Acid ceramidase 1 expression correlates with a better prognosis in ER-positive breast cancer

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.

Caveolin-1 and lipids: Association and their dualism in oncogenic regulation

Caveolin-1 (Cav-1) is a structural protein of caveolae that functions as a molecular organizer for different cellular functions including endocytosis and cellular signaling. Cancer cells take advantage of the physical position of Cav-1, as it can communicate with extracellular matrix, help to organize growth factor receptors, redistribute cholesterol and glycosphingolipids, and finally transduce signals within the cells for oncogenesis. Recent studies emphasize the exceeding involvement of Cav-1 with different lipid bodies and in altering the metabolism, especially lipid metabolism. However, the association of Cav-1 with different lipid bodies like lipid rafts, lipid droplets, cholesterols, sphingolipids, and fatty acids is remarkably dynamic. The lipid-Cav-1 alliance plays a dual role in carcinogenesis. Both cancer progression and regression are modified and affected by the type of lipid molecule's association with Cav-1. Accordingly, this Cav-1-lipid cooperation exemplifies a cancer-type-specific treatment strategy for a better prognosis of the disease. In this review, we first present Cav-1 as an oncogenic molecule and its communication via lipid raft. We discussed the involvement of Cav-1 with lipid droplets, Cholesterol, sphingolipids, gangliosides, and ceramides. Further, we describe the Cav-1-mediated altered Fatty acid metabolism in cancer and the strategic therapeutic approaches toward Cav-1 targeting.

Natural Products and Small Molecules Targeting Cellular Ceramide Metabolism to Enhance Apoptosis in Cancer Cells

Molecular targeting strategies have been used for years in order to control cancer progression and are often based on targeting various enzymes involved in metabolic pathways. Keeping this in mind, it is essential to determine the role of each enzyme in a particular metabolic pathway. In this review, we provide in-depth information on various enzymes such as ceramidase, sphingosine kinase, sphingomyelin synthase, dihydroceramide desaturase, and ceramide synthase which are associated with various types of cancers. We also discuss the physicochemical properties of well-studied inhibitors with natural product origins and their related structures in terms of these enzymes. Targeting ceramide metabolism exhibited promising mono- and combination therapies at preclinical stages in preventing cancer progression and cemented the significance of sphingolipid metabolism in cancer treatments. Targeting ceramide-metabolizing enzymes will help medicinal chemists design potent and selective small molecules for treating cancer progression at various levels.

The Critical Impact of Sphingolipid Metabolism in Breast Cancer Progression and Drug Response

Breast cancer is the second leading cause of cancer-related death in women in the world, and its management includes a combination of surgery, radiation therapy, chemotherapy, and immunotherapy, whose effectiveness depends largely, but not exclusively, on the molecular subtype (Luminal A, Luminal B, HER2+ and Triple Negative). All breast cancer subtypes are accompanied by peculiar and substantial changes in sphingolipid metabolism. Alterations in sphingolipid metabolite levels, such as ceramides, dihydroceramide, sphingosine, sphingosine-1-phosphate, and sphingomyelin, as well as in their biosynthetic and catabolic enzymatic pathways, have emerged as molecular mechanisms by which breast cancer cells grow, respond to or escape therapeutic interventions and could take on diagnostic and prognostic value. In this review, we summarize the current landscape around two main themes: 1. sphingolipid metabolites, enzymes and transport proteins that have been found dysregulated in human breast cancer cells and/or tissues; 2. sphingolipid-driven mechanisms that allow breast cancer cells to respond to or evade therapies. Having a complete picture of the impact of the sphingolipid metabolism in the development and progression of breast cancer may provide an effective means to improve and personalize treatments and reduce associated drug resistance.

Emerging Roles of Ceramides in Breast Cancer Biology and Therapy

One of the classic hallmarks of cancer is the imbalance between elevated cell proliferation and reduced cell death. Ceramide, a bioactive sphingolipid that can regulate this balance, has long been implicated in cancer. While the effects of ceramide on cell death and therapeutic efficacy are well established, emerging evidence indicates that ceramide turnover to downstream sphingolipids, such as sphingomyelin, hexosylceramides, sphingosine-1-phosphate, and ceramide-1-phosphate, is equally important in driving pro-tumorigenic phenotypes, such as proliferation, survival, migration, stemness, and therapy resistance. The complex and dynamic sphingolipid network has been extensively studied in several cancers, including breast cancer, to find key sphingolipidomic alterations that can be exploited to develop new therapeutic strategies to improve patient outcomes. Here, we review how the current literature shapes our understanding of how ceramide synthesis and turnover are altered in breast cancer and how these changes offer potential strategies to improve breast cancer therapy.

