Inhibition of fatty acid synthase suppresses c-Met receptor kinase and induces apoptosis in diffuse large B-cell lymphoma

Unraveling the intricate relationship between lipid metabolism and oncogenic signaling pathways

Lipids, the primary constituents of the cell membrane, play essential roles in nearly all cellular functions, such as cell-cell recognition, signaling transduction, and energy provision. Lipid metabolism is necessary for the maintenance of life since it regulates the balance between the processes of synthesis and breakdown. Increasing evidence suggests that cancer cells exhibit abnormal lipid metabolism, significantly affecting their malignant characteristics, including self-renewal, differentiation, invasion, metastasis, and drug sensitivity and resistance. Prominent oncogenic signaling pathways that modulate metabolic gene expression and elevate metabolic enzyme activity include phosphoinositide 3-kinase (PI3K)/AKT, MAPK, NF-kB, Wnt, Notch, and Hippo pathway. Conversely, when metabolic processes are not regulated, they can lead to malfunctions in cellular signal transduction pathways. This, in turn, enables uncontrolled cancer cell growth by providing the necessary energy, building blocks, and redox potentials. Therefore, targeting lipid metabolism-associated oncogenic signaling pathways could be an effective therapeutic approach to decrease cancer incidence and promote survival. This review sheds light on the interactions between lipid reprogramming and signaling pathways in cancer. Exploring lipid metabolism as a target could provide a promising approach for creating anticancer treatments by identifying metabolic inhibitors. Additionally, we have also provided an overview of the drugs targeting lipid metabolism in cancer in this review.

Ferroptosis mechanisms and its novel potential therapeutic targets for DLBCL

Diffuse large B-cell lymphoma (DLBCL), a heterogeneous lymphoid malignancy, poses a significant threat to human health. The standard therapeutic regimen for patients with DLBCL is rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), with a typical cure rate of 50-70%. However, some patients either relapse after complete remission (CR) or exhibit resistance to R-CHOP treatment. Therefore, novel therapeutic approaches are imperative for managing high-risk or refractory DLBCL. Ferroptosis is driven by iron-dependent phospholipid peroxidation, a process that relies on the transition metal iron, reactive oxygen species (ROS), and phospholipids containing polyunsaturated fatty acids-containing phospholipids (PUFA-PLs). Research indicates that ferroptosis is implicated in various carcinogenic and anticancer pathways. Several hematological disorders exhibit heightened sensitivity to cell death induced by ferroptosis. DLBCL cells, in particular, demonstrate an increased demand for iron and an upregulation in the expression of fatty acid synthase. Additionally, there exists a correlation between ferroptosis-associated genes and the prognosis of DLBCL. Therefore, ferroptosis may be a promising novel target for DLBCL therapy. In this review, we elucidate ferroptosis mechanisms, its role in DLBCL, and the potential therapeutic targets in DLBCL. This review offers novel insights into the application of ferroptosis in treatment strategies for DLBCL.

A novel lipid metabolism-based risk model associated with immunosuppressive mechanisms in diffuse large B-cell lymphoma

BACKGROUND

The molecular diversity exhibited by diffuse large B-cell lymphoma (DLBCL) is a significant obstacle facing current precision therapies. However, scoring using the International Prognostic Index (IPI) is inadequate when fully predicting the development of DLBCL. Reprogramming lipid metabolism is crucial for DLBCL carcinogenesis and expansion, while a predictive approach derived from lipid metabolism-associated genes (LMAGs) has not yet been recognized for DLBCL.

METHODS

Gene expression profiles of DLBCL were generated using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. The LASSO Cox regression was used to construct an effective predictive risk-scoring model for DLBCL patients. The Kaplan-Meier survival assessment was employed to compare a given risk score with the IPI score and its impact on the survival of DLBCL patients. Functional enrichment examination was performed utilizing the KEGG pathway. After identifying hub genes via single-sample GSEA (ssGSEA), immunohistochemical staining and immunofluorescence were performed on lymph node samples from control and DLBCL patients to confirm these identified genes.

RESULTS

Sixteen lipid metabolism- and survival-associated genes were identified to construct a prognostic risk-scoring approach. This model demonstrated robust performance over various datasets and emerged as an autonomous risk factor for predicting the development of DLBCL patients. The risk score could significantly distinguish the development of DLBCL patients from the low-risk and elevated-risk IPI classes. Results from the inhibitory immune-related pathways and lower immune scores suggested an immunosuppressive phenotype within the elevated-risk group. Three hub genes, MECR, ARSK, and RAN, were identified to be negatively correlated with activated CD8 T cells and natural killer T cells in the elevated-risk score class. Ultimately, it was determined that these three genes were expressed by lymphoma cells but not by T cells in clinical samples from DLBCL patients.

CONCLUSION

The risk level model derived from 16 lipid metabolism-associated genes represents a prognostic biomarker for DLBCL that is novel, robust, and may have an immunosuppressive role. It can compensate for the limitations of the IPI score in predicting overall survival and has potential clinical application value.

