Serum and glucocorticoid inducible protein kinases (SGKs): a potential target for cancer intervention

Discovery of novel 4-trifluoromethyl-2-anilinoquinoline derivatives as potential anti-cancer agents targeting SGK1

Given the critical necessity for the development of more potent anti-cancer drugs, a series of novel compounds incorporating trifluoromethyl groups within the privileged 2-anilinoquinoline scaffold was designed, synthesized, and subjected to biological evaluation through a pharmacophore hybridization strategy. Upon evaluating the in vitro anti-cancer characteristics of the target compounds, it became clear that compound 8b, which contains a (4-(piperazin-1-yl)phenyl)amino substitution at the 2-position of the quinoline skeleton, displayed superior efficacy against four cancer cell lines by inducing apoptosis and cell cycle arrest. Following research conducted in a PC3 xenograft mouse model, it was found that compound 8b exhibited significant anti-cancer efficacy while demonstrating minimal toxicity. Additionally, the analysis of a 217-kinase panel pinpointed SGK1 as a potential target for this compound class with anti-cancer capabilities. This finding was further verified through molecular docking analysis and cellular thermal shift assays. To conclude, our results emphasize that compound 8b can be used as a lead compound for the development of anti-cancer drugs that target SGK1.

GSK2334470 attenuates high salt-exacerbated rheumatoid arthritis progression by restoring Th17/Treg homeostasis

High salt (HS) consumption is a risk factor for multiple autoimmune disorders via disturbing immune homeostasis. Nevertheless, the exact mechanisms by which HS exacerbates rheumatoid arthritis (RA) pathogenesis remain poorly defined. Herein, we found that heightened phosphorylation of PDPK1 and SGK1 upon HS exposure attenuated FoxO1 expression to enhance the glycolytic capacity of CD4 T cells, resulting in strengthened Th17 but compromised Treg program. GSK2334470 (GSK), a dual PDPK1/SGK1 inhibitor, effectively mitigated the HS-induced enhancement in glycolytic capacity and the overproduction of IL-17A. Therefore, administration of GSK markedly alleviated HS-exacerbated RA progression in collagen-induced arthritis (CIA) model. Collectively, our data indicate that HS consumption subverts Th17/Treg homeostasis through the PDPK1-SGK1-FoxO1 signaling, while GSK could be a viable drug against RA progression in clinical settings.

SGK3 promotes vascular calcification via Pit-1 in chronic kidney disease

Rationale: Vascular calcification (VC) is a life-threatening complication in patients with chronic kidney disease (CKD) caused mainly by hyperphosphatemia. However, the regulation of VC remains unclear despite extensive research. Although serum- and glucocorticoid-induced kinase 3 (SGK3) regulate the sodium-dependent phosphate cotransporters in the intestine and kidney, its effect on VC in CKD remains unknown. Additionally, type III sodium-dependent phosphate cotransporter-1 (Pit-1) plays a significant role in VC development induced by high phosphate in vascular smooth muscle cells (VSMCs). However, it remains unclear whether SGK3 regulates Pit-1 and how exactly SGK3 promotes VC in CKD via Pit-1 at the molecular level. Thus, we investigated the role of SGK3 in the certified outflow vein of arteriovenous fistulas (AVF) and aortas of uremic mice. Methods and Results: In our study, using uremic mice, we observed a significant upregulation of SGK3 and calcium deposition in certified outflow veins of the AVF and aortas, and the increase expression of SGK3 was positively correlated with calcium deposition in uremic aortas. In vitro, the downregulation of SGK3 reversed VSMCs calcification and phenotype switching induced by high phosphate. Mechanistically, SGK3 activation enhanced the mRNA transcription of Pit-1 through NF-κB, downregulated the ubiquitin-proteasome mediated degradation of Pit-1 via inhibiting the activity of neural precursor cells expressing developmentally downregulated protein 4 subtype 2 (Nedd4-2), an E3 ubiquitin ligase. Moreover, under high phosphate stimulation, the enhanced phosphate uptake induced by SGK3 activation was independent of the increased protein expression of Pit-1. Our co-immunoprecipitation and in vitro kinase assays confirmed that SGK3 interacts with Pit-1 through Thr468 in loop7, leading to enhanced phosphate uptake. Conclusion: Thus, it is justifiable to conclude that SGK3 promotes VC in CKD by enhancing the expression and activities of Pit-1, which indicate that SGK3 could be a therapeutic target for VC in CKD.

AGC kinase inhibitors regulate STING signaling through SGK-dependent and SGK-independent mechanisms

Type 1 IFN expression is critical in the innate immune response, but aberrant expression is associated with autoimmunity and cancer. Here, we identify N-[4-(1H46 pyrazolo[3,4-b] pyrazin-6-yl)-phenyl]-sulfonamide (Sanofi-14h), a compound with preference for inhibition of the AGC family kinase SGK3, as an inhibitor of Ifnb1 gene expression in response to STING stimulation of macrophages. Sanofi-14h abrogated SGK activity and also impaired activation of the critical TBK1/IRF3 pathway downstream of STING activation, blocking interaction of STING with TBK1. Deletion of SGK1/3 in a macrophage cell line did not block TBK1/IRF3 activation but decreased expression of transcription factors, such as IRF7 and STAT1, required for the innate immune response. Other AGC kinase inhibitors blocked TBK1 and IRF3 activation suggesting common action on a critical regulatory node in the STING pathway. These studies reveal both SGK-dependent and SGK-independent mechanisms in the innate immune response and indicate an approach to block aberrant Ifnb1 expression.

