Identification of SPHK1 as a therapeutic target and marker of poor prognosis in cholangiocarcinoma

Identification of the function of FOSB in cholangiocarcinoma using bioinformatics analysis

Background

Exploring the potential mechanism of cholangiocarcinoma (CCA) metabolic reprogramming is significant for guiding clinical treatment. However, related research and exploration are still lacking. Therefore, we aimed to identify a reliable metabolism-related gene or biomarker of CCA using bioinformatics analysis.

Methods

The GSE26566, GSE45001, and GSE132305 datasets were obtained from the Gene Expression Omnibus (GEO) database. Differently expressed genes (DEGs) between CCA tissues and adjacent tissues were screened out. The key gene was identified through enrichment and functional analysis, and its immune and clinical correlation was investigated utilizing the Tumor Immune Evaluation Resource (TIMER2.0), the Tumor-Immune System Interactions Database (TISIDB), the Gene Expression Profiling Interactive Analysis (GEPIA2), and the Kaplan-Meier Plotter. Finally, immunohistochemistry (IHC) was performed to validate the results.

Results

By analysis, the expression of FBJ murine osteosarcoma viral oncogene homolog B (FOSB) was significantly downregulated in CCA tissues when compared with adjacent tissues. Moreover, the expression levels of FOSB positively correlated with tumor-infiltrating immune cells in most tumors, and patients with high FOSB expression tended to have a better prognosis. The FOSB and SIRT3/HIF1A axes have similar expression trends and metabolic functions in CCA cells, and the correlation between of them was preliminarily explored by IHC experiments.

Conclusions

The expression levels of FOSB are closely related to the prognosis of CCA patients, which may be a predictive indicator for prognosis and immunotherapy.

Metabolic reprogramming and its clinical implication for liver cancer

Cancer cells often encounter hypoxic and hypo-nutrient conditions, which force them to make adaptive changes to meet their high demands for energy and various biomaterials for biomass synthesis. As a result, enhanced catabolism (breakdown of macromolecules for energy production) and anabolism (macromolecule synthesis from bio-precursors) are induced in cancer. This phenomenon is called "metabolic reprogramming," a cancer hallmark contributing to cancer development, metastasis, and drug resistance. HCC and cholangiocarcinoma (CCA) are 2 different liver cancers with high intertumoral heterogeneity in terms of etiologies, mutational landscapes, transcriptomes, and histological representations. In agreement, metabolism in HCC or CCA is remarkably heterogeneous, although changes in the glycolytic pathways and an increase in the generation of lactate (the Warburg effect) have been frequently detected in those tumors. For example, HCC tumors with activated β-catenin are addicted to fatty acid catabolism, whereas HCC tumors derived from fatty liver avoid using fatty acids. In this review, we describe common metabolic alterations in HCC and CCA as well as metabolic features unique for their subsets. We discuss metabolism of NAFLD as well, because NAFLD will likely become a leading etiology of liver cancer in the coming years due to the obesity epidemic in the Western world. Furthermore, we outline the clinical implication of liver cancer metabolism and highlight the computation and systems biology approaches, such as genome-wide metabolic models, as a valuable tool allowing us to identify therapeutic targets and develop personalized treatments for liver cancer patients.

The role and implication of autophagy in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a malignant tumor that originates from the biliary epithelial cells. It is characterized by a difficult diagnosis and limited treatment options. Autophagy is a cellular survival mechanism that maintains nutrient and energy homeostasis and eliminates intracellular pathogens. It is involved in various physiological and pathological processes, including the development of cancer. However, the role, mechanism, and potential therapeutic targets of autophagy in CCA have not been thoroughly studied. In this review, we introduce the classification, characteristics, process, and related regulatory genes of autophagy. We summarize the regulation of autophagy on the progression of CCA and collect the latest research progress on some autophagy modulators with clinical potential in CCA. In conclusion, combining autophagy modulators with immunotherapy, chemotherapy, and targeted therapy has great potential in the treatment of CCA. This combination may be a potential therapeutic target for CCA in the future.

