Clinical Significance of Carnitine in the Treatment of Cancer: From Traffic to the Regulation

Effect of the oral microbiota, blood metabolome, and inflammatory proteins on oral cavity cancer: a bidirectional two-sample Mendelian randomization study and mediation analysis

OBJECTIVE

Oral Cavity Cancer (OCC) pathogenesis is complex, extending beyond traditional risk factors. While observational studies link oral microbiome dysbiosis, metabolic disturbances, and inflammation to OCC, inherent confounding limits causal inference regarding the putative 'microbiome-metabolite-inflammation' axis in OCC. Establishing causality is crucial.

METHODS

We employed a two-sample Mendelian randomization (MR) framework using large-scale GWAS data to address this gap. We systematically evaluated causal effects of 43 oral microbial taxa, 1400 diverse circulating metabolites, and 91 inflammatory proteins on OCC risk. We performed univariable MR (UVMR) for direct effects, multivariable MR (MVMR) adjusting for interactions, and mediation MR dissecting causal pathways.

RESULTS

UVMR identified protective effects for Clostridiales (OR = 0.89) and Rothia sp. ASV0016 (OR = 0.91), and increased risk for Bacteroidales (OR = 1.09). Furthermore, 60 metabolites (e.g., glycohyocholate increasing risk; 16α-hydroxy DHEAS-3-sulfate decreasing risk) and two proteins (Cystatin D increasing risk, OR = 1.26; MCP-1 decreasing risk, OR = 0.69) showed causal links to OCC. Crucially, mediation analyses indicated protective microbial effects were partially mediated via specific metabolites, including 5α-androstan-3α,17β-diol disulfate (Clostridiales) and carboxyethyl-GABA (Rothia sp.).

CONCLUSIONS

This study provides robust genetic evidence supporting causal roles for specific oral microbes and metabolites in OCC etiology. It offers mechanistic insights into the 'oral microbiome-host metabolism' axis, providing a basis for novel microbiome/metabolite-based biomarkers for early detection and risk assessment, and identifying potential preventative or therapeutic targets.

Tobacco smoke exposure is a driver of altered oxidative stress response and immunity in head and neck cancer

BACKGROUND

Exposomes are critical drivers of carcinogenesis. However, how they modulate tumor behavior remains unclear. Extensive clinical data show cigarette smoke to be a key exposome that promotes aggressive tumors, higher rates of metastasis, reduced response to chemoradiotherapy, and suppressed anti-tumor immunity. We sought to determine whether smoke itself can modulate aggressive tumor behavior in head and neck squamous cell carcinoma (HNSCC) through reprogramming of the cellular reductive state.

METHODS

Using established human and murine HNSCC cell lines and syngeneic mouse models, we utilized conventional western blotting, steady state and flux metabolomics, RNA sequencing, quantitative proteomics and flow cytometry to analyze the impact of smoke exposure on HNSCC tumor biology and anti-tumor immunity.

RESULTS

Cigarette smoke persistently activated Nrf2 target genes essential for maintenance of the cellular reductive state and survival under conditions of increased oxidative stress in HNSCC regardless of human papillomavirus (HPV) association. In contrast to e-cigarette vapor, conventional cigarette smoke mobilizes cellular metabolism toward oxidative stress adaptation, resulting in development of cross-resistance to cisplatin. In parallel, smoke exposure modulates expression of PDL1 and the secretory phenotype of HNSCC cells resulting in an altered tumor immune microenvironment (TIME) in syngeneic mouse models and downregulated expression of antigen presentation and costimulatory genes in myeloid cells.

CONCLUSION

The cigarette smoke exposome is a potent activator of the Nrf2 pathway and appears to be the primary trigger for a tripartite phenotype of aggressive HNSCC consisting of: (1) reduced chemotherapy sensitivity, (2) enhanced metastatic potential and (3) suppressed anti-tumor immunity.

Metabolites and metabolic pathway reactions links to sensitization of immunotherapy in pan-cancer

Metabolic features are crucial in tumor immune interactions, but their relationship with antitumor immune responses is not yet fully understood. This study used Mendelian randomization analysis to identify the causal relationships between blood metabolites and immune cells and to evaluate the effects of metabolic pathways and reactions on antitumor immune responses in various cancers. Levels of 156 metabolites exhibited significant associations with selected immune cells. Metabolic enrichment analysis indicated laurate, propionyl-carnitine, carnitine and l-acetylcarnitine are enriched in fatty acid (FA) metabolism pathways. These enriched pathways are significantly correlated to CD8+ T cell function signatures in tumor environment and favor better prognostic outcomes. Metabolic reactions contributing to better immunotherapy responses were identified and used to establish the immuno-metabolic reaction score (IMRS). IMRS were significantly correlated to CD8+ T cell infiltration levels and CD8+ T cell signature scores in either 10× Visium spatial transcriptomic or RNA-seq samples. Finally, IMRS could significantly predict favorable survival outcomes in different cancer patients treated with immunotherapy. Our study revealed a link between certain metabolites and their related metabolic pathways to tumor immune landscape and immune functions. These results could promote the accurate stratification of patients before treatment and improve the efficacy of immunotherapy.

