SPHK1 Is a Novel Target of Metformin in Ovarian Cancer

Synergistic anticancer effects of doxorubicin and metformin combination therapy: A systematic review

INTRODUCTION

Doxorubicin (DOX) a chemotherapy drug often leads to the development of resistance, in cancer cells after prolonged treatment. Recent studies have suggested that using metformin plus doxorubicin could result in synergic effects. This study focuses on exploring the co-treat treatment of doxorubicin and metformin for various cancers.

METHOD

Following the PRISMA guidelines we conducted a literature search using different databases such as Embase, Scopus, Web of Sciences, PubMed, Science Direct and Google Scholar until July 2023. We selected search terms based on the objectives of this study. After screening a total of 30 articles were included.

RESULTS

The combination of doxorubicin and metformin demonstrated robust anticancer effects, surpassing the outcomes of monotherapy drug treatment. In vitro experiments consistently demonstrated inhibition of cancer cell growth and increased rates of cell death. Animal studies confirmed substantial reductions in tumor growth and improved survival rates, emphasizing the synergistic impact of the combined therapy. The research' discoveries collectively emphasize the capability of the co-treat doxorubicin-metformin as a compelling approach in cancer treatment, highlighting its potential to address medicate resistance and upgrade generally helpful results.

CONCLUSION

The findings of this study show that the combined treatment regimen including doxorubicin and metformin has significant promise in fighting cancer. The observed synergistic effects suggest that this combination therapy could be valuable, in a setting. This study highlights the need for clinical research to validate and enhance the application of the doxorubicin metformin regimen.

Repurposing metformin as adjuvant therapy in patients with ulcerative colitis treated with mesalamine: A randomized controlled double-blinded study

BACKGROUND

Ulcerative colitis (UC) is a type of inflammatory bowel disease associated with persistent inflammation. Animal studies proved the efficacy of metformin in UC.

AIM

To investigate the potential role of metformin and its protective pathways in patients with UC.

METHODS

This is a randomized, controlled, and double-blinded clinical trial that included 60 participants with mild to moderate UC and was divided randomly into two groups (n = 30). For 6 months, the mesalamine group received 1 g of mesalamine three times daily (t.i.d.). For six months, the metformin group received mesalamine 1 g t.i.d. and metformin 500 mg twice daily. A gastroenterologist evaluated patients at baseline and 6 months after starting the treatment in order to measure serum levels of zonulin, sphingosine 1 phosphate (S1P), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). Biopsies from the colon were used to measure gene expression of zonula occuldin-1 (ZO-1), signal transducer and activator of factor-3 (STAT-3), and intracellular adhesion molecule-1 (ICAM-1). The numeric pain rating scale (NRS) and partial Mayo score were also assessed for each patient.

RESULTS

When compared to the mesalamine group, the metformin group demonstrated a statistical decrease in serum IL-6, zonulin, TNF-α, SIP, gene expression of ICAM-1 and STAT-3, and a significant increase in colonic ZO-1 when compared to the mesalamine group. The metformin group also showed a significant decrease in NRS and partial Mayo score index in comparison with the mesalamine group.

CONCLUSION

Metformin may be a promising additional therapy for UC patients. Trial registration identifier: NCT05553704.

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

Pancreatic Acinar Cells-Derived Sphingosine-1-Phosphate Contributes to Fibrosis of Chronic Pancreatitis via Inducing Autophagy and Activation of Pancreatic Stellate Cells

BACKGROUND & AIMS

Studies have demonstrated that activated pancreatic stellate cells (PSCs) play a crucial role in pancreatic fibrogenesis in chronic pancreatitis (CP); however, the precise mechanism for PSCs activation has not been fully elucidated. We analyzed the role of injured pancreatic acinar cells (iPACs) in the activation of PSCs of CP.

METHODS

Sphingosine kinase 1 (SPHK1)/sphingosine-1-phosphate (S1P) signaling was evaluated in experimental CP induced by cerulein injection or pancreatic duct ligation, as well as in PACs injured by cholecystokinin. The activation of PSCs and pancreatic fibrosis in CP samples was evaluated by immunohistochemical and immunofluorescence analyses. In vitro coculture assay of iPACs and PSCs was created to evaluate the effect of the SPHK1/S1P pathway and S1P receptor 2 (SIPR2) on autophagy and activation of PSCs. The pathogenesis of CP was assessed in SPHK1-/- mice or PACs-specific SPHK1-knockdown mice with recombinant adeno-associated virus serotypes 9-SPHK1-knockdown, as well as in mice treated with inhibitor of SPHK1 and S1P receptor 2 (S1PR2).

RESULTS

SPHK1/S1P was remarkably increased in iPACs and acinar cells in pancreatic tissues of CP mice. Meanwhile, the pathogenesis, fibrosis, and PSCs activation of CP was significantly prevented in SPHK1-/- mice and recombinant adeno-associated virus serotypes 9-SPHK1-knockdown mice. Meanwhile, iPACs obviously activated PSCs, which was prevented by SPHK1 knockdown in iPACs. Moreover, iPACs-derived S1P specifically combined to S1PR2 of PSCs, by which modulated 5' adenosine monophosphate-activated protein kinase/mechanistic target of rapamycin pathway and consequently induced autophagy and activation of PSCs. Furthermore, hypoxia-inducible factor 1-α and -2α promoted SPHK1 transcription of PACs under hypoxia conditions, which is a distinct characteristic of the CP microenvironment. Coincidently, inhibition of SPHK1 and S1PR2 activity with inhibitor PF-543 and JTE-013 obviously impeded pancreatic fibrogenesis of CP mice.

CONCLUSIONS

The activated SPHK1/S1P pathway in iPACs induces autophagy and activation of PSCs by regulating the S1PR2/5' adenosine monophosphate-activated protein kinase/mammalian target of rapamycin pathway, which promotes fibrogenesis of CP. The hypoxia microenvironment might contribute to the cross talk between PACs and PSCs in pathogenesis of CP.

TIMELESS promotes the proliferation and migration of lung adenocarcinoma cells by activating EGFR through AMPK and SPHK1 regulation

BACKGROUND

Lung adenocarcinoma (LUAD) has high morbidity and is prone to recurrence. TIMELESS (TIM), which regulates circadian rhythms in Drosophila, is highly expressed in various tumors. Its role in LUAD has gained attention, but the detailed function and mechanism have not been clarified completely at present.

METHODS

Tumor samples from patients with LUAD patient data from public databases were used to confirm the relationship of TIM expression with lung cancer. LUAD cell lines were used and siRNA of TIM was adopted to knock down TIM expression in LUAD cells, and further cell proliferation, migration and colony formation were analyzed. By using Western blot and qPCR, we detected the influence of TIM on epidermal growth factor receptor (EGFR), sphingosine kinase 1 (SPHK1) and AMP-activated protein kinase (AMPK). With proteomics analysis, we comprehensively inspected the different changed proteins influenced by TIM and did global bioinformatic analysis.

RESULTS

We found that TIM expression was elevated in LUAD and that this high expression was positively correlated with more advanced tumor pathological stages and shorter overall and disease-free survival. TIM knockdown inhibited EGFR activation and also AKT/mTOR phosphorylation. We also clarified that TIM regulated the activation of SPHK1 in LUAD cells. And with SPHK1 siRNA to knock down the expression level of SPHK1, we found that EGFR activation were inhibited greatly too. Quantitative proteomics techniques combined with bioinformatics analysis clarified the global molecular mechanisms regulated by TIM in LUAD. The results of proteomics suggested that mitochondrial translation elongation and termination were altered, which were closely related to the process of mitochondrial oxidative phosphorylation. We further confirmed that TIM knockdown reduced ATP content and promoted AMPK activation in LUAD cells.

CONCLUSIONS

Our study revealed that siTIM could inhibit EGFR activation through activating AMPK and inhibiting SPHK1 expression, as well as influencing mitochondrial function and altering the ATP level; TIM's high expression in LUAD is an important factor and a potential key target in LUAD.

Pharmacometabolomic Approach to Investigate the Response to Metformin in Patients with Type 2 Diabetes: A Cross-Sectional Study

Metformin constitutes the foundation therapy in type 2 diabetes (T2D). Despite its multiple beneficial effects and widespread use, there is considerable inter-individual variability in response to metformin. Our objective is to identify metabolic signatures associated with poor and good responses to metformin, which may improve our ability to predict outcomes for metformin treatment. In this cross-sectional study, clinical and metabolic data for 119 patients with type 2 diabetes taking metformin were collected from the Qatar Biobank. Patients were empirically dichotomized according to their HbA1C levels into good and poor responders. Differences in the level of metabolites between these two groups were compared using orthogonal partial least square discriminate analysis (OPLS-DA) and linear models. Good responders showed increased levels of sphingomyelins, acylcholines, and glutathione metabolites. On the other hand, poor responders showed increased levels of metabolites resulting from glucose metabolism and gut microbiota metabolites. The results of this study have the potential to increase our knowledge of patient response variability to metformin and carry significant implications for enabling personalized medicine.

