p53 transcriptionally regulates SQLE to repress cholesterol synthesis and tumor growth

Mechanism of Metabolic Dysfunction-associated Steatotic Liver Disease: Important role of lipid metabolism

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease, has a high global prevalence and can progress to metabolic dysfunction-associated steatohepatitis, cirrhosis, and hepatocellular carcinoma. The pathogenesis of MASLD is primarily driven by disturbances in hepatic lipid metabolism, involving six key processes: increased hepatic fatty acid uptake, enhanced fatty acid synthesis, reduced oxidative degradation of fatty acids, increased cholesterol uptake, elevated cholesterol synthesis, and increased bile acid synthesis. Consequently, maintaining hepatic lipid metabolic homeostasis is essential for effective MASLD management. Numerous novel molecules and Chinese proprietary medicines have demonstrated promising therapeutic potential in treating MASLD, primarily by inhibiting lipid synthesis and promoting lipid oxidation. In this review, we summarized recent research on MASLD, elucidated the molecular mechanisms by which lipid metabolism disorders contribute to MASLD pathogenesis, and discussed various lipid metabolism-targeted therapeutic approaches for MASLD.

Lipid metabolism reprogramming in endometrial cancer: biological functions and therapeutic implications

BACKGROUND

Endometrial cancer is one of the major gynecological cancers, with increasing incidence and mortality in the past decades. Emerging preclinical and clinical data have indicated its close association with obesity and dyslipidemia. Metabolism reprogramming has been considered as the hallmark of cancer, to satisfy the extensive need of nutrients and energy for survival and growth. Particularly, lipid metabolism reprogramming has aroused the researchers' interest in the field of cancer, including tumorigenesis, invasiveness, metastasis, therapeutic resistance and immunity modulation, etc. But the roles of lipid metabolism reprogramming in endometrial cancer have not been fully understood. This review has summarized how lipid metabolism reprogramming induces oncogenesis and progression of endometrial cancer, including the biological functions of aberrant lipid metabolism pathway and altered transcription regulation of lipid metabolism pathway. Besides, we proposed novel therapeutic strategies of targeting lipid metabolism pathway and concentrated on its potential of sensitizing immunotherapy and hormonal therapy, to further optimize the existing treatment modalities of patients with advanced/metastatic endometrial cancer. Moreover, we expect that targeting lipid metabolism plus hormone therapy may block the endometrial malignant transformation and enrich the preventative approaches of endometrial cancer.

CONCLUSION

Lipid metabolism reprogramming plays an important role in tumor initiation and cancer progression of endometrial cancer. Targeting the core enzymes and transcriptional factors of lipid metabolism pathway alone or in combination with immunotherapy/hormone treatment is expected to decrease the tumor burden and provide promising treatment opportunity for patients with advanced/metastatic endometrial cancer.

SCD1 promotes the stemness of gastric cancer stem cells by inhibiting ferroptosis through the SQLE/cholesterol/mTOR signalling pathway

Cancer stem cells (CSCs) play a substantial role in cancer onset and recurrence. Anomalous iron and lipid metabolism have been documented in CSCs, suggesting that ferroptosis, a recently discovered form of regulated cell death characterised by lipid peroxidation, could potentially exert a significant influence on CSCs. However, the precise role of ferroptosis in gastric cancer stem cells (GCSCs) remains unknown. To address this gap, we screened ferroptosis-related genes in GCSCs using The Cancer Genome Atlas and corroborated our findings through quantitative polymerase chain reaction and western blotting. These results indicate that stearoyl-CoA desaturase (SCD1) is a key player in the regulation of ferroptosis in GCSCs. This study provides evidence that SCD1 positively regulates the transcription of squalene epoxidase (SQLE) by eliminating transcriptional inhibition of P53. This mechanism increases the cholesterol content and the elevated cholesterol regulated by SCD1 inhibits ferroptosis via the mTOR signalling pathway. Furthermore, our in vivo studies showed that SCD1 knockdown or regulation of cholesterol intake affects the stemness of GCSCs and their sensitivity to ferroptosis inducers. Thus, targeting the SCD1/squalene epoxidase/cholesterol signalling axis in conjunction with ferroptosis inducers may represent a promising therapeutic approach for the treatment of gastric cancer based on GCSCs.

A novel prognostic signature related to programmed cell death in osteosarcoma

Background

Osteosarcoma primarily affects children and adolescents, with current clinical treatments often resulting in poor prognosis. There has been growing evidence linking programmed cell death (PCD) to the occurrence and progression of tumors. This study aims to enhance the accuracy of OS prognosis assessment by identifying PCD-related prognostic risk genes, constructing a PCD-based OS prognostic risk model, and characterizing the function of genes within this model.

Method

We retrieved osteosarcoma patient samples from TARGET and GEO databases, and manually curated literature to summarize 15 forms of programmed cell death. We collated 1621 PCD genes from literature sources as well as databases such as KEGG and GSEA. To construct our model, we integrated ten machine learning methods including Enet, Ridge, RSF, CoxBoost, plsRcox, survivalSVM, Lasso, SuperPC, StepCox, and GBM. The optimal model was chosen based on the average C-index, and named Osteosarcoma Programmed Cell Death Score (OS-PCDS). To validate the predictive performance of our model across different datasets, we employed three independent GEO validation sets. Moreover, we assessed mRNA and protein expression levels of the genes included in our model, and investigated their impact on proliferation, migration, and apoptosis of osteosarcoma cells by gene knockdown experiments.

Result

In our extensive analysis, we identified 30 prognostic risk genes associated with programmed cell death (PCD) in osteosarcoma (OS). To assess the predictive power of these genes, we computed the C-index for various combinations. The model that employed the random survival forest (RSF) algorithm demonstrated superior predictive performance, significantly outperforming traditional approaches. This optimal model included five key genes: MTM1, MLH1, CLTCL1, EDIL3, and SQLE. To validate the relevance of these genes, we analyzed their mRNA and protein expression levels, revealing significant disparities between osteosarcoma cells and normal tissue cells. Specifically, the expression levels of these genes were markedly altered in OS cells, suggesting their critical role in tumor progression. Further functional validation was performed through gene knockdown experiments in U2OS cells. Knockdown of three of these genes-CLTCL1, EDIL3, and SQLE-resulted in substantial changes in proliferation rate, migration capacity, and apoptosis rate of osteosarcoma cells. These findings underscore the pivotal roles of these genes in the pathophysiology of osteosarcoma and highlight their potential as therapeutic targets.

Conclusion

The five genes constituting the OS-PCDS model-CLTCL1, MTM1, MLH1, EDIL3, and SQLE-were found to significantly impact the proliferation, migration, and apoptosis of osteosarcoma cells, highlighting their potential as key prognostic markers and therapeutic targets. OS-PCDS enables accurate evaluation of the prognosis in patients with osteosarcoma.

