A novel CPT1A covalent inhibitor modulates fatty acid oxidation and CPT1A-VDAC1 axis with therapeutic potential for colorectal cancer

The solid tumor microenvironment and related targeting strategies: a concise review

The malignant tumor is a serious disease threatening human life. Increasing studies have confirmed that the tumor microenvironment (TME) is composed of a variety of complex components that precisely regulate the interaction of tumor cells with other components, allowing tumor cells to continue to proliferate, resist apoptosis, evade immune surveillance and clearance, and metastasis. However, the characteristics of each component and their interrelationships remain to be deeply understood. To target TME, it is necessary to deeply understand the role of various components of TME in tumor growth and search for potential therapeutic targets. Herein, we innovatively classify the TME into physical microenvironment (such as oxygen, pH, etc.), mechanical microenvironment (such as extracellular matrix, blood vessels, etc.), metabolic microenvironment (such as glucose, lipids, etc.), inflammatory microenvironment and immune microenvironment. We introduce a concise but comprehensive classification of the TME; depict the characteristics of each component in TME; summarize the existing methods for detecting each component in TME; highlight the current strategies and potential therapeutic targets for TME; discuss current challenges in presenting TME and its clinical applications; and provide our prospect on the future research direction and clinical benefits of TME.

Proteomics-driven discovery of LCAT as a novel biomarker for liver metastasis in colorectal cancer

BACKGROUND

This study aimed to identify molecular markers that influence liver metastasis in colorectal cancer (CRC) and assess their clinical relevance.

METHODS

Proteomic analysis compared differential protein expression between CRC patients with liver metastasis (CRLM) and those without (CRNLM). Bioinformatics and survival analyses identified key proteins and validated them using the TCGA database for expression and clinical significance. Clinical and pathological data, along with tissue samples from our center, were used to create tissue microarrays for immunohistochemistry. Logistic regression assessed odds ratios (OR) for molecular markers linked to liver metastasis post-CRC surgery. Stable LCAT knockdown and overexpression CRC cell lines were constructed, and Transwell assays assessed the impact LCAT on cell migration. Nile red staining of these cells validated the effect LCAT on lipid metabolism in CRC cells.

RESULTS

Proteomic analysis identified 383 differentially expressed proteins between the CRLM and CRNLM groups (212 upregulated, 171 downregulated). Enrichment analysis linked these proteins to steroid and alcohol metabolism, inflammation, lipoproteins, and HDL particles, with key pathways in cholesterol and retinol metabolism. Lecithin cholesterol acyltransferase (LCAT), an important enzyme in this process, showed higher expression in CRC tissues, with increased LCAT linked to poorer 5-year OS, DSS, and PFI. LCAT expression also increased with tumor stage. Among 119 patients with CRC, preoperative complications, tumor staging, and LCAT scores differed significantly between patients with and without liver metastasis within 3 years post-surgery. LCAT and postoperative CEA levels were independent risk factors for liver metastasis (LCAT OR, 10.221; P = 0.002; CEA OR, 1.296; P = 0.014). Western blotting confirmed significantly higher LCAT expression in CRC tissues with liver metastasis. Transwell assays showed that LCAT overexpression enhanced migratory ability, while knockdown inhibited it. Nile red staining revealed increased lipid droplet accumulation in LCAT-overexpressing CRC cells, which was reduced by LCAT knockdown.

CONCLUSION

LCAT, which is involved in lipid metabolism, is an independent risk factor for liver metastasis following CRC surgery, suggesting its potential as a therapeutic target.

