Glycogen synthase kinase 3β as a potential therapeutic target in synovial sarcoma and fibrosarcoma

A novel GSK3β inhibitor 5n attenuates acute kidney injury

Acute kidney injury (AKI) is a clinical syndrome with high morbidity and mortality caused by various factor. The specific strategies for AKI are still lacking. GSK3β is widely expressed in the kidneys. In acute models of injury, GSK3β promotes the systemic inflammatory response, increases the proinflammatory release of cytokines, induces apoptosis, and alters cell proliferation. We screened a series of 3-(4-pyridyl)-5-(4-sulfamido-phenyl)-1,2,4-oxadiazole derivatives which are recognized as new GSK3β inhibitors, and found that 5n had the least toxicity and the best cell protection. We then tested the anti-inflammatory and reno-protective effect of 5n in cisplatin-treated tubular epithelial cells. 5n had anti-inflammation effect indicated by phosphor-NF-κB detection. Finally, we found that 5n ameliorated renal injury and inflammation in cisplatin-induced AKI mouse model. Silencing GSK3β inhibited cell injury and inflammation induced by cisplatin. We found that GSK3β interacted with PP2Ac to modulate the activity of NF-κB. In conclusion, 5n, the novel GSK3β inhibitor, protects against AKI via PP2Ac-dependent mechanisms which may provide a potential strategy for the treatment of AKI in clinic.

Prediction of histopathologic grades of myxofibrosarcoma with radiomics based on magnetic resonance imaging

PURPOSE

To develop a radiomics-based model from preoperative magnetic resonance imaging (MRI) for predicting the histopathological grades of myxofibrosarcoma.

METHODS

This retrospective study included 54 patients. The tumors were classified into high-grade and low-grade myxofibrosarcoma. The tumor size, signal intensity heterogeneity, margin, and surrounding tissue were evaluated on MRI. Using the least absolute shrinkage and selection operator (LASSO) algorithms, 1037 radiomics features were obtained from fat-suppressed T2-weighted images (T2WI), and a radiomics signature was established. Using multivariable logistic regression analysis, three models were built to predict the histopathologic grade of myxofibrosarcoma. A radiomics nomogram represents the integrative model. The three models' performance was evaluated using the receiver operating characteristics (ROC) and calibration curves.

RESULTS

The high-grade myxofibrosarcoma had greater depth (P = 0.027), more frequent heterogeneous signal intensity at T2WI (P = 0.015), and tail sign (P = 0.014) than the low-grade tumor. The area under curve (AUC) of these conventional MRI features models was 0.648, 0.656, and 0.668, respectively. Seven radiomic features were selected by LASSO to construct the radiomics signature model, with an AUC of 0.791. The AUC of the integrative model based on radiomics signature and conventional MRI features was 0.875. The integrative model's calibration curve and insignificant Hosmer-Lemeshow test statistic (P = 0.606) revealed good calibration.

CONCLUSION

An integrative model using radiomics signature and three conventional MRI features can preoperatively predict low- or high-grade myxofibrosarcoma.

Loss of PRDX6 Aborts Proliferative and Migratory Signaling in Hepatocarcinoma Cell Lines

Peroxiredoxin 6 (PRDX6), the only mammalian 1-Cys member of the peroxiredoxin family, has peroxidase, phospholipase A2 (PLA2), and lysophosphatidylcholine (LPC) acyltransferase (LPCAT) activities. It has been associated with tumor progression and cancer metastasis, but the mechanisms involved are not clear. We constructed an SNU475 hepatocarcinoma cell line knockout for PRDX6 to study the processes of migration and invasiveness in these mesenchymal cells. They showed lipid peroxidation but inhibition of the NRF2 transcriptional regulator, mitochondrial dysfunction, metabolic reprogramming, an altered cytoskeleton, down-regulation of PCNA, and a diminished growth rate. LPC regulatory action was inhibited, indicating that loss of both the peroxidase and PLA2 activities of PRDX6 are involved. Upstream regulators MYC, ATF4, HNF4A, and HNF4G were activated. Despite AKT activation and GSK3β inhibition, the prosurvival pathway and the SNAI1-induced EMT program were aborted in the absence of PRDX6, as indicated by diminished migration and invasiveness, down-regulation of bottom-line markers of the EMT program, MMP2, cytoskeletal proteins, and triggering of the "cadherin switch". These changes point to a role for PRDX6 in tumor development and metastasis, so it can be considered a candidate for antitumoral therapies.

