Inverse FASN and LDHA correlation drives metabolic resistance in breast cancer.

BACKGROUND: Breast cancer manifests as a heterogeneous pathology marked by complex metabolic reprogramming essential to satisfy its energy demands. Oncogenic signals boost the metabolism, modifying fatty acid synthesis and glucose use from the onset to progression and therapy resistant-forms. However, the exact contribution of metabolic dependencies during tumor evolution remains unclear. METHODS: In this study, we elucidate the connection between FASN and LDHA, pivotal metabolic genes, and their correlation with tumor grade and therapy response using datasets from public repositories. Subsequently, we evaluated the metabolic and proliferative functions upon FASN and LDHA inhibition in breast cancer models. Lastly, we integrated metabolomic and lipidomic analysis to define the contributions of metabolites, lipids, and precursors to the metabolic phenotypes. RESULTS: Collectively, our findings indicate metabolic shifts during breast cancer progression, unvealling two distinct functional energy phenotypes associated with aggressiveness and therapy response. Specifically, FASN exhibits reduced expression in advance-grade tumors and therapy-resistant forms, whereas LDHA demonstrates higher expression. Additionally, the biological and metabolic impact of blocking the enzymatic activity of FASN and LDHA was correlated with resistant conditions. CONCLUSIONS: These observations emphasize the intrinsic metabolic heterogeneity within breast cancer, thereby highlighting the relevance of metabolic interventions in the field of precision medicine.

Deficiency of SIAH1 promotes the formation of filopodia by increasing the accumulation of FASN in liver cancer.

It has been shown that the formation of filopodia is a key step in tumor cell metastasis, but there is limited research regarding its mechanism. In this study, we demonstrated that fatty acid synthase (FASN) promoted filopodia formation in liver cancer cells by regulating fascin actin-bundling protein 1 (FSCN1), a marker protein for filopodia. Mechanistically, on the one hand, the accumulation of FASN is caused by the enhanced deubiquitination of FASN mediated by UCHL5 (ubiquitin c-terminal hydrolase L5). In this pathway, low expression of SIAH1 (Seven in absentia homolog 1) can decrease the ubiquitination and degradation of ADRM1 (adhesion regulating molecule 1) thereby increasing its protein level, which will recruit and activate the deubiquitination enzyme UCHL5, leading to FASN undergo deubiquitination and escape from proteasomal degradation. On the other hand, the accumulation of FASN is related to its weakened ubiquitination, where SIAH1 directly acts as a ubiquitin ligase toward FASN, and low expression of SIAH1 reduces the ubiquitination and degradation of FASN. Both the two pathways are involved in the regulation of FASN in liver cancer. Our results reveal a novel mechanism for FASN accumulation due to the low expression of SIAH1 in human liver cancer and suggest an important role of FASN in filopodia formation in liver cancer cells.

Fatty Acid Synthase Promotes Hepatocellular Carcinoma Growth via S-Phase Kinase-Associated Protein 2/p27KIP1 Regulation.

Background and Objectives: Aberrant upregulation of fatty acid synthase (FASN), catalyzing de novo synthesis of fatty acids, occurs in various tumor types, including human hepatocellular carcinoma (HCC). Although FASN oncogenic activity seems to reside in its pro-lipogenic function, cumulating evidence suggests that FASN's tumor-supporting role might also be metabolic-independent. Materials and Methods: In the present study, we show that FASN inactivation by specific small interfering RNA (siRNA) promoted the downregulation of the S-phase kinase associated-protein kinase 2 (SKP2) and the consequent induction of p27KIP1 in HCC cell lines. Results: Expression levels of FASN and SKP2 directly correlated in human HCC specimens and predicted a dismal outcome. In addition, forced overexpression of SKP2 rendered HCC cells resistant to the treatment with the FASN inhibitor C75. Furthermore, FASN deletion was paralleled by SKP2 downregulation and p27KIP1 induction in the AKT-driven HCC preclinical mouse model. Moreover, forced overexpression of an SKP2 dominant negative form or a p27KIP1 non-phosphorylatable (p27KIP1-T187A) construct completely abolished AKT-dependent hepatocarcinogenesis in vitro and in vivo. Conclusions: In conclusion, the present data indicate that SKP2 is a critical downstream effector of FASN and AKT-dependent hepatocarcinogenesis in liver cancer, envisaging the possibility of effectively targeting FASN-positive liver tumors with SKP2 inhibitors or p27KIP1 activators.

