The key role of sphingolipid metabolism in cancer: New therapeutic targets, diagnostic and prognostic values, and anti-tumor immunotherapy resistance

Uncovering metabolic signatures in cancer-derived exosomes: LC-MS/MS and NMR profiling

Understanding the intricate interplay between cancer metabolism and intercellular communication within the tumour microenvironment (TME) is crucial for advancing cancer diagnostics and therapeutics. In this study, we investigate the metabolites present in exosomes derived from three distinct cancer cell lines: pancreatic cancer (MiaPaCa-2), lung cancer (A549), and glioma (C6). Exosomes were isolated using ultrafiltration and characterized using a combination of techniques including nanoparticle tracking analysis (NTA), electron microscopy (EM), western blotting (WB) and Fourier-transform infrared (FTIR) spectroscopy. Leveraging state-of-the-art metabolomics techniques, including untargeted LC-MS/MS and NMR analyses, we elucidated the metabolic signatures encapsulated within cancer-derived exosomes. Notably, our investigation represents the first exploration of exosomal metabolites from pancreatic and glioma cells, addressing a significant gap in current knowledge. Furthermore, our study investigates the correlation between metabolites derived from different cancer cells, shedding light on potential metabolic interactions within the TME. Through comprehensive analyses, this study provides insights into dysregulated metabolic pathways driving cancer progression and offers novel perspectives on the diagnostic and therapeutic utility of exosomal metabolites. Importantly, common metabolites identified among cancer types suggest potential markers detectable by multiple techniques, enhancing their clinical applicability.

Metabolomics analysis reveals resembling metabolites between humanized γδ TCR mice and human plasma

Gamma delta (γδ) T cells, which reside in mucosal and epithelial tissues, are integral to immune responses and are involved in various cancers, autoimmune, and infectious diseases. To study human γδ T cells to a translational level, we developed γδ humanized TCR-T1 (HuTCR-T1) mice using our TruHumanization platform. We compared the metabolomic profiles from plasma samples of wild-type (WT), γδ HuTCR-T1 mice, and humans using UHPLC-MS/MS. Untargeted metabolomics and lipidomics were used to screen all detectable metabolites. Principal component analysis revealed that the metabolomic profiles of γδ HuTCR-T1 mice closely resemble those of humans, with a clear segregation of metabolites between γδ HuTCR-T1 and WT mice. Most humanized γδ metabolites were classified as lipids, followed by organic compounds and amino acids. Pathway analysis identified significant alterations in the metabolism of tryptophan, tyrosine, sphingolipids, and glycerophospholipids, shifting these pathways towards a more human-like profile. Immunophenotyping showed that γδ HuTCR-T1 mice maintained normal proportions of both lymphoid and myeloid immune cell populations, closely resembling WT mice, with only a few exceptions. These findings demonstrate that the γδ HuTCR-T1 mouse model exhibits a metabolomic profile that is remarkably similar to that of humans, highlighting its potential as a relevant model for investigating the role of metabolites in disease development and progression. This model also offers an opportunity to discover therapeutic human TCRs.

Integrative Computational Framework, Dyscovr, Links Mutated Driver Genes to Expression Dysregulation Across 19 Cancer Types

Though somatic mutations play a critical role in driving cancer initiation and progression, the systems-level functional impacts of these mutations-particularly, how they alter expression across the genome and give rise to cancer hallmarks-are not yet well-understood, even for well-studied cancer driver genes. To address this, we designed an integrative machine learning model, Dyscovr, that leverages mutation, gene expression, copy number alteration (CNA), methylation, and clinical data to uncover putative relationships between nonsynonymous mutations in key cancer driver genes and transcriptional changes across the genome. We applied Dyscovr pan-cancer and within 19 individual cancer types, finding both broadly relevant and cancer type-specific links between driver genes and putative targets, including a subset we further identify as exhibiting negative genetic relationships. Our work newly implicates-and validates in cell lines-KBTBD2 and mutant PIK3CA as putative synthetic lethals in breast cancer, suggesting a novel combinatorial treatment approach.

Diagnostics and Therapy for Malignant Tumors

Malignant tumors remain one of the most significant global health challenges and contribute to high mortality rates across various cancer types. The complex nature of these tumors requires multifaceted diagnostic and therapeutic approaches. This review explores current advancements in diagnostic methods, including molecular imaging, biomarkers, and liquid biopsies. It also delves into the evolution of therapeutic strategies, including surgery, chemotherapy, radiation therapy, and novel targeted therapies such as immunotherapy and gene therapy. Although significant progress has been made in the understanding of cancer biology, the future of oncology lies in the integration of precision medicine, improved diagnostic tools, and personalized therapeutic approaches that address tumor heterogeneity. This review aims to provide a comprehensive overview of the current state of cancer diagnostics and treatments while highlighting emerging trends and challenges that lie ahead.

Integrated bulk and single-cell profiling characterize sphingolipid metabolism in pancreatic cancer

BACKGROUND

Abnormal sphingolipid metabolism (SM) is closely linked to the incidence of cancers. However, the role of SM in pancreatic cancer (PC) remains unclear. This study aims to explore the significance of SM in the prognosis, immune microenvironment, and treatment of PC.