Repurposing of Chronically Used Drugs in Cancer Therapy: A Chance to Grasp

Despite the advancement in drug discovery for cancer therapy, drug repurposing remains an exceptional opportunistic strategy. This approach offers many advantages (faster, safer, and cheaper drugs) typically needed to overcome increased challenges, i.e., side effects, resistance, and costs associated with cancer therapy. However, not all drug classes suit a patient's condition or long-time use. For that, repurposing chronically used medications is more appealing. This review highlights the importance of repurposing anti-diabetic and anti-hypertensive drugs in the global fight against human malignancies. Extensive searches of all available evidence (up to 30 March 2023) on the anti-cancer activities of anti-diabetic and anti-hypertensive agents are obtained from multiple resources (PubMed, Google Scholar, ClinicalTrials.gov, Drug Bank database, ReDo database, and the National Institutes of Health). Interestingly, more than 92 clinical trials are evaluating the anti-cancer activity of 14 anti-diabetic and anti-hypertensive drugs against more than 15 cancer types. Moreover, some of these agents have reached Phase IV evaluations, suggesting promising official release as anti-cancer medications. This comprehensive review provides current updates on different anti-diabetic and anti-hypertensive classes possessing anti-cancer activities with the available evidence about their mechanism(s) and stage of development and evaluation. Hence, it serves researchers and clinicians interested in anti-cancer drug discovery and cancer management.

Beneficial Effects of Hordenine on a Model of Ulcerative Colitis

Hordenine, a phenethylamine alkaloid, is found in a variety of plants and exhibits a broad array of biological activities and pharmacological properties, including anti-inflammatory and anti-fibrotic effects. However, the efficacy and underlying mechanisms of hordenine in treating ulcerative colitis (UC) remain unclear. To address this, we examined the therapeutic effects of hordenine on dextran sodium sulphate (DSS)-induced UC by comparing disease activity index (DAI), colon length, secretion of inflammatory factors, and degree of colonic histological lesions across diseased mice that were and were not treated with hordenine. We found that hordenine significantly reduced DAI and levels of pro-inflammatory factors, including interleukin (IL)-6, IL-1β, and tumor necrosis factor alpha (TNF-α), and also alleviated colon tissue oedema, colonic lesions, inflammatory cells infiltration and decreased the number of goblet cells. Moreover, in vitro experiments showed that hordenine protected intestinal epithelial barrier function by increasing the expression of tight junction proteins including ZO-1 and occludin, while also promoting the healing of intestinal mucosa. Using immunohistochemistry and western blotting, we demonstrated that hordenine reduced the expression of sphingosine kinase 1 (SPHK1), sphingosine-1-phosphate receptor 1 (S1PR1), and ras-related C3 botulinum toxin substrate 1 (Rac1), and it inhibited the expression of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in colon tissues. Thus, hordenine appears to be effective in UC treatment owing to pharmacological mechanisms that favor mucosal healing and the inhibition of SPHK-1/S1PR1/STAT3 signaling.

HOXC11 drives lung adenocarcinoma progression through transcriptional regulation of SPHK1

Lung adenocarcinoma (LUAD) is a fatal threat to human health, while the mechanism remains unclear, and the therapy brings limited therapeutic effects. Transcription factor Homeobox C11 (HOXC11) was previously proved to be related to hind limbs and metanephric development during the embryonic phase, and its role in tumors has been gradually recognized. Our study found that HOXC11 overexpressed in LUAD and was associated with worse overall survival. Moreover, its expression in lung cancer was regulated by IκB kinase α (IKKα), a pivotal kinase in NF-κB signaling, which was related to the ubiquitination of HOXC11. We further proved that HOXC11 could enhance the ability of proliferation, migration, invasion, colony formation, and the progression of the cell cycle in LUAD cells. Meanwhile, it also accelerated the formation of subcutaneous and lung metastases tumors. In contrast, loss of HOXC11 in LUAD cells significantly inhibited these malignant phenotypes. At the same time, HOXC11 regulated the expression of sphingosine kinase 1 (SPHK1) by directly binding to its promoter region. Therefore, we conclude that HOXC11 impacts the development of LUAD and facilitates lung cancer progression by promoting the expression of SPHK1.

Sphingosine Kinase-1 (SPHK1) promotes inflammation in infantile pneumonia by regulating NLRP3 inflammasome and SIRT1 expression

BACKGROUND

Infantile pneumonia is an acute inflammatory disorder of the lung caused by mycoplasma pneumonia. SPHK1 (sphingosine kinase-1) signaling pathway is involved in the process of inflammatory diseases. However, whether SphK1 regulates inflammatory responses in infantile pneumonia remains unclear. In this study, we investigated the role of SPHK1 in infantile pneumonia and its underlying mechanisms.

METHODS

Serum samples of 12 patients with infantile pneumonia and healthy controls were obtained from Hunan Children's Hospital. To induce pneumonia, mice were administrated with LPS (lipopolysaccharide) into the lung. RAW264.7 cells were used as an in vitro macrophage model stimulated with LPS or PBS for 4 h.

RESULTS

SPHK1 mRNA level and protein level in the LPS-treated mice and patients with infantile pneumonia were significantly increased. SPHK1 promoted inflammation and lung injury in mice with infantile pneumonia. The knockdown of SPHK1 expression inhibited inflammation and restrained lung injury in mice with infantile pneumonia. SPHK1 overexpression also exacerbated inflammation in RAW264.7 cells stimulated by LPS, and SPHK1 silencing reduced inflammatory responses. We further showed that SPHK1 induced NLRP3 (NLR Family Pyrin Domain Containing 3) activity by inhibiting SIRT1 expression.

CONCLUSION

Our study demonstrated that SPHK1 promotes inflammation of infantile pneumonia by modulating NLRP3 inflammasome via the regulation of SIRT1 expression and mitochondrial permeability transition.

Metformin as a Potential Antitumor Agent

Some recent findings suggest that metformin, an oral antidiabetic drug, may have antitumor properties. Studies have shown that metformin can alter cell metabolism, both tumor and immune cells, which can greatly influence disease outcome. In this review, we discuss the potential mechanisms in which metformin can directly induce apoptosis of tumor cells as well as mechanisms in which metformin can elicit or enhance antitumor immune response.

Targeting SPHK1/PBX1 Axis Induced Cell Cycle Arrest in Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) accounts for 85~90% of lung cancer cases, with a poor prognosis and a low 5-year survival rate. Sphingosine kinase-1 (SPHK1), a key enzyme in regulating sphingolipid metabolism, has been reported to be involved in the development of NSCLC, although the underlying mechanism remains unclear. In the present study, we demonstrated the abnormal signature of SPHK1 in NSCLC lesions and cell lines of lung cancers with a potential tumorigenic role in cell cycle regulation. Functionally, ectopic Pre-B cell leukemia homeobox-1 (PBX1) was capable of restoring the arrested G1 phase induced by SPHK1 knockdown. However, exogenous sphingosine-1-phosphate (S1P) supply had little impact on the cell cycle arrest by PBX1 silence. Furthermore, S1P receptor S1PR3 was revealed as a specific switch to transport the extracellular S1P signal into cells, and subsequently activated PBX1 to regulate cell cycle progression. In addition, Akt signaling partially participated in the SPHK1/S1PR3/PBX1 axis to regulate the cell cycle, and the Akt inhibitor significantly decreased PBX1 expression and induced G1 arrest. Targeting SPHK1 with PF-543 significantly inhibited the cell cycle and tumor growth in preclinical xenograft tumor models of NSCLC. Taken together, our findings exhibit the vital role of the SPHK1/S1PR3/PBX1 axis in regulating the cell cycle of NSCLC, and targeting SPHK1 may develop a therapeutic effect in tumor treatment.

Sphingosine kinase 1 promotes tumor immune evasion by regulating the MTA3-PD-L1 axis

Immune checkpoint blockade (ICB) exhibits considerable benefits in malignancies, but its overall response rate is limited. Previous studies have shown that sphingosine kinases (SPHKs) are critical in the tumor microenvironment (TME), but their role in immunotherapy is unclear. We performed integrative analyses including bioinformatics analysis, functional study, and clinical validation to investigate the role of SPHK1 in tumor immunity. Functionally, we demonstrated that the inhibition of SPHK1 significantly suppressed tumor growth by promoting antitumor immunity in immunocompetent melanoma mouse models and tumor T-cell cocultures. A mechanistic analysis revealed that MTA3 functions as the downstream target of SPHK1 in transcriptionally regulating tumor PD-L1. Preclinically, we found that anti-PD-1 monoclonal antibody (mAb) treatment significantly rescued tumor SPHK1 overexpression or tumor MTA3 overexpression-mediated immune evasion. Significantly, we identified SPHK1 and MTA3 as biological markers for predicting the efficacy of anti-PD-1 mAb therapy in melanoma patients. Our findings revealed a novel role for SPHK1 in tumor evasion mediated by regulating the MTA3-PD-L1 axis, identified SPHK1 and MTA3 as predictors for assessing the efficacy of PD-1 mAb treatment, and provided a therapeutic possibility for the treatment of melanoma patients.