ALG5 Regulates STF-62247-Induced Milk Fat Synthesis via the mTOR Signaling Pathway.

Milk fat content is a critical indicator of milk quality. Exploring the key regulatory genes involved in milk fat synthesis is essential for enhancing milk fat content. STF-62247 (STF), a thiazolamide compound, has the potential to bind with ALG5 and upregulate lipid droplets in fat synthesis. However, the effect of STF on the process of milk fat synthesis and whether it acts through ALG5 remains unknown. In this study, the impact of ALG5 on milk fat synthesis and its underlying mechanism were investigated using bovine mammary epithelial cells (BMECs) and mouse models through real-time PCR, western blotting, Oil Red O staining, and triglyceride analysis. Experimental findings revealed a positive correlation between STF and ALG5 with the ability to synthesize milk fat. Silencing ALG5 led to decreased expression of FASN, SREBP1, and PPARγ in BMECs, as well as reduced phosphorylation levels in the PI3K/AKT/mTOR signaling pathway. Moreover, the phosphorylation levels of the PI3K/AKT/mTOR signaling pathway were restored when ALG5 silencing was followed by the addition of STF. These results suggest that STF regulates fatty acid synthesis in BMECs by affecting the PI3K/AKT/mTOR signaling pathway through ALG5. ALG5 is possibly a new factor in milk fat synthesis.

Long noncoding RNA AI504432 upregulates FASN expression by sponging miR-1a-3p to promote lipogenesis in senescent adipocytes.

Aging affects lipid metabolism and can cause obesity as it is closely related to the disorder of many lipogenic regulatory factors. LncRNAs have been recognized as pivotal regulators across diverse biological processes, but their effects on lipogenesis in aging remain to be further studied. In this work, using RNA sequencing (RNA-Seq), we found that the expression of lncRNA AI504432 was significantly upregulated in the eWAT (epididymal white adipose tissue) of aging mice, and the knockdown of AI504432 notably reduced the expression of several adipogenic genes (e.g., Cebp/α, Srebp-1c, Fasn, Acaca, and Scd1) in senescent adipocytes. The bioinformatics investigation revealed that AI504432 possessed a binding site for miR-1a-3p, and the discovery was verified by the luciferase reporter assay. The expression of Fasn was increased upon the inhibition of miR-1a-3p but restored upon the simultaneous silencing of AI504432. Taken together, our results suggested that AI504432 controlled lipogenesis through the miR-1a-3p/Fasn signaling pathway. The findings may inspire new therapeutic approaches to target imbalanced lipid homeostasis due to aging.

Aryl Hydrocarbon Receptor Activation Limits the Fatty Acid Synthesis and Subsequent "miR-193a-3p-HDAC3-FASN" Signals to Alleviate Intestinal Fibrosis.

Intestinal fibrosis is a common complication of Crohn's disease and characterized by excessive extracellular matrix (ECM) deposition. The aryl hydrocarbon receptor (AhR) detects micronutrients and microbial metabolites in diet and can attenuate intestinal fibrosis with unclear mechanisms. In this study, AhR activation was demonstrated to downregulate the transcription of collagen I and fibronectin in a Sp1- but not Sp3- or AP-1-dependent manner. A suppressed fatty acid synthesis was highlighted using untargeted metabolomics analyses, and synthetic products, palmitic acid (PA), were used as the intermediary agent. After a screening study, fatty acid synthase (FASN) was identified as the main targeted protein, and AhR activation regulated "HDAC3-acetylation" signals but not glycosylation to enhance FASN degradation. Furthermore, results of bioinformatics analysis and others showed that after being activated, AhR targeted miR-193a-3p to control HDAC3 transcription. Collectively, AhR activation inhibited ECM deposition and alleviated intestinal fibrosis by limiting fatty acid synthesis subsequent to the inhibition of "miR-193a-3p-HDAC3-FASN" signals.

