Role of sphingolipids in oestrogen signalling in breast cancer cells: an update

Effects of adipocyte-conditioned cell culture media on S1P treatment of human triple-negative breast cancer cells

Sphingosine-1-phosphate (S1P) is a potent sphingolipid metabolite that regulates a wide range of biological functions such as cell proliferation, cell apoptosis and angiogenesis. Its cellular level is elevated in breast cancer, which, in turn, would promote cancer cell proliferation, survival, growth and metastasis. However, the cellular concentration of S1P is normally in the low nanomolar range, and our previous studies showed that S1P selectively induced apoptosis of breast cancer cells at high concentrations (high nanomolar to low micromolar). Thus, local administration of high-concentration S1P alone or in combination of chemotherapy agents could be used to treat breast cancer. The breast mainly consists of mammary gland and connective tissue stroma (adipose), which are dynamically interacting each other. Thus, in the current study, we evaluated how normal adipocyte-conditioned cell culture media (AD-CM) and cancer-associated adipocyte-conditioned cell culture media (CAA-CM) would affect high-concentration S1P treatment of triple-negative breast cancer (TNBC) cells. Both AD-CM and CAA-CM may suppress the anti-proliferative effect and reduce nuclear alteration/apoptosis caused by high-concentration S1P. This implicates that adipose tissue is likely to be detrimental to local high-concentration S1P treatment of TNBC. Because the interstitial concentration of S1P is about 10 times higher than its cellular level, we undertook a secretome analysis to understand how S1P would affect the secreted protein profile of differentiated SGBS adipocytes. At 100 nM S1P treatment, we identified 36 upregulated and 21 downregulated secretome genes. Most of these genes are involved in multiple biological processes. Further studies are warranted to identify the most important secretome targets of S1P in adipocytes and illustrate the mechanism on how these target proteins affect S1P treatment of TNBC.

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.

Network pharmacology-based study to identify the significant pathways of Lentinula edodes against cancer

Lentinula edodes (LE) is known as a good food source with potent anticancer efficacy, but its active chemical compounds and pathways against cancer have not been revealed. This study was to uncover the active chemical constituents and pathways of LE against cancer through network pharmacology. The chemical compositions were recognized by gas chromatography-mass spectrometry (GC-MS) and filtered drug-like compounds (DLCs) by SwissADME. Targets related to filtered compounds were recognized by two public databases and the final overlapping targets were identified by Venn diagram. Then, protein-protein interaction (PPI) and pathway-target-compound (PTC) networks were built by RStudio. Ultimately, we recognized the key compounds and targets via molecular docking test (MDT). A total of 33 compounds from LE were accepted by Lipinski's rule were selected as DLCs. The 33 compounds were associated with 108 targets and a key target (cyclooxygenase2 [COX2]) was identified through PPI networks. Most significantly, inactivation of pathways in cancer and activation of peroxisome proliferator activated receptor signaling pathway were significant pathways of LE. On MDT, we identified a key compound (Indole, 2-methyl-3-phenyl) on COX2 related to inactivation of athways in cancer, additionally, the number of 6 ergostane steroids was associated with the two pathways might be dual efficacy to alleviate inflammation against cancer. Overall, 13 targets, 11 compounds, and 2 key pathways of LE were identified as the significant elements to treat cancer. Hence, this study shows therapeutic evidence to verify the promising clinical effect of LE on cancer, suggesting that LE might be an important mushroom against cancer. PRACTICAL APPLICATIONS: Lentinula edodes (LE) has been used widely in cuisine as well as alternative medicines, especially, for anticancer. The LE has rich nutritional compounds including proteins, vitamins, polyphenols, and glucans, however, most of which have a critical hurdle as poor bioavailability not to be applicable for pharmaceuticals. Its main cause is very hydrophilic property. Thus, we adopted GC-MS analysis to identify lipophilic compounds to enhance cell permeability involved in bioavailability. The compounds selected from LE were confirmed by Lipinski's rule for drug-like-compounds (DLCs). Then, we retrieved targets associated with DLCs, and multiple pathways, multiple targets, and multiple compounds against cancer on network-based analysis. In summary, our study reveals the medicinal value of LE on cancer based on the multicomponents. Overall, the aim of this work is to represent the pharmacological evidence to reveal the therapeutic efficacy of AC on cancer, suggesting that DLCs from AC might be alleviators to dampen cancer.