Acid ceramidase, a double-edged sword in cancer aggression: A minireview

Acid ceramidase (AC), the key enzyme of the ceramide metabolic pathway hydrolyzes pro-apoptotic ceramide to sphingosine, which by the action of sphingosine-1-kinase is metabolized to mitogenic sphingosine-1-phosphate. The intracellular level of AC determines ceramide/sphingosine-1-phosphate rheostat which in turn decides the cell fate. The upregulated AC expression during cancerous condition acts as a "double-edged sword" by converting pro-apoptotic ceramide to anti-apoptotic sphingosine-1-phosphate, wherein on one end, the level of ceramide is decreased and on the other end, the level of sphingosine-1-phosphate is increased, thus altogether aggravating the cancer progression. In addition, cancer cells with upregulated AC expression exhibited increased cell proliferation, metastasis, chemoresistance, radioresistance and numerous strategies were developed in the past to effectively target the enzyme. Gene silencing and pharmacological inhibition of AC sensitized the resistant cells to chemo/radiotherapy thereby promoting cell death. The core objective of this review is to explore AC mediated tumour progression and the potential role of AC inhibitors in various cancer cell lines/models.

Endosomes, lysosomes, and the role of endosomal and lysosomal biogenesis in cancer development

Endosomes and lysosomes are membrane-bound organelles crucial for the normal functioning of the eukaryotic cell. The primary function of endosomes relates to the transportation of extracellular material into the intracellular domain. Lysosomes, on the other hand, are primarily involved in the degradation of macromolecules. Endosomes and lysosomes interact through two distinct pathways: kiss-and-run and direct fusion. In addition to the internalization of particles, endosomes also play an important role in cell signaling and autophagy. Disruptions in either of these processes may contribute to cancer development. Lysosomal proteins, such as cathepsins, can play a role in both tumorigenesis and cancer cell apoptosis. Since endosomal and lysosomal biogenesis and signaling are important components of normal cellular growth and proliferation, proteins involved in these processes are attractive targets for cancer research and, potentially, therapeutics. This literature review provides an overview of the endocytic pathway, endolysosome formation, and the interplay between endosomal/lysosomal biogenesis and carcinogenesis.

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.

Histotype-specific analysis of acid ceramidase expression in ovarian cancer

Acid ceramidase (ASAH1) is a key player in sphingolipid metabolism and signaling. It has prognostic value for several cancers, but histotype-specific analyses of ovarian cancer are not yet available. We used three retrospective TMA cohorts encompassing a total of 1106 ovarian cancers with follow-up data for immunohistochemical analysis of acid ceramidase (ASAH1) expression. Patients with sub-optimal debulking and persistent residual tumor after surgery introduced bias in the prognostic analysis and were excluded from further studies. Overall, we detected an association of ASAH1 expression with better prognosis in ovarian cancer patients. ASAH1 expression differed between histological ovarian cancer histotypes with most frequent expression in endometrioid and clear cell ovarian cancer, which are both associated with good prognosis. Stratified subgroup analyses within these histotypes did not reveal significant survival differences, but the power of the analysis may be limited by smaller sample sizes. In contrast to breast cancer, we found only a modest concordance between estrogen receptor status and ASAH1 expression within the endometrioid ovarian cancer histotype. In an exploratory analysis of estrogen receptor negative endometrioid ovarian cancer, ASAH1 expression was associated with significantly better overall survival (P = 0.007). Acid ceramidase is most frequently expressed in endometrioid and clear cell histotypes and could add independent prognostic value to estrogen receptor in endometrioid ovarian cancer. Modulating sphingolipid metabolism may lead to novel therapeutic intervention strategies for this disease.

Acid Ceramidase: A Novel Therapeutic Target in Cancer

Sphingolipids are important constituents of the eukaryotic cell membrane which govern various signaling pathways related to different aspects of cell survival. Ceramide and Sphingosine are interconvertible sphingolipid metabolites, out of which Ceramide is pro-apoptotic and sphingosine is anti-apoptotic in nature. The conversion of ceramide to sphingosine is mediated by Acid Ceramidase (ASAH1) thus maintaining a rheostat between a tumor suppressor and a tumor promoter. This rheostat is completely altered in many tumors leading to uncontrolled proliferation. This intriguing property of ASAH1 can be used by cancer cells to their advantage, by increasing the expression of the tumor promoter, sphingosine inside cells, thus creating a favorable environment for cancer growth. The different possibilities through which this enzyme serves its role in formation, progression and resistance of different types of cancers will lead to the possibility of making Acid Ceramidase a promising drug target. This review discusses the current understanding of the role of acid ceramidase in cancer progression, metastasis and resistance, strategies to develop novel natural and synthetic inhibitors of ASAH1 and their usefulness in cancer therapy.

Clinical application of ceramide in cancer treatment

Development of innovative strategies for cancer treatment is a pressing public health issue. Despite recent advances, the mechanisms of cancer progression and the resistance to cancer treatment have not been fully elucidated. Sphingolipids, including ceramide and sphingoshin-1-phosphate, are bioactive mediators that regulate cancer cell death and survival through the dynamic balance of what has been termed the 'sphingolipid rheostat'. Specifically, ceramide, which acts as the central hub of sphingolipid metabolism, is generated via three major pathways by many stressors, including anti-cancer treatments, environmental stresses, and cytokines. We have previously shown in breast cancer patients that elevated ceramide correlated with less aggressive cancer phenotypes, leading to a prognostic impact. Recent studies showed that ceramide have the possibility of becoming the reinforcing agent of cancer treatment as well as other roles such as nanoparticles and diagnostic biomarker. We review ceramide as one of the key molecules to investigate in overcoming resistance to current drug therapies and in becoming one of the newest cancer treatments.