Overexpression of Fatty Acid Synthase Upregulates Glutamine-Fructose-6-Phosphate Transaminase 1 and O-Linked N-Acetylglucosamine Transferase to Increase O-GlcNAc Protein Glycosylation and Promote Colorectal Cancer Growth.

Fatty acid synthesis has been extensively investigated as a therapeutic target in cancers, including colorectal cancer (CRC). Fatty acid synthase (FASN), a key enzyme of de novo lipid synthesis, is significantly upregulated in CRC, and therapeutic approaches of targeting this enzyme are currently being tested in multiple clinical trials. However, the mechanisms behind the pro-oncogenic action of FASN are still not completely understood. Here, for the first time, we show that overexpression of FASN increases the expression of glutamine-fructose-6-phosphate transaminase 1 (GFPT1) and O-linked N-acetylglucosamine transferase (OGT), enzymes involved in hexosamine metabolism, and the level of O-GlcNAcylation in vitro and in vivo. Consistently, expression of FASN significantly correlates with expression of GFPT1 and OGT in human CRC tissues. shRNA-mediated downregulation of GFPT1 and OGT inhibits cellular proliferation and the level of protein O-GlcNAcylation in vitro, and knockdown of GFPT1 leads to a significant decrease in tumor growth and metastasis in vivo. Pharmacological inhibition of GFPT1 and OGT leads to significant inhibition of cellular proliferation and colony formation in CRC cells. In summary, our results show that overexpression of FASN increases the expression of GFPT1 and OGT as well as the level of protein O-GlcNAcylation to promote progression of CRC; targeting the hexosamine biosynthesis pathway could be a therapeutic approach for this disease.

Metformin exposure during pregnancy and lactation affects offspring's long-term body weight and adipose tissue mass independent of the maternal metabolic state.

The increasing prevalence of obesity, type 2 diabetes mellitus (T2DM), and gestational diabetes (GDM) among pregnant women has risen dramatically worldwide. The antihyperglycemic drug metformin is the most common drug for T2DM treatment in non-pregnant individuals; nevertheless, it is increasingly being used for diabetes-complicated pregnancies. Studies on the long-term metabolic effects of this drug in offspring remain scarce. This work aimed to determine the effect of metformin exposure during pregnancy and lactation on the offspring of a model of diet-induced maternal hyperglycemia. Cohorts of pregnant mice were fed a 46% fat diet (HFD) or a control standard diet (SD). A group of dams were exposed to metformin during pregnancy and lactation. After weaning, the offspring were fed SD for 8 weeks and then challenged with a 46% HFD after puberty for 12 weeks. Irrespective of the maternal diet, offspring of metformin-exposed mothers had a lower body weight and reduced inguinal white adipose tissue (iWAT) mass after HFD challenge. This was associated with increased expression of Pparg, Fabp4, Glut4, Srebp1, and Fasn in the iWAT during adulthood in the metabolically impaired dams exposed to metformin, suggesting increased adipogenesis and de novo lipogenesis. Increased expression of Fasn associated with decreased methylation levels at its promoter and proximal coding region in the iWAT was found. These results suggest that metformin modulates gene expression levels by epigenetic mechanisms in maternal metabolic-impaired conditions.

Mitochondrial ACSS1-K635 acetylation knock-in mice exhibit altered metabolism, cell senescence, and nonalcoholic fatty liver disease.