Lipids Alterations Associated with Metformin in Healthy Subjects: An Investigation Using Mass Spectrometry Shotgun Approach

Metformin is an orally effective insulin-sensitizing drug widely prescribed for treating type 2 diabetes mellitus (T2DM). Metformin has been reported to alter lipid metabolism. However, the molecular mechanisms behind its impact on lipid metabolism remain partially explored and understood. In the current study, mass spectrometry-based lipid profiling was used to investigate the lipidomic changes in the serum of 26 healthy individuals after a single-dose intake of metformin. Samples were analyzed at five-time points: preadministration, before the maximum concentration of metformin (Cmax), Cmax, after Cmax, and 36 h post-administration. A total of 762 molecules were significantly altered between the five-time points. Based on a comparison between baseline level and Cmax, metformin significantly increased and decreased the level of 33 and 192 lipids, respectively (FDR ≤ 0.05 and fold change cutoff of 1.5). The altered lipids are mainly involved in arachidonic acid metabolism, steroid hormone biosynthesis, and glycerophospholipid metabolism. Furthermore, several lipids acted in an opposed or similar manner to metformin levels and included fatty acyls, sterol lipids, glycerolipids, and glycerophospholipids. The significantly altered lipid species pointed to fundamental lipid signaling pathways that could be linked to the pleiotropic effects of metformin in T2DM, insulin resistance, polycystic ovary syndrome, cancer, and cardiovascular diseases.

Inhibition of SphK1/S1P Signaling Pathway Alleviates Fibrosis and Inflammation of Rat Myocardium after Myocardial Infarction

Objective

The sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P) signaling pathway is involved in fibrosis and inflammatory responses of myocardial tissue after myocardial infarction (MI). The purpose of our study was to explore the role of SphK1/S1P signaling pathway in myocardial injury after MI.

Materials and Methods

We used Sprague-Dawley (SD) rats to make MI models and detected the changes of SphK1 and S1P in rats at 1, 7, and 14 days after MI. SphK1 inhibitor PF543 was used to treat MI rats, and we detected the changes in myocardial function and structure in rats by cardiac function test, 2,3,5-triphenyl tetrazolium staining, and histological staining. In addition, we used H₂O₂ to induce H9c2 cell injury to investigate the effect of PF543 on the viability of myocardial cells.

Results

Myocardial tissue lesions and fibrosis were observed at 7 and 14 days after MI, and the expressions of SphK1 and S1P in the injured myocardial tissues increased significantly in day 7 and day 14 in comparison to the control group. After treatment of MI rats with PF543, the structure of rat myocardial tissue was significantly improved and the degree of fibrosis was reduced. After MI, the expression of α-SMA and collagen I in the myocardium of rats was significantly increased while PF543 decreased their expression. PF543 also improved the cardiac function of MI rats and reduced the expression of IL-1β, IL-6, and TNF-α in the serum. PF543 also increased the viability of H9c2 cells in vitro.

Conclusions

The inhibition of the SphK1/S1P signaling pathway contributed to the relief of myocardial injury in MI rats. PF543 improved the myocardial structure and function of MI rats and reduced the level of fibrosis and inflammation in MI rats.

Development of a Novel Sphingolipid Signaling Pathway-Related Risk Assessment Model to Predict Prognosis in Kidney Renal Clear Cell Carcinoma

This study aimed to explore underlying mechanisms by which sphingolipid-related genes play a role in kidney renal clear cell carcinoma (KIRC) and construct a new prognosis-related risk model. We used a variety of bioinformatics methods and databases to complete our exploration. Based on the TCGA database, we used multiple R-based extension packages for data transformation, processing, and statistical analyses. First, on analyzing the CNV, SNV, and mRNA expression of 29 sphingolipid-related genes in various types of cancers, we found that the vast majority were protective in KIRC. Subsequently, we performed cluster analysis of patients with KIRC using sphingolipid-related genes and successfully classified them into the following three clusters with significant prognostic differences: Cluster 1, Cluster 2, and Cluster 3. We performed differential analyses of transcription factor activity, drug sensitivity, immune cell infiltration, and classical oncogenes to elucidate the unique roles of sphingolipid-related genes in cancer, especially KIRC, and provide a reference for clinical treatment. After analyzing the risk rates of sphingolipid-related genes in KIRC, we successfully established a risk model composed of seven genes using LASSO regression analysis, including SPHK1, CERS5, PLPP1, SGMS1, SGMS2, SERINC1, and KDSR. Previous studies have suggested that these genes play important biological roles in sphingolipid metabolism. ROC curve analysis results showed that the risk model provided good prediction accuracy. Based on this risk model, we successfully classified patients with KIRC into high- and low-risk groups with significant prognostic differences. In addition, we performed correlation analyses combined with clinicopathological data and found a significant correlation between the risk model and patient’s M, T, stage, grade, and fustat. Finally, we developed a nomogram that predicted the 5-, 7-, and 10-year survival in patients with KIRC. The model we constructed had strong predictive ability. In conclusion, we believe that this study provides valuable data and clues for future studies on sphingolipid-related genes in KIRC.

Aberrantly methylated-differentially expressed genes and related pathways in cholangiocarcinoma

This study aimed to explore aberrantly methylated-differentially expressed genes and related pathways in cholangiocarcinoma (CCA).The mRNA expression data (GSE26566) and methylation profiling data (GSE44965) were collected from the Gene Expression Omnibus (GEO) Datasets. Differentially expressed genes and differentially methylated genes were identified using GEO2R. Gene ontology analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed using clusterprofiler in R. MCODE clustering tool was used to screen modules of the protein-protein interaction network in Cytoscape. Related pathways of hub gene by using gene set enrichment analysis.Eighty-one hypermethylated, lowly expressed genes (Hyper-LGs) and 76 hypomethylated, highly expressed genes (Hypo-HGs) were identified in this study. Hyper-LGs were enriched in ion channel binding and transcription factor activity, which was associated with Mineral absorption and Cell adhesion molecules. Hypo-HGs were enriched in cysteine-type endopeptidase activity, which was associated with Sphingolipid signaling pathway and T cell receptor signaling pathway. Based on protein-protein interaction networks, MYC and VWF were identified as hub genes for Hyper-LGs, and no hub genes for Hypo-HGs.This study found methylated-differentially expressed genes and signaling pathways that are connected with the CCA by using a series of bioinformatics databases and tools. MYC and VWF act as hub genes of CCA, which can be used as biomarkers based on aberrant methylation for the accurate diagnosis and treatment of CCA.

Development and evaluation of core-shell nanocarrier system for enhancing the cytotoxicity of doxorubicin/ metformin combination against breast cancer cell line

Breast cancer is the most invasive and life-threatening cancer in women. The treatment options are usually a combination of mastectomy, radiation therapy, hormonal therapy and chemotherapy. As a standard practice, doxorubicin (DOX) is one of the commonly used drugs for breast cancer treatment. However, DOX is known to have many harmful adverse effects including its cardiotoxicity. Hence, recent reports used metformin (MET), an anti-diabetic drug, as an adjuvant therapy to decrease the severity of DOX's adverse effects and to improve its ultimate therapeutic outcome. The current study is aimed at co-loading and enhancing the encapsulation efficiency of the hydrophilic DOX and MET in poly(lactic-co-glycolic acid) (PLGA) nanocapsules (NCs) with oil core for breast cancer treatment. The NCs were developed by single emulsification-solvent diffusion technique, and were optimized through using two types of oils, pluronics and PLGA (50:50) of different molecular weights followed by various physicochemical characterizations. The obtained DOX/MET-loaded NCs showed the size and polydispersity index (PDI) of 203.0 ± 3.4 nm and 0.081 ± 0.03, respectively with a surface charge of -2.15 ± 0.2 mV. The entrapment efficiency of DOX and MET were about 93.7% ± 2.9 and 70% ± 1.6, respectively. The developed PLGA core-shell NCs successfully sustained the DOX/MET release for more than 30 days. The in-vitro results showed a significant enhancement in DOX cytotoxic effect as well as a duplication in its apoptotic effect upon addition of MET for both free DOX/MET combination and DOX/MET-loaded PLGA NCs against MCF-7. Besides, flow cytometry demonstrated that the DOX/MET-loaded NCs possess their antitumor effect by preventing DNA replication and cell division. This study provides a promising facile, rapid and reproducible single emulsification-solvent diffusion technique for improving the encapsulation and release of hydrophilic drugs in nanocapsules for biomedical applications.