Sex Differences in Cardiovascular Diseases: A Matter of Estrogens, Ceramides, and Sphingosine 1-Phosphate

The medical community recognizes sex-related differences in pathophysiology and cardiovascular disease outcomes (CVD), culminating with heart failure. In general, pre-menopausal women tend to have a better prognosis than men. Explaining why this occurs is not a simple matter. For decades, sex hormones like estrogens (Es) have been identified as one of the leading factors driving these sex differences. Indeed, Es seem protective in women as their decline, during and after menopause, coincides with an increased CV risk and HF development. However, clinical trials demonstrated that E replacement in post-menopause women results in adverse cardiac events and increased risk of breast cancer. Thus, a deeper understanding of E-related mechanisms is needed to provide a vital gateway toward better CVD prevention and treatment in women. Of note, sphingolipids (SLs) and their metabolism are strictly related to E activities. Among the SLs, ceramide and sphingosine 1-phosphate play essential roles in mammalian physiology, particularly in the CV system, and appear differently modulated in males and females. In keeping with this view, here we explore the most recent experimental and clinical observations about the role of E and SL metabolism, emphasizing how these factors impact the CV system.

The central role of Sphingosine kinase 1 in the development of neuroendocrine prostate cancer (NEPC): A new targeted therapy of NEPC

Background

Neuroendocrine prostate cancer (NEPC) is often diagnosed as a sub‐type from the castration‐resistant prostate cancer (CRPC) recurred from the second generation of anti‐androgen treatment and is a rapidly progressive fatal disease. The molecular mechanisms underlying the trans‐differentiation from CRPC to NEPC are not fully characterized, which hampers the development of effective targeted therapy.

Methods

Bioinformatic analyses were conducted to determine the clinical correlation of sphingosine kinase 1 (SphK1) in CRPC progression. To investigate the transcriptional regulation SphK1 and neuroendocrine (NE) transcription factor genes, both chromosome immunoprecipitation and luciferase reporter gene assays were performed. To demonstrate the role of SphK1 in NEPC development, neurosphere assay was carried out along with several biomarkers determined by quantitative PCR and western blot. Furthermore, in vivo NEPC xenograft models and patient‐derived xenograft (PDX) model were employed to determine the effect of SphK1 inhibitors and target validation.

Results

Significant prevalence of SphK1 in NEPC development is observed from clinical datasets. SphK1 is transcriptionally repressed by androgen receptor‐RE1‐silencing transcription factor (REST) complex. Furthermore, sphingosine 1‐phosphate produced by SphK1 can modulate REST protein turnover via MAPK signaling pathway. Also, decreased REST protein levels enhance the expression of NE markers in CRPC, enabling the transition to NEPC. Finally, specific SphK1 inhibitors can effectively inhibit the growth of NEPC tumors and block the REST protein degradation in PDX.

Conclusions

SphK1 plays a central role in NEPC development, which offers a new target for this lethal cancer using clinically approved SphK1 inhibitors.

Deep Pathway Analysis V2.0: A Pathway Analysis Framework Incorporating Multi-Dimensional Omics Data

Pathway analysis is essential in cancer research particularly when scientists attempt to derive interpretation from genome-wide high-throughput experimental data. If pathway information is organized into a network topology, its use in interpreting omics data can become very powerful. In this paper, we propose a topology-based pathway analysis method, called DPA V2.0, which can combine multiple heterogeneous omics data types in its analysis. In this method, each pathway route is encoded as a Bayesian network which is initialized with a sequence of conditional probabilities specifically designed to encode directionality of regulatory relationships defined in the pathway. Unlike other topology-based pathway tools, DPA is capable of identifying pathway routes as representatives of perturbed regulatory signals. We demonstrate the effectiveness of our model by applying it to two well-established TCGA data sets, namely, breast cancer study (BRCA) and ovarian cancer study (OV). The analysis combines mRNA-seq, mutation, copy number variation, and phosphorylation data publicly available for both TCGA data sets. We performed survival analysis and patient subtype analysis and the analysis outcomes revealed the anticipated strengths of our model. We hope that the availability of our model encourages wet lab scientists to generate extra data sets to reap the benefits of using multiple data types in pathway analysis. The majority of pathways distinguished can be confirmed by biological literature. Moreover, the proportion of correctly indentified pathways is 10 percent higher than previous work where only mRNA-seq and mutation data is incorporated for breast cancer patients. Consequently, such an in-depth pathway analysis incorporating more diverse data can give rise to the accuracy of perturbed pathway detection.