Acetyl-CoA synthetase short-chain family member 1 (ACSS1) uses acetate to generate mitochondrial acetyl-CoA and is regulated by deacetylation by sirtuin 3. We generated an ACSS1-acetylation (Ac) mimic mouse, where lysine-635 was mutated to glutamine (K635Q). Male Acss1K635Q/K635Q mice were smaller with higher metabolic rate and blood acetate and decreased liver/serum ATP and lactate levels. After a 48-hour fast, Acss1K635Q/K635Q mice presented hypothermia and liver aberrations, including enlargement, discoloration, lipid droplet accumulation, and microsteatosis, consistent with nonalcoholic fatty liver disease (NAFLD). RNA sequencing analysis suggested dysregulation of fatty acid metabolism, cellular senescence, and hepatic steatosis networks, consistent with NAFLD. Fasted Acss1K635Q/K635Q mouse livers showed increased fatty acid synthase (FASN) and stearoyl-CoA desaturase 1 (SCD1), both associated with NAFLD, and increased carbohydrate response element-binding protein binding to Fasn and Scd1 enhancer regions. Last, liver lipidomics showed elevated ceramide, lysophosphatidylethanolamine, and lysophosphatidylcholine, all associated with NAFLD. Thus, we propose that ACSS1-K635-Ac dysregulation leads to aberrant lipid metabolism, cellular senescence, and NAFLD.

DPP3 promotes breast cancer tumorigenesis by stabilizing FASN and promoting lipid synthesis.

DPP3, a dipeptidyl peptidase, participates in a variety of pathophysiological processes. DPP3 is upregulated in cancer and might serve as a key factor in the tumorigenesis and progression of various malignancies. However, its specific role and molecular mechanism are still unknown. In this study, the expression of DPP3 in breast cancer tissues is analyzed using TCGA database. Kaplan-Meier survival analysis is performed to estimate the effect of DPP3 on the survival outcomes. To explore the biological function and mechanisms of DPP3 in breast cancer, biochemical and cell biology assays are conducted in vitro. DPP3 expresses at a higher level in breast cancer tissues than that in adjacent tissues in both TCGA database and clinical samples. Patients with high expression of DPP3 have poor survival outcomes. The proliferation and migration abilities of tumor cells with stable DPP3 knockout in breast cancer cell lines are significantly inhibited, and apoptosis is increased in vitro. GSEA analysis shows that DPP3 can affect lipid metabolism and fatty acid synthesis in tumors. Subsequent experiments show that DPP3 could stabilize FASN expression and thus promote fatty acid synthesis in tumor cells. The results of the metabolomic analysis also confirm that DPP3 can affect the content of free fatty acids. This study demonstrates that DPP3 plays a role in the reprogramming of fatty acid metabolism in tumors and is associated with poor prognosis in breast cancer patients. These findings will provide a new therapeutic target for the treatment of breast cancer.

PRMT5 activates lipid metabolic reprogramming via MYC contributing to the growth and survival of mantle cell lymphoma.

Mantle cell lymphoma (MCL) is an incurable and aggressive subtype of non-Hodgkin B-cell lymphoma. Increased lipid uptake, storage, and lipogenesis occur in a variety of cancers and contribute to rapid tumor growth. However, no data has been explored for the roles of lipid metabolism reprogramming in MCL. Here, we identified aberrant lipid metabolism reprogramming and PRMT5 as a key regulator of cholesterol and fatty acid metabolism reprogramming in MCL patients. High PRMT5 expression predicts adverse outcome prognosis in 105 patients with MCL and GEO database (GSE93291). PRMT5 deficiency resulted in proliferation defects and cell death by CRISPR/Cas9 editing. Moreover, PRMT5 inhibitors including SH3765 and EPZ015666 worked through blocking SREBP1/2 and FASN expression in MCL. Furthermore, PRMT5 was significantly associated with MYC expression in 105 MCL samples and the GEO database (GSE93291). CRISPR MYC knockout indicated PRMT5 can promote MCL outgrowth by inducing SREBP1/2 and FASN expression through the MYC pathway.