Tumor Derived Extracellular Vesicles Drive T Cell Exhaustion in Tumor Microenvironment through Sphingosine Mediated Signaling and Impacting Immunotherapy Outcomes in Ovarian Cancer

SPHK1 (sphingosine kinase-1) catalyzes the phosphorylation of sphingosine to sphingosine-1-phosphate (S1P), is found to be highly expressed in solid tumors. Here, extracellular vesicles (EVs) are identified as the key transporters of SPHK1 to the tumor microenvironment. Consequently, SPHK1-packaged EVs elevate S1P levels in the tumor microenvironment, where S1P appears as an immunosuppressive agent. However, the exact mechanism of how S1P mediates its immunosuppressive effects in cancer is not understood. It is investigated that S1P can induce T cell exhaustion. S1P can also upregulate programmed death ligand-1 (PDL-1) expression through E2F1-mediated transcription. Notably, an SPHK1 inhibitor PF543 improves T cell-mediated cytotoxicity. Furthermore, combining PF543 with an anti-PD-1 antibody reduces tumor burden and metastasis more effectively than PF543 alone in vivo. These data demonstrate a previously unrecognized mechanism of how SPHK1-packaged EVs contribute to the progression of ovarian cancer and thus present the potential clinical application of inhibiting SPHK1/S1P signaling to improve immune checkpoint blockage (anti-PD-1 antibody) therapy in ovarian cancer.

Design, Synthesis and Biological Activity Testing of Library of Sphk1 Inhibitors

Our team discovered a moderate SphK1 inhibitor, SAMS10 (IC₅₀ = 9.8 μM), which was screened by computer-assisted screening. In this study, we developed a series of novel diaryl derivatives with improved antiproliferative activities by modifying the structure of the lead compound SAMS10. A total of 50 new compounds were synthesized. Among these compounds, the most potent compound, named CHJ04022Rb, has significant anticancer activity in melanoma A375 cell line (IC₅₀ = 2.95 μM). Further underlying mechanism studies indicated that CHJ04022R exhibited inhibition effect against PI3K/NF-κB signaling pathways, inhibited the migration of A375 cells, promoted apoptosis and exerted antiproliferative effect by inducing G2/M phase arrest in A375 cells. Furthermore, acute toxicity experiment indicated CHJ04022R exhibited good safety in vivo. Additionally, it showed a dose-dependent inhibitory effect on the growth of xenograft tumor in nude mice. Therefore, CHJ04022R may be a potential candidate for the treatment of melanoma.

Effects of Metformin as Add-On Therapy against Glioblastoma: An Old Medicine for Novel Oncology Therapeutics

Simple Summary

Glioblastoma is the most common and malignant primary brain tumor, with a median survival of around 14 months. The aggressiveness of glioblastoma is due to intense cell proliferation, angiogenesis, invasiveness, genetic instability, resistance to therapies and high frequency of relapses. These features render glioblastoma almost incurable, considered an extreme therapeutic challenge. In the last few decades, it has been observed a reduced cancer incidence in diabetic patients treated with metformin, an oral hypoglycemic drug. The reported ability of metformin to arrest cancer cell growth in in vitro and in vivo experimental tumor models, have suggested the possibility to reconsider metformin as an anti-cancer add-on therapy, but further investigations about molecular mechanisms and optimal therapeutic regimens are needed. Here, we tested the efficacy of metformin against primary glioblastoma endothelial cells, responsible for tumor angiogenesis, invasiveness and resistance to therapy, reporting promising results and advancing a novel target of metformin, the “sphingolipid rheostat”.

Abstract

Background: Glioblastoma is the most aggressive primary brain malignancy in adults, with a poor prognosis of about 14 months. Recent evidence ascribed to metformin (MET), an antihyperglycemic drug, the potential to reduce cancer incidence and progression, but the molecular mechanisms underlying these effects need to be better investigated. Methods: Here, we tested the efficacy of MET on n = 10 primary glioblastoma endothelial cells (GECs), by viability and proliferation tests, as MTT and Live/Dead assays, apoptosis tests, as annexin V assay and caspase 3/7 activity, functional tests as tube-like structure formation and migration assay and by mRNA and protein expression performed by quantitative real-time PCR analysis (qRT-PCR) and Western Blot, respectively. Results: Data resulting revealed a time- and μ-dependent ability of MET to decrease cell viability and proliferation, increasing pro-apoptotic mechanisms mediated by caspases 3/7. Also, MET impacted GEC functionality with a significant decrease of angiogenesis and invasiveness potential. Mechanistically, MET was able to interfere with sphingolipid metabolism, weakening the oncopromoter signaling promoted by sphingosine-1-phosphate (S1P) and shifting the balance toward the production of the pro-apoptotic ceramide. Conclusions: These observations ascribed to MET the potential to serve as add-on therapy against glioblastoma, suggesting a repurposing of an old, totally safe and tolerable drug for novel oncology therapeutics.

Inflammation-Related Gene Signature: An Individualized Risk Prediction Model for Kidney Renal Clear Cell Carcinoma

Background. There is much evidence that confirms the inextricable link between inflammation and malignancy. Inflammation-related regulators were involved in the progression of kidney renal clear cell carcinoma (KIRC). However, the predictive role of single gene biomarkers is inadequate, and more accurate prognostic models are necessary. We undertook the current research to construct a robust inflammation-related gene signature that could stratify patients with KIRC. Methods. The transcriptome sequencing data along with clinicopathologic information of KIRC were obtained from TCGA. A list of inflammation-related genes was acquired from the Molecular Signatures Database. Using the RNA-seq and survival time data from the TCGA training cohort, an inflammation-related gene signature was built using bioinformatic methods, and its performance in predicting patient prognosis was assessed by Kaplan–Meier and ROC curve analyses. Furthermore, we explored the association of risk score with immune score, stromal score, tumor immune-infiltrating cells (TIICs), immunosuppressive molecules, m6A regulators, and autophagy-related biomarkers. Results. Herein, nine inflammation-related hub genes (ROS1, PLAUR, ACVR2A, KLF6, GABBR1, APLNR, SPHK1, PDPN, and ADORA2B) were determined and used to build a predictive model. All sets, including training set, four testing sets, and the entire TCGA group, were divided into two groups (low and high risk), and Kaplan–Meier curves all showed an adverse prognosis for patients in the high-risk group. ESTIMATE algorithm revealed a higher immune score in the high-risk subgroup. CIBERSORT algorithm illustrated that the high-risk group showed higher-level immune infiltrates. Furthermore, LAG3, TIGIT, and CTLA4 were overexpressed in the high-risk subgroup and positively associated with risk scores. Moreover, except for METTL3 and ALKBH5, the other m6A regulators decreased in the high-risk subgroup. Conclusions. In conclusion, a novel inflammation-related gene signature comprehensively constructed in the current study may help stratify patients with KIRC.

Identification of a Five Autophagy Subtype-Related Gene Expression Pattern for Improving the Prognosis of Lung Adenocarcinoma

Background: Autophagy plays an important role in lung adenocarcinoma (LUAD). In this study, we aimed to explore the autophagy-related gene (ARG) expression pattern and to identify promising autophagy-related biomarkers to improve the prognosis of LUAD.

Methods: The gene expression profiles and clinical information of LUAD patients were downloaded from the Cancer Genome Atlas (TCGA), and validation cohort information was extracted from the Gene Expression Omnibus database. The Human Autophagy Database (HADb) was used to extract ARGs. Gene expression data were analyzed using the limma package and visualized using the ggplot2 package as well as the pheatmap package in R software. Functional enrichment analysis was also performed for the differentially expressed ARGs (DEARGs). Then, consensus clustering revealed autophagy-related tumor subtypes, and differentially expressed genes (DEGs) were screened according to the subtypes. Next, the univariate Cox and multivariate Cox regression analyses were used to identify independent prognostic ARGs. After overlapping DEGs and the independent prognostic ARGs, the predictive risk model was established and validated. Correlation analyses between ARGs and clinicopathological variables were also explored. Finally, the TIMER and TISIDB databases were used to further explore the correlation analysis between immune cell infiltration levels and the risk score as well as clinicopathological variables in the predictive risk model.

Results: A total of 222 genes from the HADb were identified as ARGs, and 28 of the 222 genes were pooled as DEARGs. The most significant GO term was autophagy (p = 3.05E-07), and KEGG analysis results indicated that 28 DEARGs were significantly enriched in the ErbB signaling pathway (p < 0.001). Then, consensus clustering analysis divided the LUAD into two clusters, and a total of 168 DEGs were identified according to cluster subtypes. Then univariate and multivariate Cox regression analyses were used to identify 12 genes that could serve as independent prognostic indicators. After overlapping 168 DEGs and 12 genes, 10 genes (ATG4A, BAK1, CAPNS1, CCR2, CTSD, EIF2AK3, ITGB1, MBTPS2, SPHK1, ST13) were selected for the further exploration of the prognostic pattern. Survival analysis results indicated that this risk model identified the prognosis (p = 4.379E-10). Combined with the correlation analysis results between ARGs and clinicopathological variables, five ARGs were screened as prognostic genes. Among them, SPHK1 expression levels were positively correlated with CD4⁺ T cells and dendritic cell infiltration levels.