Sphingosine Kinase 1 Signaling in Breast Cancer: A Potential Target to Tackle Breast Cancer Stem Cells

Sphingosine kinases (SPHKs) are conserved lipid enzymes that catalyze the formation of sphingosine-1-phosphate (S1P) through ATP-dependent phosphorylation of sphingosine. Two distinct SPHK isoforms, namely SPHK1 and SPHK2, have been identified to date, and the former has been implicated for its oncogenic roles in cancer development and progression. While SPHK1 signaling axis has been extensively studied in non-stem breast cancer cells, recent evidence has emerged to suggest a role of SPHK1 in regulating cancer stem cells (CSCs). With the clinical implications of CSCs in disease relapse and metastasis, it is believed that therapeutic approaches that can eradicate both non-stem cancer cells and CSCs could be a key to cancer cure. In this review, we first explore the oncogenic functions of sphingosine kinase 1 in human cancers and summarize current research findings of SPHK1 signaling with a focus on breast cancer. We also discuss the therapeutic potentials and perspectives of targeting SPHK1 signaling in breast cancer and cancer stem cells. We aim to offer new insights and inspire future studies looking further into the regulatory functions of SPHK1 in CSC-driven tumorigenesis, uncovering novel therapeutic avenues of using SPHK1-targeted therapy in the treatment of CSC-enriched refractory cancers.

Hormone-Independent Mouse Mammary Adenocarcinomas with Different Metastatic Potential Exhibit Different Metabolic Signatures

The metabolic characteristics of metastatic and non-metastatic breast carcinomas remain poorly studied. In this work, untargeted Nuclear Magnetic Resonance (NMR) metabolomics was used to compare two medroxyprogesterone acetate (MPA)-induced mammary carcinomas lines with different metastatic abilities. Different metabolic signatures distinguished the non-metastatic (59-2-HI) and the metastatic (C7-2-HI) lines, with glucose, amino acid metabolism, nucleotide metabolism and lipid metabolism as the major affected pathways. Non-metastatic tumours appeared to be characterised by: (a) reduced glycolysis and tricarboxylic acid cycle (TCA) activities, possibly resulting in slower NADH biosynthesis and reduced mitochondrial transport chain activity and ATP synthesis; (b) glutamate accumulation possibly related to reduced glutathione activity and reduced mTORC1 activity; and (c) a clear shift to lower phosphoscholine/glycerophosphocholine ratios and sphingomyelin levels. Within each tumour line, metabolic profiles also differed significantly between tumours (i.e., mice). Metastatic tumours exhibited marked inter-tumour changes in polar compounds, some suggesting different glycolytic capacities. Such tumours also showed larger intra-tumour variations in metabolites involved in nucleotide and cholesterol/fatty acid metabolism, in tandem with less changes in TCA and phospholipid metabolism, compared to non-metastatic tumours. This study shows the valuable contribution of untargeted NMR metabolomics to characterise tumour metabolism, thus opening enticing opportunities to find metabolic markers related to metastatic ability in endocrine breast cancer.

Ether lipid and sphingolipid expression patterns are estrogen receptor-dependently altered in breast cancer cells

Identifying co-expression of lipid species is challenging, but indispensable to identify novel therapeutic targets for breast cancer treatment. Lipid metabolism is often dysregulated in cancer cells, and changes in lipid metabolism affect cellular processes such as proliferation, autophagy, and tumor development. In addition to mRNA analysis of sphingolipid metabolizing enzymes, we performed liquid chromatography time-of-flight mass spectrometry analysis in three breast cancer cell lines. These breast cancer cell lines differ in estrogen receptor and G-protein coupled estrogen receptor 1 status. Our data show that sphingolipids and non-sphingolipids are strongly increased in SKBr3 cells. SKBr3 cells are estrogen receptor negative and G-protein coupled estrogen receptor 1 positive. Treatment with G15, a G-protein coupled estrogen receptor 1 antagonist, abolishes the effect of increased sphingolipid and non-sphingolipid levels in SKBr3 cells. In particular, ether lipids are expressed at much higher levels in cancer compared to normal cells and are strongly increased in SKBr3 cells. Our analysis reveals that this is accompanied by increased sphingolipid levels such as ceramide, sphingadiene-ceramide and sphingomyelin. This shows the importance of focusing on more than one lipid class when investigating molecular mechanisms in breast cancer cells. Our analysis allows unbiased screening for different lipid classes leading to identification of co-expression patterns of lipids in the context of breast cancer. Co-expression of different lipid classes could influence tumorigenic potential of breast cancer cells. Identification of co-regulated lipid species is important to achieve improved breast cancer treatment outcome.

