pathway.

Neural stem cell (NSC) differentiation and proliferation are important biological processes in the cerebral neural network. However, these two abilities of NSCs are limited. Thus, the induction of differentiation and/or proliferation through the administration of plant-derived small-molecule compounds could be used to repair damaged neural networks. The present study reported that gallic acid (GA), an important phenolic acid found in tea, selectively caused NSCs to differentiate into immature neurons and promoted NSC proliferation by activating the mitogen-activated protein kinase/extracellular-regulated kinase (MAPK/ERK) pathway. In addition, it was found that 3,4-dihydroxybenzoic acid was the main active structure exhibiting neurotrophic activity. The substitution of the carboxyl group on the benzene ring with the ester group may promote differentiation based on the structure of 3,4-dihydroxybenzoic acid. Furthermore, the introduction of the 5-hydroxyl group may promote proliferation. The present study identified that GA can promote the differentiation and proliferation of NSCs in vitro and exert pharmacological activity on NSCs.

Triamcinolone acetonide modulates TGF‑β2‑induced angiogenic and tissue‑remodeling effects in cultured human retinal pigment epithelial cells

Transforming growth factor-β2 (TGF-β2) has been implicated in the pathogenesis of proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR), due to its ability to stimulate the overproduction of pro-angiogenic factors, such as vascular endothelial growth factor (VEGF), and remodeling of the extracellular matrix (ECM). Although intravitreal triamcinolone acetonide (TA) is clinically useful in the treatment of PVR and PDR, its molecular mechanism has yet to be fully elucidated. The present study investigated whether TA treatment altered TGF-β2-driven biological effects on the behavior of cultured human retinal pigment epithelial (RPE) cells, in order to determine which signaling pathway may be essential for the pharmacological action of TA. The R-50 human RPE cell line was treated with TA in the presence of TGF-β2, followed by analyses of cell viability and contraction using cell viability and collagen gel contraction assays. VEGF mRNA expression and protein production were measured using reverse transcription-quantitative PCR and ELISA, respectively. The phosphorylation status of signaling mediators and the protein expression of type I collagen (COL1A1), α-smooth muscle actin (α-SMA), and ECM-remodeling enzymes, including MMP-2 and MMP-9, were analyzed using western blotting. The gelatinolytic activity of MMPs was detected using gelatin zymography. TA treatment exhibited no prominent cytotoxicity but markedly antagonized TGF-β2-induced cytostatic effects on RPE cell viability and TGF-β2-enhanced contractility in collagen gels. In the context of TGF-β2-related signaling, TA significantly attenuated TGF-β2-elicited Smad2, extracellular-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) phosphorylation. Moreover, TA markedly mitigated TGF-β2-induced VEGF upregulation through ablation of p38 signaling activity. TA also partially attenuated TGF-β2-elicted expression of COL1A1, α-SMA, MMP-2, and MMP-9, but only suppressed TGF-β2-induced MMP-9 gelatinolytic activity. Mechanistically, the MEK/ERK signaling pathway may have a critical role in the TGF-β2-induced upregulation of COL1A1, α-SMA and MMP-9. In conclusion, TA may be considered a useful therapeutic agent for treating TGF-β2-associated intraocular angiogenesis and tissue remodeling, the underlying mechanism of which may involve the ERK and p38 MAPK signaling pathways.

The RNA-Binding Protein CELF2 Inhibits Ovarian Cancer Progression by Stabilizing FAM198B