Dynamics of the Trypanosoma cruzi infection in adipose tissue: Assessing gene expression of PNPLA2, FASN, and ACAT1 under Benzonidazole treatment and indirect mononuclear immune cells interaction.

Trypanosoma cruzi is a parasite with a high capacity to adapt to the host. Animal models have already demonstrated that the tropism of this parasite occurs not only in cardiac/digestive tissues but also in adipose tissue (AT). That said, the consequences ofT. cruziinfection for AT and the implications of treatment with Benzonidazole in this tissue are under discussion. Here, we tested the hypothesis that T. cruzi infection in adipose tissue upon treatment with Benzonidazole (Bz) and the interaction of mononuclear immune cells (PBMC) influences the relative expression of ACAT1, FASN, and PNPLA2 genes. Thus, stem cells derived from adipose tissue (ADSC) after adipogenic differentiation were indirectly cultivated with PBMC after infection with the T. cruzi Y strain and treatment with Bz. We use the TcSAT-IAM system and RT-qPCR to evaluate the parasite load and the relative quantification (ΔCt) of the ACAT1, FASN, and PNPLA2 genes. Our results demonstrate that treatment with Bz did not reduce adipocyte infection in the presence (p-value: 0.5796) or absence (p-value: 0.1854) of cultivation with PBMC. In addition, even though there is no statistical difference when compared to the control group (AT), T. cruzi induces the FASN expression (Rq: 14.00). However, treatment with Bz in AT suggests the increases of PNPLA2 expression levels (Rq: 12.58), even in the absence of T. cruzi infection. During indirect cultivation with PBMC, T. cruzi smooths the expression of PNPLA2 (Rq: 0.824) and instigates the expression of ACAT1 (Rq: 1.632) and FASN (Rq: 1.394). Furthermore, the treatment with Bz during infection induces PNPLA2 expression (Rq: 1.871), maintaining FASN expression levels (Rq: 1.334). Given this, our results indicate that treatment with Benzonidazole did not decrease T. cruzi infection in adipose tissue. However, treating the adipocyte cells with Bz during the interaction with PBMC cells influences the lipid pathways scenario, inducing lipolytic metabolism through the expression of PNPLA2.

FASN-mediated fatty acid biosynthesis remodels immune environment in Clonorchis sinensis infection-related intrahepatic cholangiocarcinoma.

BACKGROUND & AIMS: Intrahepatic cholangiocarcinoma (iCCA) is the second most common primary liver cancer and is highly lethal. Clonorchis sinensis (C. sinensis) infection is an important risk factor for iCCA. Here we investigated the clinical impact and underlying molecular characteristics of C. sinensis infection-related iCCA. METHODS: We performed single-cell RNA sequencing, whole-exome sequencing, RNA sequencing, metabolomics and spatial transcriptomics in 251 patients with iCCA from three medical centers. Alterations in metabolism and the immune microenvironment of C. sinensis-related iCCAs were validated through an in vitro co-culture system and in a mouse model of iCCA. RESULTS: We revealed that C. sinensis infection was significantly associated with iCCA patients' overall survival and response to immunotherapy. Fatty acid biosynthesis and the expression of fatty acid synthase (FASN), a key enzyme catalyzing long-chain fatty acid synthesis, were significantly enriched in C. sinensis-related iCCAs. iCCA cell lines treated with excretory/secretory products of C. sinensis displayed elevated FASN and free fatty acids. The metabolic alteration of tumor cells was closely correlated with the enrichment of tumor-associated macrophage (TAM)-like macrophages and the impaired function of T cells, which led to formation of an immunosuppressive microenvironment and tumor progression. Spatial transcriptomics analysis revealed that malignant cells were in closer juxtaposition with TAM-like macrophages in C. sinensis-related iCCAs than non-C. sinensis-related iCCAs. Importantly, treatment with a FASN inhibitor significantly reversed the immunosuppressive microenvironment and enhanced anti-PD-1 efficacy in iCCA mouse models treated with excretory/secretory products from C. sinensis. CONCLUSIONS: We provide novel insights into metabolic alterations and the immune microenvironment in C. sinensis infection-related iCCAs. We also demonstrate that the combination of a FASN inhibitor with immunotherapy could be a promising strategy for the treatment of C. sinensis-related iCCAs. IMPACT AND IMPLICATIONS: Clonorchis sinensis (C. sinensis)-infected patients with intrahepatic cholangiocarcinoma (iCCA) have a worse prognosis and response to immunotherapy than non-C. sinensis-infected patients with iCCA. The underlying molecular characteristics of C. sinensis infection-related iCCAs remain unclear. Herein, we demonstrate that upregulation of FASN (fatty acid synthase) and free fatty acids in C. sinensis-related iCCAs leads to formation of an immunosuppressive microenvironment and tumor progression. Thus, administration of FASN inhibitors could significantly reverse the immunosuppressive microenvironment and further enhance the efficacy of anti-PD-1 against C. sinensis-related iCCAs.