Sulforaphane Diminishes the Formation of Mammary Tumors in Rats Exposed to 17β-Estradiol

Elevated levels of estrogen are a risk factor for breast cancer. In addition to inducing DNA damage, estrogens can enhance cell proliferation as well as modulate fatty acid metabolism that collectively contributes to mammary tumorigenesis. Sulforaphane (SFN) is an isothiocyanate derived from broccoli that is currently under evaluation in multiple clinical trials for prevention of several diseases, including cancer. Previous studies showed that SFN suppressed DNA damage and lipogenesis pathways. Therefore, we hypothesized that administering SFN to animals that are co-exposed to 17β-estradiol (E2) would prevent mammary tumor formation. In our study, 4–6 week old female August Copenhagen Irish rats were implanted with slow-release E2 pellets (3 mg x 3 times) and gavaged 3x/week with either vehicle or 100 μmol/kg SFN for 56 weeks. SFN-treated rats were protected significantly against mammary tumor formation compared to vehicle controls. Mammary glands of SFN-treated rats showed decreased DNA damage while serum free fatty acids and triglyceride species were 1.5 to 2-fold lower in SFN-treated rats. Further characterization also showed that SFN diminished expression of enzymes involved in mammary gland lipogenesis. This study indicated that SFN protects against breast cancer development through multiple potential mechanisms in a clinically relevant hormonal carcinogenesis model.

Sphingosine kinase and sphingosine-1-phosphate receptor signaling pathway in inflammatory gastrointestinal disease and cancers: A novel therapeutic target

Inflammatory gastrointestinal (GI) diseases and malignancies are associated with growing morbidity and cancer-related mortality worldwide. GI tumor and inflammatory cells contain activated sphingolipid-metabolizing enzymes, including sphingosine kinase 1 (SphK1) and SphK2, that generate sphingosine-1-phosphate (S1P), a highly bioactive compound. Many inflammatory responses, including lymphocyte trafficking, are directed by circulatory S1P, present in high concentrations in both the plasma and the lymph of cancer patients. High fat and sugar diet, disbalanced intestinal flora, and obesity have recently been linked to activation of inflammation and SphK/S1P/S1P receptor (S1PR) signaling in various GI pathologies, including cancer. SphK1 overexpression and activation facilitate and enhance the development and progression of esophageal, gastric, and colon cancers. SphK/S1P axis, a mediator of inflammation in the tumor microenvironment, has recently been defined as a target for the treatment of GI disease states, including inflammatory bowel disease and colitis. Several SphK1 inhibitors and S1PR antagonists have been developed as novel anti-inflammatory and anticancer agents. In this review, we analyze the mechanisms of SphK/S1P signaling in GI tissues and critically appraise recent studies on the role of SphK/S1P/S1PR in inflammatory GI disorders and cancers. The potential role of SphK/S1PR inhibitors in the prevention and treatment of inflammation-mediated GI diseases, including GI cancer, is also evaluated.

iNOS as a metabolic enzyme under stress conditions

Nitric oxide (NO) is a free radical acting as a cellular signaling molecule in many different biochemical processes. NO is synthesized from l-arginine through the action of the nitric oxide synthase (NOS) family of enzymes, which includes three isoforms: endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS). iNOS-derived NO has been associated with the pathogenesis and progression of several diseases, including liver diseases, insulin resistance, obesity and diseases of the cardiovascular system. However, transient NO production can modulate metabolism to survive and cope with stress conditions. Accumulating evidence strongly imply that iNOS-derived NO plays a central role in the regulation of several biochemical pathways and energy metabolism including glucose and lipid metabolism during inflammatory conditions. This review summarizes current evidence for the regulation of glucose and lipid metabolism by iNOS during inflammation, and argues for the role of iNOS as a metabolic enzyme in immune and non-immune cells.