Causal effects of metabolites on malignant neoplasm of bone and articular cartilage: a mendelian randomization study

Objective

Previous research has demonstrated that metabolites play a significant role in modulating disease phenotypes; nevertheless, the causal association between metabolites and malignant malignancies of bones and joint cartilage (MNBAC)has not been fully elucidated.

Methods

This study used two-sample Mendelian randomization (MR) to explore the causal correlation between 1,400 metabolites and MNBAC. Data from recent genome-wide association studies (GWAS) involving 8,299 individuals were summarized. The GWAS summary data for metabolites were acquired from the IEU Open GWAS database, while those for MNBAC were contributed by the Finnish Consortium. We employed eight distinct MR methodologies: simple mode, maximum likelihood estimator, MR robust adjusted profile score, MR-Egger, weighted mode, weighted median, MR-PRESSO and inverse variance weighted to scrutinize the causal association between metabolites engendered by each gene and MNBAC. Consequently, we evaluated outliers, horizontal pleiotropy, heterogeneity, the impact of single nucleotide polymorphisms (SNPs), and adherence to the normal distribution assumption in the MR analysis.

Results

Our findings suggested a plausible causative relationship between N-Formylmethionine (FMet) levels, lignoceroylcarnitine (C24) levels, and MNBAC. We observed a nearly significant causal association between FMet levels and MNBAC within the cohort of 1,400 metabolites (P = 0.024, odds ratio (OR) = 3.22; 95% CI [1.16-8.92]). Moreover, we ascertained a significant causal link between levels of C24 and MNBAC (P = 0.0009; OR = 0.420; 95%CI [0.25-0.70]). These results indicate a potential causative relationship between FMet, C24 level and MNBAC.

Conclusion

The occurrence of MNBAC may be causally related to metabolites. This might unveil new possibilities for investigating early detection and treatment of MNBAC.

Global metabolomic profiling of tumor tissue and paired serum samples to identify biomarkers for response to neoadjuvant FOLFIRINOX treatment of human pancreatic cancer

Neoadjuvant chemotherapy (NAT) is increasingly used for the treatment of non-metastatic pancreatic ductal adenocarcinoma (PDAC) and is established as a standard of care for borderline resectable and locally advanced PDAC. However, full exploitation of its clinical benefits is limited by the lack of biomarkers that assess treatment response. To address this unmet need, global metabolomic profiling was performed on tumor tissue and paired serum samples from patients with treatment-naïve (TN; n = 18) and neoadjuvant leucovorin calcium (folinic acid), fluorouracil, irinotecan hydrochloride and oxaliplatin (FOLFIRINOX)-treated (NAT; n = 17) PDAC using liquid chromatography mass spectrometry. Differentially abundant metabolites (DAMs) in TN versus NAT groups were identified and their correlation with various clinical parameters was assessed. Metabolomics profiling identified 40 tissue and five serum DAMs in TN versus NAT PDAC. In general, DAMs associated with amino acid and nucleotide metabolism were lower in NAT compared to TN. Four DAMs-3-hydroxybutyric acid (BHB), 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), glycochenodeoxycholate and citrulline-were common to both tissue and serum and showed a similar pattern of differential abundance in both groups. A strong positive correlation was observed between serum carbohydrate 19-9 antigen (CA 19-9) and tissue carnitines (C12, C18, C18:2) and N8-acetylspermidine. The reduction in CA 19-9 following NAT correlated negatively with serum deoxycholate levels, and the latter correlated positively with survival. This study revealed neoadjuvant-chemotherapy-induced changes in metabolic pathways in PDAC, mainly amino acid and nucleotide metabolism, and these correlated with reduced CA 19-9 following neoadjuvant FOLFIRINOX treatment.

Metabolic consequences of erastin-induced ferroptosis in human ovarian cancer cells: an untargeted metabolomics study

Introduction

Ovarian cancer has been difficult to cure due to acquired or intrinsic resistance and therefore, newer or more effective drugs/approaches are needed for a successful treatment in the clinic. Erastin (ER), a ferroptosis inducer, kills tumor cells by generating and accumulating reactive oxygen species (ROS) within the cell, resulting in an iron-dependent oxidative damage-mediated ferroptotic cell death.