Inhibition of SGK1 potentiates the anticancer activity of PI3K inhibitor in NSCLC cells through modulation of mTORC1, p‑ERK and β‑catenin signaling

Non-small cell lung cancer (NSCLC) is one of the deadliest types of cancer with poor prognosis, accounting for 85% of all lung cancer cases. The phosphoinositide 3-kinase (PI3K) signaling pathway is most frequently altered in NSCLC; nonetheless, targeting this pathway yields limited success primarily because of drug-induced resistance. PI3K-independent activation of serum and glucocorticoid-induced kinase 1 (SGK1) is responsible for development of resistance to PI3K/AKT inhibitors in breast cancer. The present study investigated potential of inhibiting SGK1 activity for the potentiation of PI3K inhibitor activity in NSCLC cell lines using in vitro anti-proliferation assays, protein expression profiling using western blotting and cell cycle analysis. The findings revealed that combined inhibition of PI3K/AKT and SGK1 resulted in synergistic anticancer activity, with increased apoptosis, DNA damage and cell cycle arrest in G1 phase. Furthermore, high SGK1 protein expression in NSCLC cell lines was associated with increased resistance to PI3K inhibitors. Therefore, enhanced SGK1 expression may serve as a marker to predict therapeutic response to PI3K/AKT inhibitors. Profiling of downstream signaling proteins demonstrated that, at the molecular level SGK1-mediated sensitization of NSCLC cell lines to PI3K inhibitors was achieved via inhibition of mTORC1 signaling. Increased sensitivity of NSCLC cell lines was also mediated by other oncogenic pathways, such as Ras/MEK/ERK and Wnt/β-catenin signaling.

The SGK3-Catalase antioxidant signaling axis drives cervical cancer growth and therapy resistance

Cancer cells frequently exhibit aberrant redox homeostasis and adaptation to oxidative stress. Hence abrogation of redox adaptation in cancer cells can be exploited for therapeutic benefit. Here we report SGK3 functions as an anti-oxidative factor to promote cell growth and drug resistance in cervical cancers harboring PIK3CA helical domain mutations. Mechanistically, SGK3 is activated upon oxidative stress and exerts anti-ROS activity by stabilizing and activating the antioxidant enzyme catalase. SGK3 interacts with and phosphorylates catalase, promoting its tetrameric state and activity. Meanwhile, SGK3 phosphorylates GSK3β and protects catalase from GSK3β-β-TrCP mediated ubiquitination and proteasomal degradation. Furthermore, SGK3 inhibition not only potentiates CDK4/6 inhibitor Palbociclib-mediated cytotoxicity, but also overcomes cisplatin resistance through ROS-mediated mechanisms. These data uncover the role of SGK3 in maintaining redox homeostasis and suggest that the SGK3-catalase antioxidant signaling axis may be therapeutically targeted to improve treatment efficacy for cervical cancers carrying PIK3CA helical domain mutations.

Expression profiles of glucocorticoid-inducible proteins in human papilloma virus-related oropharyngeal squamous cell carcinoma

Introduction

Human papillomavirus virus-related oropharyngeal squamous cell carcinoma (HPV-OPSCC) comprises a significant portion of head and neck cancers. Several glucocorticoid-inducible proteins play important roles in pathogenesis of some cancers but their status and roles in HPV-OPSCC remain elusive; these include the glucocorticoid-induced leucine zipper (GILZ), Annexin-A1 and serum glucocorticoid-regulated kinase-1 (SGK-1).

Methods

We determined expression profiles of these proteins, using immunohistochemistry, in archived biopsy samples of patients diagnosed with HPV-OPSCC; samples of non-cancer oral lesions (e.g., hyperkeratosis) were used as controls.

Results

GILZ staining was primarily confined to nuclei of all tissues but, in HPV-OPSCC specimens, neoplastic cells exhibiting mitosis displayed prominent cytoplasmic GILZ expression. On the other hand, nuclear, cytoplasmic and membranous Annexin-A1 staining was observed in suprabasal cell layers of control specimens. A noted feature of the HPV-OPSCC specimens was few clusters of matured and differentiated nonbasaloid cells that showed prominent nuclear and cytoplasmic Annexin-A1 staining while the remainder of the tumor mass was devoid of staining. Cytoplasmic and nuclear staining for SGK-1 was prominent for control than PV-OPSCC specimens while staining for phosphorylated SGK-1 (pSGK-1; active) was prominent for cell membrane and cytoplasm of control specimens but HPV-OPSCC specimens showed mild and patchy nuclear and cytoplasmic staining. Semi-quantitative analysis of GILZ immunostaining indicated increased staining area but similar normalized staining for HPV-OPSCC compared to control specimens. By contrast, staining area and normalized staining were reduced for other proteins in HPV-OPSCC than control specimens.

Discussion

Our collective observations suggest differential cellular localization and expression of glucocorticoid-inducible proteins in HPV-OPSCC suggestive of different functional roles in pathogenesis of this condition.

SGK3 overexpression correlates with a poor prognosis in endoscopically resected superficial esophageal squamous cell neoplasia: A long-term study

BACKGROUND

The expression status of serum and glucocorticoid-induced protein kinase 3 (SGK3) in superficial esophageal squamous cell neoplasia (ESCN) remains unknown.

AIM

To evaluate the SGK3 overexpression rate in ESCN and its influence on the prognosis and outcomes of patients with endoscopic resection.