A Guanidine-Based Synthetic Compound Suppresses Angiogenesis via Inhibition of Acid Ceramidase

Angiogenesis generates new blood vessels from pre-existing vessels. Tumors induce the formation of new blood vessels to ensure sufficient oxygen and nutrients for their growth. Normally, angiogenesis is induced by various pro-angiogenesis factors, including vascular endothelial growth factor (VEGF). Inhibition of VEGF is a promising approach to cancer treatment. A guanidine-based synthetic compound, E2, was identified as a potent hit from 68 guanidine-based derivatives by screening for angiogenesis inhibitors showing antiproliferative activity in human umbilical vein endothelial cells (HUVECs). To explore the mode of action of E2, target proteins were investigated using phage display biopanning, and acid ceramidase 1 (ASAH1) was identified as an E2-binding protein. Drug affinity responsive target stability (DARTS) and ASAH1 activity assays revealed the direct binding of E2 to ASAH1. Moreover, siRNA knockdown of ASAH1 demonstrated its role as an angiogenesis factor. Consequently, E2 inhibited chemoinvasion and tube formation of HUVECs in a dose-dependent manner. E2 also potently suppressed neo-vascularization of chorioallantoic membranes in vivo. Collectively, these data suggest that E2 is a novel angiogenesis inhibitor and ASAH1 is proposed to be a new antiangiogenesis target.

Lysosomal acid ceramidase ASAH1 controls the transition between invasive and proliferative phenotype in melanoma cells

Phenotypic plasticity and subsequent generation of intratumoral heterogeneity underly key traits in malignant melanoma such as drug resistance and metastasis. Melanoma plasticity promotes a switch between proliferative and invasive phenotypes characterized by different transcriptional programs of which MITF is a critical regulator. Here, we show that the acid ceramidase ASAH1, which controls sphingolipid metabolism, acted as a rheostat of the phenotypic switch in melanoma cells. Low ASAH1 expression was associated with an invasive behavior mediated by activation of the integrin alphavbeta5-FAK signaling cascade. In line with that, human melanoma biopsies revealed heterogeneous staining of ASAH1 and low ASAH1 expression at the melanoma invasive front. We also identified ASAH1 as a new target of MITF, thereby involving MITF in the regulation of sphingolipid metabolism. Together, our findings provide new cues to the mechanisms underlying the phenotypic plasticity of melanoma cells and identify new anti-metastatic targets.

Anticancer effect of acid ceramidase inhibitor ceranib-2 in human breast cancer cell lines MCF-7, MDA MB-231 by the activation of SAPK/JNK, p38 MAPK apoptotic pathways, inhibition of the Akt pathway, downregulation of ERα

Acid ceramidase is the key enzyme of the ceramide metabolic pathway, which plays a vital role in regulating ceramide - sphingosine-1-phosphate rheostat. Ceramide acts as a proapoptotic molecule, but its metabolite sphingosine-1-phosphate, in contrast, signals for cell proliferation, cell survival, and angiogenesis. Acid ceramidase is highly upregulated in breast tumors and treatment with an acid ceramidase inhibitor, ceranib-2, significantly induced apoptosis in human breast cancer cell lines. However, the mechanisms underlying the induction of apoptosis remain ambiguous to date. Hence, in the present study, we have explored ceranib-2-mediated apoptotic signaling pathways in human breast cancer cell lines. MCF-7 and MDA MB-231 cells were treated with IC50 doses of ceranib-2 and tamoxifen. Nuclear changes showed the apoptotic effect of ceranib-2 in both the cell lines. Loss in the mitochondrial membrane potential was observed only in ceranib-2-treated MCF-7 cells. Ceranib-2 activated intrinsic and extrinsic apoptotic pathways in MCF-7 cells, but only the extrinsic apoptotic pathway was activated in MDA MB-231 cells. Further, ceranib-2 induced apoptosis by activating SAPK/JNK (stress-activated protein kinase/c-Jun N-terminal kinase), p38 MAPK (mitogen-activated protein kinase) apoptotic pathways and by inhibiting the Akt (antiapoptotic) pathway in both the cell lines. Most importantly, ERα (estrogen receptor-α) expression was highly downregulated after ceranib-2 treatment and a docking study predicted the highest binding affinity of ceranib-2 than tamoxifen with ERα in MCF-7 cells. Hence, ceranib-2 may have potential as a chemotherapeutic drug of breast cancer.

The value of detection of S100A8 and ASAH1 in predicting the chemotherapy response for breast cancer patients

Chemotherapy plays an important role in the treatment of breast cancer. However, chemoresistance remains the main obstacle for effective treatment, leading to poor prognosis. This study aims to investigate the value of detection of S100A8 and ASAH1 in predicting the chemotherapy response. Miller and Payne grades were used to assess the chemotherapy response in breast cancers. The expression of S100A8 and ASAH1, as well as ER, PR, HER2 and Ki-67 were assessed by immunohistochemical staining in 120 cases of non-special type invasive ductal carcinoma (IDC-NOS). S100A8 expression was higher in chemosensitive breast cancers than chemoresistant ones. Moreover, S100A8 expression was significantly correlated with the molecular subtypes and histological grade, but not with patients' age, tumor size and lymph nodes status. However, there was no significant difference in ASAH1 expression between chemoresistant and chemosensitive group. We also found that higher ASAH1 expression was correlated with positive lymph nodes status, but not with age, tumor size, molecular subtypes and histological grade. S100A8 was valuable in predicting chemotherapy response in breast cancers. The expression of ASAH1 was associated significantly with lymph nodes metastasis, indicating that ASAH1 may serve as a biomarker to predict patients' lymph nodes status in breast cancers.