SLC31A1 promotes chemoresistance through inducing CPT1A-mediated fatty acid oxidation in ER-positive breast cancer

Over 60% of breast cancer cases are diagnosed with estrogen-receptor (ER) positive. Tamoxifen (TAM), a commonly employed medication for ER-positive breast cancer, often yields suboptimal therapeutic outcomes due to the emergence of TAM resistance, leading to the recurrence and a poor prognosis. The copper transporter, solute carrier family 31 member 1 (SLC31A1), has been associated with tumor aggressiveness and unfavorable outcomes in various types of tumors. In our current study, we found high expression of SLC31A1 that predicted poor survival in patients with breast cancer. Significantly, ER-positive breast cancer tissues in patients with recurrence post-TAM treatment exhibited considerably stronger SLC31A1 expression levels. In vitro experiments verified that TAM-resistant ER-positive breast cancer cell lines expressed notably higher SLC31A1 levels compared to the parental cell lines. Of great significance, SLC31A1 depletion notably rescued TAM sensitivity in chemoresistant ER-positive breast cancer cells, as demonstrated by the attenuated cell proliferative and invasive capabilities. Conversely, promoting SLC31A1 significantly facilitated the proliferation and invasion of wild-type breast cancer cells. Subsequently, we detected reduced copper levels in TAM-resistant breast cancer cells with SLC31A1 depletion. Mechanistically, we observed that in chemoresistant breast cancer cell lines, SLC31A1 knockdown resulted in a substantial decrease in the expression of carnitine palmitoyltransferase 1A (CPT1A), a rate-limiting enzyme of fatty acid oxidation (FAO). RNA-Seq analysis indicated that FAO might be implicated in SLC31A1-mediated breast cancer progression. CPT1A was also overexpressed in TAM-resistant breast cancer cells, accompanied by enhanced FAO rates and ATP levels. Suppressing CPT1A significantly enhanced the chemosensitivity of TAM-resistant breast cancer cells in response to TAM treatments. Intriguingly, copper exposure dose-dependently increased CPT1A expression in chemoresistant breast cancer cells, but this could be abolished upon SLC31A1 knockdown, along with enhanced apoptosis, which elucidated that copper uptake contributed to CPT1A expression. Furthermore, SLC31A1 overexpression significantly augmented CPT1A expression in parental breast cancer cells, accompanied by facilitated copper levels, FAO rates, and ATP levels, while being notably diminished upon CPT1A suppression. Finally, our in vivo studies confirmed that SLC31A1 deficiency re-sensitized TAM-resistant breast cancer cells to TAM treatment and abolished tumor growth. Collectively, all our studies demonstrated that SLC31A1/copper suppression could enhance TAM responses for chemoresistant ER-positive breast cancer cells through constraining the CPT1A-mediated FAO process.

International Union of Basic and Clinical Pharmacology: Fundamental insights and clinical relevance regarding the carnitine palmitoyltransferase family of enzymes

The carnitine palmitoyltransferases (CPTs) play a key role in controlling the oxidation of long-chain fatty acids and are potential therapeutic targets for diseases with a strong metabolic component, such as obesity, diabetes, and cancer. Four distinct proteins are CPT1A, CPT1B, CPT1C, and CPT2, differing in tissue expression and catalytic activity. CPT1s are finely regulated by malonyl-CoA, a metabolite whose intracellular levels reflect the cell's nutritional state. Although CPT1C does not exhibit significant catalytic activity, it is capable of modulating the functioning of other neuronal proteins. Structurally, all CPTs share a Y-shaped catalytic tunnel that allows the entry of 2 substrates and accommodation of the acyl group in a hydrophobic pocket. Several molecules targeting these enzymes have been described, some showing potential in normalizing blood glucose levels in diabetic patients, and others that, through a central mechanism, are anorexigenic and enhance energy expenditure. However, given the critical roles that CPTs play in certain tissues, such as the heart, liver, and brain, it is essential to fully understand the differences between the various isoforms. We analyze in detail the structure of these proteins, their cellular and physiological functions, and their potential as therapeutic targets in diseases such as obesity, diabetes, and cancer. We also describe drugs identified to date as having inhibitory or activating capabilities for these proteins. This knowledge will support the design of new drugs specific to each isoform, and the development of nanomedicines that can selectively target particular tissues or cells. SIGNIFICANCE STATEMENT: Carnitine palmitoyltransferase (CPT) proteins, as gatekeepers of fatty acid oxidation, have great potential as pharmacological targets to treat metabolic diseases like obesity, diabetes, and cancer. In recent years, significant progress has been made in understanding the 3-dimensional structure of CPTs and their pathophysiological functions. A deeper understanding of the differences between the various CPT family members will enable the design of selective drugs and therapeutic approaches with fewer side effects.