METHODS

Single-cell and bulk transcriptome data of PC were acquired via TCGA and GEO databases. SM-related genes (SMRGs) were obtained via MSigDB database. Consensus clustering was utilized to construct SM-related molecular subtypes. LASSO and Cox regression were utilized to build SM-related prognostic signature. ESTIMATE and CIBERSORT algorithms were employed to assess the tumour immune microenvironment. OncoPredict package was used to predict drug sensitivity. CCK-8, scratch, and transwell experiments were performed to analyze the function of ANKRD22 in PC cell line PANC-1 and BxPC-3.

RESULTS

A total of 153 SMRGs were acquired, of which 48 were linked to PC patients' prognosis. Two SM-related subtypes (SMRGcluster A and B) were identified in PC. SMRGcluster A had a poorer outcome and more active SM process compared to SMRGcluster B. Immune analysis revealed that SMRGcluster B had higher immune and stromal scores and CD8 + T cell abundance, while SMRGcluster A had a higher tumour purity score and M0 macrophages and activated dendritic cell abundance. PC with SMRGcluster B was more susceptible to gemcitabine, paclitaxel, and oxaliplatin. Then SM-related prognostic model (including ANLN, ANKRD22, and DKK1) was built, which had a very good predictive performance. Single-cell analysis revealed that in PC microenvironment, macrophages, epithelial cells, and endothelial cells had relatively higher SM activity. ANKRD22, DKK1, and ANLN have relatively higher expression levels in epithelial cells. Cell subpopulations with high expression of ANKRD22, DKK1, and ANLN had more active SM activity. In vitro experiments showed that ANKRD22 knockdown can inhibit the proliferation, migration, and invasion of PC cells.

CONCLUSION

This study revealed the important significance of SM in PC and identified SM-associated molecular subtypes and prognostic model, which provided novel perspectives on the stratification, prognostic prediction, and precision treatment of PC patients.

Leveraging ML for profiling lipidomic alterations in breast cancer tissues: a methodological perspective

In this study, a comprehensive methodology combining machine learning and statistical analysis was employed to investigate alterations in the metabolite profiles, including lipids, of breast cancer tissues and their subtypes. By integrating biological and machine learning feature selection techniques, along with univariate and multivariate analyses, a notable lipid signature was identified in breast cancer tissues. The results revealed elevated levels of saturated and monounsaturated phospholipids in breast cancer tissues, consistent with external validation findings. Additionally, lipidomics analysis in both the original and validation datasets indicated lower levels of most triacylglycerols compared to non-cancerous tissues, suggesting potential alterations in lipid storage and metabolism within cancer cells. Analysis of cancer subtypes revealed that levels of PC 30:0 were relatively reduced in HER2(-) samples that were ER(+) and PR(+) compared to those that were ER(-) and PR(-). Conversely, HER2(+) tumors, which were ER(-) and PR(-), exhibited increased concentrations of PC 30:0. This increase could potentially be linked to the role of Stearoyl-CoA-Desaturase 1 in breast cancer. Comprehensive metabolomic analyses of breast cancer can offer crucial insights into cancer development, aiding in early detection and treatment evaluation of this devastating disease.

Immunofluorescence-Verified Sphingolipid Signatures Indicate Improved Prognosis in Liver Cancer Patients

Background: Hepatocellular carcinoma (HCC) is a highly heterogeneous malignancy, with its pathogenesis involving a complex interplay of molecular mechanisms, including cell cycle dysregulation, evasion of apoptosis, enhanced angiogenesis, and aberrant immune responses. Precision medicine approaches that target specific molecular subtypes through multi-omics integration hold promise for improving patient survival. Among the various molecular players, sphingolipids have emerged as pivotal regulators of tumor growth and apoptosis, positioning them as key targets in the search for novel anticancer therapies. Methods: To identify critical genes involved in sphingolipid metabolism (SM), we employed the AUCell algorithm and correlation analysis in conjunction with scRNA-seq data. A robust prognostic risk model was developed using Cox proportional hazards and Lasso regression, and its predictive performance was validated using an independent cohort from the International Cancer Genome Consortium (ICGC). The model's evaluation also incorporated analyses of the tumor microenvironment (TME), immunotherapy responses, mutational landscape, and pathway enrichment across different risk strata. Finally, we conducted multiplex immunofluorescence assays to investigate the functional role of ZC3HAV1 in HCC. Results: Our analysis yielded a 9-gene signature risk model with strong prognostic capabilities, effectively stratifying HCC patients into high- and low-risk groups, with significant differences in survival outcomes. Notably, the model revealed distinct variations in the immune microenvironment and responsiveness to immunotherapy between the risk groups. Further experimental validation identified ZC3HAV1 as a key gene, with multiplex immunofluorescence suggesting its involvement in promoting malignant progression in HCC through modulation of the epithelial-mesenchymal transition (EMT). Conclusion: This sphingolipid metabolism-based prognostic model is not only predictive of survival in HCC but also indicative of immunotherapy efficacy in certain patient subsets. Our findings underscore the crucial role of sphingolipid metabolism in shaping the immune microenvironment, offering new avenues for targeted therapeutic interventions.