Methods

We have utilized human ovarian cancer cell lines, OVCAR-8 and its adriamycin-selected, multi-drug resistance protein (MDR1)-expressing NCI/ADR-RES, both equally sensitive to ER, to identify metabolic biomarkers of ferroptosis.

Results

Our studies showed that ER treatment rapidly depleted cellular glutathione and cysteine and enhanced formation of ophthalamate (OPH) in both cells. Opthalalmate has been proposed to be a biomarker of oxidative stress in cells. Our study also found significant decreases in cellular taurine, a natural antioxidant in cells. Additionally, we found that ER treatment decreased cellular levels of NAD+/NADP+, carnitines and glutamine/glutamate in both cells, suggesting significant oxidative stress, decrease in energy production, and cellular and mitochondrial disfunctions, leading to cell death.

Conclusion

Our studies identified several potential biomarkers of ER-induced ferroptosis including OPH, taurine, NAD+, NADP+ and glutamate in ovarian cancer cells. Identifying specific metabolic biomarkers that are predictive of whether a cancer is susceptible to ferroptosis will help us devise more successful treatment modalities.

Altered carnitine transporter genes (SLC22A5, SLC22A16, SLC6A14) expression pattern among lung cancer patients

Background

Despite the decrease of morbidity rate of non-small cell lung cancer (NSCLC) in recent years, it is still a cancer with poor prognosis. Lung cancers (LCs) are usually diagnosed at a late stage of the disease due to non-specific clinical symptoms. Proper regulation of carnitine levels is important in the context of development and increased risk of cancer cells proliferation. The expression profiles and clinical value of SLC family members in LC remain largely unexplored. The aim of the study was the assessment of SLC22A16, SLC22A5 and SLC6A14 mRNA expression level among patients suffering from NSCLC. The obtained results were compared with the clinical and the pathological features of NSCLC patients.

Methods

Through reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and bioinformatics studies, the evaluation of carnitine transporting genes (SLC22A16, SLC22A5 and SLC6A14) mRNA levels was performed in order to elucidate their connection to clinical features of patients and influence on overall survival (OS).

Results

The analysis showed a significant difference for the SLC22A5 gene of NSCLC patients and for SLC6A14 and SLC22A5 genes in LUSC patients in terms of sex (P=0.002, P=0.02 and P=0.001, respectively) and in terms of tobacco smoking (P=0.04). Analysis also revealed a significant negative correlation for SLC22A5 and SLC22A16 genes expression level in the lung adenocarcinoma (LUAD) subtype with standardized uptake value (SUV) (r=-0.40, P=0.02 and r=-0.43, P=0.04). The significant downregulation of gene expression compared to normal adjacent tissue was observed for SLC22A5 in lung squamous cell carcinoma (LUSC) and for SLC6A14 in both LUAD and LUSC subtypes. The effect of the SLC22A5, SLC22A16 and SLC6A14 gene expression at the time of diagnosis on the OS time of LC patients revealed that lower expression correlated with a shorter 5 years OS (all P values <0.01). The effects were distinct after division for LUAD and LUSC subtypes.

Conclusions

The expression levels of genes encoding carnitine transporters are diverse, hinting at a potentially altered carnitine metabolism in LC patients. Notably, this variance is not uniform and exhibits specificity across LC subtypes, with marked distinctions between LUAD and LUSC. The correlation between gene expression levels and OS of patients underlines the prognostic significance of SLC genes within these cancer subtypes.

The Role of the CPT Family in Cancer: Searching for New Therapeutic Strategies

Along with abnormalities in glucose metabolism, disturbances in the balance of lipid catabolism and synthesis have emerged as a new area of cancer metabolism that needs to be studied in depth. Disturbances in lipid metabolic homeostasis, represented by fatty acid oxidation (FAO) imbalance, leading to activation of pro-cancer signals and abnormalities in the expression and activity of related metabolically critical rate-limiting enzymes, have become an important part of metabolic remodeling in cancer. The FAO process is a metabolic pathway that facilitates the breakdown of fatty acids into CO2 and H2O and releases large amounts of energy in the body under aerobic conditions. More and more studies have shown that FAO provides an important energy supply for the development of cancer cells. At the same time, the CPT family, including carnitine palmitoyltransferase 1 (CPT1) and carnitine palmitoyltransferase 2 (CPT2), are key rate-limiting enzymes for FAO that exert a pivotal influence on the genesis and progression of neoplastic growth. Therefore, we look at molecular structural properties of the CPT family, the roles they play in tumorigenesis and development, the target drugs, and the possible regulatory roles of CPTs in energy metabolism reprogramming to help understand the current state of CPT family research and to search for new therapeutic strategies.