CPT1A mediates succinylation of LDHA at K318 site promoteing metabolic reprogramming in NK/T-cell lymphoma nasal type

Carnitine palmitoyltransferase 1A (CPT1A), a succinylating enzyme, is highly expressed in various malignant tumors and promotes tumor progression. Succinylation is a posttranslational modification that has been reported in various diseases, but its role in NK/T-Cell lymphoma nasal type (ENKTL-NT) remains underexplored. In this study, bioinformatics analysis showed that glycolytic is a major metabolic pathway in ENKTL-NT as the expression of many glycolytic related kinases are increased. CPT1A probably mediates glycolytic process, as indicated by GO-enrichment analysis. Studies showed that CPT1A was upregulated in ENKTL-NT tissues, and that high CPT1A expression was associated with poor prognosis of ENKTL-NT. CPT1A promoted the proliferation, colony formation, invasion and glycolytic process of ENKTL-NT cells and suppresses apoptosis. Mechanistically, CPT1A promotes succinylation of LDHA at lysine 318 (K318), which increase the protein stability and the final protein level of LDHA. Both knockdown and mutation (K318R) of LDHA abolished the cancer-promoting effects of CPT1A in ENKTL-NT. In all, this study reveals the mechanism underlying the cancer-promoting effects of CPT1A via inducing LDHA succinylation and metabolic reprogramming in ENKTL-NT. These findings might provide potential targets for the diagnosis or therapy of ENKTL-NT.

Metabolic crossroads: unravelling immune cell dynamics in gastrointestinal cancer drug resistance

Metabolic reprogramming within the tumor microenvironment (TME) plays a critical role in driving drug resistance in gastrointestinal cancers (GI), particularly through the pathways of fatty acid oxidation and glycolysis. Cancer cells often rewire their metabolism to sustain growth and reshape the TME, creating conditions such as nutrient depletion, hypoxia, and acidity that impair antitumor immune responses. Immune cells within the TME also undergo metabolic alterations, frequently adopting immunosuppressive phenotypes that promote tumor progression and reduce the efficacy of therapies. The competition for essential nutrients, particularly glucose, between cancer and immune cells compromises the antitumor functions of effector immune cells, such as T cells. Additionally, metabolic by-products like lactate and kynurenine further suppress immune activity and promote immunosuppressive populations, including regulatory T cells and M2 macrophages. Targeting metabolic pathways such as fatty acid oxidation and glycolysis presents new opportunities to overcome drug resistance and improve therapeutic outcomes in GI cancers. Modulating these key pathways has the potential to reinvigorate exhausted immune cells, shift immunosuppressive cells toward antitumor phenotypes, and enhance the effectiveness of immunotherapies and other treatments. Future strategies will require continued research into TME metabolism, the development of novel metabolic inhibitors, and clinical trials evaluating combination therapies. Identifying and validating metabolic biomarkers will also be crucial for patient stratification and treatment monitoring. Insights into metabolic reprogramming in GI cancers may have broader implications across multiple cancer types, offering new avenues for improving cancer treatment.