Combined GSK-3β and MEK inhibitors modulate the stemness and radiotherapy sensitivity of cervical cancer stem cells through the Wnt signaling pathway

Cancer stem cells (CSCs) are the basis of cancer and lead to the recurrence and metastasis of cervical cancer. The aim of this study was to investigate the effects of antineoplastic agents on the stemness and radiotherapy sensitivity of cervical CSCs. Side population (SP) and non-side population (NSP) cells from the SiHa cervical cancer cell line were separated using flow cytometry. The cell spheroidization, proliferation, and subcutaneous tumor formation abilities of SP cells were stronger than those of NSP cells, and cervical CSC marker expressions increased in SP cells. The proliferation, anti-apoptosis and migration of SP cells under ionizing radiation were higher than those of SiHa cells. GSK-3β and/or MEK inhibitors can increase the proliferation, migration and anti-apoptosis of SP cells, and CSC marker expressions. The Wnt pathway inhibitor decreased CSC stemness maintenance by combination of GSK-3β and MEK inhibitors. Injection of GSK-3β and MEK inhibitors under ionizing radiation promoted tumor growth and activated downstream factor expressions in the Wnt signaling pathway in vivo. This study demonstrated that combining GSK-3β and MEK inhibitors can activate Wnt signaling pathway in cervical CSCs, thereby affecting their stemness maintenance and radiotherapy sensitivity.

Glaucocalyxin A induces apoptosis of NSCLC cells by inhibiting the PI3K/Akt/GSK3β pathway

Lung cancer is one of the fastest growing malignancies in morbidity and mortality, and current therapies are in general not sufficiently effective for this deadly disease. This study characterizes the anti-cancer effects of Glaucocalyxin A (GLA) and explores the underlying mechanisms using human non-small cell lung carcinoma (NSCLC) cells. First, our data showed that GLA suppressed the viability of cancer cells, while no effect was observed in the normal bronchial epithelial cell Bease 2B cells. Second, GLA inhibited colony formation, induced apoptosis of cancer cells. Third, GLA down-regulated the expression of B-cell lymphoma-2 (Bcl-2) protein, up-regulated the expression of Bcl2-associated X protein (Bax) , and strengthened cleavage of Caspase-3 and poly ADP-ribose polymerase (PARP). Fourth, GLA also diminished mitochondrial membrane potential and inhibited phosphatidylinositol 3-kinase (PI3K)/Akt/ glycogen synthase kinase-3β (GSK3β) pathway. In addition, injection of GLA (20 mg/kg) every two days significantly inhibited A549 xenograft tumor growth, accompanied by increased apoptosis and decreased proliferation. Together, our study provides evidence that the anticancer effect of GLA in NSCLC is mediated by inducing apoptosis through inhibiting PI3K/Akt/GSK3β pathway and suggests that GLA may be used as a promising natural medicine for NSCLC therapy. This article is protected by copyright. All rights reserved.

GSK-3β-mediated activation of NLRP3 inflammasome leads to pyroptosis and apoptosis of rat cardiomyocytes and fibroblasts

We previously demonstrated that GSK-3β mediates NLRP3 inflammasome activation and IL-1β production in cardiac fibroblasts (CFs) after myocardial infarction (MI). In this study, we show how GSK-3β-mediated activation of the NLRP3 inflammasome/caspase-1/IL-1β pathway leads to apoptosis and pyroptosis of cardiomyocytes (CMs) and CFs. Administration of lipopolysaccharide (LPS)/ATP to primary newborn rat cardiac fibroblasts (RCFs) led to increase in proteins of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, IL-1β, and IL-18. Additionally, the expression of caspase-3 and N-terminal fragments of gasdermin D (N-GSDMD) and the Bax/Bcl-2 ratio increased. Administration of the GSK-3β inhibitor SB216763 reduced the levels of apoptosis- and pyroptosis-related proteins regulated by NLRP3 inflammasome activation in RCFs. Next, we transferred the culture supernatant of LPS/ATP-treated RCFs to in vitro primary newborn rat cardiomyocytes (RCMs). The results showed that SB216763 attenuate the upregulation of the ratios of Bax/Bcl-2 and the expression of caspase-3 and N-GSDMD in RCMs. Direct stimulation of RCMs and H9c2 cells with recombinant rat IL-1β increased the p-GSK-3β/GSK-3β and Bax/Bcl-2 ratios and the expression of caspase-3 and N-GSDMD, while both SB216763 and TLR1 (an IL-1β receptor inhibitor) markedly reduced these effects, as assessed using propidium iodide positive staining and the lactate dehydrogenase release assay. The caspase-11 inhibitor wedelolactone decreased the expression level of N-GSDMD but did not alter the p-GSK-3β/GSK-3β ratio. Lastly, we established a Sprague-Dawley rat MI model to confirm that SB216763 diminished the increase in caspase-3 and N-GSDMD expression and the Bax/Bcl-2 ratio in the ischemic area. These data demonstrate that GSK-3β regulates apoptosis and pyroptosis of RCMs and RCFs due to NLRP3 inflammasome activation in RCFs.

