Sphingosine 1-phosphate and cancer

An inducible sphingosine kinase 1 in hepatic stellate cells potentiates liver fibrosis

Hepatic stellate cells (HSCs) play a role in hepatic fibrosis and sphingosine kinase (SphK) is involved in biological processes. As studies on the regulatory mechanisms and functions of SphK in HSCs during liver fibrosis are currently limited, this study aimed to elucidate the regulatory mechanism and connected pathways of SphK upon HSC activation. The expression of SphK1 was higher in HSCs than in hepatocytes, and upregulated in activated primary HSCs. SphK1 was also increased in liver homogenates of carbon tetrachloride-treated or bile duct ligated mice and in transforming growth factor-β (TGF-β)-treated LX-2 cells. TGF-β-mediated SphK1 induction was due to Smad3 signaling in LX-2 cells. SphK1 modulation altered the expression of liver fibrogenesis-related genes. This SphK1-mediated profibrogenic effect was dependent on SphK1/sphingosine-1-phosphate/sphingosine-1-phosphate receptor signaling through ERK. Epigallocatechin gallate blocked TGF-β-induced SphK1 expression and hepatic fibrogenesis by attenuating Smad and MAPK activation. SphK1 induced by TGF-β facilitates HSC activation and liver fibrogenesis, which is reversed by epigallocatechin gallate. Accordingly, SphK1 and related signal transduction may be utilized to treat liver fibrosis.

The Drug Transporter P-Glycoprotein and Its Impact on Ceramide Metabolism-An Unconventional Ally in Cancer Treatment

The tumor-suppressor sphingolipid ceramide is recognized as a key participant in the cytotoxic mechanism of action of many types of chemotherapy drugs, including anthracyclines, Vinca alkaloids, the podophyllotoxin etoposide, taxanes, and the platinum drug oxaliplatin. These drugs can activate de novo synthesis of ceramide or stimulate the production of ceramide via sphingomyelinases to limit cancer cell survival. On the contrary, dysfunctional sphingolipid metabolism, a prominent factor in cancer survival and therapy resistance, blunts the anticancer properties of ceramide-orchestrated cell death pathways, especially apoptosis. Although P-glycoprotein (P-gp) is famous for its role in chemotherapy resistance, herein, we propose alternate interpretations and discuss the capacity of this multidrug transporter as a "ceramide neutralizer", an unwelcome event, highlighting yet another facet of P-gp's versatility in drug resistance. We introduce sphingolipid metabolism and its dysfunctional regulation in cancer, present a summary of factors that contribute to chemotherapy resistance, explain how P-gp "neutralizes" ceramide by hastening its glycosylation, and consider therapeutic applications of the P-gp-ceramide connection in the treatment of cancer.

The nuclear export protein exportin-1 in solid malignant tumours: From biology to clinical trials

BACKGROUND

Exportin-1 (XPO1), a crucial protein regulating nuclear-cytoplasmic transport, is frequently overexpressed in various cancers, driving tumor progression and drug resistance. This makes XPO1 an attractive therapeutic target. Over the past few decades, the number of available nuclear export-selective inhibitors has been increasing. Only KPT-330 (selinexor) has been successfully used for treating haematological malignancies, and KPT-8602 (eltanexor) has been used for treating haematologic tumours in clinical trials. However, the use of nuclear export-selective inhibitors for the inhibition of XPO1 expression has yet to be thoroughly investigated in clinical studies and therapeutic outcomes for solid tumours.

METHODS

We collected numerous literatures to explain the efficacy of XPO1 Inhibitors in preclinical and clinical studies of a wide range of solid tumours.

RESULTS

In this review, we focus on the nuclear export function of XPO1 and results from clinical trials of its inhibitors in solid malignant tumours. We summarized the mechanism of action and therapeutic potential of XPO1 inhibitors, as well as adverse effects and response biomarkers.

CONCLUSION

XPO1 inhibition has emerged as a promising therapeutic strategy in the fight against cancer, offering a novel approach to targeting tumorigenic processes and overcoming drug resistance. SINE compounds have demonstrated efficacy in a wide range of solid tumours, and ongoing research is focused on optimizing their use, identifying response biomarkers, and developing effective combination therapies.

KEY POINTS

Exportin-1 (XPO1) plays a critical role in mediating nucleocytoplasmic transport and cell cycle. XPO1 dysfunction promotes tumourigenesis and drug resistance within solid tumours. The therapeutic potential and ongoing researches on XPO1 inhibitors in the treatment of solid tumours. Additional researches are essential to address safety concerns and identify biomarkers for predicting patient response to XPO1 inhibitors.

Expression and prognostic role of sphingosine 1-phosphate receptor 4 (S1PR4) as a biomarker of skin cutaneous melanoma

Background

Skin cutaneous melanoma (SKCM) is one of the most lethal skin malignancies worldwide. Sphingosine 1-phosphate (S1P) regulates tumor cells through S1P receptors (S1PRs). Unlike S1PR1/2/3/5, whose anti-apoptotic effects have been widely studied, the regulatory effect of S1PR4 on tumors has not been studied extensively. In this study, we aimed to investigate the correlation between S1PR4 expression and survival, clinical manifestations, tumor microenvironment, and immune infiltration in patients with SKCM.

Results

Low S1PR4 expression was associated with poor prognosis in patients with SKCM. Patients in the high-expression group had significantly longer disease survival and progression-free survival than those in the low-expression group.

Conclusion

High S1PR4 expression was highly associated with better prognosis and milder clinical manifestations; thus, S1PR4 may be used as a prognostic marker to help physicians monitor patients with SKCM.

Solid tumor treatment via augmentation of bioactive C6 ceramide levels with thermally ablative focused ultrasound

Sparse scan partial thermal ablation (TA) with focused ultrasound (FUS) may be deployed to treat solid tumors and increase delivery of systemically administered therapeutics. Furthermore, C6-ceramide-loaded nanoliposomes (CNLs), which rely upon the enhanced-permeation and retention (EPR) effect for delivery, have shown promise for treating solid tumors and are being tested in clinical trials. Here, our objective was to determine whether CNLs synergize with TA in the control of 4T1 breast tumors. CNL monotherapy of 4T1 tumors yielded significant intratumoral bioactive C6 accumulation by the EPR effect, but tumor growth was not controlled. TA increased bioactive C6 accumulation by ~ 12.5-fold over the EPR effect. In addition, TA + CNL caused shifts in long-chain to very-long-chain ceramide ratios (i.e., C16/24 and C18/C24) that could potentially contribute to tumor control. Nonetheless, these changes in intratumoral ceramide levels were still insufficient to confer tumor growth control beyond that achieved when combining with TA with control "ghost" nanoliposomes (GNL). While this lack of synergy could be due to increased "pro-tumor" sphingosine-1-phosphate (S1P) levels, this is unlikely because S1P levels exhibited only a moderate and statistically insignificant increase with TA + CNL. In vitro studies showed that 4T1 cells are highly resistant to C6, offering the most likely explanation for the inability of TA to synergize with CNL. Thus, while our results show that sparse scan TA is a powerful approach for markedly enhancing CNL delivery and generating "anti-tumor" shifts in long-chain to very-long-chain ceramide ratios, resistance of the tumor to C6 can still be a rate-limiting factor for some solid tumor types.

Lipid-lowering drugs affect lung cancer risk via sphingolipid metabolism: a drug-target Mendelian randomization study