TCTN1 Induces Fatty Acid Oxidation to Promote Melanoma Metastasis

Metabolic reprogramming promotes and sustains multiple steps of melanoma metastasis. Identification of key regulators of metabolic reprogramming could lead to the development of treatments for preventing and treating metastatic melanoma. In this study, we identified that tectonic family member 1 (TCTN1) promotes melanoma metastasis by increasing fatty acid oxidation (FAO). In clinical melanoma samples, high expression of TCTN1 correlated with increased metastasis and shorter patient survival. Functionally, TCTN1 promoted melanoma invasion and migration in vitro and distant metastasis in vivo and induced a mesenchymal-like phenotype switch. Mechanistically, TCTN1 acted as a protein scaffold to promote the binding of HADHA and HADHB, subunits of the mitochondrial trifunctional protein complex, thus leading to FAO activation. TCTN1-mediated FAO activated the p38/MAPK signaling pathway in melanoma cells, promoting tumor epithelial-mesenchymal transition and stemness. Molecular docking indicated that the prostaglandin F receptor agonist fluprostenol can block HADHA/HADHB binding, which was confirmed experimentally. Treatment with fluprostenol was able to inhibit TCTN1-induced melanoma invasion and metastasis. Taken together, these findings elucidate the mechanism of TCTN1-mediated promotion of melanoma metastasis and support the potential application of fluprostenol for targeted therapy of metastatic melanoma. Significance: TCTN1 activates fatty acid oxidation to induce melanoma mesenchymal phenotype switching and invasion by promoting the binding of the subunits of MTP, which can be targeted with fluprostenol to inhibit melanoma metastasis.

Polystyrene nanoplastics promote colitis-associated cancer by disrupting lipid metabolism and inducing DNA damage

Nanoplastics (NPs) have attracted widespread attention owing to their presence in the body. Recent studies highlighted the detrimental effects of NPs on the digestive tract. However, no studies have reported an association between NPs exposure and colitis-associated cancer (CAC). An azoxymethane/dextran sodium sulfate-induced CAC model was used, and polystyrene nanoparticles (PS-NPs) were selected for long-term exposure. Non-targeted metabolomics and 16S rRNA sequencing were used to detect changes in colonic metabolites and gut microbes following PS-NPs exposure. A lipopolysaccharide (LPS)-treated cancer cell model (Caco-2) exposed to PS-NPs was used to investigate the underlying molecular mechanism. Compared to the normal control group, mice in the PS-NPs group exhibited more tumor nodes and reactive oxygen species (ROS), higher expression of pan-CK and Ki-67, and more severe DNA damage. 16S rRNA sequencing revealed that exposure to PS-NPs altered the abundance of Allobaculum and Lactobacillus, whereas metabolic analysis showed that the most significant metabolites were enriched mostly in fatty acid metabolism. Experiments in LPS intervened Caco-2 cells showed that exposure to PS-NPs led to lipid peroxidation, oxidative stress, and DNA damage in Caco-2. Exposure to PS-NPs activated the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway both in the AOM/DSS mouse model and cellular model. Key proteins involved in fatty acid metabolism were downregulated in Caco-2 cells exposed to PS-NPs. The metabolic effects of cancer cells exposed to PS-NPs were significantly inhibited by the activation of the fatty acid metabolism pathway by fenofibrate. PS-NPs exposure disturbed lipid metabolism and induced DNA damage via the activation of PI3K/AKT/mTOR to promote CAC progression. Inhibition of fatty acid metabolism is a therapeutic target for controlling PS-NP-induced CAC. Our study provides an important reference for the prevention and treatment of CAC from the perspective of the environment and enhances awareness of the necessity of plastic control.

CPT1A mediates radiation sensitivity in colorectal cancer

The prevalence and mortality rates of colorectal cancer (CRC) are increasing worldwide. Radiation resistance hinders radiotherapy, a standard treatment for advanced CRC, leading to local recurrence and metastasis. Elucidating the molecular mechanisms underlying radioresistance in CRC is critical to enhance therapeutic efficacy and patient outcomes. Bioinformatic analysis and tumour tissue examination were conducted to investigate the CPT1A mRNA and protein levels in CRC and their correlation with radiotherapy efficacy. Furthermore, lentiviral overexpression and CRISPR/Cas9 lentiviral vectors, along with in vitro and in vivo radiation experiments, were used to explore the effect of CPT1A on radiosensitivity. Additionally, transcriptomic sequencing, molecular biology experiments, and bioinformatic analyses were employed to elucidate the molecular mechanisms by which CPT1A regulates radiosensitivity. CPT1A was significantly downregulated in CRC and negatively correlated with responsiveness to neoadjuvant radiotherapy. Functional studies suggested that CPT1A mediates radiosensitivity, influencing reactive oxygen species (ROS) scavenging and DNA damage response. Transcriptomic and molecular analyses highlighted the involvement of the peroxisomal pathway. Mechanistic exploration revealed that CPT1A downregulates the FOXM1-SOD1/SOD2/CAT axis, moderating cellular ROS levels after irradiation and enhancing radiosensitivity. CPT1A downregulation contributes to radioresistance in CRC by augmenting the FOXM1-mediated antioxidant response. Thus, CPT1A is a potential biomarker of radiosensitivity and a novel target for overcoming radioresistance, offering a future direction to enhance CRC radiotherapy.