GSK3-beta as a candidate therapeutic target in soft tissue sarcomas

Soft tissue sarcoma (STS) is a predominantly fatal rare malignancy with inadequate treatment options. Glycogen synthase kinase 3β (GSK-3β) is an emerging target in human malignancies. Its therapeutic relevance in STS is unknown. We analyzed the prognostic impact of GSK-3β gene and protein expression in two independent cohorts of patients with STS. We then treated STS cell lines and mice xenografts with a novel GSK-3 inhibitor 9-ING-41 alone or in combination with chemotherapy. We demonstrated that 9-ING-41 treatment induced significant STS cells apoptosis and was synergistic in vivo when combined with chemotherapy. Mechanistically, 9-ING-41 induces significant apoptosis of STS cells via suppression of NF-κB-mediated X-linked inhibitor of apoptosis protein (XIAP) expression. These data support the inclusion of patients with STS in clinical studies of 9-ING-41 alone and in combination with chemotherapy.

GSK-3 Inhibition Is Cytotoxic in Glioma Stem Cells through Centrosome Destabilization and Enhances the Effect of Radiotherapy in Orthotopic Models

BACKGROUND

Previous data on glycogen synthase kinase 3 (GSK-3) inhibition in cancer models support a cytotoxic effect with selectivity for tumor cells compared to normal tissue but the effect of these inhibitors in glioma has not been widely studied. Here, we investigate their potential as cytotoxics in glioma.

METHODS

We assessed the effect of pharmacologic GSK-3 inhibition on established (U87, U251) and patient-derived (GBM1, GBM4) glioblastoma (GBM) cell lines using cytotoxicity assays as well as undertaking a detailed investigation of the effect on cell cycle, mitosis, and centrosome biology. We also assessed drug uptake and efficacy of GSK-3 inhibition alone and in combination with radiation in xenograft models.

RESULTS

Using the selective GSK-3 inhibitor AZD2858, we demonstrated single agent cytotoxicity in two patient-derived glioma cell lines (GBM1, GBM4) and two established cell lines (U251 and U87) with IC50 in the low micromolar range promoting centrosome disruption, failed mitosis, and S-phase arrest. Glioma xenografts exposed to AZD2858 also showed growth delay compared to untreated controls. Combined treatment with radiation increased the cytotoxic effect of clinical radiation doses in vitro and in orthotopic glioma xenografts.

CONCLUSIONS

These data suggest that GSK-3 inhibition promotes cell death in glioma through disrupting centrosome function and promoting mitotic failure and that AZD2858 is an effective adjuvant to radiation at clinical doses.

WNT/β-Catenin Pathway in Soft Tissue Sarcomas: New Therapeutic Opportunities?

Simple Summary

The WNT/β-catenin signaling pathway is involved in fundamental processes for the proliferation and differentiation of mesenchymal stem cells. However, little is known about its relevance for mesenchymal neoplasms, such us soft tissue sarcomas (STS). Chemotherapy based on doxorubicin (DXR) still remains the standard first-line treatment for locally advanced unresectable or metastatic STS, although overall survival could not be improved by combination with other chemotherapeutics. In this sense, the development of new therapeutic approaches continues to be an unmatched goal. This review covers the most important molecular alterations of the WNT signaling pathway in STS, broadening the current knowledge about STS as well as identifying novel drug targets. Furthermore, the current therapeutic options and drug candidates to modulate WNT signaling, which are usually classified by their interaction site upstream or downstream of β-catenin, and their presumable clinical impact on STS are discussed.