Detection and Validation of Organic Metabolites in Urine for Clear Cell Renal Cell Carcinoma Diagnosis

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) comprises the majority, approximately 70-80%, of renal cancer cases and often remains asymptomatic until incidentally detected during unrelated abdominal imaging or at advanced stages. Currently, standardized screening tests for renal cancer are lacking, which presents challenges in disease management and improving patient outcomes. This study aimed to identify ccRCC-specific volatile organic compounds (VOCs) in the urine of ccRCC-positive patients and develop a urinary VOC-based diagnostic model.

METHODS

This study involved 233 pretreatment ccRCC patients and 43 healthy individuals. VOC analysis utilized stir-bar sorptive extraction coupled with thermal desorption gas chromatography/mass spectrometry (SBSE-TD-GC/MS). A ccRCC diagnostic model was established via logistic regression, trained on 163 ccRCC cases versus 31 controls, and validated with 70 ccRCC cases versus 12 controls, resulting in a ccRCC diagnostic model involving 24 VOC markers.

RESULTS

The findings demonstrated promising diagnostic efficacy, with an Area Under the Curve (AUC) of 0.94, 86% sensitivity, and 92% specificity.

CONCLUSIONS

This study highlights the feasibility of using urine as a reliable biospecimen for identifying VOC biomarkers in ccRCC. While further validation in larger cohorts is necessary, this study's capability to differentiate between ccRCC and control groups, despite sample size limitations, holds significant promise.

Resveratrol: biology, metabolism, and detrimental role on the tumor microenvironment of colorectal cancer

A substantial increase in colorectal cancer (CRC)-associated fatalities can be attributed to tumor recurrence and multidrug resistance. Traditional treatment options, including radio- and chemotherapy, also exhibit adverse side effects. Ancient treatment strategies that include phytochemicals like resveratrol are now widely encouraged as an alternative therapeutic option. Resveratrol is the natural polyphenolic stilbene in vegetables and fruits like grapes and apples. It inhibits CRC progression via targeting dysregulated cancer-promoting pathways, including PI3K/Akt/Kras, targeting transcription factors like NF-κB and STAT3, and an immunosuppressive tumor microenvironment. In addition, combination therapies for cancer include resveratrol as an adjuvant to decrease multidrug resistance that develops in CRC cells. The current review discusses the biology of resveratrol and explores different mechanisms of action of resveratrol in inhibiting CRC progression. Further, the detrimental role of resveratrol on the immunosuppressive tumor microenvironment of CRC has been discussed. This review illustrates clinical trials on resveratrol in different cancers, including resveratrol analogs, and their efficiency in promoting CRC inhibition.

Exploring the therapeutic potential of cannabinoids in cancer by modulating signaling pathways and addressing clinical challenges

For centuries, cannabinoids have been utilized for their medicinal properties, particularly in Asian and South-Asian countries. Cannabis plants, known for their psychoactive and non-psychoactive potential, were historically used for spiritual and remedial healing. However, as cannabis became predominantly a recreational drug, it faced prohibition. Recently, the therapeutic potential of cannabinoids has sparked renewed research interest, extending their use to various medical conditions, including cancer. This review aims to highlight current data on the involvement of cannabinoids in cancer signaling pathways, emphasizing their potential in cancer therapy and the need for further investigation into the underlying mechanisms. A comprehensive literature review was conducted using databases such as PubMed/MedLine, Google Scholar, Web of Science, Scopus, and Embase. The search focused on peer-reviewed articles, review articles, and clinical trials discussing the anticancer properties of cannabinoids. Inclusion criteria included studies in English on the mechanisms of action and clinical efficacy of cannabinoids in cancer. Cannabinoids, including Δ9-THC, CBD, and CBG, exhibit significant anticancer activities such as apoptosis induction, autophagy stimulation, cell cycle arrest, anti-proliferation, anti-angiogenesis, and metastasis inhibition. Clinical trials have demonstrated cannabinoids' efficacy in tumor regression and health improvement in palliative care. However, challenges such as variability in cannabinoid composition, psychoactive effects, regulatory barriers, and lack of standardized dosing remain. Cannabinoids show promising potential as anticancer agents through various mechanisms. Further large-scale, randomized controlled trials are essential to validate these findings and establish standardized therapeutic protocols. Future research should focus on elucidating detailed mechanisms, optimizing dosing, and exploring cannabinoids as primary chemotherapeutic agents.

Inflammation-associated intramyocellular lipid alterations in human pancreatic cancer cachexia

BACKGROUND

Cancer cachexia is a multifactorial metabolic syndrome characterized by systemic inflammation and ongoing skeletal muscle loss resulting in weakness, poor quality of life, and decreased survival. Whereas lipid accumulation in skeletal muscle is associated with cancer cachexia as well as the prognosis of cancer patients, surprisingly little is known about the nature of the lipids that accumulate in the muscle during cachexia, and whether this is related to inflammation. We aimed to identify the types and distributions of intramyocellular lipids in patients with and without cancer cachexia.

