Elevated FOXG1 in glioblastoma stem cells cooperates with Wnt/β-catenin to induce exit from quiescence

Glioblastoma (GBM) stem cells (GSCs) display phenotypic and molecular features reminiscent of normal neural stem cells and exhibit a spectrum of cell cycle states (dormant, quiescent, proliferative). However, mechanisms controlling the transition from quiescence to proliferation in both neural stem cells (NSCs) and GSCs are poorly understood. Elevated expression of the forebrain transcription factor FOXG1 is often observed in GBMs. Here, using small-molecule modulators and genetic perturbations, we identify a synergistic interaction between FOXG1 and Wnt/β-catenin signaling. Increased FOXG1 enhances Wnt-driven transcriptional targets, enabling highly efficient cell cycle re-entry from quiescence; however, neither FOXG1 nor Wnt is essential in rapidly proliferating cells. We demonstrate that FOXG1 overexpression supports gliomagenesis in vivo and that additional β-catenin induction drives accelerated tumor growth. These data indicate that elevated FOXG1 cooperates with Wnt signaling to support the transition from quiescence to proliferation in GSCs.

Therapeutic Targeting of the GSK3β-CUGBP1 Pathway in Myotonic Dystrophy

Myotonic Dystrophy type 1 (DM1) is a neuromuscular disease associated with toxic RNA containing expanded CUG repeats. The developing therapeutic approaches to DM1 target mutant RNA or correct early toxic events downstream of the mutant RNA. We have previously described the benefits of the correction of the GSK3β-CUGBP1 pathway in DM1 mice (HSALR model) expressing 250 CUG repeats using the GSK3 inhibitor tideglusib (TG). Here, we show that TG treatments corrected the expression of ~17% of genes misregulated in DM1 mice, including genes involved in cell transport, development and differentiation. The expression of chloride channel 1 (Clcn1), the key trigger of myotonia in DM1, was also corrected by TG. We found that correction of the GSK3β-CUGBP1 pathway in mice expressing long CUG repeats (DMSXL model) is beneficial not only at the prenatal and postnatal stages, but also during adulthood. Using a mouse model with dysregulated CUGBP1, which mimics alterations in DM1, we showed that the dysregulated CUGBP1 contributes to the toxicity of expanded CUG repeats by changing gene expression and causing CNS abnormalities. These data show the critical role of the GSK3β-CUGBP1 pathway in DM1 muscle and in CNS pathologies, suggesting the benefits of GSK3 inhibitors in patients with different forms of DM1.

GSK3 inhibitor enhances gemtuzumab ozogamicin-induced apoptosis in primary human leukemia cells by overcoming multiple mechanisms of resistance

In acute myeloid leukemia (AML), the heterogeneity of genetic and epigenetic characteristics makes treatment difficult. The prognosis for AML is therefore poor, and there is an urgent need for new treatments for this condition. Gemtuzumab ozogamicin (GO), the first antibody-drug conjugate (ADC), targets the CD33 antigen expressed in over 90% of AML cases. GO therefore has the potential to counter the heterogeneity of AML patients. However, a major clinical problem is that drug resistance to GO diminishes its effect over time. Here, we report that the inhibition of glycogen synthase kinase 3 (GSK3) alone overcomes several forms of GO resistance at concentrations without antileukemic effects. The GSK3 inhibitors tested significantly enhanced the cytotoxic effect of GO in AML cell lines. We elucidated four mechanisms of enhancement: (1) increased expression of CD33, the target antigen of GO; (2) activation of a lysosomal function essential for hydrolysis of the GO linker; (3) reduced expression of MDR1 that eliminates calicheamicin, the payload of GO; and (4) reduced expression of the anti-apoptotic factor Bcl-2. A similar combination effect was observed against patient-derived primary AML cells. Combining GO with GSK3 inhibitors may be efficacious in treating heterogeneous AML.

Mouse embryonic stem cells require multiple amino acids

Previous studies suggest that mouse embryonic stem cells (mESCs) have a unique requirement for threonine when cultured in serum and leukemia inhibitory factor (LIF). Here, we replicated the experiments and found that the growth of mESCs (E14 and AB2.2) in serum/LIF was significantly attenuated by the individual absence of multiple amino acids. When mESCs were maintained in naïve pluripotency by the MEK inhibitor, GSK3 inhibitor (2i), and LIF, their growth was significantly affected by the lack of any one of the nine essential amino acids or some non-essential amino acids. There was no unique requirement for threonine in both culture conditions. This study shows that, like many other cells, mESCs do not have any special requirements for amino acids.