Abstract

Soft tissue sarcomas (STS) are a very heterogeneous group of rare tumors, comprising more than 50 different histological subtypes that originate from mesenchymal tissue. Despite their heterogeneity, chemotherapy based on doxorubicin (DXR) has been in use for forty years now and remains the standard first-line treatment for locally advanced unresectable or metastatic STS, although overall survival could not be improved by combination with other chemotherapeutics. In this sense, the development of new therapeutic approaches continues to be a largely unmatched goal. The WNT/β-catenin signaling pathway is involved in various fundamental processes for embryogenic development, including the proliferation and differentiation of mesenchymal stem cells. Although the role of this pathway has been widely researched in neoplasms of epithelial origin, little is known about its relevance for mesenchymal neoplasms. This review covers the most important molecular alterations of the WNT signaling pathway in STS. The detection of these alterations and the understanding of their functional consequences for those pathways controlling sarcomagenesis development and progression are crucial to broaden the current knowledge about STS as well as to identify novel drug targets. In this regard, the current therapeutic options and drug candidates to modulate WNT signaling, which are usually classified by their interaction site upstream or downstream of β-catenin, and their presumable clinical impact on STS are also discussed.

CHIR99021, trough GSK-3β Targeting, Reduces Epithelioid Sarcoma Cell Proliferation by Activating Mitotic Catastrophe and Autophagy

Epithelioid sarcoma (ES) is a rare disease representing <1% of soft tissue sarcomas. Current therapies are based on anthracycline alone or in combination with ifosfamide or other cytotoxic drugs. ES is still characterized by a poor prognosis with high rates of recurrence. Indeed, for years, ES survival rates have remained stagnant, suggesting that conventional treatments should be revised and improved. New therapeutic approaches are focused to target the key regulators of signaling pathways, the causative markers of tumor pathophysiology. To this end, we selected, among the drugs to which an ES cell line is highly sensitive, those that target signaling pathways known to be dysregulated in ES. In particular, we found a key role for GSK-3β, which results in up-regulation in tumor versus normal tissue samples and associated to poor prognosis in sarcoma patients. Following this evidence, we evaluated CHIR99021, a GSK-3 inhibitor, as a potential drug for use in ES therapy. Our data highlight that, in ES cells, CHIR99021 induces cell cycle arrest, mitotic catastrophe (MC) and autophagic response, resulting in reduced cell proliferation. Our results support the potential efficacy of CHIR99021 in ES treatment and encourage further preclinical and clinical studies.

GSK3 as a Regulator of Cytoskeleton Architecture: Consequences for Health and Disease

Glycogen synthase kinase 3 (GSK3) was initially isolated as a critical protein in energy metabolism. However, subsequent studies indicate that GSK-3 is a multi-tasking kinase that links numerous signaling pathways in a cell and plays a vital role in the regulation of many aspects of cellular physiology. As a regulator of actin and tubulin cytoskeleton, GSK3 influences processes of cell polarization, interaction with the extracellular matrix, and directional migration of cells and their organelles during the growth and development of an animal organism. In this review, the roles of GSK3–cytoskeleton interactions in brain development and pathology, migration of healthy and cancer cells, and in cellular trafficking of mitochondria will be discussed.

Targeting Glycogen Synthase Kinase 3 Beta Regulates CD47 Expression After Myocardial Infarction in Rats via the NF-κB Signaling Pathway

The aim of this study was to investigate the effects of the GSK-3β/NF-κB pathway on integrin-associated protein (CD47) expression after myocardial infarction (MI) in rats. An MI Sprague Dawley rat model was established by ligating the left anterior descending coronary artery. The rats were divided into three groups: Sham, MI, and SB + MI (SB216763) groups. Immunohistochemistry was used to observe the changes in cardiac morphology. A significant reduction in the sizes of fibrotic scars was observed in the SB + MI group compared to that in the MI group. SB216763 decreased the mRNA and protein expression of CD47 and NF-κB during MI. Primary rat cardiomyocytes (RCMs) and the H9c2 cell line were used to establish in vitro hypoxia models. Quantitative real-time PCR and western blotting analyses were conducted to detect mRNA and protein expression levels of CD47 and NF-κB and apoptosis-related proteins, respectively. Apoptosis of hypoxic cells was assessed using flow cytometry. SB216763 reduced the protein expression of CD47 and NF-κB in RCMs and H9c2 cells under hypoxic conditions for 12 h, and alleviated hypoxia-induced apoptosis. SN50 (an NF-κB inhibitor) also decreased CD47 protein expression in RCMs and H9c2 cells under hypoxic conditions for 12 h and protected cells from apoptosis. GSK-3β upregulates CD47 expression in cardiac tissues after MI by activating NF-κB, which in turn leads to myocardial cell damage and apoptosis.