METHODS

Rectus abdominis muscle biopsies were collected during surgery of patients with pancreatic ductal adenocarcinoma (n = 10 without cachexia, n = 20 cachectic without inflammation (CRP < 10 mg/L), n = 10 cachectic with inflammation (CRP ≥ 10 mg/L). L3-CT scans were analysed to assess body composition based on validated thresholds in Hounsfield units (HU). Muscle sections were stained with Oil-Red O and H&E to assess general lipid accumulation and atrophy. Untargeted lipidomic analyses were performed on laser-microdissected myotubes using LC-MS/MS. The spatial distribution of intramyocellular lipids with differential abundance between groups was visualized by mass-spectrometry imaging. Genes coding for inflammation markers and enzymes involved in de novo ceramide synthesis were studied by qPCR.

RESULTS

Muscle radiation attenuation was lower in cachectic patients with inflammation (median 24.3 [18.6-30.8] HU) as compared with those without inflammation (34.2 [29.3-38.7] HU, P = 0.033) or no cachexia (37.4 [33.9-42.9] HU, P = 0.012). Accordingly, intramyocellular lipid content was lower in non-cachectic patients (1.9 [1.6-2.1]%) as compared with those with cachexia with inflammation (5.5 [4.5-7.3]%, P = 0.002) or without inflammation (4.8 [2.6-6.0]%, P = 0.017). Intramyocellular lipid accumulation was associated with both local IL-6 mRNA levels (rs = 0.57, P = 0.015) and systemic CRP levels (rs = 0.49, P = 0.024). Compared with non-cachectic subjects, cachectic patients had a higher relative abundance of intramyocellular glycerophospholipids and a lower relative abundance of glycerolipids. Furthermore, increases in several intramyocellular lipids such as SM(d36:1), PC(34:1), and TG(48:1) were found in cachectic patients with inflammation and correlated with specific cachexia features. Altered intramyocellular lipid species such as PC(34:1), LPC(18:2), and TG(48:1) showed an uneven distribution in muscle sections of cachectic and non-cachectic patients, with areas featuring abundance of these lipids next to areas almost devoid of them.

CONCLUSIONS

Intramyocellular lipid accumulation in patients with cachexia is associated with both local and systemic inflammation, and characterized by changes in defined lipid species such as glycerolipids and glycerophospholipids.

Targeting sphingolipid metabolism in chronic lymphocytic leukemia

Elevated levels of circulating C16:0 glucosylceramides (GluCer) and increased mRNA expression of UDP-glucose ceramide glycosyltransferase (UGCG), the enzyme responsible for converting ceramides (Cer) to GluCer, represent unfavorable prognostic markers in chronic lymphocytic leukemia (CLL) patients. To evaluate the therapeutic potential of inhibiting GluCer synthesis, we genetically repressed the UGCG pathway using in vitro models of leukemic B cells, in addition to UGCG pharmacological inhibition with approved drugs such as eliglustat and ibiglustat, both individually and in combination with ibrutinib, assessed in cell models and primary CLL patient cells. Cell viability, apoptosis, and proliferation were evaluated in vitro, and survival and apoptosis were examined ex vivo. UGCG inhibition efficacy was confirmed by quantifying intracellular sphingolipid levels through targeted lipidomics using mass spectrometry. Other inhibitors of sphingolipid biosynthesis pathways were similarly assessed. Blocking UGCG significantly decreased cell viability and proliferation, highlighting the oncogenic role of UGCG in CLL. The efficient inhibition of UGCG was confirmed by a significant reduction in GluCer intracellular levels. The combination of UGCG inhibitors with ibrutinib demonstrated synergistic effect. Inhibitors that target alternative pathways within sphingolipid metabolism, like sphingosine kinases inhibitor SKI-II, also demonstrated promising therapeutic effects both alone and when used in combination with ibrutinib, reinforcing the oncogenic impact of sphingolipids in CLL cells. Targeting sphingolipid metabolism, especially the UGCG pathway, represents a promising therapeutic strategy and as a combination therapy for potential treatment of CLL patients, warranting further investigation.

Sphingosine 1-Phosphate Stimulates ER to Golgi Ceramide Traffic to Promote Survival in T98G Glioma Cells

Glioblastoma multiforme is the most common and fatal brain tumor among human cancers. Ceramide (Cer) and Sphingosine 1-phosphate (S1P) have emerged as bioeffector molecules that control several biological processes involved in both cancer development and resistance. Cer acts as a tumor suppressor, inhibiting cancer progression, promoting apoptosis, enhancing immunotherapy and sensitizing cells to chemotherapy. In contrast, S1P functions as an onco-promoter molecule, increasing proliferation, survival, invasiveness, and resistance to drug-induced apoptosis. The pro-survival PI3K/Akt pathway is a recognized downstream target of S1P, and we have previously demonstrated that in glioma cells it also improves Cer transport and metabolism towards complex sphingolipids in glioma cells. Here, we first examined the possibility that, in T98G glioma cells, S1P may regulate Cer metabolism through PI3K/Akt signaling. Our research showed that exogenous S1P increases the rate of vesicular trafficking of Cer from the endoplasmic reticulum (ER) to the Golgi apparatus through S1P receptor-mediated activation of the PI3K/Akt pathway. Interestingly, the effect of S1P results in cell protection against toxicity arising from Cer accumulation in the ER, highlighting the role of S1P as a survival factor to escape from the Cer-generating cell death response.