An increasing number of studies have clarified the functional roles of RNA-binding proteins (RBPs) in driving post-transcriptional mechanisms of cancer progression. In this study, we integrated data from the RBP database and Gene Expression Omnibus (GEO) data with RNA sequencing (RNA-seq) data from 10 ovarian cancer tissues and 8 normal ovarian tissues and identified an RBP, CUGBP- and ETR-3-like family 2 (CELF2). We found that CELF2 expression was downregulated in ovarian cancer and positively correlated with the overall survival (OS) and progression-free survival (PFS) of patients with ovarian cancer. Altered CELF2 expression led to changes in the proliferation, migration, and invasion of ovarian cancer cells in vitro and in vivo. CELF2 expression increased the stability of its target, FAM198B, by binding to AU/U-rich elements (AREs) in the 3′ untranslated region (3′ UTR). FAM198B knockdown restored the CELF2-mediated suppression of proliferation and migration. We also found that CELF2/FAM198B may repress ovarian cancer progression by inhibiting the mitogen-activated protein kinase/extracellular-regulated protein kinase (MAPK/ERK) signaling pathway. Finally, a curcumin-induced increase in CELF2 expression resulted in increased ovarian cancer cell sensitivity to cisplatin. Our study elucidated a novel mechanism by which the CELF2/FAM198B axis regulates proliferation and metastasis in ovarian cancer, providing novel, potential therapeutic targets for ovarian cancer.

Anti-Melanoma Activities and Phytochemical Compositions of Sorbus commixta Fruit Extracts.

Sorbus commixta Hedl. (Rosaceae family) has a long history as a medicinal plant in East Asian countries. In this study, we evaluated the effect of S. commixta fruit extracts prepared with different ethanol concentrations on anti-melanoma activity, and the extraction yield of phenolic compounds and flavonoids. Using the partitioned fractions from the EtOH extract, we found that the butanol fraction (BF) possessed strong cytotoxic activity against SK-MEL-2 cells (human melanoma cells) but not against HDFa cells (human dermal fibroblast adult cells). Additionally, BF-induced cell death was mediated by the inhibition of the mitogen-activated protein kinase/extracellular regulated kinase (MEK/ERK) signaling pathway, coupled with the upregulation of caspase-3 activity in SK-MEL-2 cells. Furthermore, HPLC analysis of polyphenolic compounds suggested that S. commixta fruits contained several active compounds including chlorogenic acid, rutin, protocatechuic acid, and hydroxybenzoic acid, all of which are known to possess anti-cancer activities. Although this study has been carried out by cell-based approach, these results suggest that S. commixta fruits contain promising anti-melanoma compounds.

Osteogenic growth peptide-loaded 3D-printed PCL scaffolds for the promotion of osteogenesis through the ERK pathway

This study aims to improve the osteogenic differentiation in vitro and bone formation in vivo through polycaprolactone (PCL) scaffolds modified with the osteogenic growth peptide (OGP). Three-dimensional (3D)-printed PCL scaffolds were designed with computer-aided design (CAD) software and fabricated by 3D layer-by-layer fused deposition. After the scaffold surfaces were modified by surface amination, the OGP was successfully loaded onto the scaffolds using a electrostatic self-assembly method. The effects of these scaffolds on the biocompatibility and osteogenic differentiation of rat bone marrow-derived stem cells (BMSCs) were studied in vitro. The modification did not influence the adhesion or proliferation, but had a notable osteogenic effect in vitro. This may be attributed to the activation of the mitogen-activated protein kinase/extracellular regulated protein kinase (MAPK/ERK) signalling pathway. Based on the results obtained after implantation into a rat cranial defect model, the PCL/OGP scaffolds notably promoted bone formation and accelerated mineralisation. The innovative modification method introduced in this work, will improve the application of PCL scaffolds in tissue engineering.

Hypoxia and EGF Stimulation Regulate VEGF Expression in Human Glioblastoma Multiforme (GBM) Cells by Differential Regulation of the PI3K/Rho-GTPase and MAPK Pathways.