Efficient hepatic differentiation and regeneration potential under xeno-free conditions using mass-producible amnion-derived mesenchymal stem cells

BACKGROUND

Amnion-derived mesenchymal stem cells (AM-MSCs) are an attractive source of stem cell therapy for patients with irreversible liver disease. However, there are obstacles to their use due to low efficiency and xeno-contamination for hepatic differentiation.

METHODS

We established an efficient protocol for differentiating AM-MSCs into hepatic progenitor cells (HPCs) by analyzing transcriptome-sequencing data. Furthermore, to generate the xeno-free conditioned differentiation protocol, we replaced fetal bovine serum (FBS) with polyvinyl alcohol (PVA). We investigated the hepatocyte functions with the expression of mRNA and protein, secretion of albumin, and activity of CYP3A4. Finally, to test the transplantable potential of HPCs, we transferred AM-MSCs along with hepatic progenitors after differentiated days 11, 12, and 13 based on the expression of hepatocyte-related genes and mitochondrial function. Further, we established a mouse model of acute liver failure using a thioacetamide (TAA) and cyclophosphamide monohydrate (CTX) and transplanted AM-HPCs in the mouse model through splenic injection.

RESULTS

We analyzed gene expression from RNA sequencing data in AM-MSCs and detected downregulation of hepatic development-associated genes including GATA6, KIT, AFP, c-MET, FGF2, EGF, and c-JUN, and upregulation of GSK3. Based on this result, we established an efficient hepatic differentiation protocol using the GSK3 inhibitor, CHIR99021. Replacing FBS with PVA resulted in improved differentiation ability, such as upregulation of hepatic maturation markers. The differentiated hepatocyte-like cells (HLCs) not only synthesized and secreted albumin, but also metabolized drugs by the CYP3A4 enzyme. The best time for translation of AM-HPCs was 12 days from the start of differentiation. When the AM-HPCs were transplanted into the liver failure mouse model, they settled in the damaged livers and differentiated into hepatocytes.

CONCLUSION

This study offers an efficient and xeno-free conditioned hepatic differentiation protocol and shows that AM-HPCs could be used as transplantable therapeutic materials. Thus, we suggest that AM-MSC-derived HPCs are promising cells for treating liver disease.

Immune checkpoint inhibition in syngeneic mouse cancer models by a silicasome nanocarrier delivering a GSK3 inhibitor

Checkpoint blocking antibodies that interfere in the PD-1/PD-L1 axis provide effective cancer immunotherapy for tumors that are immune inflamed or induced to become "hot". It has also been demonstrated that a small molecule inhibitor of the signaling hub kinase GSK3 can interfere in the PD-1/PD-L1 axis in T-cells by suppressing PD-1 expression. This provides an alternative approach to intervening in the PD-1/PD-L1 axis to provide cancer immunotherapy. In this communication, we demonstrate the remote loading of GSK3 inhibitor AZD1080 into the porous interior of mesoporous silica nanoparticles coated with a lipid bilayer (a.k.a. silicasomes). In a MC38 colon cancer model, intravenous injection (IV) of silicasome-encapsulated AZD1080 significantly improved biodistribution and drug delivery to the tumor site. The improved drug delivery was accompanied by cytotoxic MC38 tumor cell killing by perforin-releasing CD8⁺ T-cells, exhibiting reduced PD-1 expression. IV injection of encapsulated AZD1080 also resulted in significant tumor shrinkage in other syngeneic mouse tumor models, including another colorectal tumor (CT26), as well as pancreas (KPC) and lung (LLC) cancer models. Not only was the therapeutic efficacy of encapsulated AZD1080 similar or better than anti-PD-1 antibody, but the treatment was devoid of treatment toxicity. These results provide proof-of-principal demonstration of the feasibility of using encapsulated delivery of a GSK3 inhibitor to provide cancer immunotherapy, with the possibility to be used as a monotherapy or in combination with chemotherapy or other immunomodulatory agents.