The Role of Lipid Metabolism Disorders in the Development of Thyroid Cancer

Thyroid cancer (TC) is a neoplasm with an increasing incidence worldwide. Its etiology is complex and based on a multi-layered interplay of factors. Among these, disorders of lipid metabolism have emerged as an important area of investigation. Cancer cells are metabolically reprogrammed to promote their rapid growth, proliferation, and survival. This reprogramming is associated with significant changes at the level of lipids, mainly fatty acids (FA), as they play a critical role in maintaining cell structure, facilitating signaling pathways, and providing energy. These lipid-related changes help cancer cells meet the increased demands of continued growth and division while adapting to the tumor microenvironment. In this review, we examine lipid metabolism at different stages, including synthesis, transport, and oxidation, in the context of TC and the effects of obesity and hormones on TC development. Recent scientific efforts have revealed disturbances in lipid homeostasis that are specific to thyroid cancer, opening up potential avenues for early detection and targeted therapeutic interventions. Understanding the intricate metabolic pathways involved in FA metabolism may provide insights into potential interventions to prevent cancer progression and mitigate its effects on surrounding tissues.

Ablation of the dystrophin Dp71f alternative C-terminal variant increases sarcoma tumour cell aggressiveness

Alterations in Dp71 expression, the most ubiquitous dystrophin isoform, have been associated with patient survival across tumours. Intriguingly, in certain malignancies, Dp71 acts as a tumour suppressor, while manifesting oncogenic properties in others. This diversity could be explained by the expression of two Dp71 splice variants encoding proteins with distinct C-termini, each with specific properties. Expression of these variants has impeded the exploration of their unique roles. Using CRISPR/Cas9, we ablated the Dp71f variant with the alternative C-terminus in a sarcoma cell line not expressing the canonical C-terminal variant, and conducted molecular (RNAseq) and functional characterisation of the knockout cells. Dp71f ablation induced major transcriptomic alterations, particularly affecting the expression of genes involved in calcium signalling and ECM-receptor interaction pathways. The genome-scale metabolic analysis identified significant downregulation of glucose transport via membrane vesicle reaction (GLCter) and downregulated glycolysis/gluconeogenesis pathway. Functionally, these molecular changes corresponded with, increased calcium responses, cell adhesion, proliferation, survival under serum starvation and chemotherapeutic resistance. Knockout cells showed reduced GLUT1 protein expression, survival without attachment and their migration and invasion in vitro and in vivo were unaltered, despite increased matrix metalloproteinases release. Our findings emphasise the importance of alternative splicing of dystrophin transcripts and underscore the role of the Dp71f variant, which appears to govern distinct cellular processes frequently dysregulated in tumour cells. The loss of this regulatory mechanism promotes sarcoma cell survival and treatment resistance. Thus, Dp71f is a target for future investigations exploring the intricate functions of specific DMD transcripts in physiology and across malignancies.

Racial Differences in Vaginal Fluid Metabolites and Association with Systemic Inflammation Markers among Ovarian Cancer Patients: A Pilot Study

The vaginal microbiome differs by race and contributes to inflammation by directly producing or consuming metabolites or by indirectly inducing host immune response, but its potential contributions to ovarian cancer (OC) disparities remain unclear. In this exploratory cross-sectional study, we examine whether vaginal fluid metabolites differ by race among patients with OC, if they are associated with systemic inflammation, and if such associations differ by race. Study participants were recruited from the Ovarian Cancer Epidemiology, Healthcare Access, and Disparities Study between March 2021 and September 2022. Our study included 36 study participants with ovarian cancer who provided biospecimens; 20 randomly selected White patients and all 16 eligible Black patients, aged 50-70 years. Acylcarnitines (n = 45 species), sphingomyelins (n = 34), and ceramides (n = 21) were assayed on cervicovaginal fluid, while four cytokines (IL-1β, IL-10, TNF-α, and IL-6) were assayed on saliva. Seven metabolites showed >2-fold differences, two showed significant differences using the Wilcoxon rank-sum test (p < 0.05; False Discovery Rate > 0.05), and 30 metabolites had coefficients > ±0.1 in a Penalized Discriminant Analysis that achieved two distinct clusters by race. Arachidonoylcarnitine, the carnitine adduct of arachidonic acid, appeared to be consistently different by race. Thirty-eight vaginal fluid metabolites were significantly correlated with systemic inflammation biomarkers, irrespective of race. These findings suggest that vaginal fluid metabolites may differ by race, are linked with systemic inflammation, and hint at a potential role for mitochondrial dysfunction and sphingolipid metabolism in OC disparities. Larger studies are needed to verify these findings and further establish specific biological mechanisms that may link the vaginal microbiome with OC racial disparities.