Glioblastoma multiforme (GBM) is one of the most common and deadly cancers of the central nervous system (CNS). It is characterized by the presence of hypoxic regions, especially in the core, leading to an increase in vascularity. This increased vascularization is driven by the expression of the major angiogenic inducer VEGF and the indirect angiogenic inducer Epidermal growth factor (EGF), which stimulates VEGF expression. In this study, we examine the regulation of VEGF by both hypoxia and the EGF signaling pathway. We also examine the involvement of pathways downstream from EGF signaling, including the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway and the Phosphatidylinositol-3-kinase/RhoA/C (PI3K/RhoA/C) pathway in this regulation. Our results show that VEGF expression and secretion levels increase following either hypoxia or EGF stimulation, with the two stimuli signaling in parallel. We also observed an increase in ERK and protein kinase B (Akt) phosphorylation, in response to EGF stimulation, with kinetics that correlated with the kinetics of the effect on VEGF. Using pharmacological inhibitors against ERK and PI3K and small interfering RNAs (siRNAs) against RhoA and RhoC, we found that both the ERK and the PI3K/RhoA/C pathways have to cooperate in order to lead to an increase in VEGF expression, downstream from EGF. In response to hypoxia, however, only ERK was involved in the regulation of VEGF. Hypoxia also led to a surprising decrease in the activation of PI3K and RhoA/C. Finally, the decrease in the activation of these Rho-GTPases was found to be mediated through a hypoxia-driven overexpression of the Rho-GTPase GTPase activating protein (GAP), StarD13. Therefore, while under normoxic conditions, EGF stimulates the activation of both the PI3K and the MAPK pathways and the induction of VEGF, in glioblastoma cells, hypoxic conditions lead to the suppression of the PI3K/RhoA/C pathway and an exclusive switch to the MAPK pathway.

Qishen capsule safely boosts cardiac function and angiogenesis via the MEK/ERK pathway in a rat myocardial infarction model.

BackgroundQishen (QS) capsules, a Traditional Chinese Medicine, has been widely used to treat coronary heart disease in China. However, evidence of its effectiveness remains unclear.MethodsTo explore whether QS has cardioprotective efficacy and/or promotes angiogenesis after myocardial infarction (MI), we performed experiments in a preclinical rat MI model. One month after left anterior descending coronary artery ligation, the rats received either QS solution (0.4 g/kg/day) or the same volume of saline by intragastric injection for four weeks.ResultsEchocardiographic and hemodynamic analyses demonstrated relatively preserved cardiac function in MI rats administered QS. Indeed, QS treatment was associated with reduced infarct scar size and heart weight index, and these beneficial effects were responsible for enhancing angiogenesis. Mechanistically, QS treatment increased phosphorylation of protein kinase B (Akt) and downregulated phosphorylation of mitogen-activated protein kinase/extracellular-regulated kinase (MEK/ERK).ConclusionsQS therapy can improve the cardiac function of rats after MI by an underlying mechanism involving increased angiogenesis, at least partially via activation of the Akt signaling pathway and inhibition of MEK/ERK phosphorylation.

EGFR promotes the proliferation of quail follicular granulosa cells through the MAPK/extracellular signal-regulated kinase (ERK) signaling pathway

ABSTRACT Follicles develop into preovulatory follicles during folliculogenesis and the majority of small yellow follicles become atretic and gets reabsorbed. In this study, based the RNA-seq results of duck ovary, epidermal growth factor receptor (EGFR) was selected as a candidate gene in follicular development and the role was explored. The results demonstrated that EGFR-P8 was the quail EGFR core promoter. It had an E2F4 binding site within EGFR core promoter. E2F4 overexpression significantly increased EGFR expression in quail granulosa cells (GCs). However, the effect was abolished when the GCs were treated with corynoxeine, an inhibitor of the mitogen-activated protein kinase/extracellular regulated protein kinase (MAPK/ERK) signaling pathway. Moreover, luciferase reporter assay and chromatin immunoprecipitation experiments showed that E2F4 upregulated the expression of EGFR expression, which increased E2 and P4 production. In addition, EGFR regulated GCs proliferation and affected follicular development. Taken together, our findings suggested that EGFR, which was regulated by E2F4, enhanced the expression of MAPK/ERK pathway components and follicular development. These results provided an important basis for an improved understanding of the MAPK/ERK pathway and new insight into the development of quail follicles.