Protein signatures of molecular pathways in non-small cell lung carcinoma (NSCLC): comparison of glycoproteomics and global proteomics

Background

Non-small cell lung carcinoma (NSCLC) remains the leading cause of cancer deaths in the United States. More than half of NSCLC patients have clinical presentations with locally advanced or metastatic disease at the time of diagnosis. The large-scale genomic analysis of NSCLC has demonstrated that molecular alterations are substantially different between adenocarcinoma (ADC) and squamous cell carcinoma (SqCC). However, a comprehensive analysis of proteins and glycoproteins in different subtypes of NSCLC using advanced proteomic approaches has not yet been conducted.

Methods

We applied mass spectrometry (MS) technology featuring proteomics and glycoproteomics to analyze six primary lung SqCCs and eleven ADCs, and we compared the expression level of proteins and glycoproteins in tumors using quantitative proteomics. Glycoproteins were analyzed by enrichment using a chemoenzymatic method, solid-phase extraction of glycopeptides, and quantified by iTRAQ-LC–MS/MS. Protein quantitation was further annotated via Ingenuity Pathway Analysis.

Results

Over 6000 global proteins and 480 glycoproteins were quantitatively identified in both SqCC and ADC. ADC proteins (8337) consisted of enzymes (22.11%), kinases (5.11%), transcription factors (6.85%), transporters (6.79%), and peptidases (3.30%). SqCC proteins (6967) had a very similar distribution. The identified glycoproteins, in order of relative abundance, included membrane (42%) and extracellular matrix (>33%) glycoproteins. Oncogene-coded proteins (82) increased 1.5-fold among 1047 oncogenes identified in ADC, while 124 proteins from SqCC were up-regulated in tumor tissues among a total of 827 proteins. We identified 680 and 563 tumor suppressor genes from ADC and SqCC, respectively.

Conclusion

Our systematic analysis of proteins and glycoproteins demonstrates changes of protein and glycoprotein relative abundance in SqCC (TP53, U2AF1, and RXR) and in ADC (SMARCA4, NOTCH1, PTEN, and MST1). Among them, eleven glycoproteins were upregulated in both ADC and SqCC. Two glycoproteins (ELANE and IGFBP3) were only increased in SqCC, and six glycoproteins (ACAN, LAMC2, THBS1, LTBP1, PSAP and COL1A2) were increased in ADC. Ingenuity Pathway Analysis (IPA) showed that several crucial pathways were activated in SqCC and ADC tumor tissues.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-017-9166-9) contains supplementary material, which is available to authorized users.

Endosomal gene expression: a new indicator for prostate cancer patient prognosis?

Prostate cancer continues to be a major cause of morbidity and mortality in men, but a method for accurate prognosis in these patients is yet to be developed. The recent discovery of altered endosomal biogenesis in prostate cancer has identified a fundamental change in the cell biology of this cancer, which holds great promise for the identification of novel biomarkers that can predict disease outcomes. Here we have identified significantly altered expression of endosomal genes in prostate cancer compared to non-malignant tissue in mRNA microarrays and confirmed these findings by qRT-PCR on fresh-frozen tissue. Importantly, we identified endosomal gene expression patterns that were predictive of patient outcomes. Two endosomal tri-gene signatures were identified from a previously published microarray cohort and had a significant capacity to stratify patient outcomes. The expression of APPL1, RAB5A, EEA1, PDCD6IP, NOX4 and SORT1 were altered in malignant patient tissue, when compared to indolent and normal prostate tissue. These findings support the initiation of a case-control study using larger cohorts of prostate tissue, with documented patient outcomes, to determine if different combinations of these new biomarkers can accurately predict disease status and clinical progression in prostate cancer patients.

Targeting ceramide metabolic pathway induces apoptosis in human breast cancer cell lines

The sphingolipid ceramide is a pro apoptotic molecule of ceramide metabolic pathway and is hydrolyzed to proliferative metabolite, sphingosine 1 phosphate by the action of acid ceramidase. Being upregulated in the tumors of breast, acid ceramidase acts as a potential target for breast cancer therapy. We aimed at targeting this enzyme with a small molecule acid ceramidase inhibitor, Ceranib 2 in human breast cancer cell lines MCF 7 and MDA MB 231. Ceranib 2 effectively inhibited the growth of both the cell lines in dose and time dependant manner. Morphological apoptotic hallmarks such as chromatin condensation, fragmented chromatin were observed in AO/EtBr staining. Moreover, ladder pattern of fragmented DNA observed in DNA gel electrophoresis proved the apoptotic activity of Ceranib 2 in breast cancer cell lines. The apoptotic events were associated with significant increase in the expression of pro-apoptotic genes (Bad, Bax and Bid) and down regulation of anti-apoptotic gene (Bcl 2). Interestingly, increase in sub G1 population of cell cycle phase analysis and elevated Annexin V positive cells after Ceranib 2 treatment substantiated its apoptotic activity in MCF 7 and MDA MB 231 cell lines. Thus, we report Ceranib 2 as a potent therapeutic agent against both ER(+) and ER(-) breast cancer cell lines.