Sphingosine kinase 1 activation by estrogen receptor α36 contributes to tamoxifen resistance in breast cancer

In breast cancer, 17β-estradiol (E2) plays critical roles mainly by binding to its canonical receptor, estrogen receptor (ER) α66, and eliciting genomic effects. E2 also triggers rapid, nongenomic responses. E2 activates sphingosine kinase 1 (SphK1), increasing sphingosine-1-phosphate (S1P) that binds to its receptors, leading to important breast cancer signaling. However, the E2 receptor responsible for SphK1 activation has not yet been identified. Here, we demonstrate in triple-negative breast cancer cells, which lack the canonical ERα66 but express the novel splice variant ERα36, that ERα36 is the receptor responsible for E2-induced activation of SphK1 and formation and secretion of S1P and dihydro-S1P, the ligands for S1PRs. Tamoxifen, the first-line endocrine therapy for breast cancer, is an antagonist of ERα66, but an agonist of ERα36, and, like E2, activates SphK1 and markedly increases secretion of S1P. A major problem with tamoxifen therapy is development of acquired resistance. We found that tamoxifen resistance correlated with increased SphK1 and ERα36 expression in tamoxifen-resistant breast cancer cells, in patient-derived xenografts, and in endocrine-resistant breast cancer patients. Our data also indicate that targeting this ERα36 and SphK1 axis may be a therapeutic option to circumvent endocrine resistance and improve patient outcome.

Integrative pathway-based survival prediction utilizing the interaction between gene expression and DNA methylation in breast cancer

Background

Integrative analysis on multi-omics data has gained much attention recently. To investigate the interactive effect of gene expression and DNA methylation on cancer, we propose a directed random walk-based approach on an integrated gene-gene graph that is guided by pathway information.

Methods

Our approach first extracts a single pathway profile matrix out of the gene expression and DNA methylation data by performing the random walk over the integrated graph. We then apply a denoising autoencoder to the pathway profile to further identify important pathway features and genes. The extracted features are validated in the survival prediction task for breast cancer patients.

Results

The results show that the proposed method substantially improves the survival prediction performance compared to that of other pathway-based prediction methods, revealing that the combined effect of gene expression and methylation data is well reflected in the integrated gene-gene graph combined with pathway information. Furthermore, we show that our joint analysis on the methylation features and gene expression profile identifies cancer-specific pathways with genes related to breast cancer.

Conclusions

In this study, we proposed a DRW-based method on an integrated gene-gene graph with expression and methylation profiles in order to utilize the interactions between them. The results showed that the constructed integrated gene-gene graph can successfully reflect the combined effect of methylation features on gene expression profiles. We also found that the selected features by DA can effectively extract topologically important pathways and genes specifically related to breast cancer.

Fingolimod interrupts the cross talk between estrogen metabolism and sphingolipid metabolism within prostate cancer cells

Sphingolipids are critical regulators of tumor microenvironments and play an important role in estrogen-dependent cancers. Estrogen and estrogen metabolites were found to be involved in prostate cancer. Fingolimod (FTY720) is a sphingokinase-1 (SphK1) inhibitor with anticancer properties against various tumor cell types. Herein, we investigated the interference of FTY720 with the cross talk between sphingolipid metabolism and estrogen metabolism within prostate cancer cells. FTY720 showed cytotoxic antiproliferative effects against androgen-dependent and -independent prostate cancer cells with IC₅₀ ranging from 3.0 ± 0.3 to 6.8 ± 1.7 μM. Exposure of prostate cancer cells to FTY720 resulted in a dramatic decrease in the concentration of estradiol, estrone, 4-hydroxyestradiol and 16α-hydroxyestrone compared to control cells. However, FTY720 significantly increased the concentration of 2-methoxyestrone and 2-methoxyestradiol within prostate cancer cells. This was mirrored by significant downregulating of the expression of estrogen and catechol estrogen-synthesizing enzymes (CYP19, CYP1A1 and CYP1B1) within prostate cancer cells. On the other hand, FTY720 significantly upregulated the expression of catechol estrogen-detoxifying enzyme (COMT). Additionally, FTY720 abolished estrogen-stimulated expression of ERα and basal expression of ERβ within prostate cancer cells. Furthermore, FTY720 suppressed the expression of the ER-downstream regulated genes, CXCR4 and cyclin D1. Reciprocally, it was found that estradiol and catechol estrogens significantly induced the expression of SphK1 while methoxylated catechol estrogen suppressed its expression within prostate cancer cells in a dose-dependent manner. Current research has highlighted the hazardous influence of the estrogenic component to prostate cancer. We found that fingolimod (FTY720) could modulate the estrogenic micromilieu and interrupt its cross talk with sphingolipid metabolism.