LncRNA HOXA-AS3 Sponges miR-29c to Facilitate Cell Proliferation, Metastasis, and EMT Process and Activate the MEK/ERK Signaling Pathway in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a prevalent malignant tumor with high morbidity and mortality across the world. Recent findings have suggested that long noncoding (lnc)RNA HOXA-AS3 plays an important role in tumorigenesis and metastasis in a variety of cancers. However, the role of lncRNA HOXA-AS3 in the initiation and progression of HCC remains largely unclear. In the present study, HOXA-AS3 was highly expressed in HCC tumor tissues and cell lines. High HOXA-AS3 expression was correlated with low survival of HCC patients. Loss-of-function experiments showed that knockdown of HOXA-AS3 inhibited cell proliferation, migration, invasion, the epithelial-mesenchymal transition (EMT) process, and the mitogen-activated protein kinase/extracellular regulated protein kinase (MEK/ERK) signaling pathway in HCC. Molecular mechanism exploration uncovered that HOXA-AS3 could directly interact with and negatively regulate miR-29c. BMP1 is a downstream target gene of miR-29c, and HOXA-AS3 could regulate BMP1 expression by targeting miR-29c. miR-29c negatively regulated and BMP1 promoted the progression of HCC. Rescue experiments revealed that miR-29c inhibitor could partially counteract the impact induced by HOXA-AS3 knockdown in HCC. Taken together, our study is the first to show the interaction of HOXA-AS3 with miR-29c in facilitating cell proliferation, metastasis, EMT process, and MEK/ERK signaling pathway in HCC.

A Magnesium-Enriched 3D Culture System that Mimics the Bone Development Microenvironment for Vascularized Bone Regeneration.

The redevelopment/regeneration pattern of amputated limbs from a blastema in salamander suggests that enhanced regeneration might be achieved by mimicking the developmental microenvironment. Inspired by the discovery that the expression of magnesium transporter‐1 (MagT1), a selective magnesium (Mg) transporter, is significantly upregulated in the endochondral ossification region of mouse embryos, a Mg‐enriched 3D culture system is proposed to provide an embryonic‐like environment for stem cells. First, the optimum concentration of Mg ions (Mg2+) for creating the osteogenic microenvironment is screened by evaluating MagT1 expression levels, which correspond to the osteogenic differentiation capacity of stem cells. The results reveal that Mg2+ selectively activates the mitogen‐activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway to stimulate osteogenic differentiation, and Mg2+ influx via MagT1 is profoundly involved in this process. Then, Mg‐enriched microspheres are fabricated at the appropriate size to ensure the viability of the encapsulated cells. A series of experiments show that the Mg‐enriched microenvironment not only stimulates the osteogenic differentiation of stem cells but also promotes neovascularization. Obvious vascularized bone regeneration is achieved in vivo using these Mg‐enriched cell delivery vehicles. The findings suggest that biomaterials mimicking the developmental microenvironment might be promising tools to enhance tissue regeneration.

Regulation of 25-hydroxyvitamin D-1-hydroxylase and 24-hydroxylase in keratinocytes by PTH and FGF23.