Acid ceramidase is associated with an improved prognosis in both DCIS and invasive breast cancer

Acid ceramidase (ASAH1) a key enzyme of sphingolipid metabolism converting pro-apoptotic ceramide to sphingosine has been shown to be overexpressed in various cancers. We previously demonstrated higher expression of ASAH1 in ER positive compared to ER negative breast cancer. In the current study we performed subtype specific analyses of ASAH1 gene expression in invasive and non invasive breast cancer. We show that expression of ASAH1 is mainly associated with luminal A - like cancers which are known to have the best prognosis of all breast cancer subtypes. Moreover tumors with high ASAH1 expression among the other subtypes are also characterized by an improved prognosis. The good prognosis of tumors with high ASAH1 is independent of the type of adjuvant treatment in breast cancer and is also detected in non small cell lung cancer patients. Moreover, even in pre-invasive DCIS of the breast ASAH1 is associated with a luminal phenotype and a reduced frequency of recurrences. Thus, high ASAH1 expression is generally associated with an improved prognosis in invasive breast cancer independent of adjuvant treatment and could also be valuable as prognostic factor for pre-invasive DCIS.

High CerS5 expression levels associate with reduced patient survival and transition from apoptotic to autophagy signalling pathways in colorectal cancer

Ceramide synthase 5 is involved in the de novo synthesis of ceramide, a sphingolipid involved in cell death and proliferation. In this study, we investigated the role of ceramide synthase 5 in colorectal cancer by examining ceramide synthase 5 expression, clinico-pathological parameters and association with survival/death signalling pathways in cancer. Immunohistochemical analysis of CerS5 was performed on 102 colorectal cancer samples using tissue microarrays constructed from formalin-fixed and paraffin-embedded tissues. We found strong membranous ceramide synthase 5 staining in 57 of 102 (56%) colorectal cancers. A multivariate Cox regression analysis of ceramide synthase 5 expression adjusted for disease stage, differentiation and lymphovascular invasion revealed reduced 5-year overall survival (p = 0.001) and 5-year recurrence-free survival (p = 0.002), with hazard ratios of 4.712 and 4.322, respectively. The effect of ceramide synthase 5 expression on tumourigenic processes was further characterised by reverse phase protein array analysis. Reverse phase protein arrays were generated from laser capture microdissection-enriched carcinoma cells from 19 fresh-frozen colorectal cancer tissues. Measurements of phosphorylation and total levels of signalling proteins involved in apoptosis, autophagy and other cancer-related pathways revealed two distinct signalling networks; weak membranous ceramide synthase 5 intensity was associated with a proteomic network dominated by signalling proteins linked to apoptosis, whereas strong ceramide synthase 5 intensity was associated with a proteomic sub-network mostly composed of proteins linked to autophagy. In conclusion, high ceramide synthase 5 expression was found in colorectal cancer tissue and was associated with poorer patient outcomes. Our findings suggest that this may be mediated by a transition from apoptotic to autophagy signalling pathways in ceramide synthase 5 High expressing tumours, thus implicating ceramide synthase 5 in the progression of colorectal cancer.

Ceramide synthases CerS4 and CerS5 are upregulated by 17β-estradiol and GPER1 via AP-1 in human breast cancer cells

Ceramide synthases (CerS) are important enzymes of the sphingolipid pathway, responsible for the production of ceramides with distinct chain lengths. In human breast cancer tissue, we detected a significant increase in CerS4 and CerS6 mRNA in estrogen receptor positive (ER+) cancer tissue. To clarify the molecular mechanism of this upregulation, we cloned CerS2, -4, -5 and CerS6 promoter and 3'-UTR fragments into luciferase reporter gene plasmids and determined luciferase activity in MCF-7 (ERα/β) and MDA-MB-231 (ERβ) cells after 17β-estradiol treatment. Only the activities of CerS4 and CerS5 promoter Luc constructs, as well as CerS2- and CerS5-3'-UTR Luc constructs increased after estradiol treatment in MCF-7 cells, and this could be inhibited by the anti-estrogen fulvestrant. Co-transfection with the G protein-coupled estrogen receptor 1 (GPER1) also enhanced CerS2, CerS4 and CerS6 promoter activity whereas CerS5 promoter activity was inhibited in both cell lines. Promoter deletion and mutation constructs from CerS4 and CerS5 promoters revealed that estradiol and GPER1 mediate their effects on both promoters by activating AP-1, most likely through dimerization of c-Jun and c-Fos. At least we could show, that cell proliferation induced by estradiol could be blocked by co-treatment with Fumonisin B1, indicating that upregulation of CerS in breast cancer cells by estrogen is important for cell proliferation and possibly tumor development. In conclusion, our data highlight transcriptional and posttranscriptional mechanisms regulating CerS expression in human cells which provide the basis for further studies investigating the regulation of CerS expression and ceramide synthesis after diverse stimuli in physiological and pathophysiological processess.