The emerging roles of sphingosine 1-phosphate and SphK1 in cancer resistance: a promising therapeutic target

Cancer chemoresistance is a problematic dilemma that significantly restrains numerous cancer management protocols. It can promote cancer recurrence, spreading of cancer, and finally, mortality. Accordingly, enhancing the responsiveness of cancer cells towards chemotherapies could be a vital approach to overcoming cancer chemoresistance. Tumour cells express a high level of sphingosine kinase-1 (SphK1), which acts as a protooncogenic factor and is responsible for the synthesis of sphingosine-1 phosphate (S1P). S1P is released through a Human ATP-binding cassette (ABC) transporter to interact with other phosphosphingolipids components in the interstitial fluid in the tumor microenvironment (TME), provoking communication, progression, invasion, and tumor metastasis. Also, S1P is associated with several impacts, including anti-apoptotic behavior, metastasis, mesenchymal transition (EMT), angiogenesis, and chemotherapy resistance. Recent reports addressed high levels of S1P in several carcinomas, including ovarian, prostate, colorectal, breast, and HCC. Therefore, targeting the S1P/SphK signaling pathway is an emerging therapeutic approach to efficiently attenuate chemoresistance. In this review, we comprehensively discussed S1P functions, metabolism, transport, and signaling. Also, through a bioinformatic framework, we pointed out the alterations of SphK1 gene expression within different cancers with their impact on patient survival, and we demonstrated the protein-protein network of SphK1, elaborating its sparse roles. Furthermore, we made emphasis on different machineries of cancer resistance and the tight link with S1P. We evaluated all publicly available SphK1 inhibitors and their inhibition activity using molecular docking and how SphK1 inhibitors reduce the production of S1P and might reduce chemoresistance, an approach that might be vital in the course of cancer treatment and prognosis.

Critical Roles of the Sphingolipid Metabolic Pathway in Liver Regeneration, Hepatocellular Carcinoma Progression and Therapy

The sphingolipid metabolic pathway, an important signaling pathway, plays a crucial role in various physiological processes including cell proliferation, survival, apoptosis, and immune regulation. The liver has the unique ability to regenerate using bioactive lipid mediators involving multiple sphingolipids, including ceramide and sphingosine 1-phosphate (S1P). Dysregulation of the balance between sphingomyelin, ceramide, and S1P has been implicated in the regulation of liver regeneration and diseases, including liver fibrosis and hepatocellular carcinoma (HCC). Understanding and modulating this balance may have therapeutic implications for tumor proliferation, progression, and metastasis in HCC. For cancer therapy, several inhibitors and activators of sphingolipid signaling, including ABC294640, SKI-II, and FTY720, have been discussed. Here, we elucidate the critical roles of the sphingolipid pathway in the regulation of liver regeneration, fibrosis, and HCC. Regulation of sphingolipids and their corresponding enzymes may considerably influence new insights into therapies for various liver disorders and diseases.

Sphingolipids in mitochondria-from function to disease

Sphingolipids are not only structural components of cellular membranes but also play vital roles in cell signaling and modulation of cellular processes. Within mitochondria, sphingolipids exert diverse effects on mitochondrial dynamics, energy metabolism, oxidative stress, and cell death pathways. In this review, we summarize literature addressing the crucial role of sphingolipids in mitochondria, highlighting their impact on mitochondrial dynamics, cellular bioenergetics, and important cell processes including apoptosis and mitophagy.

Ceramide Is Involved in Temozolomide Resistance in Human Glioblastoma U87MG Overexpressing EGFR

Glioblastoma multiforme (GBM) is the most frequent and deadly brain tumor. Many sphingolipids are crucial players in the regulation of glioma cell growth as well as in the response to different chemotherapeutic drugs. In particular, ceramide (Cer) is a tumor suppressor lipid, able to induce antiproliferative and apoptotic responses in different types of tumors including GBM, most of which overexpress the epidermal growth factor receptor variant III (EGFRvIII). In this paper, we investigated whether Cer metabolism is altered in the U87MG human glioma cell line overexpressing EGFRvIII (EGFR+ cells) to elucidate their possible interplay in the mechanisms regulating GBM survival properties and the response to the alkylating agent temozolomide (TMZ). Notably, we demonstrated that a low dose of TMZ significantly increases Cer levels in U87MG cells but slightly in EGFR+ cells (sensitive and resistant to TMZ, respectively). Moreover, the inhibition of the synthesis of complex sphingolipids made EGFR+ cells sensitive to TMZ, thus involving Cer accumulation/removal in TMZ resistance of GBM cells. This suggests that the enhanced resistance of EGFR+ cells to TMZ is dependent on Cer metabolism. Altogether, our results indicate that EGFRvIII expression confers a TMZ-resistance phenotype to U87MG glioma cells by counteracting Cer increase.

Ceramide Analog 5cc Overcomes TRAIL Resistance by Enhancing JNK Activation and Repressing XIAP Expression in Metastatic Colon Cancer Cells

INTRODUCTION

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to be an effective apoptosis inducer due to its selectivity for tumor cells. However, many cancer cells, especially metastatic cancer cells, often exhibit resistance to TRAIL because their apoptotic pathway is impaired or their pro-survival pathway is overactivated. TRAIL resistance is the main obstacle to current TRAIL therapy. Nowadays, ceramide analogs represent a new class of potential anticancer agents. Therefore, we hypothesized that disrupting pro-survival signaling with ceramide analogs would increase TRAIL-mediated apoptosis.

METHODS

MTT assay and flow cytometry were conducted to evaluate the synergistic effect of ceramide analog 5cc on TRAIL in metastatic colon cancer cells. Western blot was used to detect signaling proteins affected by 5cc. RNA interference was performed to analyze the effects of specific gene on 5cc-enhanced apoptosis.