Endogenous p53 inhibitor TIRR dissociates systemic metabolic health from oncogenic activity

It is unclear whether metabolic health corresponds to reduced oncogenesis or vice versa. We study Tudor-interacting repair regulator (TIRR), an inhibitor of p53 binding protein 1 (53BP1)-mediated p53 activation, and the physiological consequences of enhancing tumor suppressor activity. Deleting TIRR selectively activates p53, significantly protecting against cancer but leading to a systemic metabolic imbalance in mice. TIRR-deficient mice are overweight and insulin resistant, even under normal chow diet. Similarly, reduced TIRR expression in human adipose tissue correlates with higher BMI and insulin resistance. Despite the metabolic challenges, TIRR loss improves p53 heterozygous (p53HET) mouse survival and correlates with enhanced progression-free survival in patients with various p53HET carcinomas. Finally, TIRR's oncoprotective and metabolic effects are dependent on p53 and lost upon p53 deletion in TIRR-deficient mice, with glucose homeostasis and orexigenesis being primarily regulated by TIRR expression in the adipose tissue and the CNS, respectively, as evidenced by tissue-specific models. In summary, TIRR deletion provides a paradigm of metabolic deregulation accompanied by reduced oncogenesis.

ESR1 and p53 interactome alteration defines mechanisms of tamoxifen response in luminal breast cancer

The canonical mechanism behind tamoxifen's therapeutic effect on estrogen receptor α/ESR1+ breast cancers is inhibition of ESR1-dependent estrogen signaling. Although ESR1+ tumors expressing wild-type p53 were reported to be more responsive to tamoxifen (Tam) therapy, p53 has not been factored into choice of this therapy and the mechanism underlying the role of p53 in Tam response remains unclear. In a window-of-opportunity trial on patients with newly diagnosed stage I-III ESR1+/HER2/wild-type p53 breast cancer who were randomized to arms with or without Tam prior to surgery, we reveal that the ESR1-p53 interaction in tumors was inhibited by Tam. This resulted in functional reactivation of p53 leading to transcriptional reprogramming that favors tumor-suppressive signaling, as well as downregulation of oncogenic pathways. These findings illustrating the convergence of ESR1 and p53 signaling during Tam therapy enrich mechanistic understanding of the impact of p53 on the response to Tam therapy.

Depletion of squalene epoxidase in synergy with glutathione peroxidase 4 inhibitor RSL3 overcomes oxidative stress resistance in lung squamous cell carcinoma

Background

Lung squamous cell carcinoma (LUSC) lacks effective targeted therapies and has a poor prognosis. Disruption of squalene epoxidase (SQLE) has been implicated in metabolic disorders and cancer. However, the role of SQLE as a monooxygenase involved in oxidative stress remains unclear.

Methods

We analyzed the expression and prognosis of lung adenocarcinoma (LUAD) and LUSC samples from GEO and TCGA databases. The proliferative activity of the tumors after intervention of SQLE was verified by cell and animal experiments. JC-1 assay, flow cytometry, and Western blot were used to show changes in apoptosis after intervention of SQLE. Flow cytometry and fluorescence assay of ROS levels were used to indicate oxidative stress status.

Results

We investigated the unique role of SQLE expression in the diagnosis and prognosis prediction of LUSC. Knockdown of SQLE or treatment with the SQLE inhibitor terbinafine can suppress the proliferation of LUSC cells by inducing apoptosis and reactive oxygen species accumulation. However, depletion of SQLE also results in the impairment of lipid peroxidation and ferroptosis resistance such as upregulation of glutathione peroxidase 4. Therefore, prevention of SQLE in synergy with glutathione peroxidase 4 inhibitor RSL3 effectively mitigates the proliferation and growth of LUSC.

Conclusion

Our study indicates that the low expression of SQLE employs adaptive survival through regulating the balance of apoptosis and ferroptosis resistance. In future, the combinational therapy of targeting SQLE and ferroptosis could be a promising approach in treating LUSC.

The constitutively active form of a key cholesterol synthesis enzyme is lipid droplet-localized and upregulated in endometrial cancer tissues

Cholesterol is essential for both normal cell viability and cancer cell proliferation. Aberrant activity of squalene monooxygenase (SM, also known as squalene epoxidase), the rate-limiting enzyme of the committed cholesterol synthesis pathway, is accordingly implicated in a growing list of cancers. We previously reported that hypoxia triggers the truncation of SM to a constitutively active form, thus preserving sterol synthesis during oxygen shortfalls. Here, we show SM truncation is upregulated and correlates with the magnitude of hypoxia in endometrial cancer tissues, supporting the in vivo relevance of our earlier work. To further investigate the pathophysiological consequences of SM truncation, we examined its lipid droplet-localized pool using complementary immunofluorescence and cell fractionation approaches and found that it exclusively comprises the truncated enzyme. This partitioning is facilitated by the loss of an endoplasmic reticulum-embedded region at the SM N terminus, whereas the catalytic domain containing membrane-associated C-terminal helices is spared. Moreover, we determined multiple amphipathic helices contribute to the lipid droplet localization of truncated SM. Taken together, our results expand on the striking differences between the two forms of SM and suggest upregulated truncation may contribute to SM-related oncogenesis.

Effect of Calebin-A on Critical Genes Related to NAFLD: A Protein-Protein Interaction Network and Molecular Docking Study

Background

Calebin-A is a minor phytoconstituent of turmeric known for its activity against inflammation, oxidative stress, cancerous, and metabolic disorders like Non-alcoholic fatty liver disease(NAFLD). Based on bioinformatic tools. Subsequently, the details of the interaction of critical proteins with Calebin-A were investigated using the molecular docking technique.

Methods

We first probed the intersection of genes/ proteins between NAFLD and Calebin-A through online databases. Besides, we performed an enrichment analysis using the ClueGO plugin to investigate signaling pathways and gene ontology. Next, we evaluate the possible interaction of Calebin-A with significant hub proteins involved in NAFLD through a molecular docking study.

Results

We identified 87 intersection genes Calebin-A targets associated with NAFLD. PPI network analysis introduced 10 hub genes (TP53, TNF, STAT3, HSP90AA1, PTGS2, HDAC6, ABCB1, CCT2, NR1I2, and GUSB). In KEGG enrichment, most were associated with Sphingolipid, vascular endothelial growth factor A (VEGFA), C-type lectin receptor, and mitogen-activated protein kinase (MAPK) signaling pathways. The biological processes described in 87 intersection genes are mostly concerned with regulating the apoptotic process, cytokine production, and intracellular signal transduction. Molecular docking results also directed that Calebin-A had a high affinity to bind hub proteins linked to NAFLD.

Conclusion

Here, we showed that Calebin-A, through its effect on several critical genes/ proteins and pathways, might repress the progression of NAFLD.

Squalene Epoxidase: Its Regulations and Links with Cancers

Squalene epoxidase (SQLE) is a key enzyme in the mevalonate-cholesterol pathway that plays a critical role in cellular physiological processes. It converts squalene to 2,3-epoxysqualene and catalyzes the first oxygenation step in the pathway. Recently, intensive efforts have been made to extend the current knowledge of SQLE in cancers through functional and mechanistic studies. However, the underlying mechanisms and the role of SQLE in cancers have not been fully elucidated yet. In this review, we retrospected current knowledge of SQLE as a rate-limiting enzyme in the mevalonate-cholesterol pathway, while shedding light on its potential as a diagnostic and prognostic marker, and revealed its therapeutic values in cancers. We showed that SQLE is regulated at different levels and is involved in the crosstalk with iron-dependent cell death. Particularly, we systemically reviewed the research findings on the role of SQLE in different cancers. Finally, we discussed the therapeutic implications of SQLE inhibitors and summarized their potential clinical values. Overall, this review discussed the multifaceted mechanisms that involve SQLE to present a vivid panorama of SQLE in cancers.