Ceramide kinase promotes tumor cell survival and mammary tumor recurrence

Recurrent breast cancer is typically an incurable disease and, as such, is disproportionately responsible for deaths from this disease. Recurrent breast cancers arise from the pool of disseminated tumor cells (DTC) that survive adjuvant or neoadjuvant therapy, and patients with detectable DTCs following therapy are at substantially increased risk for recurrence. Consequently, the identification of pathways that contribute to the survival of breast cancer cells following therapy could aid in the development of more effective therapies that decrease the burden of residual disease and thereby reduce the risk of breast cancer recurrence. We now report that ceramide kinase (Cerk) is required for mammary tumor recurrence following HER2/neu pathway inhibition and is spontaneously upregulated during tumor recurrence in multiple genetically engineered mouse models for breast cancer. We find that Cerk is rapidly upregulated in tumor cells following HER2/neu downregulation or treatment with Adriamycin and that Cerk is required for tumor cell survival following HER2/neu downregulation. Consistent with our observations in mouse models, analysis of gene expression profiles from more than 2,200 patients revealed that elevated CERK expression is associated with an increased risk of recurrence in women with breast cancer. In addition, although CERK expression is associated with aggressive subtypes of breast cancer, including those that are estrogen receptor-negative, HER2(+), basal-like, or high grade, its association with poor clinical outcome is independent of these clinicopathologic variables. Together, our findings identify a functional role for Cerk in breast cancer recurrence and suggest the clinical utility of agents targeted against this prosurvival pathway.

Re-configuration of sphingolipid metabolism by oncogenic transformation

The sphingolipids are one of the major lipid families in eukaryotes, incorporating a diverse array of structural variants that exert a powerful influence over cell fate and physiology. Increased expression of sphingosine kinase 1 (SPHK1), which catalyses the synthesis of the pro-survival, pro-angiogenic metabolite sphingosine 1-phosphate (S1P), is well established as a hallmark of multiple cancers. Metabolic alterations that reduce levels of the pro-apoptotic lipid ceramide, particularly its glucosylation by glucosylceramide synthase (GCS), have frequently been associated with cancer drug resistance. However, the simple notion that the balance between ceramide and S1P, often referred to as the sphingolipid rheostat, dictates cell survival contrasts with recent studies showing that highly potent and selective SPHK1 inhibitors do not affect cancer cell proliferation or survival, and studies demonstrating higher ceramide levels in some metastatic cancers. Recent reports have implicated other sphingolipid metabolic enzymes such as acid sphingomyelinase (ASM) more strongly in cancer pathogenesis, and highlight lysosomal sphingolipid metabolism as a possible weak point for therapeutic targeting in cancer. This review describes the evidence implicating different sphingolipid metabolic enzymes and their products in cancer pathogenesis, and suggests how newer systems-level approaches may improve our overall understanding of how oncogenic transformation reconfigures sphingolipid metabolism.

CCNA2 is a prognostic biomarker for ER+ breast cancer and tamoxifen resistance

Identification of effective prognostic biomarkers and targets are of crucial importance to the management of estrogen receptor positive (ER+) breast cancer. CCNA2 (also known as CyclinA2) belongs to the highly conserved cyclin family and is significantly overexpressed in various cancer types. In this study, we demonstrated that CCNA2 had significant predictive power in distant metastasis free survival, disease free survival, recurrence free survival and overall survival of ER+ breast cancer patients. We also found that CCNA2 was closely associated with tamoxifen resistance. In addition, gene set enrichment analysis (GSEA) revealed that its expression was positively associated with genes overexpressed in endocrine therapy resistant samples. Finally, though CCNA2-Drug interaction network, we demonstrated the interactions between CCNA2 and several available cancer drugs. Overall, we suggest that CCNA2 is a biomarker for the prognosis of ER+ breast cancer and monitoring of tamoxifen efficacy. It's also a promising target for developing new strategies to prevent or even reverse tamoxifen resistance. Moreover, CCNA2 expression may help monitoring tamoxifen efficacy and directing personalized therapies. Nevertheless, in vivo and in vitro experiments and multi-center randomized controlled clinical trials are still needed before its application in clinical settings.

Evolving concepts in cancer therapy through targeting sphingolipid metabolism

Traditional methods of cancer treatment are limited in their efficacy due to both inherent and acquired factors. Many different studies have shown that the generation of ceramide in response to cytotoxic therapy is generally an important step leading to cell death. Cancer cells employ different methods to both limit ceramide generation and to remove ceramide in order to become resistant to treatment. Furthermore, sphingosine kinase activity, which phosphorylates sphingosine the product of ceramide hydrolysis, has been linked to multidrug resistance, and can act as a strong survival factor. This review will examine several of the most frequently used cancer therapies and their effect on both ceramide generation and the mechanisms employed to remove it. The development and use of inhibitors of sphingosine kinase will be focused upon as an example of how targeting sphingolipid metabolism may provide an effective means to improve treatment response rates and reduce associated treatment toxicity. This article is part of a Special Issue entitled Tools to study lipid functions.