Renal 25-hydroxyvitamin D-1α-hydroxylase (1αOHase, CYP27B1) and 24-hydroxylase (24OHase, CYP24A1) are tightly regulated. However, little is known about the regulation of 1α(OH)ase and 24(OH)ase in extrarenal tissue such as the epidermis. This study was to determine the roles of parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF 23) in the regulation of 1α(OH)ase and 24(OH)ase in epidermal keratinocytes as well as epidermal keratinocyte proliferation and differentiation. The results showed that PTH increased the protein level of 1α(OH)ase in human epidermal keratinocyte cell line HaCaT, but had no effect on the level of 24(OH)ase. The effect of PTH on 1α(OH)ase was blocked by the PKC inhibitor. Treatment with FGF23 decreased mRNA and protein levels of 1α(OH)ase and increased mRNA and protein levels of 24(OH)ase in HaCaT cells. The effect of FGF23 on 1α(OH)ase and 24(OH)ase was blocked by the mitogen-activated protein kinase/extracellular regulated protein kinase (MAPK/ERK) inhibitor. In addition, treatment with PTH enhanced levels of differentiation markers including keratin 1, involucrin, loricrin, and filaggrin but reduced levels of BrdU incorporation in HaCaT cells. These effects were inhibited by the PKC inhibitor. FGF23 enhanced proliferation of HaCaT cells, but reduced levels of early differentiation markers including keratin 1 and involucrin and enhanced levels of the later differentiation markers including loricrin and filaggrin. These results suggest that PTH stimulates 1α(OH)ase expression and differentiation of HaCaT cells and inhibits proliferation via PKC. The data also suggest that FGF23 inhibits 1α(OH)ase expression and stimulates 24(OH)ase expression via MAPK/ERK. In addition, FGF23 enhances proliferation and late differentiation and inhibits early differentiation of HaCaT keratinocytes.

Discovery of Quinazolines That Activate SOS1-Mediated Nucleotide Exchange on RAS.

Proteins in the RAS family are important regulators of cellular signaling and, when mutated, can drive cancer pathogenesis. Despite considerable effort over the last 30 years, RAS proteins have proven to be recalcitrant therapeutic targets. One approach for modulating RAS signaling is to target proteins that interact with RAS, such as the guanine nucleotide exchange factor (GEF) son of sevenless homologue 1 (SOS1). Here, we report hit-to-lead studies on quinazoline-containing compounds that bind to SOS1 and activate nucleotide exchange on RAS. Using structure-based design, we refined the substituents attached to the quinazoline nucleus and built in additional interactions not present in the initial HTS hit. Optimized compounds activate nucleotide exchange at single-digit micromolar concentrations in vitro. In HeLa cells, these quinazolines increase the levels of RAS-GTP and cause signaling changes in the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway.

Effects of norcantharidin on proliferation and apoptosis of glioma cells via mitogen-activated protein kinase/extracellular regulated protein kinase signaling pathway

Objective To investigate the effects of norcantharidin (NCTD) on the proliferation and apoptosis on glioma cells. Methods Glioma U87 cells were treated with various concentrations of NCTD (25, 50, 100, 200 μmol/L) for 24, 48 h. The effects of NCTD on the proliferation and apoptosis of glioma cells were measured by methyl thiazol tetrazolium (MTT) assay and flow cytometry. The Mitogen-activated protein kinase/extracellular regulated protein kinase (MAPK/ERK) signaling pathway changes were detected by Western blotting. Results The results showed that NCTD effectively inhibited cell growth and induced apoptosis in U87 cells in a time- and dose-dependent manner. After incubation with NCTD for 24 h and 48 h, the average half maximal inhibitory concentration (IC50) was 147.7 μmol/L and 62.5 μmol/L, respectively. It could significantly inhibit proliferation at 24 h and 48 h (F=30.234, 42.106, P=0.000). As compared with the control group [(1.2±0.9)%], the cell apoptosis rate induced by 30, 50 μmol/L of NCTD for 10 h was (6.8±1.2)% and (17.2±2.0)%, respectively, which indicated that NCTD could induce apoptosis of cells in a dose-dependent manner (F=405.761, P=0.000). Western blotting results revealed that the phospho-MEK and phospho-ERK were down-regulated significantly in NCTD group as compared with control group (P=0.007). Conclusion Our findings demonstrated that NCTD inhibited proliferation and induced apoptosis of U87 glioma cells through MAPK/ERK signaling pathway. Key words: Glioma; Norcantharidin; Mitogen-activated protein kinase/extracellular regulated protein kinase signaling pathway; Apoptosis

Discovery of Aminopiperidine Indoles That Activate the Guanine Nucleotide Exchange Factor SOS1 and Modulate RAS Signaling.