Background: The causal relationship between lipid-lowering drug (LLD) use and lung cancer risk is controversial, and the role of sphingolipid metabolism in this effect remains unclear. Methods: Genome-wide association study data on low-density lipoprotein (LDL), apolipoprotein B (ApoB), and triglycerides (TG) were used to develop genetic instrumental variables (IVs) for LLDs. Two-step Mendelian randomization analyses were performed to examine the causal relationship between LLDs and lung cancer risk. The effects of ceramide, sphingosine-1-phosphate (S1P), and ceramidases on lung cancer risk were explored, and the proportions of the effects of LLDs on lung cancer risk mediated by sphingolipid metabolism were calculated. Results: APOB inhibition decreased the lung cancer risk in ever-smokers via ApoB (odds ratio [OR] 0.81, 95% confidence interval [CI] 0.70-0.92, p = 0.010), LDL (OR 0.82, 95% CI 0.71-0.96, p = 0.040), and TG (OR 0.63, 95% CI 0.46-0.83, p = 0.015) reduction by 1 standard deviation (SD), decreased small-cell lung cancer (SCLC) risk via LDL reduction by 1 SD (OR 0.71, 95% CI 0.56-0.90, p = 0.016), and decreased the plasma ceramide level and increased the neutral ceramidase level. APOC3 inhibition decreased the lung adenocarcinoma (LUAD) risk (OR 0.60, 95% CI 0.43-0.84, p = 0.039) but increased SCLC risk (OR 2.18, 95% CI 1.17-4.09, p = 0.029) via ApoB reduction by 1 SD. HMGCR inhibition increased SCLC risk via ApoB reduction by 1 SD (OR 3.04, 95% CI 1.38-6.70, p = 0.014). The LPL agonist decreased SCLC risk via ApoB (OR 0.20, 95% CI 0.07-0.58, p = 0.012) and TG reduction (OR 0.58, 95% CI 0.43-0.77, p = 0.003) while increased the plasma S1P level. PCSK9 inhibition decreased the ceramide level. Neutral ceramidase mediated 8.1% and 9.5% of the reduced lung cancer risk in ever-smokers via ApoB and TG reduction by APOB inhibition, respectively, and mediated 8.7% of the reduced LUAD risk via ApoB reduction by APOC3 inhibition. Conclusion: We elucidated the intricate interplay between LLDs, sphingolipid metabolites, and lung cancer risk. Associations of APOB, APOC3, and HMGCR inhibition and LPL agonist with distinct lung cancer risks underscore the multifaceted nature of these relationships. The observed mediation effects highlight the considerable influence of neutral ceramidase on the lung cancer risk reduction achieved by APOB and APOC3 inhibition.

Role of Leptin and Adiponectin in Carcinogenesis

Hormones produced by adipocytes, leptin and adiponectin, are associated with the process of carcinogenesis. Both of these adipokines have well-proven oncologic potential and can affect many aspects of tumorigenesis, from initiation and primary tumor growth to metastatic progression. Involvement in the formation of cancer includes interactions with the tumor microenvironment and its components, such as tumor-associated macrophages, cancer-associated fibroblasts, extracellular matrix and matrix metalloproteinases. Furthermore, these adipokines participate in the epithelial-mesenchymal transition and connect to angiogenesis, which is critical for cancer invasiveness and cancer cell migration. In addition, an enormous amount of evidence has demonstrated that altered concentrations of these adipocyte-derived hormones and the expression of their receptors in tumors are associated with poor prognosis in various types of cancer. Therefore, leptin and adiponectin dysfunction play a prominent role in cancer and impact tumor invasion and metastasis in different ways. This review clearly and comprehensively summarizes the recent findings and presents the role of leptin and adiponectin in cancer initiation, promotion and progression, focusing on associations with the tumor microenvironment and its components as well as roles in the epithelial-mesenchymal transition and angiogenesis.

Rational targeting of autophagy in colorectal cancer therapy: From molecular interactions to pharmacological compounds

The abnormal progression of tumors has been a problem for treatment of cancer and therapeutic should be directed towards targeting main mechanisms involved in tumorigenesis in tumors. The genomic mutations can result in changes in biological mechanisms in human cancers. Colorectal cancer is one of the most malignant tumors of gastrointestinal tract and its treatment has been faced some difficulties due to development of resistance in tumor cells and also, their malignant behavior. Hence, new therapeutic modalities for colorectal cancer are being investigated. Autophagy is a "self-digestion" mechanism that is responsible for homeostasis preserving in cells and its aberrant activation/inhibition can lead to tumorigenesis. The current review focuses on the role of autophagy mechanism in colorectal cancer. Autophagy may be associated with increase/decrease in progression of colorectal cancer due to mutual function of this molecular mechanism. Pro-survival autophagy inhibits apoptosis to increase proliferation and survival rate of colorectal tumor cells and it is also involved in cancer metastasis maybe due to EMT induction. In contrast, pro-death autophagy decreases growth and invasion of colorectal tumor cells. The status of autophagy (upregulation and down-regulation) is a determining factor for therapy response in colorectal tumor cells. Therefore, targeting autophagy can increase sensitivity of colorectal tumor cells to chemotherapy and radiotherapy. Interestingly, nanoparticles can be employed for targeting autophagy in cancer therapy and they can both induce/suppress autophagy in tumor cells. Furthermore, autophagy modulators can be embedded in nanostructures in improving tumor suppression and providing cancer immunotherapy.

Solid Tumor Treatment via Augmentation of Bioactive C6 Ceramide Levels with Thermally Ablative Focused Ultrasound

Sparse scan partial thermal ablation (TA) with focused ultrasound (FUS) may be deployed to treat solid tumors and increase delivery of systemically administered therapeutics. Further, C6-ceramide-loaded nanoliposomes (CNLs), which rely upon the enhanced permeation and retention (EPR) effect for delivery, have shown promise for treating solid tumors and are being tested in clinical trials. Here, our objective was to determine whether CNLs synergize with TA in the control of 4T1 breast tumors. CNL-monotherapy of 4T1 tumors yielded significant intratumoral bioactive C6 accumulation by the EPR effect, but tumor growth was not controlled. TA increased bioactive C6 accumulation by ∼12.5-fold over the EPR effect. In addition, TA+CNL caused shifts in long-chain to very-long-chain ceramide ratios (i.e., C16/24 and C18/C24) that could potentially contribute to tumor control. Nonetheless, these changes in intratumoral ceramide levels were still insufficient to confer tumor growth control beyond that achieved when combining with TA with control "ghost" nanoliposomes (GNL). While this lack of synergy could be due to increased "pro-tumor" sphingosine-1-phosphate (S1P) levels, this is unlikely because S1P levels exhibited only a moderate and statistically insignificant increase with TA+CNL. In vitro studies showed that 4T1 cells are highly resistant to C6, offering the most likely explanation for the inability of TA to synergize with CNL. Thus, while our results show that sparse scan TA is a powerful approach for markedly enhancing CNL delivery and generating "anti-tumor" shifts in long-chain to very-long-chain ceramide ratios, resistance of the tumor to C6 can still be a rate-limiting factor for some solid tumor types.

Multiomics Analysis Reveals Cuproptosis-Related Signature for Evaluating Prognosis and Immunotherapy Efficacy in Colorectal Cancer

Cuproptosis is a copper-induced form of mitochondrial cell death which is engaged in the proliferation and migration of a variety of tumors. Nevertheless, the role of cuproptosis in tumor microenvironment (TME) remodeling and antitumor therapy is still poorly understood. We characterized two diverse cuproptosis-associated molecular isoforms in CRC which exhibit distinct prognostic and TME characteristics. Subsequently, we constructed a cuproptosis-associated prognostic model containing five genes and divided the patients into a high CPS-score group and a low CPS-score group. Univariate and multivariate Cox analyses showed that the CPS score could be used as an independent prognostic factor. The nomogram, and its consequent calibration curves, indicated that this prognostic signature had good predictive power for CRC. The analysis of single-cell sequencing data showed the significant expression of HES4 and SPHK1 in various immune and stromal (including fibroblasts) cells. Further studies showed that tumor mutational burden (TMB), high microsatellite instability (MSI-H) ratio, immune checkpoint blockade (ICB), and human leukocyte antigen (HLA) gene expression all positively correlated with the CPS score, predicting a better reaction to immunotherapy in high CPS-core patients. The CPS score constructed from cuproptosis subtypes can be used as a predictive tool to evaluate the prognosis of CRC patients and their response to immunotherapy.

Down-regulation of S1PR2 is correlated with poor prognosis and immune infiltrates in cervical squamous cell carcinoma and endocervical adenocarcinoma

Objectives: Cervical squamous cell carcinoma and cervical adenocarcinoma (CESC) are the second leading cause of deaths from malignant tumors in women, while their therapeutic and diagnostic aims are still finited. A growing body of evidence indicated that sphingosine-1-phosphate receptor 2 (S1PR2) plays essential roles in the occurrence and development about several human cancers. Nevertheless, the key mechanism and role mechanism of S1PR2 in CESC are still unclear.Methods: We first used Tissue Expression (GTEx) and Genotypic Cancer Genome Atlas (TCGA) data to perform pan-cancer analysis on the expression and prognosis of S1PR2, and found that S1PR2 may have a potential impact on CESC. To generate a protein-protein interaction (PPI) network using the STRING database. The clusterProfiler package is used for feature-rich analysis. The Tumor IMmune Estimation Resource was used to determine the connection between S1PR2 mRNA expression and immune infiltrates. Results: S1PR2 expression in CESC tissues was down-regulated compared with adjacent normal tissues. Kaplan-Meier analysis indicated that compared with patients with high expression of S1PR2, CESC patients with low S1PR2 expression had a worse prognosis. Reduced S1PR2 expression is associated with patients with high clinical stage, more histological types of squamous cell carcinoma, and poor primary treatment outcomes. The receiver operating characteristic curve of S1PR2 was 0.870. Correlation analysis showed that the mRNA expression of S1PR2 was related to immune infiltrates and tumor purity.Conclusion: Down-regulated S1PR2 expression is related to poor survival and immune infiltration in CESC. S1PR2 is a potential biomarker for poor prognosis and as a potential target for CESC immune therapy.