GSK3 inhibitor-loaded osteotropic Pluronic hydrogel effectively mitigates periodontal tissue damage associated with experimental periodontitis

Periodontitis is a chronic inflammatory disease caused by complex interactions between the host immune system and pathogens that affect the integrity of periodontium. To prevent disease progression and thus preserve alveolar bone structure, simultaneous anti-inflammatory and osteogenic intervention are essential. Hence, a glycogen synthase kinase 3 beta inhibitor (BIO) was selected as a potent inflammation modulator and osteogenic agent to achieve this treatment objective. BIO's lack of osteotropicity, poor water solubility, and potential long-term systemic side effects, however, have hampered its clinical applications. To address these limitations, pyrophosphorylated Pluronic F127 (F127-PPi) was synthesized and mixed with regular F127 to prepare an injectable and thermoresponsive hydrogel formulation (PF127) of BIO, which could adhere to hard tissue and gradually release BIO to exert its therapeutic effects locally. Comparing to F127 hydrogel, PF127 hydrogels exhibited stronger binding to hydroxyapatite (HA). Additionally, BIO's solubility in PF127 solution was dramatically improved over F127 solution and the improvement was proportional to the polymer concentration. When evaluated on a rat model of periodontitis, PF127-BIO hydrogel treatment was found to be very effective in preserving alveolar bone and ligament, and preventing periodontal inflammation, as shown by the micro-CT and histological data, respectively. Altogether, these findings suggested that the thermoresponsive PF127 hydrogel is an effective local drug delivery system for better clinical management of periodontitis and associated pathologies.

Inhibition of GSK3 Represses the Expression of Retinoic Acid Synthetic Enzyme ALDH1A2 via Wnt/β-Catenin Signaling in WiT49 Cells

Organogenesis, including renal development, requires an appropriate retinoic acid concentration, which is established by differential expression of aldehyde dehydrogenase 1 family member A2 (ALDH1A2) and cytochrome P450 family 26 subfamily A/B/C member 1 (CYP26A1/B1/C1). In the fetal kidney, ALDH1A2 expresses in the developing stroma and renal vesicle and its derivatives but does not present in the ureteric bud. It remains unclear what may contribute to this expression pattern. Here we show that the glycogen synthase kinase 3 alpha/beta (GSK3A/B) inhibitor CHIR99021 significantly represses ALDH1A2 expression in WiT49, which is a Wilms’ tumor cell line that exhibits “triphasic” differential potential and is used as a fetal kidney cell model. CHIR99021 fails to suppress ALDH1A2 as β-catenin is inhibited, suggesting that the downregulation of ALDH1A2 by CHIR99021 is through Wnt/β-catenin signaling. Ectopic expression of mouse Wnt1, Wnt3a, Wnt4, and Wnt9b represses ALDH1A2 expression in WiT49 cells. Using immunohistochemistry, we show an inverse correlation of Aldh1a2 expression with β-catenin in rat E18.5 kidney. ChIP demonstrated that β-catenin is recruited to the ALDH1A2 promoter, the conserved intron1G, and another site within intron 1 of ALDH1A2. Using a luciferase assay, we further show that the ALDH1A2 promoter and the intron1G element are involved in the repression of ALDH1A2 expression by CHIR99021. Our work demonstrates that ALDH1A2 expression can be directly repressed by the Wnt/β-catenin signaling in fetal kidney cells, suggesting that Wnt/β-catenin may play a role in maintaining the expression pattern of ALDH1A2 in the fetal kidney, thus controlling the availability and localization of retinoic acid and regulating aspects of kidney development.

Optimized conditions for the supplementation of human-induced pluripotent stem cell cultures with a GSK-3 inhibitor during embryoid body formation with the aim of inducing differentiation into mesodermal and cardiac lineage

We optimized the conditions for the differentiation of human induced pluripotent stem cells (hiPSCs) into mesoderm lineage-committed cells by supplementing the cultures with CHIR, a selective GSK-3 inhibitor, during embryoid body (EB) formation. In vitro treatment with 4 μM CHIR during the late 2 days of a 4-day suspension culture period was most effective at promoting mesodermal differentiation. The resulting EBs showed a significant increase in the expression levels of mesoderm-associated genes (WNT3A, T, DKK1, GATA4, FOXC1, and MESP1) and a maintenance of OCT3/4 and NANOG expressions. Upon subsequent differentiation into a cardiac cell lineage, these EBs were shown to generate contractile cardiomyocytes. When shortening the CHIR treatment period to 1 day, the resulting EBs showed reduced expression of mesoderm-associated genes in comparison to the 2-day CHIR treatment. In particular, the expression level of FOXC1 in the 1-day CHIR-treated EBs was much lower than that of the 2-day CHIR-treated EBs. When the treatment period with CHIR was extended to 4 days, the resulting EBs presented significantly reduced expression of WNT3A, OCT3/4, and NANOG upon CHIR concentrations above 4 μM. Similarly, when CHIR treatment was conducted after the formation of EBs, the effectiveness of the GSK-3 inhibitor was reduced compared to a treatment performed during EB formation. Our results indicate that spatiotemporal constraints associated with EB formation, i.e., three-dimensional structuration and cell development in EBs, should be taken into account when designing EB formation-based differentiation protocol involving CHIR treatment.