Expansion of Sphingosine Kinase and Sphingosine-1-Phosphate Receptor Function in Normal and Cancer Cells: From Membrane Restructuring to Mediation of Estrogen Signaling and Stem Cell Programming

Sphingolipids, sphingolipid metabolizing enzymes, and their receptors network are being recognized as part of the signaling mechanisms, which govern breast cancer cell growth, migration, and survival during chemotherapy treatment. Approximately 70% of breast cancers are estrogen receptor (ER) positive and, thus, rely on estrogen signaling. Estrogen activates an intracellular network composed of many cytoplasmic and nuclear mediators. Some estrogen effects can be mediated by sphingolipids. Estrogen activates sphingosine kinase 1 (SphK1) and amplifies the intracellular concentration of sphingosine-1-phosphate (S1P) in breast cancer cells during stimulation of proliferation and survival. Specifically, Estrogen activates S1P receptors (S1PR) and induces growth factor receptor transactivation. SphK, S1P, and S1PR expression are causally associated with endocrine resistance and progression to advanced tumor stages in ER-positive breast cancers in vivo. Recently, the network of SphK/S1PR was shown to promote the development of ER-negative cancers and breast cancer stem cells, as well as stimulating angiogenesis. Novel findings confirm and broaden our knowledge about the cross-talk between sphingolipids and estrogen network in normal and malignant cells. Current S1PRs therapeutic inhibition was indicated as a promising chemotherapy approach in non-responsive and advanced malignancies. Considering that sphingolipid signaling has a prominent role in terminally differentiated cells, the impact should be considered when designing specific SphK/S1PR inhibitors. This study analyzes the dynamic of the transformation of sphingolipid axis during a transition from normal to pathological condition on the level of the whole organism. The sphingolipid-based mediation and facilitation of global effects of estrogen were critically accented as a bridging mechanism that should be explored in cancer prevention.

Insulin-like growth factor receptor and sphingosine kinase are prognostic and therapeutic targets in breast cancer

Background

Targeting the type 1 insulin-like growth factor receptor (IGF1R) in breast cancer remains an ongoing clinical challenge. Oncogenic IGF1R-signaling occurs via activation of PI3K/AKT/MAPK downstream mediators which regulate cell proliferation and protein synthesis. To further understand IGF1R signaling we have investigated the involvement of the oncogenic IGF1R-related sphingosine kinase (SphK) pathway.

Methods

The prognostic (overall survival, OS) and therapeutic (anti-endocrine therapy) co-contribution of IGF1R and SphK1 were investigated using breast cancer patient samples (n = 236) for immunohistochemistry to measure total and phosphorylated IGF1R and SphK1. Kaplan-Meier and correlation analyses were performed to determine the contribution of high versus low IGF1R and/or SphK1 expression to OS in patients treated with anti-endocrine therapy. Cell viability and colony formation in vitro studies were completed using estrogen receptor (ER) positive and negative breast cancer cell-lines to determine the benefit of IGF1R inhibitor (OSI-906) and SphK inhibitor (SKI-II) co-therapy. Repeated measures and 1-way ANOVA were performed to compare drug treatments groups and the Chou-Talalay combination index (CI) was calculated to estimate drug synergism in vitro (CI < 1).

Results

High IGF1R and SphK1 protein co-expression in tumor tissue was associated with improved OS specifically in ER-positive disease and stratified for anti-endocrine therapy. A significant synergistic inhibition of cell viability and/or colony formation following OSI-906 and SKI-II co-treatment in vitro was evident (p < 0.05, CI < 1).