Expression Profile of Sphingosine Kinase 1 Isoforms in Human Cancer Tissues and Cells: Importance and Clinical Relevance of the Neglected 1b-Isoform

Background

Overexpression of sphingosine kinase 1 (SphK1) is casually associated with many types of cancer, and inhibitors of SphK1 sensitize tumors to chemotherapy. SphK1 is expressed as two major isoforms, SphK1a and SphK1b. To date, no information has been reported on the SphK1 isoform expression profile and its clinical relevance.

Objective

The objective is to examine the expression profile of the SphK1a and SPhK1b isoforms in human cancer and noncancer tissues and cell lines and explore their clinical relevance.

Methods

We used PCR to qualitatively examine the expression profile of these two isoforms in breast, liver, and prostate cancer tissues plus paired adjacent tissues and in 11 cancer and normal cell lines (breast, cervical, bone, prostate, colon, brain, mesothelioma tumor and benign, and human kidney cells).

Results

We found that SphK1a was ubiquitously expressed in all cancer cells and tissues tested; in contrast, SphK1b was only expressed in selective cell types in breast, prostate, and lung cancer.

Conclusions

Our data suggest that SphK1a is important for generic SphK1/S1P functions, and SphK1b mediates specialized and/or unique pathways in a specific type of tissue and could be a biomarker for cancer. This discovery is important for future SphK1-related cancer research and may have clinical implications in drug development associated with SphK1-directed cancer treatment.

Suppression of Calcium Entry Modulates the Expression of TRβ1 and Runx2 in Thyroid Cancer Cells, Two Transcription Factors That Regulate Invasion, Proliferation and Thyroid-Specific Protein Levels

The thyroid hormone receptor beta 1 (TRβ1) is downregulated in several human cancer cell types, which has been associated with development of an aggressive tumor phenotype and the upregulation of Runt-related transcription factor 2 (Runx2). In this study, we show that the expression of TRβ1 protein is downregulated in human thyroid cancer tissues and cell lines compared with the normal thyroid tissues and primary cell line, whilst Runx2 is upregulated under the same conditions. In contrast, the expression of TRβ1 is upregulated, whereas Runx2 is downregulated, in STIM1, Orai1 and TRPC1 knockdown cells, compared to mock transfected cells. To study the functional significance of Runx2 in follicular thyroid cancer ML-1 cells, we downregulated it by siRNA. This increased store-operated calcium entry (SOCE), but decreased cell proliferation and invasion. Moreover, restoring TRβ1 expression in ML-1 cells decreased SOCE, basal and sphingosine 1-phosphate (S1P)-evoked invasion, the expression of the promigratory S1P3 receptor and pERK1/2, and at the same time increased the expression of the thyroid specific proteins thyroglobulin, thyroperoxidase, and thyroid transcription factor-1. In conclusion, we show that TRβ1 is downregulated in thyroid cancer cells and that restoration of its expression can reverse the cancer cell phenotype towards a normal thyroid cell phenotype.

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.

Harnessing the power of sphingolipids: Prospects for acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive, heterogenous malignancy characterized by clonal expansion of bone marrow-derived myeloid progenitor cells. While our current understanding of the molecular and genomic landscape of AML has evolved dramatically and opened avenues for molecularly targeted therapeutics to improve upon standard intensive induction chemotherapy, curative treatments are elusive, particularly in older patients. Responses to current AML treatments are transient and incomplete, necessitating the development of novel treatment strategies to improve outcomes. To this end, harnessing the power of bioactive sphingolipids to treat cancer shows great promise. Sphingolipids are involved in many hallmarks of cancer of paramount importance in AML. Leukemic blast survival is influenced by cellular levels of ceramide, a bona fide pro-death molecule, and its conversion to signaling molecules such as sphingosine-1-phosphate and glycosphingolipids. Preclinical studies demonstrate the efficacy of therapeutics that target dysregulated sphingolipid metabolism as well as their combinatorial synergy with clinically-relevant therapeutics. Thus, increased understanding of sphingolipid dysregulation may be exploited to improve AML patient care and outcomes. This review summarizes the current knowledge of dysregulated sphingolipid metabolism in AML, evaluates how pro-survival sphingolipids promote AML pathogenesis, and discusses the therapeutic potential of targeting these dysregulated sphingolipid pathways.

Posttranslational control of lipogenesis in the tumor microenvironment

Metabolic reprogramming of cancer cells within the tumor microenvironment typically occurs in response to increased nutritional, translation and proliferative demands. Altered lipid metabolism is a marker of tumor progression that is frequently observed in aggressive tumors with poor prognosis. Underlying these abnormal metabolic behaviors are posttranslational modifications (PTMs) of lipid metabolism-related enzymes and other factors that can impact their activity and/or subcellular localization. This review focuses on the roles of these PTMs and specifically on how they permit the re-wiring of cancer lipid metabolism, particularly within the context of the tumor microenvironment.

Reprogramming lipid metabolism as potential strategy for hematological malignancy therapy

Hematological malignancies are one of the most lethal illnesses that seriously threaten human life and health. Lipids are important constituents of various biological membranes and substances for energy storage and cell signaling. Furthermore, lipids are critical in the normal physiological activities of cells. In the process of the lethal transformation of hematological malignancies, lipid metabolism reprogramming meets the material and energy requirements of rapidly proliferating and dividing tumor cells. A large number of studies have shown that dysregulated lipid metabolism, commonly occurs in hematological malignancies, mediating the proliferation, growth, migration, invasion, apoptosis, drug resistance and immune escape of tumor cells. Targeting the lipid metabolism pathway of hematological malignancies has become an effective therapeutic approach. This article reviews the oncogenic mechanisms of lipid metabolism reprogramming in hematological malignancies, including fatty acid, cholesterol and phospholipid metabolism, thereby offering an insight into targeting lipid metabolism in the treatment of hematological malignancies.

Autophagy: A Versatile Player in the Progression of Colorectal Cancer and Drug Resistance

Colorectal cancer (CRC) is among the topmost malignancies for both genders. Despite the high incidence rate and advances in diagnostic tools, treatment in many cases is still ineffective. Most cancerous lesions in CRC begin as benign, followed by the development of invasive forms and metastases. The development of CRC has been linked to defects in autophagy, which plays both a pro-and anti-tumor role and is mainly context-dependent. Autophagy suppression could enhance apoptosis via p53 activation, or autophagy also promotes tumor progression by maintaining tumor growth and increasing resistance to chemotherapy. Autophagy promotes the invasion and metastasis of CRC cells via increased epithelial-mesenchymal transition (EMT). Moreover, dysbiosis of gut microbiota upregulated autophagy and metastasis markers. Autophagy responses may also modulate the tumor microenvironment (TME) via regulating the differentiation process of several innate immune cells. Treatments that promote tumor cell death by stimulating or inhibiting autophagy could be beneficial if used as an adjunct treatment, but the precise role of various autophagy-modulating drugs in CRC patients is needed to be explored. In this article, we present an overview of the autophagy process and its role in the pathogenesis and therapeutic resistance of CRC. Also, we focused on the current understanding of the role of the EMT and TME, including its relation to gut microbiota and immune cells, in autophagic manipulation of CRC. We believe that there is a potential link between autophagy, TME, EMT, and drug resistance, suggesting that further studies are needed to explore this aspect.

Involvement of Ceramide Signalling in Radiation-Induced Tumour Vascular Effects and Vascular-Targeted Therapy

Sphingolipids are well-recognized critical components in several biological processes. Ceramides constitute a class of sphingolipid metabolites that are involved in important signal transduction pathways that play key roles in determining the fate of cells to survive or die. Ceramide accumulated in cells causes apoptosis; however, ceramide metabolized to sphingosine promotes cell survival and angiogenesis. Studies suggest that vascular-targeted therapies increase endothelial cell ceramide resulting in apoptosis that leads to tumour cure. Specifically, ultrasound-stimulated microbubbles (USMB) used as vascular disrupting agents can perturb endothelial cells, eliciting acid sphingomyelinase (ASMase) activation accompanied by ceramide release. This phenomenon results in endothelial cell death and vascular collapse and is synergistic with other antitumour treatments such as radiation. In contrast, blocking the generation of ceramide using multiple approaches, including the conversion of ceramide to sphingosine-1-phosphate (S1P), abrogates this process. The ceramide-based cell survival "rheostat" between these opposing signalling metabolites is essential in the mechanotransductive vascular targeting following USMB treatment. In this review, we aim to summarize the past and latest findings on ceramide-based vascular-targeted strategies, including novel mechanotransductive methodologies.