Expression of sphingosine‑1‑phosphate receptor 2 is correlated with migration and invasion of human colon cancer cells: A preliminary clinical study

Sphingosine-1-phosphate (S1P) is a bioactive phospholipid that serves as a potent mediator of cell proliferation, differentiation and apoptosis by binding to S1P receptors (S1PRs). S1P signalling is involved in the pathogenesis of numerous types of disease, including cancer. To the best of our knowledge, however, little is known about the expression patterns of S1PRs and their role in human colorectal cancer (CRC) cell migration and invasion. The aim of the present study was to investigate the role of S1P signalling in the metastasis of colon cancer cells and the expression of S1PRs in patients with CRC. The protein and mRNA expression levels of S1PRs and sphingosine kinases (SPHKs) in 55 patients with CRC were detected by western blotting (WB), immunohistochemical (IHC) analysis and reverse transcription-quantitative PCR. The levels of S1P in serum from patients and healthy individuals were quantified by ELISA. S1PRs antagonists JTE013, FTY720 and S1PR2-small interfering (si)RNA were used to determine the role of S1PR2 in human CRC LOVO and SW480 cell lines. Migration and invasion assays were performed for functional analysis. The levels of S1P in serum were significantly increased in patients with CRC compared with healthy individuals. The relative mRNA expression levels of S1PR2 were significantly downregulated in tumour compared with normal tissue, whereas S1PR1 and SPHK1 were upregulated. WB showed that 58% (32/55 cases) of patients presented downregulated S1PR2 protein expression. IHC analysis indicated that expression of S1PR2 was lower in tumour than in normal tissue in 65.5% (36/55 cases) of patients. Exogenous addition of S1P promoted migration and invasion in the different cell types. S1P stimulated the migration and invasion of SW480 cells. The inhibition of S1PR2 by JTE013 or S1PR2-siRNA significantly promoted the migration and invasion of SW480 cells, while FTY720 reversed these effects. The present study indicated that expression levels of S1PRs, particularly S1PR2, were associated with migration and invasion of CRC cells. The present findings revealed a novel mechanism by which S1P inhibited tumour cell migration and invasion via a S1PR2-dependent pathway, suggesting that S1PR2 may be a therapeutic target for treatment of colon cancer.

Increased Sphingosine Kinase 1 Expression Is Associated with Poor Prognosis in Human Solid Tumors: A Meta-Analysis

Methods

PubMed, Web of Science, Embase, CNKI, and Wanfang databases were thoroughly searched for eligible studies, in which the relationship between SPHK1 expression and cancer prognosis was evaluated. Hazard ratios (HRs) and 95% confidence intervals (CIs) were pooled to estimate the impact of SPHK1 expression on cancer patients' survival. Odds ratios (ORs) and 95% CIs were combined to assess the association between SPHK1 expression and clinicopathological characteristics of cancer patients. The certainty of evidence was evaluated by Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) criteria.

Results

Thirty studies comprising 32 cohorts with 5965 patients were included in this meta-analysis. The outcomes indicated that elevated SPHK1 expression was associated with worse overall survival (OS) (HR = 1.71, 95% CI: 1.45-2.01, P < 0.001) and disease-free survival (DFS) (HR = 1.34, 95% CI: 1.13-1.59, P = 0.001). What is more, SPHK1 overexpression was significantly correlated with certain phenotypes of tumor aggressiveness, such as clinical stage (OR = 2.07, 95% CI: 1.39-3.09, P < 0.001), tumor invasion (OR = 2.16, 95% CI: 1.47-3.18, P < 0.001), lymph node metastasis (OR = 2.04, 95% CI: 1.71-2.44, P < 0.001), and distant metastasis (OR = 3.16, 95% CI: 2.44-4.09, P < 0.001). The quality of the evidence for both OS and DFS was low.

Conclusions

Increased SPHK1 expression is related to poor prognosis in human cancers and may serve as a promising prognostic marker and therapeutic target for malignant patients. However, conclusions need to be treated with caution because of lack of high quality of evidence.