Cholesterol metabolism in tumor microenvironment: cancer hallmarks and therapeutic opportunities

Cholesterol is crucial for cell survival and growth, and dysregulation of cholesterol homeostasis has been linked to the development of cancer. The tumor microenvironment (TME) facilitates tumor cell survival and growth, and crosstalk between cholesterol metabolism and the TME contributes to tumorigenesis and tumor progression. Targeting cholesterol metabolism has demonstrated significant antitumor effects in preclinical and clinical studies. In this review, we discuss the regulatory mechanisms of cholesterol homeostasis and the impact of its dysregulation on the hallmarks of cancer. We also describe how cholesterol metabolism reprograms the TME across seven specialized microenvironments. Furthermore, we discuss the potential of targeting cholesterol metabolism as a therapeutic strategy for tumors. This approach not only exerts antitumor effects in monotherapy and combination therapy but also mitigates the adverse effects associated with conventional tumor therapy. Finally, we outline the unresolved questions and suggest potential avenues for future investigations on cholesterol metabolism in relation to cancer.

Squalene monooxygenase facilitates bladder cancer development in part by regulating PCNA

Bladder cancer (BC) is one of the most common cancers worldwide. Although the treatment and survival rate of BC are being improved, the risk factors and the underlying mechanisms causing BC are incompletely understood. Squalene monooxygenase (SQLE) has been associated with the occurrence and development of multiple cancers but whether it contributes to BC development is unclear. In this study, we performed bioinformatics analysis on paired BC and adjacent non-cancerous tissues and found that SQLE expression is significantly upregulated in BC samples. Knockdown of SQLE impairs viability, induces apoptosis, and inhibits the migration and invasion of BC cells. RNA-seq data reveals that SQLE deficiency leads to dysregulated expression of genes regulating proliferation, migration, and apoptosis. Mass spectrometry-directed interactome screening identifies proliferating cell nuclear antigen (PCNA) as an SQLE-interacting protein and overexpression of PCNA partially rescues the impaired viability, migration, and invasion of BC cells caused by SQLE knockdown. In addition, we performed xenograft assays and confirmed that SQLE deficiency inhibits BC growth in vivo. In conclusion, these data suggest that SQLE promotes BC development and SQLE inhibition may be therapeutically useful in BC treatment.

Metabolism-regulating non-coding RNAs in breast cancer: roles, mechanisms and clinical applications

Breast cancer is one of the most common malignancies that pose a serious threat to women's health. Reprogramming of energy metabolism is a major feature of the malignant transformation of breast cancer. Compared to normal cells, tumor cells reprogram metabolic processes more efficiently, converting nutrient supplies into glucose, amino acid and lipid required for malignant proliferation and progression. Non-coding RNAs(ncRNAs) are a class of functional RNA molecules that are not translated into proteins but regulate the expression of target genes. NcRNAs have been demonstrated to be involved in various aspects of energy metabolism, including glycolysis, glutaminolysis, and fatty acid synthesis. This review focuses on the metabolic regulatory mechanisms and clinical applications of metabolism-regulating ncRNAs involved in breast cancer. We summarize the vital roles played by metabolism-regulating ncRNAs for endocrine therapy, targeted therapy, chemotherapy, immunotherapy, and radiotherapy resistance in breast cancer, as well as their potential as therapeutic targets and biomarkers. Difficulties and perspectives of current targeted metabolism and non-coding RNA therapeutic strategies are discussed.

Dysregulated cholesterol regulatory genes in hepatocellular carcinoma

Cholesterol is an indispensable component in mammalian cells, and cholesterol metabolism performs important roles in various biological activities. In addition to the Warburg effect, dysregulated cholesterol metabolism is one of the metabolic hallmarks of several cancers. It has reported that reprogrammed cholesterol metabolism facilitates carcinogenesis, metastasis, and drug-resistant in various tumors, including hepatocellular carcinoma (HCC). Some literatures have reported that increased cholesterol level leads to lipotoxicity, inflammation, and fibrosis, ultimately promoting the development and progression of HCC. Contrarily, other clinical investigations have demonstrated a link between higher cholesterol level and lower risk of HCC. These incongruent findings suggest that the connection between cholesterol and HCC is much complicated. In this report, we summarize the roles of key cholesterol regulatory genes including cholesterol biosynthesis, uptake, efflux, trafficking and esterification in HCC. In addition, we discuss promising related therapeutic targets for HCC.

Host genetics and gut microbiota jointly regulate blood biochemical indicators in chickens

Blood biochemical indicators play a crucial role in assessing an individual's overall health status and metabolic function. In this study, we measured five blood biochemical indicators, including total cholesterol (CHOL), low-density lipoprotein cholesterol (LDL-CH), triglycerides (TG), high-density lipoprotein cholesterol (HDL-CH), and blood glucose (BG), as well as 19 growth traits of 206 male chickens. By integrating host whole-genome information and 16S rRNA sequencing of the duodenum, jejunum, ileum, cecum, and feces microbiota, we assessed the contributions of host genetics and gut microbiota to blood biochemical indicators and their interrelationships. Our results demonstrated significant negative phenotypic and genetic correlations (r =  - 0.20 ~  - 0.67) between CHOL and LDL-CH with growth traits such as body weight, abdominal fat content, muscle content, and shin circumference. The results of heritability and microbiability indicated that blood biochemical indicators were jointly regulated by host genetics and gut microbiota. Notably, the heritability of HDL-CH was estimated to be 0.24, while the jejunal microbiability for BG and TG reached 0.45 and 0.23. Furthermore, by conducting genome-wide association study (GWAS) with the single-nucleotide polymorphism (SNPs), insertion/deletion (indels), and structural variation (SV), we identified RAP2C, member of the RAS oncogene family (RAP2C), dedicator of cytokinesis 11 (DOCK11), neurotensin (NTS) and BOP1 ribosomal biogenesis factor (BOP1) as regulators of HDL-CH, and glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5), dihydrodiol dehydrogenase (DHDH), and potassium voltage-gated channel interacting protein 1 (KCNIP1) as candidate genes of BG. Moreover, our findings suggest that cecal RF39 and Clostridia_UCG_014 may be linked to the regulation of CHOL, and jejunal Streptococcaceae may be involved in the regulation of TG. Additionally, microbial GWAS results indicated that the presence of gut microbiota was under host genetic regulation. Our findings provide valuable insights into the complex interaction between host genetics and microbiota in shaping the blood biochemical profile of chickens. KEY POINTS: • Multiple candidate genes were identified for the regulation of CHOL, HDL-CH, and BG. • RF39, Clostridia_UCG_014, and Streptococcaceae were implicated in CHOL and TG modulation. • The composition of gut microbiota is influenced by host genetics.

Squalene epoxidase promotes breast cancer progression by regulating CCNB1 protein stability

BACKGROUND

Breast cancer (BC) is a prevalent malignancy affecting women, characterized by a substantial occurrence rate. Squalene epoxidase (SQLE) is a crucial regulator of ferroptosis and has been associated with promoting cell growth and invasion in different types of human cancers. This study aimed to investigate the functional significance of SQLE in BC and elucidate the underlying molecular mechanisms involved.