Geniposide alleviates VEGF-induced angiogenesis by inhibiting VEGFR2/PKC/ERK1/2-mediated SphK1 translocation

BACKGROUND

Rheumatoid arthritis (RA) is an angiogenesis-dependent disease caused by the imbalance of pro- and anti-angiogenic factors. More effective strategies to block synovial angiogenesis in RA should be studied. Geniposide (GE), a natural product isolated from the fruit of Gardenia jasminoides Ellis (GJ), is reported to have anti-inflammatory, anti-angiogenic and other pharmacological effects. However, the underlying mechanism through which GE affects synovial angiogenesis in RA remains unclear.

PURPOSE

In this research, we aimed to elucidate the effect and potential mechanisms of GE on angiogenesis in RA.

MATERIALS AND METHODS

Synovial angiogenesis in patients with RA and a rat model of adjuvant arthritis (AA) was detected by hematoxylin and eosin (HE) staining, immunohistochemistry (IHC), and western blottiing. The biological functions of vascular endothelial cells (VECs) and sphingosine kinase 1 (SphK1) translocation were checked by CCK-8, EdU, Transwell, tube formation, co-immunoprecipitation assays, and laser scanning confocal microscopy. The effect of the SphK1 gene on angiogenesis was assessed by transfection of SphK1-siRNA in cells and mices. The effect of GE on VEGF-induced angiogenesis was measured by Matrigel plug assay in a mouse model of AA.

RESULTS

GE effectively inhibited synovial angiogenesis and alleviated the disease process. SphK1, as a new regulatory molecule, has a potentially important relationship in regulating VEGF/VEGFR2 and S1P/S1PR1 signals. SphK1 translocation was activated via the VEGFR2/PKC/ERK1/2 pathway and was closely linked to the biological function of VECs. GE significantly reduced SphK1 translocation, thereby ameliorating the abnormal biological function of VECs. Furthermore, after transfection of SphK1 siRNA in VECs and C57BL/6 mice, silencing SphK1 caused effectively attenuation of VEGF-induced VEC biological functions and angiogenesis. In vivo, the Matrigel plug experiment indicated that GE significantly inhibited pericyte coverage, basement membrane formation, vascular permeability, and fibrinogen deposition.

CONCLUSIONS

Our findings suggest that GE inhibited VEGF-induced VEC biological functions and angiogenesis by reducing SphK1 translocation. Generally, studies have revealed that GE down-regulated VEGFR2/PKC/ERK1/2-mediated SphK1 translocation and inhibited S1P/S1PR1 signaling activation, thereby alleviating VEGF-stimulated angiogenesis. The above evidences indicated that angiogenesis inhibition may provide a new direction for RA treatment.

Sphingosine-1-phosphate in mitochondrial function and metabolic diseases

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite. The past decade has witnessed exponential growth in the field of S1P research, partly attributed to drugs targeting its receptors or kinases. Accumulating evidence indicates that changes in the S1P axis (i.e., S1P production, transport, and receptors) may modify metabolism and eventually mediate metabolic diseases. Dysfunction of the mitochondria on a master monitor of cellular metabolism is considered the leading cause of metabolic diseases, with aberrations typically induced by abnormal biogenesis, respiratory chain complex disorders, reactive oxygen species overproduction, calcium deposition, and mitophagy impairment. Accordingly, we discuss decades of investigation into changes in the S1P axis and how it controls mitochondrial function. Furthermore, we summarize recent scientific advances in disorders associated with the S1P axis and their involvement in the pathogenesis of metabolic diseases in humans, including type 2 diabetes mellitus and cardiovascular disease, from the perspective of mitochondrial function. Finally, we review potential challenges and prospects for S1P axis application to the regulation of mitochondrial function and metabolic diseases; these data may provide theoretical guidance for the treatment of metabolic diseases.

Splicing deregulation, microRNA and Notch aberrations: fighting the three-headed dog to overcome drug resistance in malignant mesothelioma

INTRODUCTION

Malignant mesothelioma (MMe) is an aggressive rare cancer of the mesothelium, associated with asbestos exposure. MMe is currently an incurable disease at all stages mainly due to resistance to treatments. It is therefore necessary to elucidate key mechanisms underlying chemoresistance, in an effort to exploit them as novel therapeutic targets.

AREAS COVERED

Chemoresistance is frequently elicited by microRNA (miRNA) alterations and splicing deregulations. Indeed, several miRNAs, such as miR-29c, have been shown to exert oncogenic or oncosuppressive activity. Alterations in the splicing machinery might also be involved in chemoresistance. Moreover, the Notch signaling pathway, often deregulated in MMe, plays a key role in cancer stem cells formation and self-renewal, leading to drug resistance and relapses.

EXPERT OPINION

The prognosis of MMe in patients varies among different tumors and patient characteristics, and novel biomarkers and therapies are warranted. This work aims at giving an overview of MMe, with a special focus on state-of-the-art treatments and new therapeutic strategies against vulnerabilities emerging from studies on epigenetics factors. Besides, this review is also the first to discuss the interplay between miRNAs and alternative splicing as well as the role of Notch as new promising frontiers to overcome drug resistance in MMe.

Upregulated flotillins and sphingosine kinase 2 derail AXL vesicular traffic to promote epithelial-mesenchymal transition

Altered endocytosis and vesicular trafficking are major players during tumorigenesis. Flotillin overexpression, a feature observed in many invasive tumors and identified as a marker of poor prognosis, induces a deregulated endocytic and trafficking pathway called upregulated flotillin-induced trafficking (UFIT). Here, we found that in non-tumoral mammary epithelial cells, induction of the UFIT pathway promotes epithelial-to-mesenchymal transition (EMT) and accelerates the endocytosis of several transmembrane receptors, including AXL, in flotillin-positive late endosomes. AXL overexpression, frequently observed in cancer cells, is linked to EMT and metastasis formation. In flotillin-overexpressing non-tumoral mammary epithelial cells and in invasive breast carcinoma cells, we found that the UFIT pathway-mediated AXL endocytosis allows its stabilization and depends on sphingosine kinase 2, a lipid kinase recruited in flotillin-rich plasma membrane domains and endosomes. Thus, the deregulation of vesicular trafficking following flotillin upregulation, and through sphingosine kinase 2, emerges as a new mechanism of AXL overexpression and EMT-inducing signaling pathway activation.

NF-κB and EGFR participate in S1PR3-mediated human renal cell carcinomas progression

The bioactive lipid sphingosine 1-phosphate (S1P) is implicated in many pivotal processes for the physiological and pathological actions via activating five types of G-protein-coupled S1P receptors (S1PR1-5). The role of S1P in renal cell carcinoma (RCC) and its receptor subtype specific mediating mechanism are poorly studied. So we focus on the regulatory role of S1P in RCC progression and the receptor subtypes involved in S1P-induced actions, intending to further clarify a novel therapeutic target for RCC. Analysis of The Cancer Genome Atlas (TCGA) databases showed that the patients with high expression of S1PR3 had significantly worse overall than with low expression. We further demonstrated that S1P could promote proliferation, migration, and epithelial-mesenchymal transition (EMT) of renal cancer cells in vitro, and the actions were enhanced with the increase of S1PR3 expression. Meanwhile, the results in animal experiments also showed that S1PR3 could accelerate tumorigenesis and metastasis of RCC. Our study also clarified the mechanism for S1P induced cell proliferation is mediated by S1PR3/Gi/p38/Akt/p65/cyclin D1-CDK4 pathway and the main pathway for migration is S1PR3/Gi/q/ERK/p38/p65. In addition, S1PR3 was involved in epidermal growth factor (EGF)-induced actions by enhancing protein expression, not by transactivation of epidermal growth factor receptor (EGFR). These results also further supported our conclusion that the carcinogenic role of S1P/S1PR3 axis. Thus, our findings provide that S1PR3 may be a promising small molecular therapeutic target for S1PR3 expressed cancers.