Conclusion

We conclude that high IGF1R and SphK1 co-expression act together as prognostic indicators and are potentially, dual therapeutic targets for the development of a more effective IGF1R-directed combination breast cancer therapy.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3809-0) contains supplementary material, which is available to authorized users.

Sphingosine kinase 1 in breast cancer

Breast cancer affects 1 out of 8 women in the US and is the second highest cause of death from cancer for women, leading to considerable research examining the causes, progression, and treatment of breast cancer. Over the last two decades, sphingosine-1-phosphate (S1P), a potent sphingolipid metabolite, has been implicated in many processes important for breast cancer including growth, progression, transformation and metastasis, and is the focus of this review. In particular, one of the kinases that produces S1P, sphingosine kinase 1 (SphK1), has come under increasing scrutiny as it is commonly upregulated in breast cancer cells and has been linked with poorer prognosis and progression, possibly leading to resistance to certain anti-cancer therapies. In this review, we will also discuss preclinical studies of both estrogen receptor (ER) positive as well as triple-negative breast cancer mouse models with inhibitors of SphK1 and other compounds that target the S1P axis and have shown good promise in reducing tumor growth and metastasis. It is hoped that in the future this will lead to development of novel combination approaches for effective treatment of both conventional hormonal therapy-resistant breast cancer and triple-negative breast cancer.

Plasma and ovarian tissue sphingolipids profiling in patients with advanced ovarian cancer

PURPOSE

The role of lipids in carcinogenesis through induction of abnormal cell lines in the human body is currently undisputable. Based on the literature, bioactive sphingolipids play an essential role in the development and progression of cancer and are involved in the metastatic process. The aim of this study was to determine the concentration of selected sphingolipids in patients with advanced ovarian cancer (AOC, FIGO III/IV, high grade ovarian cancer).

METHODS

Seventy-four patients with ovarian cancer were enrolled. Plasma concentrations of C16-Cer, C18:1-Cer and C18-Cer were assessed by LC/MS/MS. The content of tissue sphingolipids was measured using a UHPLC/MS/MS.

RESULTS

Plasma concentration of 3 ceramides: C16-Cer, C18:1-Cer and C18-Cer was significantly elevated in women with advanced ovarian cancer compared to control group (P=0.031; 0.022; 0.020; respectively). There were increases in concentration of 5 ceramides: C16-Cer, C18:1-Cer, C18-Cer, C24:1-Cer, C24-Cer (P=0.025; 0.049; 0.032; 0.005; 0.013, respectively) and S1P (P=0.004) in ovarian tissue of women with advanced ovarian cancer compared to healthy individuals. Importantly, significantly higher risk of ovarian cancer when the plasma concentration of C16-Cer>311.88ng/100μl (AUC: 0.76, P=0.0261); C18:1-Cer>4.75ng/100μl (AUC: 0.77, P=0.0160) and C18-Cer>100.76ng/100μl (AUC:0.77, P=0.0136) was noticed.

CONCLUSIONS

Bioactive sphingolipids play an essential role in the development and progression of cancer and they also take part in the process of metastasizing. This study suggests that some sphingolipids can be used as potential biomarkers of advanced ovarian cancer and that they can play an important role in the pathogenesis of this disease.

A route-based pathway analysis framework integrating mutation information and gene expression data

We propose a new way of analyzing biological pathways in which the analysis combines both transcriptome data and mutation information and uses the outcome to identify "routes" of aberrant pathways potentially responsible for the etiology of disease. Each pathway route is encoded as a Bayesian Network which is initialized with a sequence of conditional probabilities which are designed to encode directionality of regulatory relationships encoded in the pathways, i.e. activation and inhibition relationships. First, we demonstrate the effectiveness of our model through simulation in which the model was able to easily separate Test samples from Control samples using fictitiously perturbed pathway routes. Second, we apply our model to analyze the Breast Cancer data set, available from TCGA, against many cancer pathways available from KEGG and rank the significance of identified pathways. The outcome is consistent with what have already been reported in the literature. Third, survival analysis has been carried out on the same data set by using pathway routes as features. Overall, we envision that our model of using pathway routes for analysis can further refine the conventional ways of subtyping cancer patients as it can discover additional characteristics specific to individual's tumor.

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.