METHODS

SQLE expression levels in BC tissues were evaluated using quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry. Cell viability, invasion, migration, and cell cycle distribution were assessed using a combination of assays, including the Cell Counting Kit-8, EdU, colony formation, Transwell, and wound healing assays and flow cytometry analysis. Measurement of intracellular reactive oxygen species (ROS), malondialdehyde assay, and glutathione assay were utilized to investigate ferroptosis. Furthermore, co-immunoprecipitation and immunofluorescence assays were conducted to explore the correlation between SQLE and CCNB1. The in vivo tumor growth was evaluated by conducting a xenograft tumorigenicity assay to investigate the impact of SQLE.

RESULTS

SQLE expression was significantly increased in BC, and higher SQLE expression levels were significantly associated with an unfavorable prognosis. In vitro functional assays revealed that the overexpression of SQLE markedly enhanced the proliferation, migration, and invasion capacities of BC cells. Furthermore, SQLE overexpression facilitated tumor growth in nude mice. Mechanistically, SQLE alleviated the ubiquitination modification of CCNB1, leading to enhanced stability of the CCNB1 protein and decreased intracellular ROS levels. Ultimately, this inhibited ferroptosis and facilitated the progression of BC. Our findings have provided insights into a crucial pathway by which elevated SQLE expression confers protection to BC cells against ferroptosis, thus promoting cancer progression. SQLE may serve as a novel oncological marker and a potential therapeutic target for BC progression.

CONCLUSIONS

In conclusion, this study provides evidence that SQLE plays a regulatory role in BC progression by modulating CCNB1 and ferroptosis. These findings offer valuable insights into the role of SQLE in the pathogenesis of BC and demonstrate its potential as a therapeutic target for treating BC.

Cholesterol esterification and p53-mediated tumor suppression

Many human cancers carry missense mutations in or deletions of the tumor protein 53 (TP53) tumor suppressor gene. TP53's product, p53 regulates many biological processes, including cell metabolism. Cholesterol is a key lipid needed for the maintenance of membrane function and tissue homeostasis while also serving as a precursor for steroid hormone and bile acid synthesis. An over-abundance of cholesterol can lead to its esterification and storage as cholesterol esters. The recent study has shown that the loss of p53 leads to excessive cholesterol ester biosynthesis, which promotes hepatocellular carcinoma in mice. Blocking cholesterol esterification improves treatment outcomes, particularly for liver cancers with p53 deletions/mutations that originate in a background of non-alcoholic fatty liver disease.

Cholesterol Metabolism in Pancreatic Cancer

Pancreatic cancer's substantial impact on cancer-related mortality, responsible for 8% of cancer deaths and ranking fourth in the US, persists despite advancements, with a five-year relative survival rate of only 11%. Forecasts predict a 70% surge in new cases and a 72% increase in global pancreatic cancer-related deaths by 2040. This review explores the intrinsic metabolic reprogramming of pancreatic cancer, focusing on the mevalonate pathway, including cholesterol biosynthesis, transportation, targeting strategies, and clinical studies. The mevalonate pathway, central to cellular metabolism, significantly shapes pancreatic cancer progression. Acetyl coenzyme A (Acetyl-CoA) serves a dual role in fatty acid and cholesterol biosynthesis, fueling acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia (PanIN) development. Enzymes, including acetoacetyl-CoA thiolase, 3-hydroxy-3methylglutaryl-CoA (HMG-CoA) synthase, and HMG-CoA reductase, are key enzymes in pancreatic cancer. Inhibiting HMG-CoA reductase, e.g., by using statins, shows promise in delaying PanIN progression and impeding pancreatic cancer. Dysregulation of cholesterol modification, uptake, and transport significantly impacts tumor progression, with Sterol O-acyltransferase 1 (SOAT1) driving cholesterol ester (CE) accumulation and disrupted low-density lipoprotein receptor (LDLR) expression contributing to cancer recurrence. Apolipoprotein E (ApoE) expression in tumor stroma influences immune suppression. Clinical trials targeting cholesterol metabolism, including statins and SOAT1 inhibitors, exhibit potential anti-tumor effects, and combination therapies enhance efficacy. This review provides insights into cholesterol metabolism's convergence with pancreatic cancer, shedding light on therapeutic avenues and ongoing clinical investigations.

Molecular characterization of ferroptosis in soft tissue sarcoma constructs a prognostic and immunotherapeutic signature through experimental and bioinformatics analyses

Ferroptosis regulators have been found to affect tumor progression. However, studies focusing on ferroptosis and soft tissue sarcoma (STS) are rare. Somatic mutation, copy number variation, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, consensus clustering, differentially expressed genes analysis (DEGs), principal component analysis (PCA) and gene set enrichment analysis (GSEA) were used to identify and explore different ferroptosis modifications in STS. A nomogram was constructed to predict the prognosis of STS. Moreover, three immunotherapy datasets were used to assess the Fescore. Western blotting, siRNA transfection, EdU assay and reactive oxygen species (ROS) measurement were performed. 16 prognostic ferroptosis regulators were screened and significant differences were observed in somatic mutation, copy number variation (CNV) and RT-qPCR among these ferroptosis regulators. 2 different ferroptosis modification patterns were found (Fe cluster A and B). Fe cluster A with higher Fescore was correlated with p53 pathway and had better prognosis of STS (p = 0.002) while Fe cluster B with lower Fescore was correlated with angiogenesis and MYC pathway and showed a poorer outcome. Besides, the nomogram effectively predicted the outcome of STS and the Fescore could also well predict the prognosis of other 16 tumors and immunotherapy response. Downregulation of LOX also inhibited growth and increased ROS production in sarcoma cells. The molecular characterization of ferroptosis regulators in STS was explored and an Fescore was constructed. The Fescore quantified ferroptosis modification in STS patients and effectively predicted the prognosis of a variety of tumors, providing novel insights for precision medicine.

SQLE Knockdown inhibits bladder cancer progression by regulating the PTEN/AKT/GSK3β signaling pathway through P53

Bladder cancer (BCa) is one of the most common malignancies worldwide. However, the lack of accurate and effective targeted drugs has become a major problem in current clinical treatment of BCa. Studies have demonstrated that squalene epoxidase (SQLE), as a key rate-limiting enzyme in cholesterol biosynthesis, is involved in cancer development. In this study, our analysis of The Cancer Genome Atlas, The Genotype-Tissue Expression, and Gene Expression Omnibus databases showed that SQLE expression was significantly higher in cancer tissues than it was in adjacent normal tissues, and BCa tissues with a high SQLE expression displayed a poor prognosis. We then confirmed this result in qRT-PCR and immunohistochemical staining experiments, and our vitro studies demonstrated that SQLE knockdown inhibited tumor cell proliferation and metastasis through the PTEN/AKT/GSK3β signaling pathway. By means of rescue experiments, we proved that that P53 is a key molecule in SQLE-mediated regulation of the PTEN/AKT/GSK3β signaling pathway. Simultaneously, we verified the above findings through a tumorigenesis experiment in nude mice. In conclusion, our study shows that SQLE promotes BCa growth through the P53/PTEN/AKT/GSK3β axis, which may serve as a therapeutic biological target for BCa.