Potential of a sphingosine 1‑phosphate receptor antagonist and sphingosine kinase inhibitors as targets for multiple myeloma treatment

Sphingosine 1-phosphate (S1P) is a bioactive lipid involved in cancer progression through its binding to S1P receptors (S1PRs). However, the association between multiple myeloma (MM) and S1P is unclear. The current study aimed to investigate the potential anti-cancer effects of fingolimod and sphingosine kinase (SK) inhibitors in myeloma cells and the effects of S1P-induced chemoresistance and neovascularization on MM cell proliferation. MM cell lines were treated with the S1PR1 antagonist fingolimod and the SK inhibitors ABC294640 and SK1-I, after which cell proliferation was measured. Protein expression was also assessed under each condition using immunoblotting. Serum S1P levels in patients with MM, monoclonal gammopathy of undetermined significance and healthy volunteers were assessed. Human umbilical vessel cells (HUVECs) were co-cultured with anti-S1P agents to assess the effect on cell migration. All treatments suppressed myeloma cell proliferation and caspase-3-mediated apoptosis by suppressing S1P activity. These findings suggest that S1P activation is associated with proliferation and survival for MM cells. S1P attenuated the proteosome inhibitor (PI) effect, while the anti-S1P agents recovered the effect. In addition, S1P promoted the migration and proliferation of HUVECs, whereas the S1P inhibitors reduced the influence of S1P. This study highlights the therapeutic potential of anti-S1P agents for MM treatment. Inhibition of S1P function may overcome resistance to PI developed by myeloma cells and inhibit the changes to the bone marrow microenvironment via neovascularization.

The role of isoflavones in augmenting the effects of radiotherapy

Cancer is one of the major health problems and the second cause of death worldwide behind heart disease. The traditional soy diet containing isoflavones, consumed by the Asian population in China and Japan has been identified as a protective factor from hormone-related cancers. Over the years the research focus has shifted from emphasizing the preventive effect of isoflavones from cancer initiation and promotion to their efficacy against established tumors along with chemo- and radiopotentiating effects. Studies performed in mouse models and results of clinical trials emphasize that genistein or a mixture of isoflavones, containing in traditional soy diet, could be utilized to both potentiate the response of cancer cells to radiotherapy and reduce radiation-induced toxicity in normal tissues. Currently ongoing clinical research explores a potential of another significant isoflavone, idronoxil, also known as phenoxodiol, as radiation enhancing agent. In the light of the recent clinical findings, this article reviews the accumulated evidence which support the clinically desirable interactions of soy isoflavones with radiation therapy resulting in improved tumor treatment. This review discusses important aspects of the development of isoflavones as anticancer agents, and mechanisms potentially relevant to their activity in combination with radiation therapy of cancer. It gives a critical overview of studies characterizing isoflavone targets such as topoisomerases, ENOX2/PMET, tyrosine kinases and ER receptor signaling, and cellular effects on the cell cycle, DNA damage, cell death, and immune responses.

S1P/S1P2 Signaling Axis Regulates Both NLRP3 Upregulation and NLRP3 Inflammasome Activation in Macrophages Primed with Lipopolysaccharide

The activation of NLRP3 inflammasome is a key factor for various inflammatory diseases. Here, we provide experimental evidence supporting the regulatory role of sphingosine-1-phosphate (S1P) in NLRP3 inflammasome activation in mouse bone-marrow-derived macrophages (BMDMs), along with the S1P receptor subtype involved and underlying regulatory mechanisms. During the priming stage, S1P induced NLRP3 upregulation in BMDMs only when primed with lipopolysaccharide (LPS). In this event, S1P₂, but not S1P₁, was involved based on the attenuated NLRP3 upregulation with JTE013 (S1P₂ antagonist) or S1P₂ knockdown. During the activation stage, S1P induced NLRP3 inflammasome activation in LPS-primed BMDMs via caspase-1 activation, interleukin 1β maturation, apoptosis-associated speck-like protein containing a CARD (ASC) speck formation, and IL-1β secretion. Such NLRP3 inflammasome activation was blocked by either pharmacological inhibition or genetic knockdown of S1P₂. NF-κB, PI3K/Akt, and ERK1/2 were identified as effector pathways underlying S1P/S1P₂ signaling in the regulation of NLRP3 upregulation in LPS-primed BMDMs. Further, reactive oxygen species (ROS) production was dependent on the S1P/S1P₂ signaling axis in these cells, and the ROS generated regulate NLRP3 inflammasome activation, but not NLRP3 priming. Collectively, our findings suggest that S1P promotes NLRP3 upregulation and NLRP3 inflammasome activation in LPS-primed BMDMs via S1P₂ and subsequent effector pathways.

Profile of sphingolipid-related genes and its association with prognosis highlights sphingolipid metabolism in oral cancer

BACKGROUND

Sphingolipids are bioactive lipids that play a role in cancer development. However, the clinical role of sphingolipid (SPL)-related genes in oral cancer (OC) remains not fully understood.

OBJECTIVE

This study, aimed to examine the mRNA expression of 14 sphingolipid-related genes in oral cancer patients and their implication with clinicopathological features and prognosis.

METHODS

qPCR analysis was performed in 50 OC tissues and their matched surgical margins. Next, Kaplan-Meier, Cox regression, and Receiver operating characteristics (ROC) analysis were applied to evaluate the impact of sphingolipid-related genes expression on the prognosis of OC.

RESULTS

The genes SET, ACER3, SK1 and S1PR5 were predominantly up-regulated, while ABCG2, S1PR1, ABCB1 and SPNS2 were down-regulated in OC patients. Analyzing the Cancer Genome Atlas Head-Neck Squamous Cell Carcinoma (TCGA-HNSC) data, which are predominantly composed of OC samples, these genes displayed a similar profile. In OC patients, high levels of SK1 were associated with lymph node metastasis, extracapsular invasion, desmoplasia, locoregional relapse, and disease status. Low levels of SPNS2 were associated with lymph node metastasis, perineural invasion, and disease status. Furthermore, OC and HNSC patients with higher SK1 expression demonstrated shorter disease-free survival (p= 0.0037; p= 0.0087), whereas those with lower SPNS2 expression exhibited shorter overall survival (p= 0.051; p= 0.0012). High levels of ACER3 and low levels of S1PR1 were associated with shorter disease-free and overall survival in HNSC patients.

CONCLUSION

Several sphingolipid-related genes are deregulated in OC at the mRNA level and are associated with clinicopathological features and presented potencial for the prediction of poor prognosis in OC patients.

Stromal interaction molecule 1 (STIM1) knock down attenuates invasion and proliferation and enhances the expression of thyroid-specific proteins in human follicular thyroid cancer cells

Stromal interaction molecule 1 (STIM1) and the ORAI1 calcium channel mediate store-operated calcium entry (SOCE) and regulate a multitude of cellular functions. The identity and function of these proteins in thyroid cancer remain elusive. We show that STIM1 and ORAI1 expression is elevated in thyroid cancer cell lines, compared to primary thyroid cells. Knock-down of STIM1 or ORAI1 attenuated SOCE, reduced invasion, and the expression of promigratory sphingosine 1-phosphate and vascular endothelial growth factor-2 receptors in thyroid cancer ML-1 cells. Cell proliferation was attenuated in these knock-down cells due to increased G1 phase of the cell cycle and enhanced expression of cyclin-dependent kinase inhibitory proteins p21 and p27. STIM1 protein was upregulated in thyroid cancer tissue, compared to normal tissue. Downregulation of STIM1 restored expression of thyroid stimulating hormone receptor, thyroid specific proteins and increased iodine uptake. STIM1 knockdown ML-1 cells were more susceptible to chemotherapeutic drugs, and significantly reduced tumor growth in Zebrafish. Furthermore, STIM1-siRNA-loaded mesoporous polydopamine nanoparticles attenuated invasion and proliferation of ML-1 cells. Taken together, our data suggest that STIM1 is a potential diagnostic and therapeutic target for treatment of thyroid cancer.

SphK1-driven autophagy potentiates focal adhesion paxillin-mediated metastasis in colorectal cancer

Invasion and metastasis are the main causes of colorectal cancer (CRC)‐related death. Accumulating evidence suggested that sphingosine kinase 1 (SphK1) promoted the metastasis of CRC and autophagy played an important role in SphK1 promoting the metastasis of malignancy. However, the mechanism by which SphK1‐driven autophagy promotes invasion and metastasis in CRC remains to be clarified. In the present study, immunohistochemical detection showed the expression of SphK1 and paxillin was higher in human CRC tissues than those of normal colorectal mucosal tissues, they were both associated with TNM staging, lymphatic, and distance metastasis. In addition, study of in situ tumor transplantation model in nude mice showed that the suppression of SphK1 inhibited the growth of colonic orthotopic implantation tumors and the expression of paxillin, p‐paxillin, LC3 in the tumor. So, SphK1 may promote CRC metastasis via inducing the expression of paxillin expression and its phosphorylation, in vivo. Furthermore, results of CCK8 assay, transwell and wound healing assays showed that SphK1 promoted the viability, invasion, and metastasis of CRC cells. Transmission electron microscopy detection showed that SphK1 is the key factor in autophagy induction in CRC cells. Moreover, western blot examination indicated that the expression of LC3Ⅱ/Ⅰ, paxillin, p‐paxillin, MMP‐2, and vimentin was enhanced in SphK1‐overexpressed CRC cells and suppressed in SphK1 knockdown CRC cells, meanwhile, the expression of E‐cadherin was suppressed in SphK1‐overexpressed CRC cells and enhanced in SphK1 knockdown CRC cells. Suppression of autophagy by 3MA reversed the expression of paxillin and its phosphorylation in SphK1‐overexpressed CRC cells, indicated that SphK1‐driven autophagy induced the expression of paxillin and its phosphorylation in CRC cells. Together, these findings reveal that SphK1‐driven autophagy may promote the invasion and metastasis of CRC via promoting the expression of focal adhesion paxillin and its phosphorylation.