Transcriptomic insights into the lipotoxicity of high-fat high-fructose diet in rat and mouse.

Along with the increasing prevalence of obesity worldwide, the deleterious effects of high-calorie diet are gradually recognized through more and more epidemiological studies. However, the concealed and chronic causality whitewashes its unhealthy character. Given an ingenious mechanism orchestrates the metabolic adaptation to high-fat high-fructose (HFF) diet and connive its lipotoxicity, in this study, an experimental rat/mouse model of obesity was induced and a comparative transcriptomic analysis was performed to probe the mystery. Our results demonstrated that HFF diet consumption altered the transcriptomic pattern as well as different high-calorie diet fed rat/mouse manifested distinct hepatic transcriptome. Validation with RT-qPCR and Western blotting confirmed that SREBP1-FASN involved in de novo lipogenesis partly mediated metabolic self-adaption. Moreover, hepatic ACSL1-CPT1A-CPT2 pathway involved in fatty acids ß-oxidation, played a key role in the metabolic adaption to HFF. Collectively, our findings enrich the knowledge of the chronic adaptation mechanisms and also shed light on future investigations. Meanwhile, our results also suggest that efforts to restore the fatty acids metabolic fate could be a promising avenue to fight against obesity and associated steatosis and insulin resistance challenged by HFF diet.

The m6A modification mediated-lncRNA POU6F2-AS1 reprograms fatty acid metabolism and facilitates the growth of colorectal cancer via upregulation of FASN.

BACKGROUND: Long noncoding RNAs (lncRNAs) have emerged as key players in tumorigenesis and tumour progression. However, the biological functions and potential mechanisms of lncRNAs in colorectal cancer (CRC) are unclear. METHODS: The novel lncRNA POU6F2-AS1 was identified through bioinformatics analysis, and its expression in CRC patients was verified via qRT-PCR and FISH. In vitro and in vivo experiments, such as BODIPY staining, Oil Red O staining, triglyceride (TAG) assays, and liquid chromatography mass spectrometry (LC-MS) were subsequently performed with CRC specimens and cells to determine the clinical significance, and functional roles of POU6F2-AS1. Biotinylated RNA pull-down, RIP, Me-RIP, ChIP, and patient-derived organoid (PDO) culture assays were performed to confirm the underlying mechanism of POU6F2-AS1. RESULTS: The lncRNA POU6F2-AS1 is markedly upregulated in CRC and associated with adverse clinicopathological features and poor overall survival in CRC patients. Functionally, POU6F2-AS1 promotes the growth and lipogenesis of CRC cells both in vitro and in vivo. Mechanistically, METTL3-induced m6A modification is involved in the upregulation of POU6F2-AS1. Furthermore, upregulated POU6F2-AS1 could tether YBX1 to the FASN promoter to induce transcriptional activation, thus facilitating the growth and lipogenesis of CRC cells. CONCLUSIONS: Our data revealed that the upregulation of POU6F2-AS1 plays a critical role in CRC fatty acid metabolism and might provide a novel promising biomarker and therapeutic target for CRC.