METHODS

A total of 92 patients who had undergone endoscopic resection for ESCN with more than 8 years of follow-up were enrolled. Immunohistochemistry was used to evaluate SGK3 expression.

RESULTS

SGK3 was overexpressed in 55 (59.8%) patients with ESCN. SGK3 overexpression showed a significant correlation with death (P = 0.031). Overall survival and disease-free survival rates were higher in the normal SGK3 expression group than in the SGK3 overexpression group (P = 0.013 and P = 0.004, respectively). Cox regression analysis models demonstrated that SGK3 overexpression was an independent predictor of poor prognosis in ESCN patients (hazard ratio 4.729; 95% confidence interval: 1.042-21.458).

CONCLUSION

SGK3 overexpression was detected in the majority of patients with endoscopically resected ESCN and was significantly associated with shortened survival. Thus, it might be a new prognostic factor for ESCN.

Serum and glucocorticoid-regulated kinase 1: Structure, biological functions, and its inhibitors

Serum and glucocorticoid-regulated kinase 1 (SGK1) is a serine/threonine kinase belonging to the protein kinase A, G, and C (AGC) family. Upon initiation of the phosphoinositide 3-kinase (PI3K) signaling pathway, mammalian target of rapamycin complex 2 (mTORC2) and phosphoinositide-dependent protein kinase 1 (PDK1) phosphorylate the hydrophobic motif and kinase domain of SGK1, respectively, inducing SGK1 activation. SGK1 modulates essential cellular processes such as proliferation, survival, and apoptosis. Hence, dysregulated SGK1 expression can result in multiple diseases, including hypertension, cancer, autoimmunity, and neurodegenerative disorders. This review provides a current understanding of SGK1, particularly in sodium transport, cancer progression, and autoimmunity. In addition, we summarize the developmental status of SGK1 inhibitors, their structures, and respective potencies evaluated in pre-clinical experimental settings. Collectively, this review highlights the significance of SGK1 and proposes SGK1 inhibitors as potential drugs for treatment of clinically relevant diseases.

Identification of Novel Inhibitors Targeting SGK1 via Ensemble-Based Virtual Screening Method, Biological Evaluation and Molecular Dynamics Simulation

Serum and glucocorticoid-regulated kinase 1 (SGK1), as a serine threonine protein kinase of the AGC family, regulates different enzymes, transcription factors, ion channels, transporters, and cell proliferation and apoptosis. Inhibition of SGK1 is considered as a valuable approach for the treatment of various metabolic diseases. In this investigation, virtual screening methods, including pharmacophore models, Bayesian classifiers, and molecular docking, were combined to discover novel inhibitors of SGK1 from the database with 29,158 compounds. Then, the screened compounds were subjected to ADME/T, PAINS and drug-likeness analysis. Finally, 28 compounds with potential inhibition activity against SGK1 were selected for biological evaluation. The kinase inhibition activity test revealed that among these 28 hits, hit15 exhibited the highest inhibition activity against SGK1, which gave 44.79% inhibition rate at the concentration of 10 µM. In order to further investigate the interaction mechanism of hit15 and SGK1 at simulated physiological conditions, a molecular dynamics simulation was performed. The molecular dynamics simulation demonstrated that hit15 could bind to the active site of SGK1 and form stable interactions with key residues, such as Tyr178, ILE179, and VAL112. The binding free energy of the SGK1-hit15 was −48.90 kJ mol−1. Therefore, the identified hit15 with novel scaffold may be a promising lead compound for development of new SGK1 inhibitors for various diseases treatment.

A Rheostat of Ceramide and Sphingosine-1-Phosphate as a Determinant of Oxidative Stress-Mediated Kidney Injury

Reactive oxygen species (ROS) modulate sphingolipid metabolism, including enzymes that generate ceramide and sphingosine-1-phosphate (S1P), and a ROS-antioxidant rheostat determines the metabolism of ceramide-S1P. ROS induce ceramide production by activating ceramide-producing enzymes, leading to apoptosis, while they inhibit S1P production, which promotes survival by suppressing sphingosine kinases (SphKs). A ceramide-S1P rheostat regulates ROS-induced mitochondrial dysfunction, apoptotic/anti-apoptotic Bcl-2 family proteins and signaling pathways, leading to apoptosis, survival, cell proliferation, inflammation and fibrosis in the kidney. Ceramide inhibits the mitochondrial respiration chain and induces ceramide channel formation and the closure of voltage-dependent anion channels, leading to mitochondrial dysfunction, altered Bcl-2 family protein expression, ROS generation and disturbed calcium homeostasis. This activates ceramide-induced signaling pathways, leading to apoptosis. These events are mitigated by S1P/S1P receptors (S1PRs) that restore mitochondrial function and activate signaling pathways. SphK1 promotes survival and cell proliferation and inhibits inflammation, while SphK2 has the opposite effect. However, both SphK1 and SphK2 promote fibrosis. Thus, a ceramide-SphKs/S1P rheostat modulates oxidant-induced kidney injury by affecting mitochondrial function, ROS production, Bcl-2 family proteins, calcium homeostasis and their downstream signaling pathways. This review will summarize the current evidence for a role of interaction between ROS-antioxidants and ceramide-SphKs/S1P and of a ceramide-SphKs/S1P rheostat in the regulation of oxidative stress-mediated kidney diseases.