Deregulated RAS activity, often the result of mutation, is implicated in approximately 30% of all human cancers. Despite this statistic, no clinically successful treatment for RAS-driven tumors has yet been developed. One approach for modulating RAS activity is to target and affect the activity of proteins that interact with RAS, such as the guanine nucleotide exchange factor (GEF) son of sevenless homologue 1 (SOS1). Here, we report on structure-activity relationships (SAR) in an indole series of compounds. Using structure-based design, we systematically explored substitution patterns on the indole nucleus, the pendant amino acid moiety, and the linker unit that connects these two fragments. Best-in-class compounds activate the nucleotide exchange process at submicromolar concentrations in vitro, increase levels of active RAS-GTP in HeLa cells, and elicit signaling changes in the mitogen-activated protein kinase-extracellular regulated kinase (MAPK-ERK) pathway, resulting in a decrease in pERK1/2T202/Y204 protein levels at higher compound concentrations.

Long non-coding RNA ASBEL promotes osteosarcoma cell proliferation, migration, and invasion by regulating microRNA-21.

Osteosarcoma is the most common malignant bone tumor in children and adolescents with high rate of incidence, high frequency of recurrence, and high degree of metastasis. This study aimed to investigate the effects of long noncoding RNA antisense ncRNA in the abundant in neuroepithelium area (ANA)/B-cell translocation gene 3 (BTG3) locus (lncRNA ASBEL) on the pathogenesis of osteosarcoma. The expression levels of ASBEL in human osteoblast cells and human osteosarcoma cells were evaluated using qRT-PCR. Effects of ASBEL knockdown on cell viability, migration, and invasion were detected using trypan blue exclusion assay, cell migration, and cell invasion assay, respectively. The regulatory effects of ASBEL on microRNA-21 (miR-21) were analyzed using qRT-PCR. The roles of miR-21 and protein phosphatase 2A (PP2A), the possible downstream factor of miR-21, in osteosarcoma cell proliferation, migration, and invasion were also explored. The results showed that ASBEL was highly expressed in osteosarcoma cells. Knockdown of ASBEL inhibited osteosarcoma cell viability, migration, and invasion, as well as the expression level of miR-21. PP2A was a direct target of miR-21, which participated in the effects of ASBEL and miR-21 on the activation of phosphatidylinositol 3-kinase/protein kinase 3/glycogen synthase kinase-3β (PI3K/AKT/GSK3β) and mitogen-activated protein kinase/extracellular regulated protein kinase (MEK/ERK) signaling pathways as well as the enhancement of osteosarcoma cell proliferation, migration, and invasion. In conclusion, we verified that ASBEL-miR-21-PP2A pathway might play critical regulatory effects on the pathogenesis of osteosarcoma and could be as the potential therapeutic target and biomarker for osteosarcoma treatment.

IGF1/MAPK/ERK signaling pathway-mediated programming alterations of adrenal cortex cell proliferation by prenatal caffeine exposure in male offspring rats

Our previous study proposed a glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis programming mechanism for prenatal caffeine exposure (PCE)-induced adrenal developmental dysfunction. Here, we focused on PCE-induced cell proliferation changes of the adrenal cortex in male offspring rats before and after birth and clarified the intrauterine programming mechanism. On gestational day (GD) 20, the PCE group had an elevated serum corticosterone level reduced fetal bodyweight, maximum adrenal sectional area, and elevated adrenal corticosterone and aldosterone contents. However, in postnatal week (PW) 6, the serum corticosterone level was decreased, and the bodyweight, with catch-up growth, adrenal cortex maximum cross-sectional area and aldosterone content were relatively increased, while the adrenal corticosterone content was lower. On GD20, the expression of adrenal IGF1, IGF1R and proliferating cell nuclear antigen (PCNA) were decreased, while the expression of these factors at PW6 were increased in the PCE group. Fetal adrenal gene chip analysis suggested that the mitogen-activated protein kinase/extracellular regulated protein kinase (MAPK/ERK) signal pathway was suppressed in the PCE group. Moreover, in the rat primary adrenal cells, corticosterone (rather than caffeine) was shown to significantly inhibit cell proliferation, IGF1 and PCNA expression, and ERK phosphorylation, which could be reversed by exogenous IGF1. Meanwhile, the effects of exogenous IGF1 were reversed by the ERK pathway inhibitor (PD184161). In conclusion, PCE could induce programming alterations in adrenal cortical cell proliferation before and after birth in male offspring rats. The underlying mechanism is associated with the inhibition of fetal adrenal IGF1-related MAPK/ERK signaling pathway caused by high glucocorticoid levels.