GSK-3 Inhibition Modulates Metalloproteases in a Model of Lung Inflammation and Fibrosis

Idiopathic pulmonary fibrosis (IPF) is mainly characterized by aberrant extracellular matrix deposition, consequent to epithelial lung injury and myofibroblast activation, and inflammatory response. Glycogen synthase kinase 3 (GSK-3) is a serine-threonine kinase involved in several pathways, and its inhibition has been already suggested as a therapeutic strategy for IPF patients. There is evidence that GSK-3 is able to induce matrix metalloproteinase (MMP) expression and that its inhibition modulates MMP expression in the tissues. The aim of our study was to investigate the role of GSK-3 and its inhibition in the modulation of MMP-9 and -2 in an in vivo mouse model of lung fibrosis and in vitro using different cell lines exposed to pro-inflammatory or pro-fibrotic stimuli. We found that GSK-3 inhibition down-modulates gene expression and protein levels of MMP-9, MMP-2, and their inhibitors TIMP-1 and TIMP-2 in inflammatory cells harvested from bronchoalveolar lavage fluid (BALF) of mice treated with bleomycin as well as in interstitial alveolar macrophages and cuboidalized epithelial alveolar cells. To the same extent, GSK-3 inhibition blunted the increased MMP-9 and MMP-2 activity induced by pro-fibrotic stimuli in a human lung fibroblast cell line. Moreover, the αSMA protein level, a marker of fibroblast-to-myofibroblast transition involved in fibrosis, was decreased in primary fibroblasts treated with TGFβ following GSK-3 inhibition. Our results confirm the implication of GSK-3 in lung inflammation and fibrosis, suggesting that it might play its role by modulating MMP expression and activity but also pushing fibroblasts toward a myofibroblast phenotype and therefore enhancing extracellular matrix deposition. Thus, its inhibition could represent a possible therapeutic strategy.

GSK-3β Regulates the Expression of P21 to Promote the Progression of Chordoma

Purpose

Chordoma is a rare malignant bone tumor transformed from the remnants of notochord. It is characterized as highly aggressive and locally invasive, difficult to be completely removed by surgery, and has a poor clinical prognosis. Glycogen synthase kinase 3 beta (GSK-3β) is involved in many cellular processes. GSK-3β overexpression has been shown to promote the development of many cancers, according to previous studies. However, the role of GSK-3β in chordoma remains unclear.

Methods

Immunohistochemistry (IHC) and Western blotting (WB) were performed on clinical specimens to measure GSK-3β expression in chordoma, and immunofluorescence and quantitative real-time polymerase chain reaction (QRT-PCR) were performed to examine the expression of GSK-3β and P21 in cell lines. Cell proliferation was detected by the CCK-8 assay and colony formation analysis, cell migration and invasion checked by Transwell experiments, and cell apoptosis was determined by Annexin V/propidium iodide staining. P21 was predicted as a downstream target gene of GSK-3β using STRING and UNIHI databases. Moreover, we used immunoprecipitation to confirm that GSK-3β and P21 interacted with each other. The double luciferase reporter gene assay showed that GSK-3β could regulate the promoter activity of P21. Finally, the role of the GSK-3β -P21 pathway in chordoma tumorigenesis was analyzed in vivo in nude mice.

Results

Our study showed that GSK-3β was significantly higher in chordoma tissues than in paracancer tissues, and siRNA knockdown of GSK-3β inhibited chordoma cell proliferation and promoted cell apoptosis. Additionally, our research found that GSK-3β bound and downregulated the expression of the P21 gene, and the expression of silencing P21 partially reversed the inhibitory effect of knockdown GSK-3β on chordoma. Furthermore, xenografts showed that knockdown GSK-3β inhibited the formation of chordomas in vivo.