Acid ceramidase (AC)--a key enzyme of sphingolipid metabolism--correlates with better prognosis in epithelial ovarian cancer

Acid ceramidase (AC), a key enzyme of sphingolipid metabolism, seems to play an important role in cancer progression. The objective of this study was to explore the expression of AC in ovarian cancer and its impact on prognosis. Expression analysis of AC in n=112 ovarian cancer patients was performed by immunohistochemical analysis of primary paraffin-embedded tumor samples. The results were scored on the basis of the staining intensity and percentage of positive tumor cells, resulting in an immunoreactive score from 0 to 12. These results were correlated to clinical and pathologic characteristics and survival. AC expression correlated significantly only with FIGO stage (0.047). In serous carcinoma, low level of AC was independently associated with reduced progression-free survival and overall survival of 12.0 mo [95% confidence interval (CI), 5.78-18.23] versus 18.1 mo (95% CI, 11.61-24.59; P=0.008) and 35.7 mo (95% CI, 22.24-47.16) versus 58.7 mo (95% CI, 36.48-80.91; P=0.032), respectively. In multivariate analysis, AC presents as an independent prognostic factor for progression-free survival (hazard ratio 1.88; 95% CI, 1.13-3.11; P=0.015). AC is a prognostic factor in epithelial ovarian cancer. Low AC expression can be associated with tumor progression in carcinoma of the ovaries. These results are in contrast to the concept of AC as a promoter for cancer progression. Nevertheless, they are supported by the lately discovered tumor-suppressing function of sphingosine, the enzymatic product of AC.

Identification of the N-acylsphingosine amidohydrolase 1 gene (ASAH1) for susceptibility to schizophrenia in a Han Chinese population

OBJECTIVES

To study the involvement of the N-acylsphingosine amidohydrolase 1 gene (ASAH1) in the susceptibility to schizophrenia in the Han Chinese population.

METHODS

We performed cDNA microarray analysis to exam the gene expression profile in six schizophrenic patients and six healthy controls. We evaluated the ASAH1 expression levels in 30 subjects with chronic schizophrenia and 30 healthy controls by using real-time polymerase chain reaction (PCR). A total of 254 unrelated probands with schizophrenia and their biological parents were also genotyped at three single nucleotide polymorphisms (SNPs: rs3753118, rs3753116, and rs7830490) of the ASAH1 gene for association analysis.

RESULTS

In the microarray analysis, the ASAH1 gene was down-regulated in all schizophrenic patients compared with healthy controls. In real-time PCR, the ASAH1 expression levels for schizophrenic patients with positive family history were significantly decreased (P = 0.020). In the association analyses, two SNPs (rs7830490 and rs3753118) and one haplotype (rs7830490 (A)-rs3753116 (G)) of ASAH1 showed significant evidence of nominal associations with schizophrenia (P = 0.026; P = 0.046; P = 0.007, respectively). The haplotype remained statistically significant (empirical P = 0.045) after correction for multiple testing.

CONCLUSIONS

This study supports that the ASAH1 gene may be a potential candidate gene for schizophrenia in Han Chinese subjects.

Clinical utility of serum autoantibodies detected by protein microarray in melanoma

Better prognostic and predictive markers in melanoma are needed to select patients for therapy. We utilized a dual-lectin affinity chromatography and a natural protein microarray-based analysis to select a subproteome of target glycoproteins to profile serum antibodies against melanoma associated antigens that may predict nodal positivity. We identified 5 melanoma-associated antigens using this microarray coupled to mass spectrometry; GRP75, GRP94, ASAH1, CTSD and LDHB. We evaluated their predictive value for nodal status adjusting for age, gender, Breslow thickness, mitotic rate and ulceration using standard logistic regression. After adjustment, ASAH1, CTSD and LDHB were significantly negatively associated with nodal status (P = 0.0008) and GRP94 was significantly positively associated (P = 0.014). Our best multivariate model for nodal positivity included Breslow thickness, presence of serum anti-ASAH1, anti-LDHB or anti-CTSD, and presence of serum anti-GRP94, with an area under the ROC curve of 0.869. If validated, these results show promise for selecting clinically node negative patients for SLN biopsy. In addition, there is strong potential for glycoprotein microarray to screen serum autoantibodies that may identify patients at high risk of distant metastases or those likely or unlikely to respond to treatment, and these proteins may serve as targets for intervention.