Multi-omics evaluation of SARS-CoV-2 infected mouse lungs reveals dynamics of host responses

The outbreak of Coronavirus disease 2019 (COVID-19) throughout the world has caused millions of death, while the dynamics of host responses and the underlying regulation mechanisms during SARS-CoV-2 infection are not well depicted. Lung tissues from a mouse model sensitized to SARS-CoV-2 infection were serially collected at different time points for evaluation of transcriptome, proteome, and phosphoproteome. We showed the ebb and flow of several host responses in the lung across the viral infection. The signaling pathways and kinases regulating networks were alternated at different phases of infection. This multiplex evaluation also revealed that many kinases of the CDK and MAPK family were interactive and served as functional hubs in mediating the signal transduction during SARS-CoV-2 infection. Our study not only revealed the dynamics of lung pathophysiology and their underlying molecular mechanisms during SARS-CoV-2 infection, but also highlighted some molecules and signaling pathways that might guide future investigations on COVID-19 therapies.

•

Multi-omics analysis profiles temporal host responses in SARS-CoV-2 infected lungs

•

Signaling pathways and kinase regulating networks are dynamically altered

•

The CDK and MAPK family are interactive and involved in regulating host responses

Expression Profiles of GILZ and SGK-1 in Potentially Malignant and Malignant Human Oral Lesions

Glucocorticoid-induced leucine zipper and serum-glucocorticoid-regulated kinase-1 (SGK-1) are major glucocorticoid-inducible proteins. Recent studies indicate the local production of cortisol in oral mucosa, which can impact the tissue generation of glucocorticoid-induced leucine zipper (GILZ) and SGK-1. Furthermore, GILZ and SGK-1 play pathogenic roles in a variety of cancers, but their status in potentially malignant (e.g., epithelial dysplasia) or malignant oral lesions remains unknown. This study tested the hypothesis that expression profiles of GILZ and SGK-1, along with the phosphorylated (active) form of SGK-1 (pSGK-1), are different in epithelial dysplasia than squamous cell carcinoma. Accordingly, archived paraffin-embedded biopsy samples were subjected to immunohistochemistry to establish tissue localization and the profile of proteins of interest, while hematoxylin-eosin stained tissues were used for histopathological assessment. Based on histopathological examinations, tissue specimens were categorized as displaying mild-moderate or severe epithelial dysplasia and squamous cell carcinoma; benign keratosis specimens served as controls. All the tissue specimens showed staining for SGK-1 and pSGK-1; however, while SGK-1 staining was primarily cytoplasmic, pSGK-1 was mainly confined to the cell membrane. On the other hand, all the tissue specimens displayed primarily nuclear staining for GILZ. A semi-quantitative analysis of immunohistochemistry staining indicates increased GILZ expression in epithelial dysplasia but reversal in squamous cell carcinoma to a level seen for benign keratosis. On the other hand, the SGK-1 and pSGK-1 expressions decreased for squamous cell carcinoma specimens compared with benign keratosis or dysplastic specimens. Collectively, in this cross-sectional study, immunostaining patterns for proteins of interest do not seemingly differentiate epithelial dysplasia from squamous cell carcinoma. However, subcellular localization and expression profiles for GILZ, SGK-1, and pSGK-1 are suggestive of differential functional roles in dysplastic or malignant oral lesions compared with benign keratosis.

Overexpression of pressure-responsive miRNA-5703 inhibits pressure-induced growth and metastasis of liver cancer

A vast majority of liver cancers coexist with cirrhosis and/or portal hypertension. A high-pressure tumour microenvironment may lead to malignant progression of liver cancer. Through quantitative reverse transcription-polymerase chain reaction, we found that miRNA-5703 was expressed at low levels in HepG2 and Huh-7 cells and pressure-treated MHCC97H implanted mouse cancer tissues, while its potential target gene, sarcoma gene (SRC), was highly expressed. The expression of miRNA-5703 was higher in liver cancer tissues from Barcelona Clinic Liver Cancer (BCLC) stage A1 patients than those from BCLC stage A2-D patients, whereas SRC showed the opposite expression pattern. Bioinformatics analysis, luciferase reporter assay, and western blotting were performed to verify the relationship between miRNA-5703 and its potential target SRC. Using intravital imaging and immunohistochemistry, we demonstrated that pressure promotes tumour growth in subcutaneous tumourigenesis nude mice, and overexpression of miRNA-5703 significantly downregulated Ki67 and upregulated NM23 in tumour tissues of mice, implying the blockage of tumour growth and metastasis. The activation of proliferation, migration, and invasion of HepG2 and Huh-7 cells by pressure, and inhibition by overexpressing miRNA-5703 were observed by cell counting kit-8 assay, flow cycle assay, transwell assay, and wound healing assay. After the intervention of pressure, inhibitor, and lentivirus to hepatoma cells, SRC, focal adhesion kinase (FAK), phosphatidylinositol 3-kinase (PI3K), serum/glucocorticoid regulated kinase-3 (SGK3), phosphoinositide dependent protein kinase 1 (PDK1), and paxillin were upregulated, and forkhead box O1 (FOXO1) and cyclin dependent kinase inhibitor 1B (P27^Kip1) were downregulated in pressure-loaded hepatoma cells, which could be reversed by overexpression of miRNA-5703 or SRC knockdown. In conclusion, upregulation of miRNA-5703 inhibited pressure-induced growth and metastasis by suppressing the SRC-FAK-FOXO1 axis and SRC-paxillin axis. This novel perspective may be conducive to the mechano-inspired anticancer drugs of liver cancer.