Conclusions: In this study, we constructed a predictive risk model and identified a five autophagy subtype-related gene expression pattern to improve the prognosis of LUAD. Understanding the subtypes of LUAD is helpful to accurately characterize the LUAD and develop personalized treatment.

Cancer and diabetes: the interlinking metabolic pathways and repurposing actions of antidiabetic drugs

Cancers are regarded as one of the main causes of death and result in high health burden worldwide. The management of cancer include chemotherapy, surgery and radiotherapy. The chemotherapy, which involves the use of chemical agents with cytotoxic actions is utilised as a single treatment or combined treatment. However, these managements of cancer such as chemotherapy poses some setbacks such as cytotoxicity on normal cells and the problem of anticancer drug resistance. Therefore, the use of other therapeutic agents such as antidiabetic drugs is one of the alternative interventions used in addressing some of the limitations in the use of anticancer agents. Antidiabetic drugs such as sulfonylureas, biguanides and thiazolidinediones showed beneficial and repurposing actions in the management of cancer, thus, the activities of these drugs against cancer is attributed to some of the metabolic links between the two disorders and these includes hyperglycaemia, hyperinsulinemia, inflammation, and oxidative stress as well as obesity. Furthermore, some studies showed that the use of antidiabetic drugs could serve as risk factors for the development of cancerous cells particularly pancreatic cancer. However, the beneficial role of these chemical agents overweighs their detrimental actions in cancer management. Hence, the present review indicates the metabolic links between cancer and diabetes and the mechanistic actions of antidiabetic drugs in the management of cancers.

Ceramide-1-phosphate and its transfer proteins in eukaryotes

Ceramide-1-phosphate (C1P) is a bioactive phosphorylated sphingolipid (SL), produced through the direct phosphorylation of ceramide by ceramide kinase. It plays important roles in regulating cell survival, migration, apoptosis and autophagy and is involved in inflammasome assembly/activation, which can stimulate group IVA cytosolic phospholipase A₂α and subsequently increase the levels of arachidonic acid and pro-inflammatory cytokines. Human C1P transfer protein (CPTP) can selectively transport C1P from the Golgi apparatus to specific cellular sites through a non-vesicular mechanism. Human CPTP also affects specific SL levels, thus regulating cell SL homeostasis. In addition, human CPTP plays a crucial role in the regulation of autophagy, inflammation and cell death; thus, human CPTP is closely associated with autophagy and inflammation-related diseases such as cardiovascular and neurodegenerative diseases, and cancers. Therefore, illustrating the functions and mechanisms of human CPTP is important for providing the research foundations for targeted therapy. The key human CPTP residues for C1P recognition and binding are highly conserved in eukaryotic orthologs, while the human CPTP homolog in Arabidopsis (accelerated cell death 11) also exhibits selective inter-membrane transfer of phyto-C1P. These results demonstrate that C1P transporters play fundamental roles in SL metabolism in cells. The present review summarized novel findings of C1P and its TPs in eukaryotes.

A Dansyl-Modified Sphingosine Kinase Inhibitor DPF-543 Enhanced De Novo Ceramide Generation

Sphingosine-1-phosphate (S1P) synthesized by sphingosine kinase (SPHK) is a signaling molecule, involved in cell proliferation, growth, differentiation, and survival. Indeed, a sharp increase of S1P is linked to a pathological outcome with inflammation, cancer metastasis, or angiogenesis, etc. In this regard, SPHK/S1P axis regulation has been a specific issue in the anticancer strategy to turn accumulated sphingosine (SPN) into cytotoxic ceramides (Cers). For these purposes, there have been numerous chemicals synthesized for SPHK inhibition. In this study, we investigated the comparative efficiency of dansylated PF-543 (DPF-543) on the Cers synthesis along with PF-543. DPF-543 deserved attention in strong cytotoxicity, due to the cytotoxic Cers accumulation by ceramide synthase (CerSs). DPF-543 exhibited dual actions on Cers synthesis by enhancing serine palmitoyltransferase (SPT) activity, and by inhibiting SPHKs, which eventually induced an unusual environment with a high amount of 3-ketosphinganine and sphinganine (SPA). SPA in turn was consumed to synthesize Cers via de novo pathway. Interestingly, PF-543 increased only the SPN level, but not for SPA. In addition, DPF-543 mildly activates acid sphingomyelinase (aSMase), which contributes a partial increase in Cers. Collectively, a dansyl-modified DPF-543 relatively enhanced Cers accumulation via de novo pathway which was not observed in PF-543. Our results demonstrated that the structural modification on SPHK inhibitors is still an attractive anticancer strategy by regulating sphingolipid metabolism.

Potential effect of EGCG on the anti-tumor efficacy of metformin in melanoma cells

Metformin, a first-line drug for type 2 diabetes mellitus, has been recognized as a potential anti-tumor agent in recent years. Epigallocatechin-3-gallate (EGCG), as the dominant catechin in green tea, is another promising adjuvant agent for tumor prevention. In the present work, the potential effect of EGCG on the anti-tumor efficacy of metformin in a mouse melanoma cell line (B16F10) was investigated. Results indicated that EGCG and metformin exhibited a synergistic effect on cell viability, migration, and proliferation, as well as signal transducer and activator of transcription 3/nuclear factor-κB (STAT3/NF-κB) pathway signaling and the production of inflammation cytokines. Meanwhile, the combination showed an antagonistic effect on cell apoptosis and oxidative stress levels. The combination of EGCG and metformin also differentially affected the nucleus (synergism) and cytoplasm (antagonism) of B16F10 cells. Our findings provide new insight into the potential effects of EGCG on the anti-tumor efficacy of metformin in melanoma cells.

The Role of Ceramide Metabolism and Signaling in the Regulation of Mitophagy and Cancer Therapy

Simple Summary

Sphingolipids are membrane-associated lipids that are involved in signal transduction pathways regulating cell death, growth, and migration. In cancer cells, sphingolipids regulate pathways relevant to cancer therapy, such as invasion, metastasis, apoptosis, and lethal mitophagy. Notable sphingolipids include ceramide, a sphingolipid that induces death and lethal mitophagy, and sphingosine-1 phosphate, a sphingolipid that induces survival and chemotherapeutic resistance. These sphingolipids participate in regulating the process of mitophagy, where cells encapsulate damaged mitochondria in double-membrane vesicles (called autophagosomes) for degradation. Lethal mitophagy is an anti-tumorigenic mechanism mediated by ceramide, where cells degrade many mitochondria until the cancer cell dies in an apoptosis-independent manner.

Abstract

Sphingolipids are bioactive lipids responsible for regulating diverse cellular functions such as proliferation, migration, senescence, and death. These lipids are characterized by a long-chain sphingosine backbone amide-linked to a fatty acyl chain with variable length. The length of the fatty acyl chain is determined by specific ceramide synthases, and this fatty acyl length also determines the sphingolipid’s specialized functions within the cell. One function in particular, the regulation of the selective autophagy of mitochondria, or mitophagy, is closely regulated by ceramide, a key regulatory sphingolipid. Mitophagy alterations have important implications for cancer cell proliferation, response to chemotherapeutics, and mitophagy-mediated cell death. This review will focus on the alterations of ceramide synthases in cancer and sphingolipid regulation of lethal mitophagy, concerning cancer therapy.

Targeting the Sphingosine Kinase/Sphingosine-1-Phosphate Signaling Axis in Drug Discovery for Cancer Therapy

Sphingolipid metabolites have emerged as critical players in the regulation of various physiological processes. Ceramide and sphingosine induce cell growth arrest and apoptosis, whereas sphingosine-1-phosphate (S1P) promotes cell proliferation and survival. Here, we present an overview of sphingolipid metabolism and the compartmentalization of various sphingolipid metabolites. In addition, the sphingolipid rheostat, a fine metabolic balance between ceramide and S1P, is discussed. Sphingosine kinase (SphK) catalyzes the synthesis of S1P from sphingosine and modulates several cellular processes and is found to be essentially involved in various pathophysiological conditions. The regulation and biological functions of SphK isoforms are discussed. The functions of S1P, along with its receptors, are further highlighted. The up-regulation of SphK is observed in various cancer types and is also linked to radio- and chemoresistance and poor prognosis in cancer patients. Implications of the SphK/S1P signaling axis in human pathologies and its inhibition are discussed in detail. Overall, this review highlights current findings on the SphK/S1P signaling axis from multiple angles, including their functional role, mechanism of activation, involvement in various human malignancies, and inhibitor molecules that may be used in cancer therapy.