RESULTS

Ceramide analog 5cc markedly enhanced TRAIL-induced apoptosis evidenced by increased propidium iodide/annexin V double-positive cells and PARP cleavage in SW620 and LS411N cells. At the molecular level, 5cc significantly reduced the expression of anti-apoptotic protein X-linked inhibitor of apoptosis protein (XIAP) through the activation of the c-Jun n-terminal kinase (JNK) pathway which is critically involved in sensitizing tumor cells to TRAIL/5cc combination. JNK-silenced cells exhibited a significant reversal of TRAIL/5cc-mediated apoptosis.

CONCLUSION

Our data demonstrated that ceramide analog 5cc overcomes TRAIL resistance by enhancing JNK activation and repressing XIAP expression in metastatic colon cancer cells.

Sphingolipid Metabolism in Tumor Cells

Sphingolipids are a diverse family of complex lipids typically composed of a sphingoid base bound to a fatty acid via amide bond. The metabolism of sphingolipids has long remained out of focus of biochemical studies. Recently, it has been attracting an increasing interest of researchers because of different and often multidirectional effects demonstrated by sphingolipids with a similar chemical structure. Sphingosine, ceramides (N-acylsphingosines), and their phosphorylated derivatives (sphingosine-1-phosphate and ceramide-1-phosphates) act as signaling molecules. Ceramides induce apoptosis and regulate stability of cell membranes and cell response to stress. Ceramides and sphingoid bases slow down anabolic and accelerate catabolic reactions, thus suppressing cell proliferation. On the contrary, their phosphorylated derivatives (ceramide-1-phosphate and sphingosine-1-phosphate) stimulate cell proliferation. Involvement of sphingolipids in the regulation of apoptosis and cell proliferation makes them critically important in tumor progression. Sphingolipid metabolism enzymes and sphingolipid receptors can be potential targets for antitumor therapy. This review describes the main pathways of sphingolipid metabolism in human cells, with special emphasis on the properties of this metabolism in tumor cells.

Glucosylceramide Synthase Inhibitors Induce Ceramide Accumulation and Sensitize H3K27 Mutant Diffuse Midline Glioma to Irradiation

H3K27M mutant (mut) diffuse midline glioma (DMG) is a lethal cancer with no effective cure. The glycosphingolipids (GSL) metabolism is altered in these tumors and could be exploited to develop new therapies. We tested the effect of the glucosylceramide synthase inhibitors (GSI) miglustat and eliglustat on cell proliferation, alone or in combination with temozolomide or ionizing radiation. Miglustat was included in the therapy protocol of two pediatric patients. The effect of H3.3K27 trimethylation on GSL composition was analyzed in ependymoma. GSI reduced the expression of the ganglioside GD2 in a concentration and time-dependent manner and increased the expression of ceramide, ceramide 1-phosphate, sphingosine, and sphingomyelin but not of sphingosine 1-phosphate. Miglustat significantly increased the efficacy of irradiation. Treatment with miglustat according to dose recommendations for patients with Niemann-Pick disease was well tolerated with manageable toxicities. One patient showed a mixed response. In ependymoma, a high concentration of GD2 was found only in the presence of the loss of H3.3K27 trimethylation. In conclusion, treatment with miglustat and, in general, targeting GSL metabolism may offer a new therapeutic opportunity and can be administered in close proximity to radiation therapy. Alterations in H3K27 could be useful to identify patients with a deregulated GSL metabolism.

Ceramide in cerebrovascular diseases

Ceramide, a bioactive sphingolipid, serves as an important second messenger in cell signal transduction. Under stressful conditions, it can be generated from de novo synthesis, sphingomyelin hydrolysis, and/or the salvage pathway. The brain is rich in lipids, and abnormal lipid levels are associated with a variety of brain disorders. Cerebrovascular diseases, which are mainly caused by abnormal cerebral blood flow and secondary neurological injury, are the leading causes of death and disability worldwide. There is a growing body of evidence for a close connection between elevated ceramide levels and cerebrovascular diseases, especially stroke and cerebral small vessel disease (CSVD). The increased ceramide has broad effects on different types of brain cells, including endothelial cells, microglia, and neurons. Therefore, strategies that reduce ceramide synthesis, such as modifying sphingomyelinase activity or the rate-limiting enzyme of the de novo synthesis pathway, serine palmitoyltransferase, may represent novel and promising therapeutic approaches to prevent or treat cerebrovascular injury-related diseases.