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.

Regulation of astrocyte metabolism by mitochondrial translocator protein 18 kDa

The mitochondrial translocator protein 18 kDa (TSPO) has been linked to functions from steroidogenesis to regulation of cellular metabolism and is an attractive therapeutic target for chronic CNS inflammation. Studies in Leydig cells and microglia indicate that TSPO function may vary between cells depending on their specialized roles. Astrocytes are critical for providing trophic and metabolic support in the brain. Recent work has highlighted that TSPO expression increases in astrocytes under inflamed conditions and may drive astrocyte reactivity. Relatively little is known about the role TSPO plays in regulating astrocyte metabolism and whether this protein is involved in immunometabolic processes in these cells. Using TSPO-deficient (TSPO-/-) mouse primary astrocytes in vitro (MPAs) and a human astrocytoma cell line (U373 cells), we performed extracellular metabolic flux analyses. We found that TSPO deficiency reduced basal cellular respiration and attenuated the bioenergetic response to glucopenia. Fatty acid oxidation was increased, and lactate production was reduced in TSPO-/- MPAs and U373 cells. Co-immunoprecipitation studies revealed that TSPO forms a complex with carnitine palmitoyltransferase 1a in U373 and MPAs, presenting a mechanism wherein TSPO may regulate FAO in these cells. Compared to TSPO+/+ cells, in TSPO-/- MPAs we observed attenuated tumor necrosis factor release following 3 h lipopolysaccharide (LPS) stimulation, which was enhanced at 24 h post-LPS stimulation. Together these data suggest that while TSPO acts as a regulator of metabolic flexibility, TSPO deficiency does not appear to modulate the metabolic response of MPAs to inflammation, at least in response to the model used in this study.

ALKBH5-mediated upregulation of CPT1A promotes macrophage fatty acid metabolism and M2 macrophage polarization, facilitating malignant progression of colorectal cancer

m6A modification has been studied in tumors, but its role in host anti-tumor immune response and TAMs polarization remains unclear. The fatty acid oxidation (FAO) process of TAMs is also attracting attention. A co-culture model of colorectal cancer (CRC) cells and macrophages was used to simulate the tumor microenvironment. Expression changes of m6A demethylase genes FTO and ALKBH5 were screened. ALKBH5 was further investigated. Gain-of-function experiments were conducted to study ALKBH5's effects on macrophage M2 polarization, CRC cell viability, proliferation, migration, and more. Me-RIP and Actinomycin D assays were performed to study ALKBH5's influence on CPT1A, the FAO rate-limiting enzyme. AMP, ADP, and ATP content detection, OCR measurement, and ECAR measurement were used to explore ALKBH5's impact on macrophage FAO level. Rescue experiments validated ALKBH5's mechanistic role in macrophage M2 polarization and CRC malignant development. In co-culture, CRC cells enhance macrophage FAO and suppress m6A modification in M2 macrophages. ALKBH5 was selected as the gene for further investigation. ALKBH5 mediates CPT1A upregulation by removing m6A modification, promoting M2 macrophage polarization and facilitating CRC development. These findings indicate that ALKBH5 enhances fatty acid metabolism and M2 polarization of macrophages by upregulating CPT1A, thereby promoting CRC development.