Myogenic progenitor specification from pluripotent stem cells

Pluripotent stem cells represent important tools for both basic and translational science as they enable to study mechanisms of development, model diseases in vitro and provide a potential source of tissue-specific progenitors for cell therapy. Concomitantly with the increasing knowledge of the molecular mechanisms behind activation of the skeletal myogenic program during embryonic development, novel findings in the stem cell field provided the opportunity to begin recapitulating in vitro the events occurring during specification of the myogenic lineage. In this review, we will provide a perspective of the molecular mechanisms responsible for skeletal myogenic commitment in the embryo and how this knowledge was instrumental for specifying this lineage from pluripotent stem cells. In addition, we will discuss the current limitations for properly recapitulating skeletal myogenesis in the petri dish, and we will provide insights about future applications of pluripotent stem cell-derived myogenic cells.

Development and validation of an LC-MS/MS method for quantitative determination of GS87, a novel antineoplastic agent, in mouse plasma

GS87 is a novel, highly specific GSK3 inhibitor, which has shown to induce extensive differentiation of acute myeloid leukemia (AML) cells in early mouse studies and has great potential for therapeutic advancement. This work described the development and validation of an LC-MS/MS method for quantitative determination of GS87 in mouse plasma. In this method, GS87 and T6447952 (a structural analog used as internal standard) were extracted from plasma using hexane as extraction solvent, and separated isocratically on a Waters XTerra^® MS C8 column (2.1 × 50 mm, 3.5 μm) using a mobile phase consisting of acetonitrile and 5.00 mM ammonium formate (35:65, v/v) pumped at a flow rate of 0.200 mL min^-1. Quantitation of GS87 was done by positive electrospray ionization tandem mass spectrometry operated in multiple-reaction-monitoring (MRM) mode. The method has been validated in accordance with the US Food and drug administration guidelines for bioanalytical method validation. It has linear calibration range of 2.50-250 ng mL^-1 with correlation coefficient of >0.999. The intra- and inter- assay accuracy and precision were ≤ ±5 and ≤6%, respectively. The IS normalized recovery of GS87 was 103-106%. The stability studies showed that GS87 was stable under all tested conditions. The method developed has been successfully applied to the measurement of GS87 concentrations in mouse plasma samples from an animal study, and may be useful for further preclinical investigation of GS87.

Glycogen synthase kinase 3 (GSK3)-inhibitor SB216763 promotes the conversion of human umbilical cord mesenchymal stem cells into neural precursors in adherent culture

The ability to generate neural progenitor cells from human umbilical cord mesenchymal stem cells (hUC-MSCs) has provided an option to treat neurodegenerative diseases. To establish a method for this purpose, we characterized the early neural markers of hUC-MSCs-derived cells under different conditions. We found that neither the elimination of signals for alternative fate nor N2 supplement was sufficient to differentiate hUC-MSCs into neural precursor cells, but the GSK3 inhibitor SB216763 could promote an efficient neural commitment of hUC-MSCs. The results indicated that Wnt/β-catenin might play an important role during the early neural differentiation of hUC-MSCs. Here, we report a method for hUC-MSCs to commit efficiently into a neural fate within a short period of time. This protocol provides an efficient method for hUC-MSCs-based neural regeneration.

Inhibition of glycogen synthase kinase-3 (GSK3) promotes the neural differentiation of full-term amniotic fluid-derived stem cells towards neural progenitor cells

The amniotic fluid has a heterogeneous population of cells. Some human amniotic fluid-derived stem (hAFS) cells have been shown to harbor the potential to differentiate into neural cells. However, the neural differentiation efficiency of hAFS cells remains low. In this study, we isolated CD117-positive hAFS cells from amniotic fluid and then examined the pluripotency of these cells through the formation of embryoid bodies (EBs). Additionally, we induced the neural differentiation of these cells using neuroectodermal medium. This study revealed that the GSK3-beta inhibitor SB216763 was able to stimulate the proliferation of CD117-positive hAFS cells without influencing their undifferentiated state. Moreover, SB216763 can efficiently promote the neural differentiation of CD117-positive hAFS cells towards neural progenitor cells in the presence of DMEM/F12 and N2 supplement. These findings provide an easy and low-cost method to maintain the proliferation of hAFS cells, as well as induce an efficacious generation of neural progenitor cells from hAFS cells. Such induction of the neural commitment of hAFS cells may provide an option for the treatment of neurodegenerative diseases by hAFS cells-based therapies.