The sphingosine 1-phosphate receptor 2/4 antagonist JTE-013 elicits off-target effects on sphingolipid metabolism

Sphingosine 1-phosphate (S1P) is a signaling lipid that has broad roles, working either intracellularly through various protein targets, or extracellularly via a family of five G-protein coupled receptors_. Agents that selectively and specifically target each of the S1P receptors have been sought as both biological tools and potential therapeutics. JTE-013, a small molecule antagonist of S1P receptors 2 and 4 (S1P₂ and S1P₄) has been widely used in defining the roles of these receptors in various biological processes. Indeed, our previous studies showed that JTE-013 had anti-acute myeloid leukaemia (AML) activity, supporting a role for S1P₂ in the biology and therapeutic targeting of AML. Here we examined this further and describe lipidomic analysis of AML cells that revealed JTE-013 caused alterations in sphingolipid metabolism, increasing cellular ceramides, dihydroceramides, sphingosine and dihydrosphingosine. Further examination of the mechanisms behind these observations showed that JTE-013, at concentrations frequently used in the literature to target S1P_2/4, inhibits several sphingolipid metabolic enzymes, including dihydroceramide desaturase 1 and both sphingosine kinases. Collectively, these findings demonstrate that JTE-013 can have broad off-target effects on sphingolipid metabolism and highlight that caution must be employed in interpreting the use of this reagent in defining the roles of S1P_2/4.

The apoM-S1P axis in hepatic diseases

Liver dysfunction is always accompanied by lipid metabolism dysfunction. Apolipoprotein M (apoM), a member of the apolipoprotein family, is primarily expressed and secreted from the liver. apoM is the main chaperone of sphingosine-1-phosphate (S1P), a small signalling molecule associated with numerous physiologic and pathophysiologic processes. In addition to transport, apoM also influences the biologic effects of S1P. Most recently, numerous studies have investigated the potential role of the apoM-S1P axis in a variety of hepatic diseases. These include liver fibrosis, viral hepatitis B and C infection, hepatobiliary disease, non-alcoholic and alcoholic steatohepatitis, acute liver injury and hepatocellular carcinoma. In this review, the roles of apoM and S1P in the development of hepatic diseases are summarized, and novel insights into the diagnosis and treatment of hepatic diseases are discussed.

Multifaceted Aspects of Metabolic Plasticity in Human Cholangiocarcinoma: An Overview of Current Perspectives

Cholangiocarcinoma (CCA) is a deadly tumor without an effective therapy. Unique metabolic and bioenergetics features are important hallmarks of tumor cells. Metabolic plasticity allows cancer cells to survive in poor nutrient environments and maximize cell growth by sustaining survival, proliferation, and metastasis. In recent years, an increasing number of studies have shown that specific signaling networks contribute to malignant tumor onset by reprogramming metabolic traits. Several evidences demonstrate that numerous metabolic mediators represent key-players of CCA progression by regulating many signaling pathways. Besides the well-known Warburg effect, several other different pathways involving carbohydrates, proteins, lipids, and nucleic acids metabolism are altered in CCA. The goal of this review is to highlight the main metabolic processes involved in the cholangio-carcinogeneis that might be considered as potential novel druggable candidates for this disease.

Design of new quinolin-2-one-pyrimidine hybrids as sphingosine kinases inhibitors

Sphingosine-1-phosphate is now emerging as an important player in cancer, inflammation, autoimmune, neurological and cardiovascular disorders. Abundance evidence in animal and humans cancer models has shown that SphK1 is linked to cancer. Thus, there is a great interest in the development new SphK1 inhibitors as a potential new treatment for cancer. In a search for new SphK1 inhibitors we selected the well-known SKI-II inhibitor as the starting structure and we synthesized a new inhibitor structurally related to SKI-II with a significant but moderate inhibitory effect. In a second approach, based on our molecular modeling results, we designed new structures based on the structure of PF-543, the most potent known SphK1 inhibitor. Using this approach, we report the design, synthesis and biological evaluation of a new series of compounds with inhibitory activity against both SphK1 and SphK2. These new inhibitors were obtained incorporating new connecting chains between their polar heads and hydrophobic tails. On the other hand, the combined techniques of molecular dynamics simulations and QTAIM calculations provided complete and detailed information about the molecular interactions that stabilize the different complexes of these new inhibitors with the active sites of the SphK1. This information will be useful in the design of new SphK inhibitors.