FASN Inhibition Decreases MHC-I Degradation and Synergizes with PD-L1 Checkpoint Blockade in Hepatocellular Carcinoma.

Immune checkpoint inhibitors (ICI) transformed the treatment landscape of hepatocellular carcinoma (HCC). Unfortunately, patients with attenuated MHC-I expression remain refractory to ICIs, and druggable targets for upregulating MHC-I are limited. Here, we found that genetic or pharmacologic inhibition of fatty acid synthase (FASN) increased MHC-I levels in HCC cells, promoting antigen presentation and stimulating antigen-specific CD8+ T-cell cytotoxicity. Mechanistically, FASN inhibition reduced palmitoylation of MHC-I that led to its lysosomal degradation. The palmitoyltransferase DHHC3 directly bound MHC-I and negatively regulated MHC-I protein levels. In an orthotopic HCC mouse model, Fasn deficiency enhanced MHC-I levels and promoted cancer cell killing by tumor-infiltrating CD8+ T cells. Moreover, the combination of two different FASN inhibitors, orlistat and TVB-2640, with anti-PD-L1 antibody robustly suppressed tumor growth in vivo. Multiplex IHC of human HCC samples and bioinformatic analysis of The Cancer Genome Atlas data further illustrated that lower expression of FASN was correlated with a higher percentage of cytotoxic CD8+ T cells. The identification of FASN as a negative regulator of MHC-I provides the rationale for combining FASN inhibitors and immunotherapy for treating HCC. SIGNIFICANCE: Inhibition of FASN increases MHC-I protein levels by suppressing its palmitoylation and lysosomal degradation, which stimulates immune activity against hepatocellular carcinoma and enhances the efficacy of immune checkpoint inhibition.

FASN negatively regulates p65 expression by reducing its stability via Thr254 phosphorylation and isomerization by Pin1.

FASN, the sole cytosolic enzyme responsible for de novo palmitate synthesis in mammalian cells, has been associated with poor prognosis in cancer and shown to cause drug and radiation resistance by upregulating DNA damage repair via suppression of p65 expression. Targeting FASN by repurposing proton pump inhibitors has generated impressive outcomes in triple-negative breast cancer patients. While p65 regulation of DNA damage repair was thought to be due to its suppression of poly(ADP-ribose) polymerase 1 gene transcription, the mechanism of FASN regulation of p65 expression was unknown. In this study, we show that FASN regulates p65 stability by controlling its phosphorylation at Thr254, which recruits the peptidyl-prolyl cis/trans isomerase Pin1 that is known to stabilize many proteins in the nucleus. This regulation is mediated by palmitate, the FASN catalytic product, not by FASN protein per se. This finding of FASN regulation of p65 stability via phosphorylation of Thr254 and isomerization by Pin1 implicates that FASN and its catalytic product palmitate may play an important role in regulating protein stability in general and p65 more specifically.

Metabolic reprogramming based on RNA sequencing of gemcitabine-resistant cells reveals the FASN gene as a therapeutic for bladder cancer.

Bladder cancer (BLCA) is the most frequent malignant tumor of the genitourinary system. Postoperative chemotherapy drug perfusion and chemotherapy are important means for the treatment of BLCA. However, once drug resistance occurs, BLCA develops rapidly after recurrence. BLCA cells rely on unique metabolic rewriting to maintain their growth and proliferation. However, the relationship between the metabolic pattern changes and drug resistance in BLCA is unclear. At present, this problem lacks systematic research. In our research, we identified and analyzed resistance- and metabolism-related differentially expressed genes (RM-DEGs) based on RNA sequencing of a gemcitabine-resistant BLCA cell line and metabolic-related genes (MRGs). Then, we established a drug resistance- and metabolism-related model (RM-RM) through regression analysis to predict the overall survival of BLCA. We also confirmed that RM-RM had a significant correlation with tumor metabolism, gene mutations, tumor microenvironment, and adverse drug reactions. Patients with a high drug resistance- and metabolism-related risk score (RM-RS) showed more active lipid synthesis than those with a low RM-RS. Further in vitro and in vivo studies were implemented using Fatty Acid Synthase (FASN), a representative gene, which promotes gemcitabine resistance, and its inhibitor (TVB-3166) that can reverse this resistance effect.