Conclusion

Our results indicated that the GSK-3β-P21 axis may be an important signaling pathway for the occurrence and development of chordoma, providing a new therapeutic target for the clinical treatment of this disorder.

Glucose Metabolism in Cancer: The Warburg Effect and Beyond

Otto Warburg observed a peculiar phenomenon in 1924, unknowingly laying the foundation for the field of cancer metabolism. While his contemporaries hypothesized that tumor cells derived the energy required for uncontrolled replication from proteolysis and lipolysis, Warburg instead found them to rapidly consume glucose, converting it to lactate even in the presence of oxygen. The significance of this finding, later termed the Warburg effect, went unnoticed by the broader scientific community at that time. The field of cancer metabolism lay dormant for almost a century awaiting advances in molecular biology and genetics, which would later open the doors to new cancer therapies [2, 3].

m5C RNA Methylation Primarily Affects the ErbB and PI3K-Akt Signaling Pathways in Gastrointestinal Cancer

5-Methylcytosine (m⁵C) is a kind of methylation modification that occurs in both DNA and RNA and is present in the highly abundant tRNA and rRNA. It has an important impact on various human diseases including cancer. The function of m⁵C is modulated by regulatory proteins, including methyltransferases (writers) and special binding proteins (readers). This study aims at comprehensive study of the m⁵C RNA methylation-related genes and the main pathways under m⁵C RNA methylation in gastrointestinal (GI) cancer. Our result showed that the expression of m⁵C writers and reader was mostly up-regulated in GI cancer. The NSUN2 gene has the highest proportion of mutations found in GI cancer. Importantly, in liver cancer, higher expression of almost all m⁵C regulators was significantly associated with lower patient survival rate. In addition, the expression level of m⁵C-related genes is significantly different at various pathological stages. Finally, we have found through bioinformatics analysis that m⁵C regulatory proteins are closely related to the ErbB/PI3K–Akt signaling pathway and GSK3B was an important target for m⁵C regulators. Besides, the compound termed streptozotocin may be a key candidate drug targeting on GSK3B for molecular targeted therapy in GI cancer.

PFKFB3 inhibitors as potential anticancer agents: Mechanisms of action, current developments, and structure-activity relationships

Cancer cells adopt aerobic glycolysis as the major source of energy and biomass production for fast cell proliferation. The bifunctional enzyme, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), plays a crucial role in the regulation of glycolysis by controlling the steady-state cytoplasmic levels of fructose-2,6-bisphosphate (F2,6BP), which is the most potent allosteric activator of 6-phosphofructo-1-kinase (PFK-1), a key rate-limiting enzyme of glycolysis. Therefore, selective inhibition of PFKFB3 has gained substantial interest as an attractive strategy for cancer therapy. In recent years, numerous class PFKFB3 inhibitors have been disclosed, and emerging trends such as the availability of PFKFB3 crystal structures, structure-based screening strategies and diverse functional assays are improving optimization and development of original leads. Herein, we review the structure and function of PFKFB3 as well as the representative small-molecule inhibitors, in particular emphasis on their chemical structures, pharmacological properties, selectivity, binding modes and structure-activity relationships (SARs).

The Role of GSK-3 in Cancer Immunotherapy: GSK-3 Inhibitors as a New Frontier in Cancer Treatment

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) was initially identified because of its key role in the regulation of glycogen synthesis. However, it is now well-established that GSK-3 performs critical functions in many cellular processes, such as apoptosis, tumor growth, cell invasion, and metastasis. Aberrant GSK-3 activity has been associated with many human diseases, including cancer, highlighting its potential therapeutic relevance as a target for anticancer therapy. Recently, newly emerging data have demonstrated the pivotal role of GSK-3 in the anticancer immune response. In the last few years, many GSK-3 inhibitors have been developed, and some are currently being tested in clinical trials. This review will discuss preclinical and initial clinical results with GSK-3β inhibitors, highlighting the potential importance of this target in cancer immunotherapy. As described in this review, GSK-3 inhibitors have been shown to have antitumor activity in a wide range of human cancer cells, and they may also contribute to promoting a more efficacious immune response against tumor target cells, thus showing a double therapeutic advantage.