Inhibition of squalene epoxidase linking with PI3K/AKT signaling pathway suppresses endometrial cancer

Endometrial cancer (EC) is a common malignant tumor that lacks any therapeutic target and, in many cases, recurrence is the leading ca use of morbidity and mortality in women. Widely known EC has a strongly positive correlation with abnormal lipid metabolism. Squalene epoxidase (SQLE), a crucial enzyme in the cholesterol synthesis pathway regulating lipid metabolic processes has been found to be associated with various cancers in recent years. Here, we focused on studying the role of SQLE in EC. Our study revealed that SQLE expression level was upregulated significantly in EC tissues. In vitro experiments showed that SQLE overexpression significantly promoted the proliferation, and inhibited cell apoptosis of EC cells, whereas SQLE knockdown or use of terbinafine showed the opposite results. Furthermore, we found out that the promotional effect of SQLE on the proliferation of EC cells might be achieved by activating the PI3K/AKT pathway. In vivo, studies confirmed that the knockdown of SQLE or terbinafine can observably inhibit tumor growth in nude mice. These results indicate that SQLE may promote the progression of EC by activating the PI3K/AKT pathway. Moreover, SQLE is a potential target for EC treatment and its inhibitor, terbinafine, has the potential to become a targeted drug for EC treatment.

Squalene epoxidase/SQLE is a candidate target for treatment of colorectal cancers with p53 mutation and elevated c-MYC expression

Elevated expression of c-MYC and inactivation of p53 represent two of the most common alterations in colorectal cancer (CRC). However, c-MYC and defective p53 are difficult to target therapeutically. Therefore, effectors downstream of both c-MYC and p53 may represent attractive, alternative targets for cancer treatment. In a bioinformatics screen we identified Squalene epoxidase/SQLE as a candidate therapeutic target that appeared to be especially relevant for cell survival in CRCs, which display elevated c-MYC expression and loss of p53 function. SQLE is a rate-limiting enzyme in the cholesterol synthesis. Here, we show that p53 supresses SQLE expression, cholesterol levels, and cell viability via the induction of miR-205, which directly targets SQLE. Furthermore, c-MYC induced SQLE expression directly and via its target gene AP4. The transcription factor AP4/TFAP4 directly induced SQLE expression and cholesterol levels, whereas inactivation of AP4 resulted in decreased SQLE expression and caused resistance to Terbinafine, an inhibitor of SQLE. Inhibition of SQLE decreased viability of CRC cells. This effect was enhanced in CRCs cells with p53 inactivation and/or enhanced c-MYC/AP4 expression. Altogether, our results demonstrate that SQLE represents a vulnerability for CRCs with p53 inactivation and elevated c-MYC activity.

αKG-driven RNA polymerase II transcription of cyclin D1 licenses malic enzyme 2 to promote cell-cycle progression

Increased metabolic activity usually provides energy and nutrients for biomass synthesis and is indispensable for the progression of the cell cycle. Here, we find a role for α-ketoglutarate (αKG) generation in regulating cell-cycle gene transcription. A reduction in cellular αKG levels triggered by malic enzyme 2 (ME2) or isocitrate dehydrogenase 1 (IDH1) depletion leads to a pronounced arrest in G1 phase, while αKG supplementation promotes cell-cycle progression. Mechanistically, αKG directly binds to RNA polymerase II (RNAPII) and increases the level of RNAPII binding to the cyclin D1 gene promoter via promoting pre-initiation complex (PIC) assembly, consequently enhancing cyclin D1 transcription. Notably, αKG addition is sufficient to restore cyclin D1 expression in ME2- or IDH1-depleted cells, facilitating cell-cycle progression and proliferation in these cells. Therefore, our findings indicate a function of αKG in gene transcriptional regulation and cell-cycle control.

Pan-cancer analysis identifies LPCATs family as a prognostic biomarker and validation of LPCAT4/WNT/β-catenin/c-JUN/ACSL3 in hepatocellular carcinoma

Lipid remodeling regulators are now being investigated as potential therapeutic targets for cancer therapy as a result of their involvement, which includes promoting cancer cells' adaptation to the restricted environment. Lysophosphatidylcholine acyltransferases (LPCATs, LPCAT1-4) are enzymes that regulate the remodeling of bio-membranes. The functions of these enzymes in cancer are largely unknown. In the current study, we found that genes belonging to the LPCAT family participated in tumor advancement and were strongly linked to dismal prognosis in many different malignancies. We constructed the LPCATs scores model and explored this model in pan-cancer. Malignant pathways in pan-cancer were positively related to LPCATs scores, and all pathways had strong links to the tumor microenvironment (TME). Multiple immune-associated features of the TME in pan-cancer were likewise associated with higher LPCATs scores. In addition, the LPCATs score functioned as a prognostic marker for immune checkpoint inhibitor (ICI) therapies in patients with cancer. LPCAT4 enhanced cell growth and cholesterol biosynthesis by up-regulating ACSL3 in hepatocellular carcinoma (HCC). WNT/β-catenin/c-JUN signaling pathway mediated LPCAT4's regulation on ACSL3. These findings demonstrated that genes in the LPCAT family might be used as cancer immunotherapy and prognosis-related biomarkers. Specifically, LPCAT4 could be a treatment target of HCC.

Development and validation of a selenium metabolism regulators associated prognostic model for hepatocellular carcinoma

BACKGROUND

Selenium metabolism has been implicated in human health. This study aimed to identify a selenium metabolism regulator-based prognostic signature for hepatocellular carcinoma (HCC) and validate the role of INMT in HCC.

METHODS

Transcriptome sequencing data and clinical information related to selenium metabolism regulators in TCGA liver cancer dataset were analysed. Next, a selenium metabolism model was constructed by multiple machine learning algorithms, including univariate, least absolute shrinkage and selection operator, and multivariate Cox regression analyses. Then, the potential of this model for predicting the immune landscape of different risk groups was evaluated. Finally, INMT expression was examined in different datasets. After knockdown of INMT, cell proliferation and colony formation assays were conducted.

RESULTS

A selenium metabolism model containing INMT and SEPSECS was established and shown to be an independent predictor of prognosis. The survival time of low-risk patients was significantly longer than that of high-risk patients. These two groups had different immune environments. In different datasets, including TCGA, GEO, and our PUMCH dataset, INMT was significantly downregulated in HCC tissues. Moreover, knockdown of INMT significantly promoted HCC cell proliferation.

CONCLUSIONS

The current study established a risk signature of selenium metabolism regulators for predicting the prognosis of HCC patients. INMT was identified as a biomarker for poor prognosis of HCC.

Targeting Microglial Metabolic Rewiring Synergizes with Immune-Checkpoint Blockade Therapy for Glioblastoma

Glioblastoma (GBM) constitutes the most lethal primary brain tumor for which immunotherapy has provided limited benefit. The unique brain immune landscape is reflected in a complex tumor immune microenvironment (TIME) in GBM. Here, single-cell sequencing of the GBM TIME revealed that microglia were under severe oxidative stress, which induced nuclear receptor subfamily 4 group A member 2 (NR4A2)-dependent transcriptional activity in microglia. Heterozygous Nr4a2 (Nr4a2+/-) or CX3CR1+ myeloid cell-specific Nr4a2 (Nr4a2fl/flCx3cr1Cre) genetic targeting reshaped microglia plasticity in vivo by reducing alternatively activated microglia and enhancing antigen presentation capacity for CD8+ T cells in GBM. In microglia, NR4A2 activated squalene monooxygenase (SQLE) to dysregulate cholesterol homeostasis. Pharmacologic NR4A2 inhibition attenuated the protumorigenic TIME, and targeting the NR4A2 or SQLE enhanced the therapeutic efficacy of immune-checkpoint blockade in vivo. Collectively, oxidative stress promotes tumor growth through NR4A2-SQLE activity in microglia, informing novel immune therapy paradigms in brain cancer.