The role of PI3'-lipid signalling in melanoma initiation, progression and maintenance

Phosphatidylinositol-3'-kinases (PI3Ks) are a family of lipid kinases that phosphorylate the 3' hydroxyl (OH) of the inositol ring of phosphatidylinositides (PI). Through their downstream effectors, PI3K generated lipids (PI3K-lipids hereafter) such as PI(3,4,5)P3 and PI(3,4)P2 regulate myriad biochemical and biological processes in both normal and cancer cells including responses to growth hormones and cytokines; the cell division cycle; cell death; cellular growth; angiogenesis; membrane dynamics; and autophagy and many aspects of cellular metabolism. Engagement of receptor tyrosine kinase by their cognate ligands leads to activation of members of the Class I family of PI3'-kinases (PI3Kα, β, δ & γ) leading to accumulation of PI3K-lipids. Importantly, PI3K-lipid accumulation is antagonized by the hydrolytic action of a number of PI3K-lipid phosphatases, most notably the melanoma suppressor PTEN (lipid phosphatase and tensin homologue). Downstream of PI3K-lipid production, the protein kinases AKT1-3 are believed to be key effectors of PI3'-kinase signalling in cells. Indeed, in preclinical models, activation of the PI3K→AKT signalling axis cooperates with alterations such as expression of the BRAFV600E oncoprotein kinase to promote melanoma progression and metastasis. In this review, we describe the different classes of PI3K-lipid effectors, and how they may promote melanomagenesis, influence the tumour microenvironment, melanoma maintenance and progression to metastatic disease. We also provide an update on both FDA-approved or experimental inhibitors of the PI3K→AKT pathway that are currently being evaluated for the treatment of melanoma either in preclinical models or in clinical trials.

Serine/Threonine-Protein Kinase 3 Facilitates Myocardial Repair After Cardiac Injury Possibly Through the Glycogen Synthase Kinase-3β/β-Catenin Pathway

Background The neonatal heart maintains its entire regeneration capacity within days after birth. Using quantitative phosphoproteomics technology, we identified that SGK3 (serine/threonine-protein kinase 3) in the neonatal heart is highly expressed and activated after myocardial infarction. This study aimed to uncover the function and related mechanisms of SGK3 on cardiomyocyte proliferation and cardiac repair after apical resection or ischemia/reperfusion injury. Methods and Results The effect of SGK3 on proliferation and oxygen glucose deprivation/reoxygenation- induced apoptosis in isolated cardiomyocytes was evaluated using cardiomyocyte-specific SGK3 overexpression or knockdown adenovirus5 vector. In vivo, gain- and loss-of-function experiments using cardiomyocyte-specific adeno-associated virus 9 were performed to determine the effect of SGK3 in cardiomyocyte proliferation and cardiac repair after apical resection or ischemia/reperfusion injury. In vitro, overexpression of SGK3 enhanced, whereas knockdown of SGK3 decreased, the cardiomyocyte proliferation ratio. In vivo, inhibiting the expression of SGK3 shortened the time window of cardiac regeneration after apical resection in neonatal mice, and overexpression of SGK3 significantly promoted myocardial repair and cardiac function recovery after ischemia/reperfusion injury in adult mice. Mechanistically, SGK3 promoted cardiomyocyte regeneration and myocardial repair after cardiac injury by inhibiting GSK-3β (glycogen synthase kinase-3β) activity and upregulating β-catenin expression. SGK3 also upregulated the expression of cell cycle promoting genes G1/S-specific cyclin-D1, c-myc (cellular-myelocytomatosis viral oncogene), and cdc20 (cell division cycle 20), but downregulated the expression of cell cycle negative regulators cyclin kinase inhibitor P 21 and cyclin kinase inhibitor P 27. Conclusions Our study reveals a key role of SGK3 on cardiac repair after apical resection or ischemia/reperfusion injury, which may reopen a novel therapeutic option for myocardial infarction.

Progression Risk Score Estimation Based on Immunostaining Data in Oral Cancer Using Unsupervised Hierarchical Clustering Analysis: A Retrospective Study in Taiwan

This study aimed to investigate whether the progression risk score (PRS) developed from cytoplasmic immunohistochemistry (IHC) biomarkers is available and applicable for assessing risk and prognosis in oral cancer patients. Participants in this retrospective case-control study were diagnosed between 2012 and 2014 and subsequently underwent surgical intervention. The specimens from surgery were stained by IHC for 16 cytoplasmic target markers. We evaluated the results of IHC staining, clinical and pathological features, progression-free survival (PFS), and overall survival (OS) of 102 oral cancer patients using a novel estimation approach with unsupervised hierarchical clustering analysis. Patients were stratified into high-risk (52) and low-risk (50) groups, according to their PRS; a metric consisting of cytoplasmic PLK1, PhosphoMet, SGK2, and SHC1 expression. Moreover, PRS could be extended for use in the Cox proportional hazard regression model to estimate survival outcomes with associated clinical parameters. Our study findings revealed that the high-risk patients had a significantly increased risk in cancer progression compared with low-risk patients (hazard ratio (HR) = 2.20, 95% confidence interval (CI) = 1.10-2.42, p = 0.026). After considering the influences of demographics, risk behaviors, and tumor characteristics, risk estimation with PRS provided distinct PFS groups for patients with oral cancer (p = 0.017, p = 0.019, and p = 0.020). Our findings support that PRS could serve as an ideal biomarker for clinical use in risk stratification and progression assessment in oral cancer.