Genetically predicted gut bacteria, circulating bacteria-associated metabolites and pancreatic ductal adenocarcinoma: a Mendelian randomisation study

Pancreatic ductal adenocarcinoma (PDAC) has high mortality and rising incidence rates. Recent data indicate that the gut microbiome and associated metabolites may play a role in the development of PDAC. To complement and inform observational studies, we investigated associations of genetically predicted abundances of individual gut bacteria and genetically predicted circulating concentrations of microbiome-associated metabolites with PDAC using Mendelian randomisation (MR). Gut microbiome-associated metabolites were identified through a comprehensive search of Pubmed, Exposome Explorer and Human Metabolome Database. Single Nucleotide Polymorphisms (SNPs) associated by Genome-Wide Association Studies (GWAS) with circulating levels of 109 of these metabolites were collated from Pubmed and the GWAS catalogue. SNPs for 119 taxonomically defined gut genera were selected from a meta-analysis performed by the MiBioGen consortium. Two-sample MR was conducted using GWAS summary statistics from the Pancreatic Cancer Cohort Consortium (PanScan) and the Pancreatic Cancer Case-Control Consortium (PanC4), including a total of 8,769 cases and 7,055 controls. Inverse variance-weighted MR analyses were performed along with sensitivity analyses to assess potential violations of MR assumptions. Nominally significant associations were noted for genetically predicted circulating concentrations of mannitol (odds ratio per standard deviation [ORSD] = 0.97; 95% confidence interval [CI]: 0.95-0.99, p = 0.006), methionine (ORSD= 0.97; 95%CI: 0.94-1.00, p = 0.031), stearic acid (ORSD= 0.93; 95%CI: 0.87-0.99, p = 0.027), carnitine = (ORSD=1.01; 95% CI: 1.00-1.03, p = 0.027), hippuric acid (ORSD= 1.02; 95%CI: 1.00-1.04, p = 0.038) and 3-methylhistidine (ORSD= 1.05; 95%CI: 1.01-1.10, p = 0.02). Two gut microbiome genera were associated with reduced PDAC risk; Clostridium sensu stricto 1 (OR: 0.88; 95%CI: 0.78-0.99, p = 0.027) and Romboutsia (OR: 0.87; 95%CI: 0.80-0.96, p = 0.004). These results, though based only on genetically predicted gut microbiome characteristics and circulating bacteria-related metabolite concentrations, provide evidence for causal associations with pancreatic carcinogenesis.

Dysfunction of the carnitine cycle in tumor progression

The carnitine cycle is responsible for the transport of cytoplasmic fatty acids to the mitochondria for subsequent β-oxidation to maintain intracellular energy homeostasis. Recent studies have identified abnormalities in the carnitine cycle in various types of tumors; these abnormalities include the altered expression levels of carnitine cycle-related metabolic enzymes and transport proteins. Dysfunction of the carnitine cycle has been shown to influence tumorigenesis and progression by altering intracellular oxidative and inflammatory status or regulating tumor metabolic flexibility. Many therapeutic strategies targeting the carnitine cycle are actively being explored to modify the dysfunction of the carnitine cycle in patients with malignant tumors; such approaches include carnitine cycle-related enzyme inhibitors and exogenous carnitine supplementation. Therefore, here, we review the studies of carnitine in tumors, aiming to scientifically illustrate the dysfunction of the carnitine cycle in tumor progression and provide new ideas for further research.

Chrysomycin A Reshapes Metabolism and Increases Oxidative Stress to Hinder Glioblastoma Progression

Glioblastoma represents the predominant and a highly aggressive primary neoplasm of the central nervous system that has an abnormal metabolism. Our previous study showed that chrysomycin A (Chr-A) curbed glioblastoma progression in vitro and in vivo. However, whether Chr-A could inhibit orthotopic glioblastoma and how it reshapes metabolism are still unclear. In this study, Chr-A markedly suppressed the development of intracranial U87 gliomas. The results from airflow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) indicated that Chr-A improved the abnormal metabolism of mice with glioblastoma. Key enzymes including glutaminase (GLS), glutamate dehydrogenases 1 (GDH1), hexokinase 2 (HK2) and glucose-6-phosphate dehydrogenase (G6PD) were regulated by Chr-A. Chr-A further altered the level of nicotinamide adenine dinucleotide phosphate (NADPH), thus causing oxidative stress with the downregulation of Nrf-2 to inhibit glioblastoma. Our study offers a novel perspective for comprehending the anti-glioma mechanism of Chr-A, highlighting its potential as a promising chemotherapeutic agent for glioblastoma.