SIGNIFICANCE

Metabolic reprogramming of microglia in GBM informs synergistic vulnerabilities for immune-checkpoint blockade therapy in this immunologically cold brain tumor. This article is highlighted in the In This Issue feature, p. 799.

Identification of a cuproptosis and copper metabolism gene-related lncRNAs prognostic signature associated with clinical and immunological characteristics of hepatocellular carcinoma

Background

The relationship between cuproptosis and HCC is still in the exploratory stage. Long noncoding RNAs (lncRNAs) have recently been linked to the progression of hepatocellular carcinoma (HCC). However, the clinical significance of lncRNAs associated with cuproptosis remains unclear.

Methods

Based on The Cancer Genome Atlas (TCGA) liver hepatocellular carcinoma (LIHC) dataset, we identified characteristic prognostic lncRNAs by univariate, LASSO, and multifactorial regression analysis, and constructed a prognostic signature of cuproptosis-related lncRNAs in HCC. The role of lncRNAs were identified through CCK-8, clone formation in Huh-7 cells with high expression of FDX1. Prognostic potential of the characteristic lncRNAs was evaluated in each of the two cohorts created by randomly dividing the TCGA cohort into a training cohort and a test cohort in a 1:1 ratio. Immune profiles in defined subgroups of cuproptosis-related lncRNA features as well as drug sensitivity were analyzed.

Results

We constructed a multigene signature based on four characteristic prognostic lncRNAs (AL590705.3, LINC02870, KDM4A-AS1, MKLN1-AS). These four lncRNAs participated in the development of cuproptosis. HCC patients were classified into high-risk and low-risk groups based on the median value of the risk score. The receiver operating characteristic curve area under the curve values for 1-, 3-, and 5-year survival were 0.773, 0.728, and 0.647, respectively, for the training cohort, and 0.764, 0.671, and 0.662, respectively, for the test cohort. Univariate and multifactorial regression analyses indicated that this prognostic feature was an independent prognostic factor for HCC. Principal component analysis plots clearly distinguished between low- and high-risk patients in terms of their probability of survival. Furthermore, gene set enrichment analysis showed that a variety of processes associated with tumor proliferation and progression were enriched in the high-risk group compared with the low-risk group. Moreover, there were significant differences in the expression of immune cell subpopulations, immune checkpoint genes, and potential drug screening, which provided distinct therapeutic recommendations for individuals with various risks.

Conclusions

We constructed a novel cuproptosis-associated lncRNA signature with a significant predictive value for the prognosis of patients with HCC. Cuproptosis-associated lncRNAs are associated with the tumor immune microenvironment of HCC and even the efficacy of tumor immunotherapy.

Squalene epoxidase facilitates cervical cancer progression by modulating tumor protein p53 signaling pathway

BACKGROUND

The mortality of cervical cancer (CC) is quite high and advanced CC is hard to cure. Accordingly, to find the mechanism of CC progression at molecular level is imminent.

METHODS

The mRNA expression data were acquired from The Cancer Genome Atlas database, and squalene epoxidase (SQLE) level in the tumor and adjuvant tissues of CC was analyzed. The pathway enrichment analysis of target mRNAs was performed based on the GSEA database. The cancerous tissues and para-cancerous tissues of CC patients were collected for immunohistochemistry. SQLE and p53 mRNA expression was ensured by qRT-polymerase chain reaction. SQLE and p53 protein levels were determined by western blot. Cell functional assays focused on evaluating the malignant behaviors of cancer cells in each treatment group. Nude mouse xenograft models were constructed for tumorigenicity analysis.

RESULTS

Bioinformatics analysis revealed that SQLE expression was high in CC tissues, which was linked to the poor prognosis. SQLE could affect the p53 signaling pathway. Cell functional assays demonstrated that SQLE expression was promoted in CC cell lines, and overexpressing SQLE facilitated the malignant phenotypes of CC cells, whereas silencing SQLE suppressed CC progression in vitro and in vivo. Besides, the repressed p53 signaling pathway could reverse the effect caused by silenced SQLE.

CONCLUSION

SQLE could promote CC progression by modulating the p53 signaling pathway.

Systematic Identification of Novel Ferroptosis-Associated Multigene Models for Predicting Patient Prognosis Based on Endometrial Cancer

Objective

Uterine corpus endometrial carcinoma (UCEC) is a frequent epithelial cancer in females. The rate of UCEC occurrence increases year by year and the age is getting younger and younger, which requires more active treatments to improve its prognosis. Ferroptosis is a kind of regulatory cell death that relies on iron and may be triggered by sorafenib, which has been elucidated in several cancers, but the mechanism of ferroptosis-related genes in UCEC has yet to be fully defined and will need more investigation.

Methods

The mRNA expression profiles and accompanying clinical data of UCEC patients included in this research were obtained from a publicly available database. We subsequently classified the patients into experimental and training sets. Next, utilizing the least absolute shrinkage and selection operator (LASSO) Cox regression model, we established the multigene features of the TCGA experimental set and verified them in the validation set.

Results

Per the findings of our investigation, the TCGA experimental set cohort had four differentially expressed genes (DEGs) that were linked to overall survival (OS). An analysis was conducted using univariate Cox regression (with all variables corrected for P < 0.05). To stratify the patients into two distinct categories, high- and low-risk, a diagnostic model premised on the identified four genes was formulated. In contrast with the low-risk population, the high-risk category exhibited a considerably lower OS (P < 0.0001). The findings of the multivariate Cox regression analysis illustrated that the risk score independently served as a predictor of OS (HR > 1, P < 0.01). The predictive capability of the model was verified by ROC curve analysis. Immune-related pathway enrichment was found using functional analysis, which illustrated that the two risk groups had significantly different immunological statuses.

Conclusions

A unique model of genes linked to ferroptosis has the potential to be a treatment option for UCEC and can be utilized for the prognostic prediction of the disease.

Cholesterol induces inflammation and reduces glucose utilization

Cholesterol stimulates inflammation and affects the normal function of islet tissues. However, the precise mechanism underlying the effects of cholesterol on islet cells requires clarification. In this study, we explored the role of cholesterol in glucose utilization in pancreatic cells. Beta-TC-6 cells and mice were treated with cholesterol. We used glucose detection kits to identify the glucose content in the cell culture supernatant and mouse serum and an enzyme-linked immunosorbent assay was used to detect insulin levels in the serum. Glucose-6-phosphatase catalytic subunit 2 (G6PC2), 78 kDa glucose-regulated protein (GRP78), 94 kDa glucose-regulated protein (GRP94), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1 (casp1), and interleukin-1β (IL-1β) expression levels were detected using immunofluorescence, immunohistochemistry, western blotting, and reverse transcription-quantitative polymerase chain reaction. Hematoxylin-eosin staining was used to detect the histological alterations in pancreatic tissues. Cholesterol decreased beta-TC-6 cell glucose utilization; enhanced pancreatic tissue pathological alterations; increased glucose and insulin levels in mouse serum; increased G6PC2, GRP78, GRP94, and NLRP3 expression levels; and elevated casp1 and pro-IL-1β cleavage. Cholesterol can attenuate glucose utilization efficiency in beta-TC-6 cells and mice, which may be related to endoplasmic reticulum stress and inflammation.