Hsa-miR-100-3p Controls the Proliferation, DNA Synthesis, and Apoptosis of Human Sertoli Cells by Binding to SGK3

Human Sertoli cell is required for completing normal spermatogenesis, and significantly, it has important applications in reproduction and regenerative medicine because of its great plasticity. Nevertheless, the molecular mechanisms underlying the fate decisions of human Sertoli cells remain to be clarified. Here, we have demonstrated the expression, function, and mechanism of Homo sapiens-microRNA (hsa-miR)-100-3p in human Sertoli cells. We revealed that miR-100-3p was expressed at a higher level in human Sertoli cells by 10% fetal bovine serum (FBS) than 0.5% FBS. MiR-100-3p mimics enhanced the DNA synthesis and the proliferation of human Sertoli cells, as indicated by 5-ethynyl-2′-deoxyuridine (EdU) and Cell Counting Kit-8 (CCK-8) assays. Flow cytometry showed that miR-100-3p mimics reduced the apoptosis of human Sertoli cells, and notably, we predicted and further identified serum/glucocorticoid regulated kinase family member 3 (SGK3) as a direct target of MiR-100-3p. SGK3 silencing increased the proliferation and decreased the apoptosis of human Sertoli cells, while SGK3 siRNA 3 assumed a similar role to miR-100-3p mimics in human Sertoli cells. Collectively, our study indicates that miR-100-3p regulates the fate decisions of human Sertoli cells by binding to SGK3. This study is of great significance, since it provides the novel epigenetic regulator for the proliferation and apoptosis of human Sertoli cells and it may offer a new clue for gene therapy of male infertility.

Complement C3a activates osteoclasts by regulating the PI3K/PDK1/SGK3 pathway in patients with multiple myeloma

OBJECTIVE

Myeloma bone disease (MBD) is the most common complication of multiple myeloma (MM). Our previous study showed that the serum levels of C3/C4 in MM patients were significantly positively correlated with the severity of bone disease. However, the mechanism of C3a/C4a in osteoclasts MM patients remains unclear.

METHODS

The formation and function of osteoclasts were analyzed after adding C3a/C4a in vitro. RNA-seq analysis was used to screen the potential pathways affecting osteoclasts, and the results were verified by Western blot, qRT-PCR, and pathway inhibitors.

RESULTS

The osteoclast area per view induced by 1 μg/mL (mean ± SD: 50.828 ± 12.984%) and 10 μg/mL (53.663 ± 12.685%) of C3a was significantly increased compared to the control group (0 μg/mL) (34.635 ± 8.916%) (P < 0.001 and P < 0.001, respectively). The relative mRNA expressions of genes, OSCAR/TRAP/RANKL/cathepsin K, induced by 1 μg/mL (median: 5.041, 3.726, 1.638, and 4.752, respectively) and 10 μg/mL (median: 5.140, 3.702, 2.250, and 5.172, respectively) of C3a was significantly increased compared to the control group (median: 3.137, 2.004, 0.573, and 2.257, respectively) (1 μg/mL P = 0.001, P = 0.003, P < 0.001, and P = 0.008, respectively; 10 μg/mL: P < 0.001, P = 0.019, P < 0.001, and P = 0.002, respectively). The absorption areas of the osteoclast resorption pits per view induced by 1 μg/mL (mean ± SD: 51.464 ± 11.983%) and 10 μg/mL (50.219 ± 12.067%) of C3a was also significantly increased (33.845 ± 8.331%) (P < 0.001 and P < 0.001, respectively) compared to the control. There was no difference between the C4a and control groups. RNA-seq analysis showed that C3a promoted the proliferation of osteoclasts using the phosphoinositide 3-kinase (PI3K) signaling pathway. The relative expressions of PIK3CA/phosphoinositide dependent kinase-1 (PDK1)/serum and glucocorticoid inducible protein kinases (SGK3) genes and PI3K/PDK1/p-SGK3 protein in the C3a group were significantly higher than in the control group. The activation role of C3a in osteoclasts of MM patients was reduced by the SGK inhibitor (EMD638683).

CONCLUSIONS

C3a activated osteoclasts by regulating the PI3K/PDK1/SGK3 pathways in MM patients, which was reduced using a SGK inhibitor. Overall, our results identified potential therapeutic targets and strategies for MBD patients.

L-plastin Ser5 phosphorylation is modulated by the PI3K/SGK pathway and promotes breast cancer cell invasiveness

Background

Metastasis is the predominant cause for cancer morbidity and mortality accounting for approximatively 90% of cancer deaths. The actin-bundling protein L-plastin has been proposed as a metastatic marker and phosphorylation on its residue Ser5 is known to increase its actin-bundling activity. We recently showed that activation of the ERK/MAPK signalling pathway leads to L-plastin Ser5 phosphorylation and that the downstream kinases RSK1 and RSK2 are able to directly phosphorylate Ser5. Here we investigate the involvement of the PI3K pathway in L-plastin Ser5 phosphorylation and the functional effect of this phosphorylation event in breast cancer cells.

Methods

To unravel the signal transduction network upstream of L-plastin Ser5 phosphorylation, we performed computational modelling based on immunoblot analysis data, followed by experimental validation through inhibition/overexpression studies and in vitro kinase assays. To assess the functional impact of L-plastin expression/Ser5 phosphorylation in breast cancer cells, we either silenced L-plastin in cell lines initially expressing endogenous L-plastin or neoexpressed L-plastin wild type and phosphovariants in cell lines devoid of endogenous L-plastin. The established cell lines were used for cell biology experiments and confocal microscopy analysis.