Drug targeting of sphingolipid metabolism: sphingomyelinases and ceramidases

Sphingolipids represent a class of diverse bioactive lipid molecules that are increasingly appreciated as key modulators of diverse physiologic and pathophysiologic processes that include cell growth, cell death, autophagy, angiogenesis, and stress and inflammatory responses. Sphingomyelinases and ceramidases are key enzymes of sphingolipid metabolism that regulate the formation and degradation of ceramide, one of the most intensely studied classes of sphingolipids. Improved understanding of these enzymes that control not only the levels of ceramide but also the complex interconversion of sphingolipid metabolites has provided the foundation for the functional analysis of the roles of sphingolipids. Our current understanding of the roles of various sphingolipids in the regulation of different cellular processes has come from loss-of-function/gain-of-function studies utilizing genetic deletion/downregulation/overexpression of enzymes of sphingolipid metabolism (e.g. knockout animals, RNA interference) and from the use of pharmacologic inhibitors of these same enzymes. While genetic approaches to evaluate the functional roles of sphingolipid enzymes have been instrumental in advancing the field, the use of pharmacologic inhibitors has been equally important in identifying new roles for sphingolipids in important cellular processes.The latter also promises the development of novel therapeutic targets with implications for cancer therapy, inflammation, diabetes, and neurodegeneration. In this review, we focus on the status and use of pharmacologic compounds that inhibit sphingomyelinases and ceramidases, and we will review the history, current uses and future directions for various small molecule inhibitors, and will highlight studies in which inhibitors of sphingolipid metabolizing enzymes have been used to effectively treat models of human disease.

C6-ceramide and targeted inhibition of acid ceramidase induce synergistic decreases in breast cancer cell growth

The sphingolipid ceramide is known to play a central role in chemo- and radiation-induced cell death. Acid ceramidase (AC) hydrolyzes ceramide, and thus reduces intracellular levels of this proapoptotic lipid. The role of AC as a putative anticancer target is supported by reports of upregulation in prostate cancer and in some breast tumors. In this study, we determined whether the introduction of an AC inhibitor would enhance the apoptosis-inducing effects of C6-ceramide (C6-cer) in breast cancer cells. Cultured breast cancer cells were treated with DM102 [(2R,3Z)-N-(1-hydroxyoctadec-3-en-2-yl)pivalamide, C6-cer, or the combination. Cell viability and cytotoxic synergy were assessed. Activation of apoptotic pathways, generation of reactive oxygen species, and mitochondrial transmembrane potential were determined. DM102 was a more effective AC inhibitor than N-oleoylethanolamine (NOE) and (1R,2R)-2-N-(tetradecanoylamino)-1-(4'-nitrophenyl)-1,3-propandiol (B-13) in MDA-MB-231, MCF-7, and BT-474 cells. As single agents, C6-cer (IC(50) 5-10 μM) and DM102 (IC(50) 20 μM) were only moderately cytotoxic in MDA-MB-231, MCF-7, and SK-BR-3 cells. Co-administration, however, produced synergistic decreases in viability (combination index <0.5) in all cell lines. Apoptosis was confirmed in MDA-MB-231 cells by detection of caspase 3 cleavage and a >3-fold increase in caspase 3/7 activation, PARP cleavage, and a >70% increase in Annexin-V positive cells. C6-cer/DM102 increased ROS levels 4-fold in MDA-MB-231 cells, shifted the ratio of Bax:Bcl-2 to >9-fold that of control cells, and resulted in mitochondrial membrane depolarization. DM102 also increased the synthesis of (3)H-palmitate-labeled long-chain ceramides by 2-fold when C6-cer was present. These data support the effectiveness of targeting AC in combination with exogenous short-chain ceramide as an anticancer strategy, and warrant continued investigation into the utility of the C6-cer/DM102 drug duo in human breast cancer.

The interplay between bioactive sphingolipids and steroid hormones

Steroid hormones regulate various physiological processes including development, reproduction, and metabolism. These regulatory molecules are synthesized from cholesterol in endocrine organs - such as the adrenal glands and gonads - via a multi-step enzymatic process that is catalyzed by the cytochrome P450 superfamily of monooxygenases and hydroxysteroid dehydrogenases. Steroidogenesis is induced by trophic peptide hormones primarily via the activation of a cAMP/protein kinase A (PKA)-dependent pathway. However, other signaling molecules, including cytokines and growth factors, control the steroid hormone biosynthetic pathway. More recently, sphingolipids, including ceramide, sphingosine-1-phosphate, and sphingosine, have been found to modulate steroid hormone secretion at multiple levels. In this review, we provide a brief overview of the mechanisms by which sphingolipids regulate steroidogenesis. In addition, we discuss how steroid hormones control sphingolipid metabolism. Finally, we outline evidence supporting the emerging role of bioactive sphingolipids in various nuclear processes and discuss a role for nuclear sphingolipid metabolism in the control of gene transcription.

Ceramide and ceramide 1-phosphate in health and disease

Sphingolipids are essential components of cell membranes, and many of them regulate vital cell functions. In particular, ceramide plays crucial roles in cell signaling processes. Two major actions of ceramides are the promotion of cell cycle arrest and the induction of apoptosis. Phosphorylation of ceramide produces ceramide 1-phosphate (C1P), which has opposite effects to ceramide. C1P is mitogenic and has prosurvival properties. In addition, C1P is an important mediator of inflammatory responses, an action that takes place through stimulation of cytosolic phospholipase A2, and the subsequent release of arachidonic acid and prostaglandin formation. All of the former actions are thought to be mediated by intracellularly generated C1P. However, the recent observation that C1P stimulates macrophage chemotaxis implicates specific plasma membrane receptors that are coupled to Gi proteins. Hence, it can be concluded that C1P has dual actions in cells, as it can act as an intracellular second messenger to promote cell survival, or as an extracellular receptor agonist to stimulate cell migration.