Identification of novel prognostic biomarkers for osteosarcoma: a bioinformatics analysis of differentially expressed genes in the mesenchymal stem cells from single-cell sequencing data set

BACKGROUND

Mesenchymal stem cells (MSCs) play a crucial role in osteosarcoma (OS) growth and progression. This study conducted a bioinformatics analysis of a single-cell ribonucleic acid sequencing data set and explored the MSC-specific differentially expressed genes (DEGs) in advanced OS.

METHODS

MSC-specific DEGs from GSE152048 was extracted using Seurat R package. These DEGs were then subjected to the functional analysis, and several key genes were further identified and underwent a prognosis analysis.

RESULTS

A total of 234 upregulated and 280 downregulated DEGs were identified between the MSCs and other cells, and a total of 188 upregulated and 158 downregulated DEGs were identified between the MSCs and osteoblastic cells. The Gene Ontology (GO) functional analysis showed that the specific DEGs between the MSCs and osteoblastic cells were enriched in GO terms such as "collagen catabolic process", "positive regulation of pathway-restricted SMAD protein phosphorylation", "osteoblast differentiation", "regulation of release of cytochrome c from mitochondria" and "interleukin-1 production". The specific DEGs between the MSCs and osteoblastic cells were subjected to a protein-protein interaction network analysis. Further, a survival analysis of 20 genes with combined scores >0.94 revealed that the low expression of ANXA1 (annexin A1) and TPM1 (tropomyosin 1) was associated with the shorter overall survival of OS patients, while the high expression of FDPS (farnesyl pyrophosphate synthase), IFITM5 (interferon-induced transmembrane protein 5), FKBP11 (FKBP prolyl isomerase 11), SP7, and SQLE (squalene epoxidase) was associated with the shorter overall survival of OS patients. In a further analysis, we compared the expression of ANXA1, FDPS, IFITM5, FKBP11, SP7, SQLE, and TPM1 between the MSCs and high-grade OS cells. Further validation studies using the GSE42352 data set revealed that ANXA1, FKBP11, SP7, and TPM1 were more upregulated in the MSCs than the high-grade OS cells, while FDPS, IFITM5, and SQLE were more downregulated in the MSCs than the high-grade OS cells.

CONCLUSIONS

Our bioinformatics analysis revealed 7 hub genes derived from the specific DEGs between the MSCs and osteoblastic cells. The 7 hub genes may serve as potential prognostic biomarkers for patients with OS.

Deletion of Smurf1 attenuates liver steatosis via stabilization of p53

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease, characterized by excessive hepatic lipid accumulation. Recently, we demonstrated that Smad ubiquitination regulatory factor 1 (Smurf1) deficiency significantly alleviates mouse hepatic steatosis. However, the mechanism of Smurf1-regulating hepatic lipid accumulation requires further exploration and clarification. Hence, this study explores the potential mechanism of Smurf1 in hepatic steatosis. In this study, hepatic Smurf1 proteins in NAFLD patients and healthy individuals were determined using immunohistochemical staining. Control and NAFLD mouse models were established by feeding Smurf1-knockout (KO) and wild-type mice with either a high-fat diet (HFD) or a chow diet (CD) for eight weeks. Oleic acid (OA)-induced steatotic hepatocytes were used as the NAFLD mode cells. Lipid content in liver tissues was analyzed. Smurf1-MDM2 interaction, MDM2 and p53 ubiquitination, and p53 target genes expression in liver tissues and hepatocytes were analyzed. We found that hepatic Smurf1 is highly expressed in NAFLD patients and HFD-induced NAFLD mice. Its deletion attenuates hepatocyte steatosis. Mechanistically, Smurf1 interacts with and stabilizes mouse double minute 2 (MDM2), promoting p53 degradation. In Smurf1-deficient hepatocytes, an increase in p53 suppresses SREBP-1c expression and elevates the expression of both malonyl-CoA decarboxylase (MCD) and lipin1 (Lpin1), two essential proteins in lipid catabolism. Contrarily, the activities of these three proteins and hepatocyte steatosis are reversed by p53 knockdown in Smurf1-deficient hepatocytes. This study shows that Smurf1 is involved in the pathogenesis of NAFLD by balancing de novo lipid synthesis and lipolysis.

The hypolipidemic mechanism of chrysanthemum flavonoids and its main components, luteolin and luteoloside, based on the gene expression profile

In this study, the following four groups of mice with hyperlipidemia were involved: the model control group (MC), the Chrysanthemum flavonoids group (CF), the luteolin group, and the luteoloside group. The whole gene expression profile was detected in the liver tissues of each group. Differential genes significantly enriched in the biological process of gene ontology (GO) items and Kyoto Encyclopedia of Genes and Genomes (KEGG) were selected, and 4 differential genes related to lipid metabolism were selected for further real-time quantitative PCR verification. Compared with the MC, 41 differential genes such as Sqle, Gck, and Idi1 were screened in the CF intervention group; 68 differential genes such as Acsl3, Cyp7a1, and Lpin1 were screened in the luteolin intervention group (CF); and 51 differential genes such as Acaca, Cyp7a1, and Lpin1 were screened in the luteoloside group. The mechanism of CF to improve hyperlipidemia is very complex, mainly involving biological processes such as cholesterol and fatty acid metabolism and glycolysis, luteolin mainly involves the synthesis and transport of cholesterol, and luteoloside mainly involves fatty acid metabolism. The functional pathways of CF may not be completely the same as luteolin and luteoloside, and further study is needed on the mechanism of action of other components.

Targeting Strategies for Aberrant Lipid Metabolism Reprogramming and the Immune Microenvironment in Esophageal Cancer: A Review

Esophageal cancer is of high importance to occurrence, development, and treatment resistance. As evidenced by recent studies, pathways (e.g., Wnt/β-catenin, AMPK, and Hippo) are critical to the proliferation, differentiation, and self-renewal of esophageal cancer. In addition, the above pathways play a certain role in regulating esophageal cancer and act as potential therapeutic targets. Over the past few years, the function of lipid metabolism in controlling tumor cells and immune cells has aroused extensive attention. It has been reported that there are intricate interactions between lipid metabolism reprogramming between immune and esophageal cancer cells, whereas molecular mechanisms should be studied in depth. Immune cells have been commonly recognized as a vital player in the esophageal cancer microenvironment, having complex crosstalk with cancer cells. It is increasingly evidenced that the function of immune cells in the tumor microenvironment (TME) is significantly correlated with abnormal lipid metabolism. In this review, the latest findings in lipid metabolism reprogramming in TME are summarized, and the above findings are linked to esophageal cancer progression. Aberrant lipid metabolism and associated signaling pathways are likely to serve as a novel strategy to treat esophageal cancer through lipid metabolism reprogramming.

Targeting the key cholesterol biosynthesis enzyme squalene monooxygenasefor cancer therapy

Cholesterol metabolism is often dysregulated in cancer. Squalene monooxygenase (SQLE) is the second rate-limiting enzyme involved in cholesterol synthesis. Since the discovery of SQLE dysregulation in cancer, compelling evidence has indicated that SQLE plays a vital role in cancer initiation and progression and is a promising therapeutic target for cancer treatment. In this review, we provide an overview of the role and regulation of SQLE in cancer and summarize the updates of antitumor therapy targeting SQLE.