Results

Our modelling approach revealed that, in addition to the ERK/MAPK pathway and depending on the cellular context, the PI3K pathway contributes to L-plastin Ser5 phosphorylation through its downstream kinase SGK3. The results of the transwell invasion/migration assays showed that shRNA-mediated knockdown of L-plastin in BT-20 or HCC38 cells significantly reduced cell invasion, whereas stable expression of the phosphomimetic L-plastin Ser5Glu variant led to increased migration and invasion of BT-549 and MDA-MB-231 cells. Finally, confocal image analysis combined with zymography experiments and gelatin degradation assays provided evidence that L-plastin Ser5 phosphorylation promotes L-plastin recruitment to invadopodia, MMP-9 activity and concomitant extracellular matrix degradation.

Conclusion

Altogether, our results demonstrate that L-plastin Ser5 phosphorylation increases breast cancer cell invasiveness. Being a downstream molecule of both ERK/MAPK and PI3K/SGK pathways, L-plastin is proposed here as a potential target for therapeutic approaches that are aimed at blocking dysregulated signalling outcome of both pathways and, thus, at impairing cancer cell invasion and metastasis formation.

Free CA125 promotes ovarian cancer cell migration and tumor metastasis by binding Mesothelin to reduce DKK1 expression and activate the SGK3/FOXO3 pathway

Objective: CA125/MUC16 is an O-glycosylated protein that is expressed on the surfaces of ovarian epithelial cells. This molecule is a widely used tumor-associated marker for diagnosis of ovarian cancer. Recently, CA125 was shown to be involved in ovarian cancer metastasis. The purpose of this study was to investigate the mechanism of CA125 during ovarian cancer metastasis.

Methods: We analyzed the Oncomine and CSIOVDB databases to determine the expression levels of DKK1 in ovarian cancer. DKK1 expression levels were upregulated or downregulated and applied with CA125 to Transwell and Western blot assays to ascertain the underlying mechanism by which CA125 stimulates cell migration via the SGK3/FOXO3 pathway. Anti-mesothelin antibodies (anti-MSLN) were used to block CA125 stimulation. Then the expression levels of DKK1were tested by enzyme-linked immunosorbent assay (ELISA) to eliminate the blocking effect of anti-MSLN to CA125 stimulation. Xenograft mouse models were used to detect the effects of CA125 and anti-MSLN on ovarian cancer metastasis in vivo.

Results: DKK1 levels were downregulated in ovarian tumor tissues according to the analyses of two databases and significantly correlated with FIGO stage, grade and disease-free survival in ovarian cancer patients. DKK1 levels were downregulated by CA125 stimulation in vitro. Overexpression of DKK1 reversed the ability of exogenous CA125 to mediate cell migration by activating the SGK3/FOXO3 signaling pathway. Anti-MSLN abrogated the DKK1 reduction and increased the apoptosis of ovarian cancer cells. The use of anti-MSLN in xenograft mouse models significantly reduced tumor growth and metastasis accelerated by CA125.

Conclusions: These experiments revealed that the SGK3/FOXO3 pathway was activated, wherein decreased expression of DKK1 was caused by CA125, which fuels ovarian cancer cell migration. Mesothelin is a potential therapeutic target for the treatment of ovarian cancer metastasis.

Risk of Nasopharyngeal Carcinoma Associated with Single Nucleotide Polymorphisms in the MicroRNA Binding Site of SGK3

Objective: Serum/glucocorticoid regulated kinase is a serine/threonine kinase that is involved in regulating cell proliferation, apoptosis, the cell cycle, and ion channel function. The aim of this study was to analyze the relationship between single nucleotide polymorphisms (SNPs) in the microRNA (miRNA) binding site of the SGK3 gene and the risk of nasopharyngeal carcinoma (NPC). Methods: Three SGK3 loci, rs77572541, rs11994200, and rs78158330, were genotyped in 226 NPC patients and 226 healthy controls via Sanger sequencing. Quantitative real-time polymerase chain reaction was used to analyze levels of SGK3 messenger RNA (mRNA), hsa-miR-3529-5p, hsa-miR-379-5p, hsa-miR-498, hsa-miR-4320, and hsa-miR-590-3p. Western blot analysis was used to assess serum and glucocorticoid regulated kinase 3 (SGK3) protein expression. Results: SGK3 rs77572541 locus G allele carriers were 3.47 times more likely to develop NPC than carriers of the A allele (95% confidence interval [CI] = 1.98-6.09, p < 0.01). The SGK3 rs11994200 locus C allele was a major risk factor for NPC (odds ratio = 2.68, 95% CI = 1.63-4.39, p < 0.01). Similarly, carriers of the C allele of the SGK3 rs78158330 locus were 3.36 times more likely to develop NPC than those with the T allele (95% CI = 1.96-5.73, p < 0.01). The SGK3 protein was highly expressed in NPC. The SGK3 rs77572541 locus G allele is the target of hsa-miR-379-5p and hsa-miR-3529-5p, but the A allele is not. The SGK3 rs11994200 locus C allele was the target of hsa-miR-4320, and the G allele was the target of hsa-miR-498. The SGK3 rs78158330 locus T allele was the target of hsa-miR-590-3p. Hsa-miR-3529-5p, hsa-miR-379-5p, and hsa-miR-4320 were down-regulated in NPC tissues (p < 0.01), whereas hsa-miR-498 and hsa-miR-590-3p were highly expressed (p < 0.01). Conclusions: SNPs at the SGK3 loci rs77572541, rs11994200, and rs78158330 are significantly associated with the risk for NPC. These effects may be related to the influence of miRNAs on different alleles, but this needs to be verified both in vitro and in vivo.