A circular network of coregulated sphingolipids dictates lung cancer growth and progression

Background

Sphingolipid metabolism is among the top dysregulated pathways in non-small cell lung carcinomas (NSCLC). However, the molecular control of sphingolipid metabolic reprogramming in cancer progression remains unclear.

Methods

We first determined the correlation between sphingolipid metabolic gene expression and patient prognosis. We then carried out sphingolipidomics analysis of health individual and NSCLC patient sera as well as B3GNT5 and GAL3ST1 genetically perturbed NSCLC cell lines. We used these cell lines to perform tumorigenesis study to determine the cellular role of B3GNT5 and GAL3ST1 in cancer growth and progression.

Findings

The expression of B3GNT5 and GAL3ST1 among sphingolipid metabolic enzymes is most significantly associated with patient prognosis, whilst sphingolipidomics analysis of healthy individual and NSCLC patient sera identifies their metabolites, lacto/neolacto-series glycosphingolipid and sulfatide species, as potential biomarkers that were more effective than current clinical biomarkers for staging patients. Further network analysis of the sphingolipidomes reveals a circular network of coregulated sphingolipids, indicating that the lacto/neolacto-series glycosphingolipid/sulfatide balance functions as a checkpoint to determine sphingolipid metabolic reprograming during patient progression. Sphingolipidomics analysis of B3GNT5/GAL3ST1 genetically perturbed NSCLC cell lines confirms their key regulatory role in sphingolipid metabolism, while B3GNT5 and GAL3ST1 expression has an opposite role on tumorigenesis.

Interpretation

Our results provide new insights whereby B3GNT5 and GAL3ST1 differentially regulate sphingolipid metabolism in lung cancer growth and progression.

Funding

This work was supported by the Natural Science Foundation of China (81872142, 81920108028); Guangzhou Science and Technology Program (201904020008); Guangdong Science and Technology Department (2020A0505100029, 2019A1515011802, 2020A1515011280, 2020B1212060018, 2020B1212030004); China Postdoctoral Science Foundation (2019M650226, 2019M650227).

Inhibition of sphingosine kinase 2 down-regulates ERK/c-Myc pathway and reduces cell proliferation in human epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) is the leading cause of death from female cancers. In our previous study, sphingosine kinase 2 (SphK2) inhibitor was shown to display anti-EOC activities. The purpose of this study was to evaluate further the expression characteristics and clinical significance of SphK2 in EOC and to explore the roles and underlying mechanisms of SphK2 in EOC cell survival.

Methods

The expression of SphK2 was examined by immunohistochemistry (IHC) and Western blot, and its clinical implications and prognostic significance were analyzed. We performed a cellular proliferation assay, and a mouse xenograft model was established to confirm the roles of SphK2 in vitro and in vivo. Cell cycle analysis, apoptosis assay, and Western blot were performed to examine cell cycle progression and apoptosis rate. Gene set enrichment analysis (GSEA), and Western blot were used to investigate the downstream signaling pathways related to SphK2 function.

Results

The expression level of SphK2 was shown to be associated with stage, histological grade, lymph node metastasis, and ascites status. More importantly, a high SphK2 expression level was a prognostic indicator of overall survival (OS) and relapse-free survival (RFS). Moreover, knockdown of SphK2 arrested cell cycle progression and inhibited EOC cell proliferation both in vitro and in vivo. Furthermore, ERK/c-Myc, the key pathway in EOC progression, was important for SphK2-mediated mitogenic action in EOC cells.

Conclusions

Our findings provided the first evidence that SphK2 played a crucial role in EOC proliferation by regulating the ERK/c-Myc pathway. This indicated that SphK2 might serve as a prognostic marker and potential therapeutic target in EOC.

Mitophagy in tumorigenesis and metastasis

Cells use mitophagy to remove dysfunctional or excess mitochondria, frequently in response to imposed stresses, such as hypoxia and nutrient deprivation. Mitochondrial cargo receptors (MCR) induced by these stresses target mitochondria to autophagosomes through interaction with members of the LC3/GABARAP family. There are a growing number of these MCRs, including BNIP3, BNIP3L, FUNDC1, Bcl2-L-13, FKBP8, Prohibitin-2, and others, in addition to mitochondrial protein targets of PINK1/Parkin phospho-ubiquitination. There is also an emerging link between mitochondrial lipid signaling and mitophagy where ceramide, sphingosine-1-phosphate, and cardiolipin have all been shown to promote mitophagy. Here, we review the upstream signaling mechanisms that regulate mitophagy, including components of the mitochondrial fission machinery, AMPK, ATF4, FoxOs, Sirtuins, and mtDNA release, and address the significance of these pathways for stress responses in tumorigenesis and metastasis. In particular, we focus on how mitophagy modulators intersect with cell cycle control and survival pathways in cancer, including following ECM detachment and during cell migration and metastasis. Finally, we interrogate how mitophagy affects tissue atrophy during cancer cachexia and therapy responses in the clinic.

SphK1 Promotes Cancer Progression through Activating JAK/STAT Pathway and Up-Regulating S1PR1 Expression in Colon Cancer Cells

BACKGROUND

SphK1 is a conserved lipid kinase, which can catalyze formation of tumor promoting factor sphingosine phosphate-1 (S1P).

OBJECTIVE

To investigate effect of SphK1 on proliferation/migration of colon cancer cells and associated mechanisms.

METHODS

Transcription of SphK1 gene in colon cancer cells was detected. Gene transcription of SphK1 was inhibited by transfecting with si-SphK1 gene in colon cancer cells. Effects of SphK1 inhibition (si-SphK1) on cell migration/proliferation were detected using transwell system and MTS. Gene transcription of SIP, S1PR1, S1PR2, S1PR3, and activation of JAK/STAT3 pathway were examined using RT-PCR and western blot assay. S1PR1 over-expressing plasmid was constructed and transfected into cells. Effects of S1PR1 over-expression on migration/proliferation of si-SphK1 transfected colon cancer cells and activation of JAK/STAT3 pathway were determined using RT-PCR and western blotting.

RESULTS

Gene transcription of SphK1 in SW480 and HT-29 colon cancer cells was significantly inhibited by transfection of si-SphK1 gene. Transwell migration and MTS findings showed that si-SphK1 transfection (si-SphK1 group) could reduce migration quantity and cell viability of colon cancer cells compared to negative control (NC) (p<0.0001). SphK1 inhibition (si-SphK1 group) significantly down-regulated S1PR1 and S1PR3 gene transcription in SW480 and HT-29 cells (p<0.0001), and decreased activation level of JAKSTAT3 signaling pathway compared to NC group (p<0.05). Over-expression of S1PR1 reversed inhibitory effects of si-SphK1 on migration/proliferation of SW480 and activation of JAK/Stat3.

CONCLUSION

SphK1 promoted proliferation and migration of colon cancer cells through promoting JAK/STAT activation and up-regulating S1PR1 expression.

Biguanides: Species with versatile therapeutic applications

Biguanides are compounds in which two guanidine moieties are fused to form a highly conjugated system. Biguanides are highly basic and hence they are available as salts mostly hydrochloride salts, these cationic species have been found to exhibit many therapeutic properties. This review covers the research and development carried out on biguanides and accounts the various therapeutic applications of drugs containing biguanide group-such as antimalarial, antidiabetic, antiviral, anticancer, antibacterial, antifungal, anti-tubercular, antifilarial, anti-HIV, as well as other biological activities. The aim of this review is to compile all the medicinal chemistry applications of this class of compounds so as to pave way for the accelerated efforts in finding the drug action mechanisms associated with this class of compounds. Importance has been given to the organic chemistry of these biguanide derivatives also.

Sphingolipids as multifaceted mediators in ovarian cancer

Ovarian cancer is the most lethal gynaecological malignancy. It is commonly diagnosed at advanced stage when it has metastasised to the abdominal cavity and treatment becomes very challenging. While current standard therapy involving debulking surgery and platinum + taxane-based chemotherapy is associated with high response rates initially, the large majority of patients relapse and ultimately succumb to chemotherapy-resistant disease. In order to improve survival novel strategies for early detection and therapeutics against treatment-refractory disease are urgently needed. A promising new target against ovarian cancer is the sphingolipid pathway which is commonly hijacked in cancer to support cell proliferation and survival and has been shown to promote chemoresistance and metastasis in a wide range of malignant neoplasms. In particular, the sphingosine kinase 1-sphingosine 1-phosphate receptor 1 axis has been shown to be altered in ovarian cancer in multiple ways and therefore represents an attractive therapeutic target. Here we review the roles of sphingolipids in ovarian cancer progression, metastasis and chemoresistance, highlighting novel strategies to target this pathway that represent potential avenues to improve patient survival.