From Lipid Signatures to Cellular Responses: Unraveling the Complexity of Melanoma and Furthering Its Diagnosis and Treatment

Recent advancements in mass spectrometry have significantly enhanced our understanding of complex lipid profiles, opening new avenues for oncological diagnostics. This review highlights the importance of lipidomics in the comprehension of certain metabolic pathways and its potential for the detection and characterization of various cancers, in particular melanoma. Through detailed case studies, we demonstrate how lipidomic analysis has led to significant breakthroughs in the identification and understanding of cancer types and its potential for detecting unique biomarkers that are instrumental in its diagnosis. Additionally, this review addresses the technical challenges and future perspectives of these methodologies, including their potential expansion and refinement for clinical applications. The discussion underscores the critical role of lipidomic profiling in advancing cancer diagnostics, proposing a new paradigm in how we approach this devastating disease, with particular emphasis on its application in comparative oncology.

Critical Role of Mitochondrial Fatty Acid Metabolism in Normal Cell Function and Pathological Conditions

There is a "popular" belief that a fat-free diet is beneficial, supported by the scientific dogma indicating that high levels of fatty acids promote many pathological metabolic, cardiovascular, and neurodegenerative conditions. This dogma pressured scientists not to recognize the essential role of fatty acids in cellular metabolism and focus on the detrimental effects of fatty acids. In this work, we critically review several decades of studies and recent publications supporting the critical role of mitochondrial fatty acid metabolism in cellular homeostasis and many pathological conditions. Fatty acids are the primary fuel source and essential cell membrane building blocks from the origin of life. The essential cell membranes phospholipids were evolutionarily preserved from the earlier bacteria in human subjects. In the past century, the discovery of fatty acid metabolism was superseded by the epidemic growth of metabolic conditions and cardiovascular diseases. The association of fatty acids and pathological conditions is not due to their "harmful" effects but rather the result of impaired fatty acid metabolism and abnormal lifestyle. Mitochondrial dysfunction is linked to impaired metabolism and drives multiple pathological conditions. Despite metabolic flexibility, the loss of mitochondrial fatty acid oxidation cannot be fully compensated for by other sources of mitochondrial substrates, such as carbohydrates and amino acids, resulting in a pathogenic accumulation of long-chain fatty acids and a deficiency of medium-chain fatty acids. Despite popular belief, mitochondrial fatty acid oxidation is essential not only for energy-demanding organs such as the heart, skeletal muscle, and kidneys but also for metabolically "inactive" organs such as endothelial and epithelial cells. Recent studies indicate that the accumulation of long-chain fatty acids in specific organs and tissues support the impaired fatty acid oxidation in cell- and tissue-specific fashion. This work, therefore, provides a basis to challenge these established dogmas and articulate the need for a paradigm shift from the "pathogenic" role of fatty acids to the critical role of fatty acid oxidation. This is important to define the causative role of impaired mitochondrial fatty acid oxidation in specific pathological conditions and develop novel therapeutic approaches targeting mitochondrial fatty acid metabolism.

Complementary and alternative medicine: A narrative review of nutritional approaches for cancer-related fatigue

Cancer-related fatigue (CRF) is a common symptom among patients with cancer, with a prevalence of >49%. CRF significantly affects the quality of life of patients and may also affect their overall survival. Pharmacological interventions serve as a last resort after carefully weighing the risks and benefits, with limited benefits for patients, many side effects, and adverse reactions. Compared to traditional medicine, nutritional approaches have fewer side effects, are highly accepted by patients, and do not affect the antitumor treatment of patients. Many studies have shown that nutritional approaches, as a form of complementary and alternative medicine, help improve the symptoms of CRF and the quality of life of patients. This study was designed to examine nutritional approaches to CRF and assess their effectiveness of nutritional approaches in improving CRF. We present an overview of clinical trials investigating nutritional approaches for CRF that have been published over the last 2 decades. A total of 33 records were obtained from 3 databases: Web of Science, MEDLINE, and PubMed. Some nutritional approaches, such as melatonin, PG2, and S-adenosyl-l-methionine, are potential options for CRF treatment. However, the trials included in the review varied widely in quality, most were weak in methodology, and there is currently insufficient evidence to conclude with certainty the effectiveness of nutritional approaches in reducing CRF. Therefore, the design and methods used in future complementary and alternative medicine trials should be more rigorous.