Autophagy as a decisive process for cell death

Autophagy is an intracellular catabolic pathway in which cellular constituents are engulfed by autophagosomes and degraded upon autophagosome fusion with lysosomes. Autophagy serves as a major cytoprotective process by maintaining cellular homeostasis and recycling cytoplasmic contents. However, emerging evidence suggests that autophagy is a primary mechanism of cell death (autophagic cell death, ACD) and implicates ACD in several aspects of mammalian physiology, including tumor suppression and psychological disorders. However, little is known about the physiological roles and molecular mechanisms of ACD. In this review, we document examples of ACD and discuss recent progress in our understanding of its molecular mechanisms.

The PI3K-AKT-mTOR Pathway and Prostate Cancer: At the Crossroads of AR, MAPK, and WNT Signaling

Oncogenic activation of the phosphatidylinositol-3-kinase (PI3K), protein kinase B (PKB/AKT), and mammalian target of rapamycin (mTOR) pathway is a frequent event in prostate cancer that facilitates tumor formation, disease progression and therapeutic resistance. Recent discoveries indicate that the complex crosstalk between the PI3K-AKT-mTOR pathway and multiple interacting cell signaling cascades can further promote prostate cancer progression and influence the sensitivity of prostate cancer cells to PI3K-AKT-mTOR-targeted therapies being explored in the clinic, as well as standard treatment approaches such as androgen-deprivation therapy (ADT). However, the full extent of the PI3K-AKT-mTOR signaling network during prostate tumorigenesis, invasive progression and disease recurrence remains to be determined. In this review, we outline the emerging diversity of the genetic alterations that lead to activated PI3K-AKT-mTOR signaling in prostate cancer, and discuss new mechanistic insights into the interplay between the PI3K-AKT-mTOR pathway and several key interacting oncogenic signaling cascades that can cooperate to facilitate prostate cancer growth and drug-resistance, specifically the androgen receptor (AR), mitogen-activated protein kinase (MAPK), and WNT signaling cascades. Ultimately, deepening our understanding of the broader PI3K-AKT-mTOR signaling network is crucial to aid patient stratification for PI3K-AKT-mTOR pathway-directed therapies, and to discover new therapeutic approaches for prostate cancer that improve patient outcome.

RICTOR/mTORC2 affects tumorigenesis and therapeutic efficacy of mTOR inhibitors in esophageal squamous cell carcinoma

Dysregulation of mTORC1/mTORC2 pathway is observed in many cancers and mTORC1 inhibitors have been used clinically in many tumor types; however, the mechanism of mTORC2 in tumorigenesis is still obscure. Here, we mainly explored the potential role of mTORC2 in esophageal squamous cell carcinoma (ESCC) and its effects on the sensitivity of cells to mTOR inhibitors. We demonstrated that RICTOR, the key factor of mTORC2, and p-AKT (Ser473) were excessively activated in ESCC and their overexpression is related to lymph node metastasis and the tumor-node-metastasis (TNM) phase of ESCC patients. Furthermore, we found that mTORC1/ mTORC2 inhibitor PP242 exhibited more efficacious anti-proliferative effect on ESCC cells than mTORC1 inhibitor RAD001 due to RAD001-triggered feedback activation of AKT signal. Another, we demonstrated that down-regulating expression of RICTOR in ECa109 and EC9706 cells inhibited proliferation and migration as well as induced cell cycle arrest and apoptosis. Noteworthy, knocking-down stably RICTOR significantly suppresses RAD001-induced feedback activation of AKT/PRAS40 signaling, and enhances inhibition efficacy of PP242 on the phosphorylation of AKT and PRAS40, thus potentiates the antitumor effect of RAD001 and PP242 both in vitro and in vivo. Our findings highlight that selective targeting mTORC2 could be a promising therapeutic strategy for future treatment of ESCC.

A patent update on PDK1 inhibitors (2015-present)

INTRODUCTION

3-Phosphoinositide-dependent kinase 1 (PDK1), the 'master kinase of the AGC protein kinase family', plays a key role in cancer development and progression. Although it has been rather overlooked, in the last decades a growing number of molecules have been developed to effectively modulate the PDK1 enzyme.

AREAS COVERED

This review collects different PDK1 inhibitors patented from October 2014 to December 2018. The molecules have been classified on the basis of the chemical structure/type of inhibition, and for each general structure, examples have been discussed in extenso.

EXPERT OPINION

The role of PDK1 in cancer development and progression as well as in metastasis formation and in chemoresistance has been confirmed by many studies. Therefore, the pharmaceutical discovery in both public and private institutions is still ongoing despite the plentiful molecules already published. The majority of the new molecules synthetized interact with binding sites different from the ATP binding site (i.e. PIF pocket or DFG-out conformation). However, many researchers are still looking for innovative PDK1 modulation strategy such as combination of well-known inhibitory agents or multitarget ligands, aiming to block, together with PDK1, other different critical players in the wide panorama of proteins involved in tumor pathways.