Targeting sphingosine kinase 2 suppresses cell growth and synergizes with BCL2/BCL-XL inhibitors through NOXA-mediated MCL1 degradation in cholangiocarcinoma

Sphingosine kinase 2 (SPHK2) is a key factor within sphingolipid metabolism, responsible for the conversion of pro-apoptotic sphingosine to the pro-survival sphingosine-1-phosphate. We have previously shown that ABC294640, a first-in-class SPHK2 inhibitor, inhibits growth of cholangiocarcinoma cells. In a Phase I study of ABC294640 in tumors, the best response was achieved in a cholangiocarcinoma patient. These data suggest SPHK2 as a novel therapeutic target of cholangiocarcinoma. However, the antitumor mechanism of ABC294640 in cholangiocarcinoma remains not clear. In the current study, we found that ABC294640 upregulated expression of pro-apoptotic NOXA. In cholangiocarcinoma patients, high NOXA mRNA expression was associated with better overall survival. Also, SPHK2 mRNA expression was negatively correlated with NOXA mRNA expression. NOXA is known to degrade MCL1, an anti-apoptotic BCL2 protein. We showed that ABC294640 directed MCL1 for proteasome degradation. Knockdown of NOXA prevented ABC294640-induced MCL1 degradation and apoptosis. In addition, ABC294640 had a synergistic effect with BCL2/BCL-XL inhibitors ABT-263 and Obatoclax in inhibiting cell growth. Combined treatment with ABC294640 and BCL2/BCL-XL inhibitors induced potent apoptosis. Silencing of MCL1 also potentiated ABT-263-induced cytotoxicity. Furthermore, we found that both SPHK2 and MCL1 protein expression were significantly higher in cholangiocarcinoma than that in nontumoral bile ducts. SPHK2 expression correlated significantly with MCL1 expression. Our study reveals that ABC294640 inhibits cholangiocarcinoma cell growth and sensitizes the antitumor effect of BCL2/BCL-XL inhibitors through NOXA-mediated MCL1 degradation. Combinations of ABC294640 with BCL2/BCL-XL inhibitors may provide novel strategies for the treatment of cholangiocarcinoma.

Sphingosine kinase 1 is a potential therapeutic target for nasopharyngeal carcinoma

Sphingosine kinase 1 (SPHK1) has been shown to be involved in the progression of various types of human cancers. We previously demonstrated that SPHK1 is overexpressed and associated with clinical stage, locoregional recurrence, distant metastasis and poor prognosis in nasopharyngeal carcinoma (NPC). However, the biological roles involving SPHK1 and its potential usefulness as a therapeutic target in NPC remain unknown. In this study, Blocking SPHK1 using siRNA or FTY720 (a SPHK1 inhibitor) significantly reduced proliferation and migration and increased cell cycle arrest and apoptosis in NPC cells. FTY720 also decreased SPHK1 activity, and overexpressing SPHK1 abrogated the FTY720-induced effects on cell viability. In addition, FTY720 sensitized NPC cells to radiotherapy by inhibiting SPHK1 activity in vitro and in vivo. Furthermore, high SPHK1 expression was associated with increased Ki-67 and p-Akt and decreased caspase-3 expression in human NPC specimens. These data suggest that SPHK1 might be a potential therapeutic target for NPC.

Sphingosine kinase 2 supports the development of BCR/ABL-independent acute lymphoblastic leukemia in mice

Background

Sphingosine kinase (SphK) 2 has been implicated in the development of a range of cancers and inhibitors of this enzyme are currently in clinical trial. We have previously demonstrated a role for SphK2 in the development of acute lymphoblastic leukemia (ALL).

Methods

In this and our previous study we use mouse models: in the previous study the disease was driven by the proto-oncogene BCR/ABL1, while in this study cancer risk was elevated by deletion of the tumor suppressor ARF.

Results

Mice lacking ARF and SphK2 had a significantly reduced incidence of ALL compared mice with wild type SphK2.