GSK-3 and miRs: Master regulators of therapeutic sensitivity of cancer cells

Glycogen synthetase kinase-3 (GSK-3) and microRNAs (miRs) affect many critical signaling pathways important in cell growth. GSK-3 is a serine/threonine (S/T) protein kinase. Often when GSK-3 phosphorylates other proteins, they are inactivated and the signaling pathway is shut down. The PI3K/PTEN/AKT/GSK3/mTORC1 pathway plays key roles in regulation of cell growth, apoptosis, drug resistance, malignant transformation and metastasis and is often deregulated in cancer. When GSK-3 is phosphorylated by AKT it is inactivated and this often leads to growth promotion. When GSK-3 is not phosphorylated by AKT or other kinases at specific negative-regulatory residues, it can modify the activity of many proteins by phosphorylation, some of these proteins promote while others inhibit cell proliferation. This is part of the conundrum regarding GSK-3. The central theme of this review is the ability of GSK-3 to serve as either a tumor suppressor or a tumor promoter in cancer which is likely due to its diverse protein substrates. The effects of multiple miRs which bind mRNAs encoding GSK-3 and other signaling molecules and how they affect cell growth and sensitivity to various therapeutics will be discussed as they serve to regulate GSK-3 and other proteins important in controlling proliferation.

Glycogen Synthase Kinase 3β in Cancer Biology and Treatment

Glycogen synthase kinase (GSK)3β is a multifunctional serine/threonine protein kinase with more than 100 substrates and interacting molecules. GSK3β is normally active in cells and negative regulation of GSK3β activity via phosphorylation of its serine 9 residue is required for most normal cells to maintain homeostasis. Aberrant expression and activity of GSK3β contributes to the pathogenesis and progression of common recalcitrant diseases such as glucose intolerance, neurodegenerative disorders and cancer. Despite recognized roles against several proto-oncoproteins and mediators of the epithelial–mesenchymal transition, deregulated GSK3β also participates in tumor cell survival, evasion of apoptosis, proliferation and invasion, as well as sustaining cancer stemness and inducing therapy resistance. A therapeutic effect from GSK3β inhibition has been demonstrated in 25 different cancer types. Moreover, there is increasing evidence that GSK3β inhibition protects normal cells and tissues from the harmful effects associated with conventional cancer therapies. Here, we review the evidence supporting aberrant GSK3β as a hallmark property of cancer and highlight the beneficial effects of GSK3β inhibition on normal cells and tissues during cancer therapy. The biological rationale for targeting GSK3β in the treatment of cancer is also discussed at length.

Glycogen synthase kinase 3β as a potential therapeutic target in synovial sarcoma and fibrosarcoma

Soft tissue sarcomas (STSs) are a rare cancer type. Almost half are unresponsive to multi-pronged treatment and might therefore benefit from biologically targeted therapy. An emerging target is glycogen synthase kinase (GSK)3β, which is implicated in various diseases including cancer. Here, we investigated the expression, activity and putative pathological role of GSK3β in synovial sarcoma and fibrosarcoma, comprising the majority of STS that are encountered in orthopedics. Expression of the active form of GSK3β (tyrosine 216-phosphorylated) was higher in synovial sarcoma (SYO-1, HS-SY-II, SW982) and in fibrosarcoma (HT1080) tumor cell lines than in untransformed fibroblast (NHDF) cells that are assumed to be the normal mesenchymal counterpart cells. Inhibition of GSK3β activity by pharmacological agents (AR-A014418, SB-216763) or of its expression by RNA interference suppressed the proliferation of sarcoma cells and their invasion of collagen gel, as well as inducing their apoptosis. These effects were associated with G0/G1-phase cell cycle arrest and decreased expression of cyclin D1, cyclin-dependent kinase (CDK)4 and matrix metalloproteinase 2. Intraperitoneal injection of the GSK3β inhibitors attenuated the growth of SYO-1 and HT1080 xenografts in athymic mice without obvious detrimental effects. It also mitigated cell proliferation and induced apoptosis in the tumors of mice. This study indicates that increased activity of GSK3β in synovial sarcoma and fibrosarcoma sustains tumor proliferation and invasion through the cyclin D1/CDK4-mediated pathway and enhanced extracellular matrix degradation. Our results provide a biological basis for GSK3β as a new and promising therapeutic target for these STS types.