The Role of Metformin in Ovarian Cancer: Does Metformin Increase Survival in Ovarian Neoplasm?

The role of metformin in ovarian cancer (OC) remains a topic of research and open discussion. Because OC has a high mortality rate for various reasons, finding a solution is vital. Although metformin has demonstrated a high level of evidence in preventing and increasing survival in other cancers, its role in OC is still not proven. This review highlights the function of metformin as an antineoplastic agent in OC and its effect on overall survival, progress-free survival, and recurrence-free survival. We conducted a literature search in the PubMed database using the medical subject heading keywords, ovarian neoplasm and metformin. The search yielded 94 articles, of which 86 remained after including only English language articles. Finally, 50 articles published between 1997 and 2020 were reviewed. We recommend more randomized controlled trials in the future to determine the safety and efficacy of metformin in OC.

Metformin alleviates inflammation in oxazolone induced ulcerative colitis in rats: plausible role of sphingosine kinase 1/sphingosine 1 phosphate signaling pathway

OBJECTIVES

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that is associated with high sphingosine kinase 1(SPHK1) expression in the colon, however its role in pathogenesis of UC is not clearly understood so, the aim of the present study was to clarify the role of SPHK1 and investigate whether the anti-inflammatory effects of metformin in UC is mediated by Sphingosine kinase 1/sphingosine 1 phosphate (S1P) signaling pathway.

MATERIAL AND METHODS

Colitis was induced in adult male wistar rats by intra rectal administration of oxazolone in the fifth and seventh days from initial presensitization. Oxazolone treated rats were divided into untreated oxazolone group, metformin and mesalazine treated groups both in a dose of 100 mg/kg/day orally for 21 days. Along with these groups normal control and saline groups were used .Colitis was assessed by colon length, disease activity index (DAI) and histological examination of colontissue. Plasma samples were used to measure S1P.SPHK1 activity, signal transducer and activator of transcription -3(STAT-3), interleukin-6 (IL-6), nitric oxide (NO), myeloperoxidase activity (MPO), reduced glutathione (GSH) and tissue expression of intracellular cell adhesion molecule -1(ICAM-1) and caspase-3 genes were measured in tissue.

RESULTS

Metformin successfully attenuated oxazolone colitis by increasing colon length, decreasing DAI and improved colon histologic picture. Metformin also induced a significant decrease in Plasma SIP, SPHK1 activity, inflammatory, oxidative stress markers, ICAM-1 and Caspase-3 genes expression compared to oxazolone group.

CONCLUSION

It is revealed that metformin alleviated inflammation and underlying mechanism may result from inhibition of SPHK1/S1P signaling pathway.

Possible Role of Metformin as an Immune Modulator in the Tumor Microenvironment of Ovarian Cancer

Growing evidence suggests that the immune component of the tumor microenvironment (TME) may be highly involved in the progression of high-grade serous ovarian cancer (HGSOC), as an immunosuppressive TME is associated with worse patient outcomes. Due to the poor prognosis of HGSOC, new therapeutic strategies targeting the TME may provide a potential path forward for preventing disease progression to improve patient survival. One such postulated approach is the repurposing of the type 2 diabetes medication, metformin, which has shown promise in reducing HGSOC tumor progression in retrospective epidemiological analyses and through numerous preclinical studies. Despite its potential utility in treating HGSOC, and that the immune TME is considered as a key factor in the disease’s progression, little data has definitively shown the ability of metformin to target this component of the TME. In this brief review, we provide a summary of the current understanding of the effects of metformin on leukocyte function in ovarian cancer and, coupled with data from other related disease states, posit the potential mechanisms by which the drug may enhance the anti-tumorigenic effects of immune cells to improve HGSOC patient survival.

LncRNA MAFG-AS1 regulates miR-125b-5p/SphK1 axis to promote the proliferation, migration, and invasion of bladder cancer cells

MAFG-AS1 is an oncogenic lncRNA in multiple types of cancer. However, its role in bladder cancer (BC) remains unclear. The present study aimed to investigate the function of MAFG-AS1 in BC. BC and paired non-tumor tissues were collected. Two BC cell lines HT01197 and HT-1376 were used. Dual luciferase activity assay, RT-qPCR, western blot, CCK-8, transwell invasion assay, and wound healing assay were performed. We found that MAFG-AS1 was significantly up-regulated in BC tissues and predicted a poor survival rate. MAFG-AS1 interacted with miR-125b-5p. However, the expression levels of MAFG‑AS1 and miR-125b-5p were not obviously correlated in BC tissues, and MAFG‑AS1 and miR-125b-5p did not regulate the expression of each other. Interestingly, we found that SphK1, a downstream target of miR-125b-5p, was negatively correlated with miR-125b-5p, while it was positively correlated with MAFG-AS1 across BC tissues. In addition, overexpression of MAFG‑AS1 upregulated the expression of SphK1 in BC cells, and attenuated the inhibitory effects of miR-125b-5p on the expression of SphK1. Functional assays showed that overexpression of MAFG‑AS1 promoted BC cell proliferation, migration, and invasion, while its effects were attenuated by overexpression of miR-125b-5p. Moreover, overexpression of miR-125b-5p inhibited BC cell proliferation, migration, and invasion, while its effects were alleviated by overexpression of SphK1. Taken together, our findings demonstrated that MAFG-AS1 has an oncogenic role in BC by regulating the miR-125b-5p/SphK1 axis. MAFG-AS1 might serve as a good diagnostic marker and a potential therapeutic target of BC.

The Tumorigenic Effect of Sphingosine Kinase 1 and Its Potential Therapeutic Target

Sphingosine kinase 1 (SPHK1) regulates cell proliferation and survival by converting sphingosine to the signaling mediator sphingosine 1-phosphate (S1P). SPHK1 is widely overexpressed in most cancers, promoting tumor progression and is associated with clinical prognosis. Numerous studies have explored SPHK1 as a promising target for cancer therapy. However, due to insufficient knowledge of SPHK1 oncogenic mechanisms, its inhibitors’ therapeutic potential in preventing and treating cancer still needs further investigation. In this review, we summarized the metabolic balance regulated by the SPHK1/S1P signaling pathway and highlighted the oncogenic mechanisms of SPHK1 via the upregulation of autophagy, proliferation, and survival, migration, angiogenesis and inflammation, and inhibition of apoptosis. Drug candidates targeting SPHK1 were also discussed at the end. This review provides new insights into the oncogenic effect of SPHK1 and sheds light on the future direction for targeting SPHK1 as cancer therapy.

Recent advances in the role of sphingosine 1-phosphate in cancer

Sphingosine 1-phosphate (S1P) is a bioactive lipid that binds to a family of G protein-coupled receptors (S1P_1-5 ) and intracellular targets, such as HDAC1/2, that are functional in normal and pathophysiologic cell biology. There is a significant role for sphingosine 1-phosphate in cancer underpinning the so-called hallmarks, such as transformation and replicative immortality. In this review, we survey the most recent developments concerning the role of sphingosine 1-phosphate receptors, sphingosine kinase and S1P lyase in cancer and the prognostic indications of these receptors and enzymes in terms of disease-specific survival and recurrence. We also provide evidence for identification of new therapeutic approaches targeting sphingosine 1-phosphate to prevent neovascularisation, to revert aggressive and drug-resistant cancers to more amenable forms sensitive to chemotherapy, and to induce cytotoxicity in cancer cells. Finally, we briefly describe current advances in the development of isoform-specific inhibitors of sphingosine kinases for potential use in the treatment of various cancers, where these enzymes have a predominant role. This review will therefore highlight sphingosine 1-phosphate signalling as a promising translational target for precision medicine in stratified cancer patients.

Mesothelial Cell HIF1α Expression Is Metabolically Downregulated by Metformin to Prevent Oncogenic Tumor-Stromal Crosstalk

The tumor microenvironment (TME) plays a pivotal role in cancer progression, and, in ovarian cancer (OvCa), the primary TME is the omentum. Here, we show that the diabetes drug metformin alters mesothelial cells in the omental microenvironment. Metformin interrupts bidirectional signaling between tumor and mesothelial cells by blocking OvCa cell TGF-β signaling and mesothelial cell production of CCL2 and IL-8. Inhibition of tumor-stromal crosstalk by metformin is caused by the reduced expression of the tricarboxylic acid (TCA) enzyme succinyl CoA ligase (SUCLG2). Through repressing this TCA enzyme and its metabolite, succinate, metformin activated prolyl hydroxylases (PHDs), resulting in the degradation of hypoxia-inducible factor 1α (HIF1α) in mesothelial cells. Disruption of HIF1α-driven IL-8 signaling in mesothelial cells by metformin results in reduced OvCa invasion in an organotypic 3D model. These findings indicate that tumor-promoting signaling between mesothelial and OvCa cells in the TME can be targeted using metformin.