Control of Skeletal Muscle Atrophy Associated to Cancer or Corticosteroids by Ceramide Kinase

Apart from cytokines and chemokines, sphingolipid mediators, particularly sphingosine-1-phosphate (S1P) and ceramide 1-phosphate (C1P), contribute to cancer and inflammation. Cancer, as well as other inflammatory conditions, are associated with skeletal muscle (SkM) atrophy, which is characterized by the unbalance between protein synthesis and degradation. Although the signaling pathways involved in SkM mass wasting are multiple, the regulatory role of simple sphingolipids is limited. Here, we report the impairment of ceramide kinase (CerK), the enzyme responsible for the phosphorylation of ceramide to C1P, associated with the accomplishment of atrophic phenotype in various experimental models of SkM atrophy: in vivo animal model bearing the C26 adenocarcinoma or Lewis lung carcinoma tumors, in human and murine SkM cells treated with the conditioned medium obtained from cancer cells or with the glucocorticoid dexamethasone. Notably, we demonstrate in all the three experimental approaches a drastic decrease of CerK expression. Gene silencing of CerK promotes the up-regulation of atrogin-1/MAFbx expression, which was also observed after cell treatment with C8-ceramide, a biologically active ceramide analogue. Conversely, C1P treatment significantly reduced the corticosteroid's effects. Altogether, these findings provide evidence that CerK, acting as a molecular modulator, may be a new possible target for SkM mass regulation associated with cancer or corticosteroids.

SPNS2 Downregulation Induces EMT and Promotes Colorectal Cancer Metastasis via Activating AKT Signaling Pathway

Spinster homologue 2 (SPNS2), a transporter of S1P (sphingosine-1-phosphate), has been reported to mediate immune response, vascular development, and pathologic processes of diseases such as cancer via S1P signaling pathways. However, its biological functions and expression profile in colorectal cancer (CRC) is elusive. In this study, we disclosed that SPNS2 expression, which was regulated by copy number variation and DNA methylation of its promoter, was dramatically upregulated in colon adenoma and CRC compared to normal tissues. However, its expression was lower in CRC than in colon adenoma, and low expression of SPN2 correlated with advanced T/M/N stage and poor prognosis in CRC. Ectopic expression of SPNS2 inhibited cell proliferation, migration, epithelial–mesenchymal transition (EMT), invasion, and metastasis in CRC cell lines, while silencing SPNS2 had the opposite effects. Meanwhile, measuring the intracellular and extracellular level of S1P after overexpression of SPNS2 pinpointed a S1P-independent model of SPNS2. Mechanically, SPNS2 led to PTEN upregulation and inactivation of Akt. Moreover, AKT inhibitor (MK2206) abrogated SPNS2 knockdown-induced promoting effects on the migration and invasion, while AKT activator (SC79) reversed the repression of migration and invasion by SPNS2 overexpression in CRC cells, confirming the pivotal role of AKT for SPNS2’s function. Collectively, our study demonstrated the suppressor role of SPNS2 during CRC metastasis, providing new insights into the pathology and molecular mechanisms of CRC progression.

Sphingosine 1-phosphate and its receptors in ischemia

Sphingosine 1-phosphate (S1P), a metabolite of sphingolipids, is mainly derived from red blood cells (RBCs), platelets and endothelial cells (ECs). It plays important roles in regulating cell survival, vascular integrity and inflammatory responses through its receptors. S1P receptors (S1PRs), including 5 subtypes (S1PR1-5), are G protein-coupled receptors and have been proved to mediate various and complex roles of S1P in atherosclerosis, myocardial infarction (MI) and ischemic stroke by regulating endothelial function and inflammatory response as well as immune cell behavior. This review emphasizes the functions of S1PRs in atherosclerosis and ischemic diseases such as MI and ischemic stroke, enabling mechanistic studies and new S1PRs targeted therapies in atherosclerosis and ischemia in the future.

Design, synthesis, and biological evaluation of novel benzimidazole derivatives as sphingosine kinase 1 inhibitor

Sphingosine kinase 1 (SphK1) has emerged as an attractive drug target for different diseases. Recently, discovered SphK1 inhibitors have been recommended in cancer therapeutics; however, selectivity and potency are great challenges. In this study, a novel series of benzimidazoles was synthesized and evaluated as SphK1 inhibitors. Our design strategy is twofold: It aimed first to study the effect of replacing the 5-position of the benzimidazole ring with a polar carboxylic acid group on the SphK1-inhibitory activity and cytotoxicity. Our second aim was to optimize the structures of the benzimidazoles through the elongation of the chain. The enzyme inhibition potentials against all the synthesized compounds toward SphK1 were evaluated, and the results revealed that most of the studied compounds inhibited SphK1 effectively. The binding affinity of the benzimidazole derivatives toward SphK1 was measured by fluorescence binding and molecular docking. Compounds 33, 37, 39, 41, 42, 43, and 45 showed an appreciable binding affinity. Therefore, the SphK1-inhibitory potentials of compounds 33, 37, 39, 41, 42, 43, and 45 were studied and IC₅₀ values were determined, to reveal high potency. The study showed that these compounds inhibited SphK1 with effective IC₅₀ values. Among the studied compounds, compound 41 was the most effective one with the lowest IC₅₀ value and a high cytotoxicity on a wide spectrum of cell lines. Molecular docking revealed that most of these compounds fit well into the ATP-binding site of SphK1 and form hydrogen bond interactions with catalytically important residues. Overall, the findings suggest the therapeutic potential of benzimidazoles in the clinical management of SphK1-associated diseases.

Kinase Inhibitors as Underexplored Antiviral Agents

Viral infections are a major health problem; therefore, there is an urgent need for novel therapeutic strategies. Antivirals used to target proteins encoded by the viral genome usually enhance drug resistance generated by the virus. A potential solution may be drugs acting at host-based targets since viruses are dependent on numerous cellular proteins and phosphorylation events that are crucial during their life cycle. Repurposing existing kinase inhibitors as antiviral agents would help in the cost and effectiveness of the process, but this strategy usually does not provide much improvement, and specific medicinal chemistry programs are needed in the field. Anyway, extensive use of FDA-approved kinase inhibitors has been quite useful in deciphering the role of host kinases in viral infection. The present perspective aims to review the state of the art of kinase inhibitors that target viral infections in different development stages.

Vincetoxicum arnottianum modulates motility features and metastatic marker expression in pediatric rhabdomyosarcoma by stabilizing the actin cytoskeleton

Background

Prevention of metastatic invasion is one of the main challenges in the treatment of alveolar rhabdomyosarcoma. Still the therapeutic options are limited. Therefore, an anti-tumor screening was initiated focusing on the anti-metastatic and anti-invasion properties of selected medicinal plant extracts and phytoestrogens, already known to be effective in the prevention and treatment of different cancer entities.

Methods

Treatment effects were first evaluated by cell viability, migration, invasion, and colony forming assays on the alveolar rhabdomyosarcoma cell line RH-30 in comparison with healthy primary cells.

Results

Initial anti-tumor screenings of all substances analyzed in this study, identified the plant extract of Vincetoxicum arnottianum (VSM) as the most promising candidate, harboring the highest anti-metastatic potential. Those significant anti-motility properties were proven by a reduced ability for migration (60%), invasion (99%) and colony formation (61%) under 48 h exposure to 25 μg/ml VSM. The restricted motility features were due to an induction of the stabilization of the cytoskeleton – actin fibers were 2.5-fold longer and were spanning the entire cell. Decreased proliferation (PCNA, AMT, GCSH) and altered metastasis (e. g. SGPL1, CXCR4, stathmin) marker expression on transcript and protein level confirmed the significant lowered tumorigenicity under VSM treatment. Finally, significant alterations in the cell metabolism were detected for 25 metabolites, with levels of uracil, N-acetyl serine and propanoyl phosphate harboring the greatest alterations. Compared to the conventional therapy with cisplatin, VSM treated cells demonstrated a similar metabolic shutdown of the primary cell metabolism. Primary control cells were not affected by the VSM treatment.