Astragaloside IV inhibits progression of glioma via blocking MAPK/ERK signaling pathway

Glioma is one of the most common primary brain tumors in adults with a high mortality rate and relapse rate. Thus, finding better effective approaches to treat glioma has become very urgent. Astragaloside IV (AS-IV), the major active triterpenoid in Radix Astragali, has shown anti-tumorigenic properties in certain cancers. However, its role in glioma remains unclear. Here, we studied the effects of AS-IV on glioma in vitro and in vivo, and explored the underlying mechanisms. Our results revealed that AS-IV dose-dependently inhibited the proliferation of U251 cells in vitro and attenuated tumor growth in vivo. In addition, the migration and invasion ability of U251 cell has been suppressed in presence of AS-IV. The levels of proliferating cell nuclear antigen (PCNA), Ki67, matrix metallopeptidase (MMP) −2, MMP-9 and vascular endothelial growth factor (VEGF) were decreased significantly by the treatment of different concentrations AS-IV. Furthermore, AS-IV also significantly weakened the activation of Mitogen-activated protein kinase/Extracellular regulated protein kinase (MAPK/ERK) signaling pathway in vitro and in vivo. Taken together our study has identified a novel function of AS-IV and provided a molecular basis for AS-IV potential applications in the treatment of glioma and other cancers.

Daidzein stimulates osteogenesis facilitating proliferation, differentiation, and antiapoptosis in human osteoblast-like MG-63 cells via estrogen receptor–dependent MEK/ERK and PI3K/Akt activation

Daidzein, a natural soy isoflavone, has a structure similar to estradiol and exhibiting bone-sparing effects against osteoporosis. However, the molecular mechanisms of osteogenesis remain unclear. We hypothesized that daidzein stimulates osteogenesis through estrogen receptor (ER)–dependent signal pathways. To test this hypothesis, we investigated the effects of daidzein compared with 17β-estradiol on proliferation, differentiation, and cisplatin-induced apoptosis in human osteoblast-like MG-63 cells containing 2 ER isoforms. The results showed that daidzein stimulated cell proliferation by altering cell cycle distribution, promoted cell differentiation by increasing the alkaline phosphatase activity and collagen content, and reduced cell apoptosis associated by up-regulating the expression of Bcl-xL. The above actions of daidzein were prevented by cotreatment with the ER antagonist ICI 182780. Using small interfering RNA technology, we further demonstrated that the effects of daidzein on alkaline phosphatase activity, collagen content, and cell apoptosis are mediated by both ERα and ERβ, whereas the effects on cell proliferation are primarily mediated by ERα. However, the effects of 17β-estradiol on osteoblastic proliferation and survival are mediated by both ER isotypes, and the effects on osteoblastic differentiation are primarily mediated by ERα. The use of specific inhibitors indicated that activation of the mitogen-activated protein kinase kinase/extracellular regulated kinase (MEK/ERK) and phosphoinositide 3-kinase/protein kinase B or PKB (PI3K/Akt) signaling pathway at least partially accounts for these effects of daidzein. Taken together, the results indicate that daidzein stimulates osteogenesis through facilitating proliferation, differentiation, and antiapoptosis in human osteoblast-like MG-63 cells via activation of MEK/ERK and PI3K/Akt in an ER-dependent manner.