PITPNC1 Suppress CD8+ T cell immune function and promote radioresistance in rectal cancer by modulating FASN/CD155.

BACKGROUND: Radioresistance is a primary factor contributing to the failure of rectal cancer treatment. Immune suppression plays a significant role in the development of radioresistance. We have investigated the potential role of phosphatidylinositol transfer protein cytoplasmic 1 (PITPNC1) in regulating immune suppression associated with radioresistance. METHODS: To elucidate the mechanisms by which PITPNC1 influences radioresistance, we established HT29, SW480, and MC38 radioresistant cell lines. The relationship between radioresistance and changes in the proportion of immune cells was verified through subcutaneous tumor models and flow cytometry. Changes in the expression levels of PITPNC1, FASN, and CD155 were determined using immunohistochemistry and western blotting techniques. The interplay between these proteins was investigated using immunofluorescence co-localization and immunoprecipitation assays. Additionally, siRNA and lentivirus-mediated gene knockdown or overexpression, as well as co-culture of tumor cells with PBMCs or CD8+ T cells and establishment of stable transgenic cell lines in vivo, were employed to validate the impact of the PITPNC1/FASN/CD155 pathway on CD8+ T cell immune function. RESULTS: Under irradiation, the apoptosis rate and expression of apoptosis-related proteins in radioresistant colorectal cancer cell lines were significantly decreased, while the cell proliferation rate increased. In radioresistant tumor-bearing mice, the proportion of CD8+ T cells and IFN-γ production within immune cells decreased. Immunohistochemical analysis of human and animal tissue specimens resistant to radiotherapy showed a significant increase in the expression levels of PITPNC1, FASN, and CD155. Gene knockdown and rescue experiments demonstrated that PITPNC1 can regulate the expression of CD155 on the surface of tumor cells through FASN. In addition, co-culture experiments and in vivo tumor-bearing experiments have shown that silencing PITPNC1 can inhibit FASN/CD155, enhance CD8+ T cell immune function, promote colorectal cancer cell death, and ultimately reduce radioresistance in tumor-bearing models. CONCLUSIONS: PITPNC1 regulates the expression of CD155 through FASN, inhibits CD8+ T cell immune function, and promotes radioresistance in rectal cancer.

Targeting ZDHHC21/FASN axis for the treatment of diffuse large B-cell lymphoma.

S-palmitoylation is essential for cancer development via regulating protein stability, function and subcellular location, yet the roles S-palmitoylation plays in diffuse large B-cell lymphoma (DLBCL) progression remain enigmatic. In this study, we uncovered a novel function of the palmitoyltransferase ZDHHC21 as a tumor suppressor in DLBCL and identified ZDHHC21 as a key regulator of fatty acid synthetase (FASN) S-palmitoylation for the first time. Specifically, ZDHHC21 was downregulated in DLBCL, and its expression level was associated with the clinical prognosis of patients with DLBCL. In vitro and in vivo experiments suggested that ZDHHC21 suppressed DLBCL cell proliferation. Mechanistically, ZDHHC21 interacted with FASN and mediated its palmitoylation at Cys1317, resulting in a decrease in FASN protein stability and fatty acid synthesis, consequently leading to the inhibition of DLBCL cell growth. Of note, an FDA-approved small-molecule compound lanatoside C interacted with ZDHHC21, increased ZDHHC21 protein stability and decreased FASN expression, which contributed to the suppression of DLBCL growth in vitro and in vivo. Our results demonstrate that ZDHHC21 strongly represses DLBCL cell proliferation by mediating FASN palmitoylation, and suggest that targeting ZDHHC21/FASN axis is a potential therapeutic strategy against DLBCL.