Conclusions

This study revealed the VSM root extract as a potential, new migrastatic drug candidate for the putative treatment of pediatric alveolar rhabdomyosarcoma with actin filament stabilizing properties and accompanied by a marginal effect on the vitality of primary cells.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03299-x.

NOX66 as Monotherapy, and in Combination With Carboplatin, in Patients With Refractory Solid Tumors: Phase Ia/b Study

•

NOX66 contains idronoxil, formulated as a rectal suppository.

•

CEP-1 is the first study to assess NOX66 in patients with refractory solid tumors.

•

NOX66 was well tolerated at 400/800 mg as monotherapy and combined with carboplatin.

•

The safety profile justifies continuation of the NOX66 clinical research program.

•

Early results suggest most patients had stable disease by study end

Background

Although oral and intravenous forms of idronoxil have been well tolerated, the safety of NOX66, with idronoxil formulated as a rectal suppository, is not known. This Phase Ia/b clinical study (protocol No. NOX66-001A), known as Chemotherapy Enhancement Program-1, is the first to assess NOX66 in patients with refractory solid tumors.

Objective

The study aimed to determine the safety profile of NOX66 both as a monotherapy and in combination with carboplatin, and to evaluate whether or not NOX66 has a meaningful anticancer effect when combined with carboplatin in this patient population.

Methods

Chemotherapy Enhancement Program-1 was a multicenter, open-label, nonrandomized, 2-dose cohort study of NOX66 as monotherapy (Phase Ia) and in combination with carboplatin (Phase Ib). Patients with refractory solid tumors who had stopped responding to standard treatments were eligible to participate. Twenty patients were screened and 19 enrolled in the study. They were divided into 2 groups: cohort 1 (n = 8) received 1 suppository daily (400 mg) and cohort 2 (n = 11) received 2 suppositories daily (800 mg) for 14 consecutive days followed by 7 days of rest. Patients who completed Phase Ia without significant toxicity continued to Phase Ib, where NOX66 was combined with carboplatin for up to 6x 28-day treatment cycles, with low-dose carboplatin (600 mg) for cycles 1B through 3B and standard dose carboplatin (900 mg) for cycles 4B through 6B. The main outcomes assessed were safety (n = 18) and efficacy signals (n = 14).

Results

NOX66 generally was well tolerated at 400 mg and 800 mg, both as monotherapy and in combination with carboplatin in patients with refractory solid tumors. The safety profile was consistent for oncology patients, with 77.8% experiencing at least 1 treatment-emergent adverse event. The most common adverse events were blood and lymphatic system disorders (44.4%), with only anemia considered as possibly related to NOX66. Although the study was primarily designed to assess safety and tolerability, the efficacy measurements demonstrated that most patients had stable disease or better by study end.

Conclusions

The favorable safety profile of NOX66 provides reassurance to justify continuation of clinical research. The efficacy findings are encouraging in terms of the chemosensitizing potential of NOX66 in refractory solid tumors. (Curr Ther Res Clin Exp. 2021; 82:XXX–XXX)

A genome-scale CRISPR Cas9 dropout screen identifies synthetically lethal targets in SRC-3 inhibited cancer cells

Steroid receptor coactivator 3 (SRC-3/NCoA3/AIB1), is a key regulator of gene transcription and it plays a central role in breast cancer (BC) tumorigenesis, making it a potential therapeutic target. Beyond its function as an important regulator of estrogen receptor transcriptional activity, SRC-3 also functions as a coactivator for a wide range of other transcription factors, suggesting SRC-3 inhibition can be beneficial in hormone-independent cancers as well. The recent discovery of a potent SRC-3 small molecule inhibitor, SI-2, enabled the further development of additional related compounds. SI-12 is an improved version of SI-2 that like SI-2 has anti-proliferative activity in various cancer types, including BC. Here, we sought to identify gene targets, that when inhibited in the presence of SI-12, would lead to enhanced BC cell cytotoxicity. We performed a genome-scale CRISPR-Cas9 screen in MCF-7 BC cells under conditions of pharmacological pressure with SI-12. A parallel screen was performed with an ER inhibitor, fulvestrant, to shed light on both common and distinct activities between SRC-3 and ERα inhibition. Bearing in mind the key role of SRC-3 in tumorigenesis of other types of cancer, we extended our study by validating potential hits identified from the MCF-7 screen in other cancer cell lines.

The sphingosine kinase 1 activator, K6PC-5, attenuates Ebola virus infection

Ebola virus (EBOV) is responsible for outbreaks with case fatality rates of up to 90% and for an epidemic in West Africa with more than ten thousand deaths. EBOV glycoprotein (EBOV-GP) is the only viral surface protein and is responsible for viral entry into cells. Here, by employing pseudotyped EBOV-GP viral particles, we uncover a critical role for sphingolipids in inhibiting viral entry. Sphingosine kinase 1 (SphK1) catalyzes the phosphorylation of sphingosine to sphingosine 1-phosphate (S1P). The administration of the SphK1 activator, K6PC-5, or S1P, or the overexpression of SphK1 consistently exhibited striking inhibitory effects in EBOV-GP-driven entry in diverse cell lines. Finally, K6PC-5 markedly reduced the EBOV titer in infected cells and the de novo production of viral proteins. These data present K6PC-5 as an efficient tool to inhibit EBOV infection in endothelial cells and suggest further studies to evaluate its systemic effects.

•

K6PC-5, a sphingosine kinase 1 activator, inhibits Ebola virus infection

•

Sphingosine 1-phosphate, the product of SphK1, attenuates the viral entry

•

Inhibiton/activation of S1P receptors has no influence on Ebola virus entry

•

These data support the endogen effect of S1P in Ebola virus infection

Synthesis of PF-543 Derivatives Using Simple Synthetic Methods and Their Biological Effect Analysis for the Development of Anticolorectal Cancer Agents

Background:

Sphingolipids, even in extremely low doses, regulate various physiological functions. Particularly, immune and cancer cells might be controlled by changes in the sphingosine- 1-phosphate (S1P) levels, and S1P has been studied for a long time as a major target for new drug development. Sphingosine kinase (SK) phosphorylates sphingosine to produce S1P. An increase in the S1P levels promotes the growth of cancer cells. SK has 2 isoforms, SK1 and SK2, both of which are involved in the growth of cancer cells.

Objective:

PF-543 has been developed as an SK1 inhibitor and has a non-lipid structure that differs from those of general SK inhibitors. While PF-543 has a potent SK1 inhibitory effect, and has low anticancer activity in some types of cancer cells. Therefore, the development of other PF-543 derivatives is needed.

Methods:

We designed a structurally simplified derivative of PF-543. To primarily demonstrate that the designed structure was biologically active, 8 derivatives were synthesized by a 2-step method using the commercial starting material, and their biological activities were evaluated.

Results:

The SK1-inhibitory effects of the synthesized derivatives were not higher than that of PF- 543. However, the anticancer activity and apoptotic effect of the derivatives were similar to those of PF-543, despite their fabrication from a simple modification of the PF-543 structure. In a docking study, the derivatives were found to bind SK1 in a form similar to PF-543.

Conclusion:

Our analogs, which are similar to PF-543, showed comparable anticancer activity, indicating that the synthesized derivatives are structurally more efficient for anticancer activity than PF-543. Therefore, our study provides important information that may be useful for developing new anticancer substances that target SK1.

Pulmonary gene delivery-Realities and possibilities

Delivery of genetic material to tissues in vivo is an important technique used in research settings and is the foundation upon which clinical gene therapy is built. The lung is a prime target for gene delivery due to a host of genetic, acquired, and infectious diseases that manifest themselves there, resulting in many pathologies. However, the in vivo delivery of genetic material to the lung remains a practical problem clinically and is considered the major obstacle needed to be overcome for gene therapy. Currently there are four main strategies for in vivo gene delivery to the lung: viral vectors, liposomes, nanoparticles, and electroporation. Viral delivery uses several different genetically modified viruses that enter the cell and express desired genes that have been inserted to the viral genome. Liposomes use combinations of charged and neutral lipids that can encapsulate genetic cargo and enter cells through endogenous mechanisms, thereby delivering their cargoes. Nanoparticles are defined by their size (typically less than 100 nm) and are made up of many different classes of building blocks, including biological and synthetic polymers, cell penetrant and other peptides, and dendrimers, that also enter cells through endogenous mechanisms. Electroporation uses mild to moderate electrical pulses to create pores in the cell membrane through which delivered genetic material can enter a cell. An emerging fifth category, exosomes and extracellular vesicles, may have advantages of both viral and non-viral approaches. These extracellular vesicles bud from cellular membranes containing receptors and ligands that may aid cell targeting and which can be loaded with genetic material for efficient transfer. Each of these vectors can be used for different gene delivery applications based on mechanisms of action, side-effects, and other factors, and their use in the lung and possible clinical considerations is the primary focus of this review.