Conclusions

These results show that the role of SphK2 in ALL development is not limited to BCR/ABL1 driven disease extending the potential use of inhibitors of this enzyme to ALL patients whose disease have driver mutations other than BCR/ABL1.

Mammalian sphingosine kinase (SphK) isoenzymes and isoform expression: challenges for SphK as an oncotarget

The various sphingosine kinase (SphK) isoenzymes (isozymes) and isoforms, key players in normal cellular physiology, are strongly implicated in cancer and other diseases. Mutations in SphKs, that may justify abnormal physiological function, have not been recorded. Nonetheless, there is a large and growing body of evidence demonstrating the contribution of gain or loss of function and the imbalance in the SphK/S1P rheostat to a plethora of pathological conditions including cancer, diabetes and inflammatory diseases. SphK is expressed as two isozymes SphK1 and SphK2, transcribed from genes located on different chromosomes and both isozymes catalyze the phosphorylation of sphingosine to S1P. Expression of each SphK isozyme produces alternately spliced isoforms. In recent years the importance of the contribution of SpK1 expression to treatment resistance in cancer has been highlighted and, additionally, differences in treatment outcome appear to also be dependent upon SphK isoform expression. This review focuses on an exciting emerging area of research involving SphKs functions, expression and subcellular localization, highlighting the complexity of targeting SphK in cancer and also comorbid diseases. This review also covers the SphK isoenzymes and isoforms from a historical perspective, from their first discovery in murine species and then in humans, their role(s) in normal cellular function and in disease processes, to advancement of SphK as an oncotarget.

Antitumor effect of the novel sphingosine kinase 2 inhibitor ABC294640 is enhanced by inhibition of autophagy and by sorafenib in human cholangiocarcinoma cells

Sphingosine kinase 2 (Sphk2) has an oncogenic role in cancer. A recently developed first-in-class Sphk2 specific inhibitor ABC294640 displays antitumor activity in many cancer models. However, the role of Sphk2 and the antitumor activity of its inhibitor ABC294640 are not known in cholangiocarcinoma. We investigated the potential of targeting Sphk2 for the treatment of cholangiocarcinoma. We found that Sphk2 is overexpressed in five established human cholangiocarcinoma cell lines (WITT, HuCCT1, EGI-1, OZ and HuH28) and a new patient-derived cholangiocarcinoma cell line (LIV27) compared to H69 normal cholangiocytes. Inhibition of Sphk2 by ABC294640 inhibited proliferation and induced caspase-dependent apoptosis. Furthermore, we found that ABC294640 inhibited STAT3 phosphorylation, one of the key signaling pathways regulating cholangiocarcinoma cell proliferation and survival. ABC294640 also induced autophagy. Inhibition of autophagy by bafilomycin A1 or chloroquine potentiated ABC294640-induced cytotoxicity and apoptosis. In addition, ABC294640 in combination with sorafenib synergistically inhibited cell proliferation of cholangiocarcinoma cells. Strong decreases in STAT3 phosphorylation were observed in WITT and HuCCT1 cells exposed to the ABC294640 and sorafenib combination. These findings provide novel evidence that Sphk2 may be a rational therapeutic target in cholangiocarcinoma. Combinations of ABC294640 with sorafenib and/or autophagy inhibitors may provide novel strategies for the treatment of cholangiocarcinoma.

Overexpression of SphK1 enhances cell proliferation and invasion in triple-negative breast cancer via the PI3K/AKT signaling pathway

Sphingosine kinase 1 (SphK1) expression is elevated in various cancers and is associated with shorter survival times for patients. However, the molecular mechanism of SphK1 up-regulation in triple-negative breast cancer (TNBC) remains unclear. In this study, we assayed the expression level of SphK1 in TNBC tissues by qRT-PCR and immunohistochemistry. The level of S1P was quantified by ELISA in the serum of TNBC patients. Our results found that the levels of SphK1 and S1P were significantly increased in TNBC patients compared with normal control. Furthermore, knockdown of SphK1 with siRNA decreased TNBC cell proliferation and inhibited cell migration/invasion. These data suggest that SphK1 has an important role in TNBC and presents an attractive therapeutic target for the treatment for TNBC.