RNA binding protein RALY activates the cholesterol synthesis pathway through an MTA1 splicing switch in hepatocellular carcinoma

Alternative splicing is an important RNA processing event that contributes to RNA complexity and protein diversity in cancer. Accumulating evidence demonstrates the essential roles of some alternatively spliced genes in carcinogenesis. However, the potential roles of alternatively spliced genes in hepatocellular carcinoma (HCC) are still largely unknown. Here we showed that the HnRNP Associated with Lethal Yellow Protein Homolog (RALY) gene is upregulated and associated with poor outcomes in HCC patients. RALY acts as a tumor-promoting factor by cooperating with splicing factor 3b subunit 3 (SF3B3) and modulating the splicing switch of Metastasis Associated 1 (MTA1) from MTA-S to MTA1-L. Normally, MTA1-S inhibits cell proliferation by reducing the transcription of cholesterol synthesis genes. In HCC, RALY and SF3B3 cooperate to regulate the MTA1 splicing switch, leading to a reduction in the MTA1-S level, and alleviating the inhibitory effect of MTA1-S on cholesterol synthesis genes, thus promoting HCC cell proliferation. In conclusion, our results revealed that the RALY-SF3B3/MTA1/cholesterol synthesis pathway contributes essentially to hepatic carcinogenesis and could serve as a promising therapeutic target for HCC.

A Novel Role of SMG1 in Cholesterol Homeostasis That Depends Partially on p53 Alternative Splicing

Simple Summary

p53 isoforms have been reported in various tumor types. Both p53β and p53γ were recently reported to retain functionalities of full-length p53α. A role for p53 and p53 loss in cholesterol metabolism has also emerged. We show that SMG1, a phosphatidylinositol 3-kinase-related kinase, when inhibited in p53 wild-type MCF7 and HepG2 cells, significantly alters the expression of cholesterol pathway genes, with a net increase in intracellular cholesterol and an increased sensitivity to Fatostatin in MCF7. We confirm a prior report that SMG1 inhibition in MCF7 cells promotes expression of p53β and show the first evidence for increases in p53γ. Further, induced p53β expression, confirmed with antibody, explained the loss of SMG1 upregulation of the ABCA1 cholesterol exporter where p53γ had no effect on ABCA1. Additionally, upregulation of ABCA1 upon SMG1 knockdown was independent of upregulation of nonsense-mediated decay target RASSF1C, previously suggested to regulate ABCA1 via a “RASSF1C-miR33a-ABCA1” axis.

Abstract

SMG1, a phosphatidylinositol 3-kinase-related kinase (PIKK), essential in nonsense-mediated RNA decay (NMD), also regulates p53, including the alternative splicing of p53 isoforms reported to retain p53 functions. We confirm that SMG1 inhibition in MCF7 tumor cells induces p53β and show p53γ increase. Inhibiting SMG1, but not UPF1 (a core factor in NMD), upregulated several cholesterol pathway genes. SMG1 knockdown significantly increased ABCA1, a cholesterol efflux pump shown to be positively regulated by full-length p53 (p53α). An investigation of RASSF1C, an NMD target, increased following SMG1 inhibition and reported to inhibit miR-33a-5p, a canonical ABCA1-inhibiting miRNA, did not explain the ABCA1 results. ABCA1 upregulation following SMG1 knockdown was inhibited by p53β siRNA with greatest inhibition when p53α and p53β were jointly suppressed, while p53γ siRNA had no effect. In contrast, increased expression of MVD, a cholesterol synthesis gene upregulated in p53 deficient backgrounds, was sensitive to combined targeting of p53α and p53γ. Phenotypically, we observed increased intracellular cholesterol and enhanced sensitivity of MCF7 to growth inhibitory effects of cholesterol-lowering Fatostatin following SMG1 inhibition. Our results suggest deregulation of cholesterol pathway genes following SMG1 knockdown may involve alternative p53 programming, possibly resulting from differential effects of p53 isoforms on cholesterol gene expression.

Squalene epoxidase metabolic dependency is a targetable vulnerability in castration-resistant prostate cancer

Considering the dismal prognosis of castration-resistant prostate cancer (CRPC), it is critical to identify novel therapeutic targets in this disease. Malignant cells have metabolic dependencies distinct from their healthy counterparts, resulting in therapeutic vulnerabilities. While PTEN and TP53 are the most frequently co-mutated or co-deleted driver genes in lethal CRPC, the metabolic dependencies underlying PTEN/p53 deficiency-driven CRPC for therapeutic intervention remain largely elusive. In this study, PTEN/p53 deficient tumors were determined to be reliant on cholesterol metabolism. Moreover, PTEN/p53 deficiency transcriptionally upregulated squalene epoxidase (SQLE) via activation of sterol regulatory element-binding protein 2 (SREBP2). In addition, PTEN deficiency enhanced the protein stability of SQLE by inhibiting the PI3K/Akt/GSK3β-mediated proteasomal pathway. Consequently, SQLE increased cholesterol biosynthesis to facilitate tumor cell growth and survival. Pharmacological blockade of SQLE with FR194738 profoundly suppressed the invasive program of CRPC. Collectively, these results demonstrate a synergistic relationship between SQLE and PTEN/p53 deficiency in CRPC development and progression. Therefore, pharmacological interventions targeting SQLE may hold promise for the treatment of CRPC patients.

Cholesterol-Lowering Phytochemicals: Targeting the Mevalonate Pathway for Anticancer Interventions

There are a plethora of cancer causes and the road to fully understanding the carcinogenesis process remains a dream that keeps changing. However, a list of role players that are implicated in the carcinogens process is getting lengthier. Cholesterol is known as bad sterol that is heavily linked with cardiovascular diseases; however, it is also comprehensively associated with carcinogenesis. There is an extensive list of strategies that have been used to lower cholesterol; nevertheless, the need to find better and effective strategies remains vastly important. The role played by cholesterol in the induction of the carcinogenesis process has attracted huge interest in recent years. Phytochemicals can be dubbed as magic tramp cards that humans could exploit for lowering cancer-causing cholesterol. Additionally, the mechanisms that are regulated by phytochemicals can be targeted for anticancer drug development. One of the key role players in cancer development and suppression, Tumour Protein 53 (TP53), is crucial in regulating the biogenesis of cholesterol and is targeted by several phytochemicals. This minireview covers the role of p53 in the mevalonate pathway and how bioactive phytochemicals target the mevalonate pathway and promote p53-dependent anticancer activities.

p53 transcriptionally regulates SQLE to repress cholesterol synthesis and tumor growth

Cholesterol is essential for membrane biogenesis, cell proliferation, and differentiation. The role of cholesterol in cancer development and the regulation of cholesterol synthesis are still under active investigation. Here we show that under normal-sterol conditions, p53 directly represses the expression of SQLE, a rate-limiting and the first oxygenation enzyme in cholesterol synthesis, in a SREBP2-independent manner. Through transcriptional downregulation of SQLE, p53 represses cholesterol production in vivo and in vitro, leading to tumor growth suppression. Inhibition of SQLE using small interfering RNA (siRNA) or terbinafine (a SQLE inhibitor) reverses the increased cell proliferation caused by p53 deficiency. Conversely, SQLE overexpression or cholesterol addition promotes cell proliferation, particularly in p53 wild-type cells. More importantly, pharmacological inhibition or shRNA-mediated silencing of SQLE restricts nonalcoholic fatty liver disease (NAFLD)-induced liver tumorigenesis in p53 knockout mice. Therefore, our findings reveal a role for p53 in regulating SQLE and cholesterol biosynthesis, and further demonstrate that downregulation of SQLE is critical for p53-mediated tumor suppression.