Probing the substitution pattern of indole-based scaffold reveals potent and selective sphingosine kinase 2 inhibitors

Elevated levels of sphingosine 1-phosphate (S1P) and increased expression of sphingosine kinase isoforms (SphK1 and SphK2) have been implicated in a variety of disease states including cancer, inflammation, and autoimmunity. Consequently, the S1P signaling axis has become an attractive target for drug discovery. Selective inhibition of either SphK1 or SphK2 has been demonstrated to be effective in modulating S1P levels in animal models. While SphK1 inhibitors have received much attention, the development of potent and selective SphK2 inhibitors are emerging. Previously, our group reported a SphK2 naphthalene-based selective inhibitor, SLC5081308, which displays approximately 7-fold selectivity for hSphK2 over hSphK1 and has a SphK2 K_i value of 1.0 μM. To improve SphK2 potency and selectivity, we designed, synthesized, and evaluated a series of indole-based compounds derived from SLC5081308. After investigating substitution patterns around the indole ring, we discovered that 1,5-disubstitution promoted optimal binding in the SphK2 substrate binding site and subsequent inhibition of enzymatic activity. Our studies led to the identification of SLC5101465 (6r, SphK2 K_i = 90 nM, >110 fold selective for SphK2 over SphK1). Molecular modeling studies revealed key nonpolar interactions with Val308, Phe548, His556, and Cys533 and hydrogen bonds with both Asp211 and Asp308 as responsible for the high SphK2 inhibition and selectivity.

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.

Lipophilic tail modifications of 2-(hydroxymethyl)pyrrolidine scaffold reveal dual sphingosine kinase 1 and 2 inhibitors

The sphingosine 1-phosphate (S1P) signaling pathway is an attractive target for pharmacological manipulation due to its involvement in cancer progression and immune cell chemotaxis. The synthesis of S1P is catalyzed by the action of sphingosine kinase 1 or 2 (SphK1 or SphK2) on sphingosine and ATP. While potent and selective inhibitors of SphK1 or SphK2 have been reported, development of potent dual SphK1/SphK2 inhibitors are still needed. Towards this end, we report the structure-activity relationship profiling of 2-(hydroxymethyl)pyrrolidine-based inhibitors with 22d being the most potent dual SphK1/SphK2 inhibitor (SphK1 K_i = 0.679 μM, SphK2 K_i = 0.951 μM) reported in this series. 22d inhibited the growth of engineered Saccharomyces cerevisiae and decreased S1P levels in histiocytic lymphoma myeloid cell line (U937 cells), demonstrating inhibition of SphK1 and 2 in vitro. Molecular modeling studies of 22d docked inside the Sph binding pocket of both SphK1 and SphK2 indicate essential hydrogen bond between the 2-(hydroxymethyl)pyrrolidine head to interact with aspartic acid and serine residues near the ATP binding pocket, which provide the basis for dual inhibition. In addition, the dodecyl tail adopts a "J-shape" conformation found in crystal structure of sphingosine bound to SphK1. Collectively, these studies provide insight into the intermolecular interactions in the SphK1 and 2 active sites to achieve maximal dual inhibitory activity.

Triple Negative Breast Cancer: How Neurokinin-1 Receptor Antagonists Could Be Used as a New Therapeutic Approach

Breast cancer (BC) is the most frequently diagnosed cancer and the leading cause of cancer death among females. BC cells not showing HER-2/Neu amplification and not expressing estrogen/ progesterone receptors are named triple-negative BC (TNBC) cells. TNBC represents 10-15% of all BC and is associated with an aggressive clinical course. TNBC patient prognosis, survival and response to current therapies are poor and for this reason, it is crucial to search for new therapeutic targets in TNBC to develop new therapeutic strategies. One of these targets is the neurokinin-1 receptor (NK-1R). It is well known that the substance P (SP)/NK-1R system is involved in cancer progression. TNBC cells overexpress the NK-1R and, after binding to this receptor, SP promotes the proliferation/ migration of TNBC cells. Non-peptide NK-1R antagonists (e.g., aprepitant) are known to exert, via the NK-1R, an antitumor action; TNBC cells die by apoptosis. In this review, we update the data on a promising therapeutic innovation: the use of NK-1R antagonists for the treatment of TNBC patients.

High-throughput metabolomic method based on liquid chromatography: high resolution mass spectrometry with chemometrics for metabolic biomarkers and pathway analysis to reveal the protective effects of baicalin on thyroid cancer

Cell metabonomics focuses on discovering metabolic biomarkers and pathway changes in cells from biological systems to obtain the cell properties and functional information under different conditions. Baicalin possesses various pharmacological activities, and plays a vital role in the oncology research field. However, the detailed mechanism of its action is still unclear. In this work, we employed ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) based non-targeted metabolomics method associated with chemometrics analysis to explore metabolic pathways and biomarkers for investigating the efficacy and pharmacological targets of baicalin against thyroid cancer cells. In addition, morphological observation, parameter calculation of cell proliferation and apoptosis were carried out, which assisted in elucidation of pharmacological activity of baicalin on the human thyroid cancer cells. The results showed that baicalin possesses an intense stimulative apoptosis and inhibits proliferation activity on SW579 human thyroid cancer cells, and partially reversed the cell metabolite abnormalities. A total of nineteen differentiated metabolites in SW579 cells were identified and deemed as potential biomarkers after the baicalin treatment, involving nine metabolic pathways, such as taurine and hypotaurine metabolism, pyrimidine metabolism, fructose and mannose metabolism, steroid hormone biosynthesis and sphingolipid metabolism. High-throughput non-targeted metabolomics provide an insight into specialized mechanism of baicalin against thyroid cancer and contributes to novel drug discovery and thyroid cancer management in clinical practice.

Lipid Phosphate Phosphatases and Cancer

Lipid phosphate phosphatases (LPPs) are a group of three enzymes (LPP1–3) that belong to a phospholipid phosphatase (PLPP) family. The LPPs dephosphorylate a wide spectrum of bioactive lipid phosphates, among which lysophosphatidate (LPA) and sphingosine 1-phosphate (S1P) are two important extracellular signaling molecules. The LPPs are integral membrane proteins, which are localized on plasma membranes and intracellular membranes, including the endoplasmic reticulum and Golgi network. LPPs regulate signaling transduction in cancer cells and demonstrate different effects in cancer progression through the breakdown of extracellular LPA and S1P and other intracellular substrates. This review is intended to summarize an up-to-date understanding about the functions of LPPs in cancers.

Blocking sphingosine 1-phosphate receptor 2 accelerates hepatocellular carcinoma progression in a mouse model of NASH

The role of sphingosine 1-phosphate (S1P) and its sphingosine-1-phosphate receptors (S1PRs) in non-alcoholic steatohepatitis (NASH) is unclear. We aimed to analyze the role of S1P/S1PRs in a Melanocortin-4 receptor (Mc4r)-deficient NASH murine model using FTY720, the functional antagonist of S1PR1, S1PR3, S1PR4, and S1PR5, and JTE-013, the antagonist of S1PR2. We observed that, compared to that in the control, the mRNA of S1pr1 tended to decrease, whereas those of S1pr2 and S1pr3 significantly increased in Mc4r-knockout (KO) mice subjected to a Western diet (WD). While the fat area did not differ, fibrosis progression differed significantly between control mice and mice in which liver S1PRs were blocked. Lipidomic and metabolomic analysis of liver tissues showed that JTE-013-administered mice showed elevation of S-adenosyl-l-methionine level, which can induce aberrant methylation due to reduction in glycine N-methyltransferase (GNMT) and elevation in diacylglycerol (DG) and triacylglycerol (TG) levels, leading to increased susceptibility to hepatocellular carcinoma (HCC). These phenotypes are similar to those of Gnmt-KO mice, suggesting that blocking the S1P/S1PR2 axis triggers aberrant methylation, which may increase DG and TG, and hepatocarcinogenesis. Our observations that the S1P/S1PR2 axis averts HCC occurrence may assist in HCC prevention in NASH.