Lipidomic Profiling Reveals Biological Differences between Tumors of Self-Identified African Americans and Non-Hispanic Whites with Cancer

In the US, the incidence and mortality of many cancers are disproportionately higher in African Americans (AA). Yet, AA remain poorly represented in molecular studies investigating the roles that biological factors might play in the development, progression, and outcomes of many cancers. Given that sphingolipids, key components of mammalian cellular membranes, have well-established roles in the etiology of cancer progression, malignancy, and responses to therapy, we conducted a robust mass spectrometry analysis of sphingolipids in normal adjacent uninvolved tissues and tumors of self-identified AA and non-Hispanic White (NHW) males with cancers of the lung, colon, liver, and head and neck and of self-identified AA and NHW females with endometrial cancer. In these cancers, AA have worse outcomes than NHW. The goal of our study was to identify biological candidates to be evaluated in future preclinical studies targeting race-specific alterations in the cancers of AA. We have identified that various sphingolipids are altered in race-specific patterns, but more importantly, the ratios of 24- to 16-carbon fatty acyl chain-length ceramides and glucosylceramides are higher in the tumors of AA. As there is evidence that ceramides with 24-carbon fatty acid chain length promote cellular survival and proliferation, whereas 16-carbon chain length promote apoptosis, these results provide important support for future studies tailored to evaluate the potential roles these differences may play in the outcomes of AA with cancer.

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.

Exercise Promotes Pro-Apoptotic Ceramide Signaling in a Mouse Melanoma Model

Simple Summary

Exercise has been shown to improve the efficacy of chemotherapy against several tumor models using mice through modulating tumor vascular perfusion, immune function, circulating growth factors, hypoxia, and metabolism in tumor cells and their surrounding microenvironment. However, little is known about the effect of exercise on tumor-cell-intrinsic death mechanisms, such as apoptosis. Ceramide is a bioactive lipid that can promote cell death. The strategy of increasing intracellular ceramide has potential as an anticancer treatment for melanoma with dysregulated ceramide metabolism, but there is not yet a clinically relevant method to do so. We found that moderate aerobic exercise increases pro-apoptotic ceramide in melanoma in mice, and activates p53 signaling, promoting tumor cell apoptosis. This finding suggests that exercise may be most effective as an adjuvant therapy to sensitize cancer cells to anticancer treatments in tumors that exhibit downregulated ceramide generation to evade cell death.

Abstract

Ceramides are essential sphingolipids that mediate cell death and survival. Low ceramide content in melanoma is one mechanism of drug resistance. Thus, increasing the ceramide content in tumor cells is likely to increase their sensitivity to cytotoxic therapy. Aerobic exercise has been shown to modulate ceramide metabolism in healthy tissue, but the relationship between exercise and ceramide in tumors has not been evaluated. Here, we demonstrate that aerobic exercise causes tumor cell apoptosis and accumulation of pro-apoptotic ceramides in B16F10 but not BP melanoma models using mice. B16F10 tumor-bearing mice were treated with two weeks of moderate treadmill exercise, or were control, unexercised mice. A reverse-phase protein array was used to identify canonical p53 apoptotic signaling as a key pathway upregulated by exercise, and we demonstrate increased apoptosis in tumors from exercised mice. Consistent with this finding, pro-apoptotic C16-ceramide, and the ceramide generating enzyme ceramide synthase 6 (CerS6), were higher in B16F10 tumors from exercised mice, while pro-survival sphingosine kinase 1 (Sphk1) was lower. These data suggest that exercise contributes to B16F10 tumor cell death, possibly by modulating ceramide metabolism toward a pro-apoptotic ceramide/sphingosine-1-phosphate balance. However, these results are not consistent in BP tumors, demonstrating that exercise can have different effects on tumors of different patient or mouse origin with the same diagnosis. This work indicates that exercise might be most effective as a therapeutic adjuvant with therapies that kill tumor cells in a ceramide-dependent manner.

Identification and validation of a prognostic risk-scoring model based on sphingolipid metabolism-associated cluster in colon adenocarcinoma

Colon adenocarcinoma (COAD) is the primary factor responsible for cancer-related mortalities in western countries, and its development and progression are affected by altered sphingolipid metabolism. The current study aimed at investigating the effects of sphingolipid metabolism-related (SLP) genes on multiple human cancers, especially on COAD. We obtained 1287 SLP genes from the GeneCard and MsigDb databases along with the public transcriptome data and the related clinical information. The univariate Cox regression analysis suggested that 26 SLP genes were substantially related to the prognosis of COAD, and a majority of SLP genes served as the risk genes for the tumor, insinuating a potential pathogenic effect of SLP in COAD development. Pan-cancer characterization of SLP genes summarized their expression traits, mutation traits, and methylation levels. Subsequently, we focused on the thorough research of COAD. With the help of unsupervised clustering, 1008 COAD patients were successfully divided into two distinct subtypes (C1 and C2). C1 subtype is characterized by a poor prognosis, activation of SLP pathways, high expression of SLP genes, disordered carcinogenic pathways, and immune microenvironment. Based on the clusters of SLP, we developed and validated a novel prognostic model, consisting of ANO1, C2CD4A, EEF1A2, GRP, HEYL, IGF1, LAMA2, LSAMP, RBP1, and TCEAL2, to quantitatively evaluate the clinical outcomes of COAD. The Kaplain-Meier survival curves and ROC curves highlighted the accuracy of our SLP model in both internal and external cohorts. Compared to normal colon tissues, expression of C2CD4A was detected to be significantly higher in COAD; whereas, expression levels of EEF1A2, IGF1, and TCEAL2 were detected to be significantly lower in COAD. Overall, our research emphasized the pathogenic role of SLP in COAD and found that targeting SLP might help improve the clinical outcomes of COAD. The risk model based on SLP metabolism provided a new horizon for prognosis assessment and customized patient intervention.