Mechanisms of metformin inhibiting cancer invasion and migration

Cancer currently ranks among the leading causes of death globally. Cancer invasion and metastasis transform locally grown cancers to a systemic and life-threatening disease, which accounts for the most significant challenge in cancer treatment. Recent studies showed that Metformin, the most commonly used first-line oral drug for the treatment of type 2 diabetes (T2DM), could prevent and treat various cancers. Moreover, multiple evidence suggested that metformin inhibited cancer invasion and metastasis, which could improve the prognosis of cancer patients administrated with metformin. To better understand the anti-cancer role of metformin, the present review summarized the potential mechanisms of inhibiting cancer invasion and metastasis by metformin, including AMPK signaling pathway, EMT signaling pathway, epigenetic modification and so on. However, multiple problems remain unresolved and more clinical trials are needed to prove the inhibition of cancer invasion and metastasis by metformin.

Effects of triptolide on the sphingosine kinase - Sphingosine-1-phosphate signaling pathway in colitis-associated colon cancer

BACKGROUNDS

Triptolide (TP) exhibits effective activity against colon cancer in multiple preclinical models, but the mechanisms underlying the observed effects are not fully understood. Sphingosine-1-phosphate (S1P) is a potent bioactive sphingolipid involved in the regulation of colon cancer progression. The aim of this study was to investigate the effect of TP on the sphingosine kinase (SPHK)-S1P signaling pathway in colitis-associated colon cancer.

METHODS

An azoxymethane (AOM)/dextran sulfate sodium (DSS) mouse model and the THP-1 cell line were used to evaluate the therapeutic effects and mechanisms of TP in colitis-associated colon cancer (CACC). Various molecular cell biology experiments, including Western blotting, real-time PCR and immunofluorescence, were used to obtain relevant experimental data. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was also established to detect the levels of S1P in tissue and plasma.

RESULTS

In the AOM/DSS mouse model, TP treatment induced a dose-dependent decrease in tumor incidence and inhibited macrophage recruitment and M2 polarization in the tumors. TP also efficiently decreased the S1P levels and SPHK1/S1PR1/S1PR2 expression and significantly inhibited activation of the S1P-mediated phosphorylation of ERK protein in macrophages.

CONCLUSIONS

The results indicated that TP might influence the recruitment and polarization of tumor-associated macrophages by suppressing the SPHK-S1P signaling pathway.

Follicle-stimulating hormone promotes the proliferation of epithelial ovarian cancer cells by activating sphingosine kinase

Follicle-stimulating hormone (FSH) is closely related to the pathogenesis and progression of epithelial ovarian cancer (EOC). However, until now, knowledge relating to FSH-driven signalling pathways that lead to the growth of EOC remained incomplete. We sought to explore whether sphingosine kinase (SphK) could mediate FSH-induced ovarian cancer cell proliferation and which pathway might be involved in this process. The expression of phospho-SphK1 and phospho-SphK2 was detected in sections of EOC tissues by Immunohistochemical staining, and clinical significances were analyzed by statistical analysis. EOC cells were treated with FSH or/and SKI-II. CCK8 assays and colony formation assays were used to investigate cell proliferation. Western blot was carried out to detect protein expression in EOC cell line after treated with FSH. Here, for the first time, we provide evidence that high expression levels of phospho-SphK1 and phospho-SphK2 were both prognostic indicators of overall survival (OS) in EOC. Additionally, the expression levels of both phospho-SphK1 and phospho-SphK2 were closely correlated with the expression level of follicle-stimulating hormone receptor (FSHR) in ovarian cancer tissues. FSH stimulated the phosphorylation of both SphK1 and SphK2 and was able to regulate the survival and growth of ovarian cancer cells by activating SphK1 and SphK2 through ERK1/2. Both isoenzymes of SphK were equally responsible for FSH-induced cell proliferation of EOC. Both Erk1/2 and Akt activation play important roles in mediating FSH-induced cell proliferation after phosphorylation of SphK. Moreover, our data demonstrated that S1P receptor 1 (S1PR1) and S1PR3, key components of the SphK signalling system, were involved in FSH-mediated proliferation of EOC. Taken together, the results of the current study revealed that SphK is an essential mediator in FSH-induced proliferation of ovarian cancer cells in EOC, which indicates a new signalling pathway that controls FSH-mediated growth in EOC and suggests a new strategy that pharmaceutically targets both isoenzymes of SphK for the management of ovarian cancer.

Metformin Promotes Beclin1-Dependent Autophagy to Inhibit the Progression of Gastric Cancer

Background

Metformin is the first-line blood sugar control drug for type 2 diabetes, but recent epidemiological studies have shown that it inhibits the growth of a variety of tumours. However, few studies have examined metformin effects on gastric cancer (GC), and the anticancer mechanism has not been fully elucidated.

Materials and Methods

We examined the inhibitory effect of metformin on GC cells by cell proliferation, migration and invasion assay. Transmission electron microscopy, confocal microscopy and Western blotting confirmed that metformin enhanced beclin1-dependent autophagy in gastric cancer cells. TCGA database and tissue chip analysis confirmed the differential expression of beclin1 in GC and adjacent tissues. Relevant functional tests verified the role of beclin1 as a tumour suppressor gene in GC. Western blotting, cell proliferation, cell migration and invasion were used to verify that metformin enhances autophagy in GC cells through the AMPK-mTOR signalling pathway. Xenograft tumour models were constructed to explore the inhibitory effect of metformin and the role of beclin1 as a suppressor on GC in vivo.

Results

In this study, we observed that metformin inhibits proliferation, migration and invasion of GC cells. Metformin could also promote beclin1-dependent autophagy in GC cells. We further discovered that beclin1 expression was downregulated in GC and that its low expression was associated with poor prognosis. Beclin1 acts as a tumour suppressor that inhibits the malignant phenotypes of GC cells in vitro and in vivo. Furthermore, we verified that metformin can upregulate beclin1-mediated autophagy to inhibit GC cells through the AMPK-mTOR signalling pathway.

Conclusion

In summary, the results revealed the role of autophagy in metformin inhibition of gastric cancer and suggest that beclin1 may be a potential target for gastric cancer therapy.

Sphk1 participates in malignant progression of breast cancer by regulating epithelial-mesenchymal transition and stem cell characteristics

BACKGROUND

Sphingosine kinase 1 (Sphk1) is abnormally expressed in various tumors. This study explored the effects of Sphk1 in the polarity of breast cancer (BC) epithelial cells and on stem cell characteristics.

MATERIALS & METHODS

Reverse transcription quantitative PCR (RT-qPCR) was performed to detect Sphk1 levels in human mammary epithelial cells (MCF-10A) and BC cell lines (MCF-7, T47D, SKBR3, MDA-MB-231, and BT-474). After Sphk1-overexpression or Sphk1 silencing, the morphology of cells and stem cell-like properties of BC cells were analyzed. Metastasis of BC cells was assessed by wound healing and Transwell assays. Western blotting was performed to detect levels of epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin, N-cadherin and Vimentin) and stem cell-specific markers (SOX2, OCT4, NANOG and ALDH1).

RESULTS

Sphk1 was increased in BC cell lines than MCF-10A. Sphk1 induced EMT, regulated expression of EMT-related proteins, and accelerated the migration and invasion of BC cells. Silencing Sphk1 inhibited the sphere formation and down-regulated the expression of stem cell-specific markers, whereas Sphk1-overexpression contributed to the maintenance of the characteristics of mammary stem cells.

CONCLUSION

Sphk1 induces migration in BC cells and promotes stem cell characteristics by regulating EMT. The current findings provide a new potential for developing targeted therapy for tumor treatment.

Metformin decreases hyaluronan synthesis by vascular smooth muscle cells

Metformin is the first-line drug in the treatment of type 2 diabetes worldwide based on its effectiveness and cardiovascular safety. Currently metformin is increasingly used during pregnancy in women with gestational diabetes mellitus, even if the long-term effects of metformin on offspring are not exactly known. We have previously shown that high glucose concentration increases hyaluronan (HA) production of cultured human vascular smooth muscle cells (VSMC) via stimulating the expression of hyaluronan synthase 2 (HAS2). This offers a potential mechanism whereby hyperglycemia leads to vascular macroangiopathy. In this study, we examined whether gestational metformin use affects HA content in the aortic wall of mouse offspring in vivo. We also examined the effect of metformin on HA synthesis by cultured human VSMCs in vitro. We found that gestational metformin use significantly decreased HA content in the intima-media of mouse offspring aortas. In accordance with this, the synthesis of HA by VSMCs was also significantly decreased in response to treatment with metformin. This decrease in HA synthesis was shown to be due to the reduction of both the expression of HAS2 and the amount of HAS substrates, particularly UDP-N-acetylglucosamine. As shown here, gestational metformin use is capable to program reduced HA content in the vascular wall of the offspring strongly supporting the idea, that metformin possesses long-term vasculoprotective effects.