The method for breast cancer grade prediction and pathway analysis based on improved multiple kernel learning

Breast cancer histologic grade represents the morphological assessment of the tumor’s malignancy and aggressiveness, which is vital in clinically planning treatment and estimating prognosis for patients. Therefore, the prediction of breast cancer grade can markedly elevate the detection of early breast cancer and efficiently guide its treatment. With the advent of high-throughput profiling technology, a large number of data of different types are rapidly generated, and each data provides its unique biological insight. Although many researches focused on cancer grade prediction, hardly most of them attempted to integrate multiple data types, by which we cannot only improve and boost results obtained from learning method, but also have a good understanding or explanation of biological issues. In this paper, we take advantage of a sophisticated supervised learning method called multiple kernel learning (MKL) to design a breast cancer grading predictor fusing heterogeneous data for classification of breast cancer histopathology. Furthermore, we modify our model by involving biological pathway information. The new model can evaluate the significance of various pathways in which differential expression genes fall between different breast cancer grades. The merits of the novel model are lucubration in bridging between omics data and various phenotypes of breast cancer grades, and providing an auxiliary method integrating omics data of cancer mechanism research. In experiments, the proposed method outperforms other state-of-the-art methods and has abundant biological interpretation in explaining differences between breast cancer grades.

Nuclear and extranuclear-initiated estrogen receptor signaling crosstalk and endocrine resistance in breast cancer

Estrogens regulate function of reproductive and non-reproductive tissues in healthy and diseased states including breast cancer. They mainly work through estrogen receptor alpha (ERα) and/or estrogen receptor beta (ERβ). There are various ERα targeting agents that have been used for treatment of ER (+) breast tumors. The impact of direct nuclear activity of ER is very well characterized in ER (+) breast cancers and development and progression of endocrine resistance. Recent studies also suggested important roles for extranuclear-initiated ERα pathways, which would decrease the potency and efficiency of ERα targeting agents. In this mini-review, we will discuss the role of nuclear and extra-nuclear ER signaling and how they relate to therapy resistance in breast cancer.

Sphingosine-1-phosphate and estrogen signaling in breast cancer

Breast cancer remains the most common malignant disease in women. The estrogen receptor-α (ERα) and its ligand 17β-estradiol (E2) play important roles in breast cancer. E2 elicits cellular effects by binding to ERα in the cytosol followed by receptor dimerization and translocation to the nucleus where it regulates gene expression by binding to ERE response elements. However, it has become apparent that E2 also exerts rapid non-genomic effects through membrane-associated receptors. There is emerging evidence that this induces formation of the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P). S1P in turn has been implicated in many processes important in breast cancer progression. One of the enzymes that produce S1P, sphingosine kinase 1 (SphK1), is upregulated in breast cancer and its expression has been correlated with poor prognosis. This review is focused on the role of the SphK/S1P axis in estrogen signaling and breast cancer progression and will discuss new therapeutic approaches targeting this axis for breast cancer treatment.

Sphingosine-1-phosphate receptor 1 transmits estrogens' effects in endothelial cells

We have previously reported that the steroid hormone estrogens stimulate activation of sphingosine kinase 1 (SphK1) and sphingosine-1-phosphate (S1P) receptors in breast cancer cells. Both estrogens and S1P are potent biological modulators of endothelial function in vasculature able to activate multiple effectors, including endothelial nitric oxide synthase (eNOS). In this study we report that treatment of endothelial cells (ECs) with 17β-estradiol (E2) resulted in a rapid, transient, and dose-dependent increase in SphK activity and increased S1P production. The effect was not reproduced by the inactive E2 analogue 17α-E2. Expression of the dominant-negative mutant SphK1(G82D) or transfection of SphK1-targeted siRNA in ECs caused not only a defect in SphK activation by E2, but also a significant inhibition of E2-induced activation of Akt/eNOS. Furthermore, E2 treatment induced internalization of plasma membrane S1P1 receptor, accompanied with an increase in the amount of cytosolic S1P1. By down-regulating S1P1 receptor expression, the S1P1-specific antisense oligonucleotides significantly inhibited E2-induced activation of Akt/eNOS in ECs. E2-induced EC migration and tube formation were also inhibited by S1P1 down-regulation. Thus, the findings indicate an important role of the SphK1/S1P1 pathway in mediating estrogen signaling and its actions in vasculature.