The Metabolism and Immune Environment in Diffuse Large B-Cell Lymphoma

Cells utilize different metabolic processes to maintain their growth and differentiation. Tumor cells have made some metabolic changes to protect themselves from malnutrition. These metabolic alterations affect the tumor microenvironment and macroenvironment. Developing drugs targeting these metabolic alterations could be a good direction. In this review, we briefly introduce metabolic changes/regulations of the tumor macroenvironment and microenvironment and summarize potential drugs targeting the metabolism in diffuse large B-cell lymphoma.

Metabolic Reprogramming and Potential Therapeutic Targets in Lymphoma

Lymphoma is a heterogeneous group of diseases that often require their metabolism program to fulfill the demand of cell proliferation. Features of metabolism in lymphoma cells include high glucose uptake, deregulated expression of enzymes related to glycolysis, dual capacity for glycolytic and oxidative metabolism, elevated glutamine metabolism, and fatty acid synthesis. These aberrant metabolic changes lead to tumorigenesis, disease progression, and resistance to lymphoma chemotherapy. This metabolic reprogramming, including glucose, nucleic acid, fatty acid, and amino acid metabolism, is a dynamic process caused not only by genetic and epigenetic changes, but also by changes in the microenvironment affected by viral infections. Notably, some critical metabolic enzymes and metabolites may play vital roles in lymphomagenesis and progression. Recent studies have uncovered that metabolic pathways might have clinical impacts on the diagnosis, characterization, and treatment of lymphoma subtypes. However, determining the clinical relevance of biomarkers and therapeutic targets related to lymphoma metabolism is still challenging. In this review, we systematically summarize current studies on metabolism reprogramming in lymphoma, and we mainly focus on disorders of glucose, amino acids, and lipid metabolisms, as well as dysregulation of molecules in metabolic pathways, oncometabolites, and potential metabolic biomarkers. We then discuss strategies directly or indirectly for those potential therapeutic targets. Finally, we prospect the future directions of lymphoma treatment on metabolic reprogramming.

Reprogramming lipid metabolism as potential strategy for hematological malignancy therapy

Hematological malignancies are one of the most lethal illnesses that seriously threaten human life and health. Lipids are important constituents of various biological membranes and substances for energy storage and cell signaling. Furthermore, lipids are critical in the normal physiological activities of cells. In the process of the lethal transformation of hematological malignancies, lipid metabolism reprogramming meets the material and energy requirements of rapidly proliferating and dividing tumor cells. A large number of studies have shown that dysregulated lipid metabolism, commonly occurs in hematological malignancies, mediating the proliferation, growth, migration, invasion, apoptosis, drug resistance and immune escape of tumor cells. Targeting the lipid metabolism pathway of hematological malignancies has become an effective therapeutic approach. This article reviews the oncogenic mechanisms of lipid metabolism reprogramming in hematological malignancies, including fatty acid, cholesterol and phospholipid metabolism, thereby offering an insight into targeting lipid metabolism in the treatment of hematological malignancies.

Lipotoxicity as a Barrier for T Cell-Based Therapies

Nowadays, T-cell-based approaches play an increasing role in cancer treatment. In particular, the use of (genetically engineered) T-cells has heralded a novel era for various diseases with previously poor outcomes. Concurrently, the relationship between the functional behavior of immune cells and their metabolic state, known as immunometabolism, has been found to be an important determinant for the success of immunotherapy. In this context, immune cell metabolism is not only controlled by the expression of transcription factors, enzymes and transport proteins but also by nutrient availability and the presence of intermediate metabolites. The lack of as well as an oversupply of nutrients can be detrimental and lead to cellular dysfunction and damage, potentially resulting in reduced metabolic fitness and/or cell death. This review focusses on the detrimental effects of excessive exposure of T cells to fatty acids, known as lipotoxicity, in the context of an altered lipid tumor microenvironment. Furthermore, implications of T cell-related lipotoxicity for immunotherapy will be discussed, as well as potential therapeutic approaches.

Antiphospholipid Antibodies and Lipids in Hematological Malignancies

One of the main groups of lipids is phospholipids, which are mainly involved in forming cell membranes. Neoplastic processes such as cell replication have increased lipid synthesis, making tumor cells dependent on this synthesis to maintain their requirements. Antiphospholipid antibodies attack phospholipids in the cell membranes. Three main types of antiphospholipid antibodies are recognized: anti-β2 glycoprotein I (anti-β2GP-I), anticardiolipin (aCL), and lupus anticoagulant (LA). These types of antibodies have been proven to be present in hematological neoplasms, particularly in LH and NHL. This review on antiphospholipid antibodies in hematological neoplasms describes their clinical relationship as future implications at the prognostic level for survival and even treatment.

The Heterogeneity of Lipid Metabolism in Cancer

The study of cancer cell metabolism has traditionally focused on glycolysis and glutaminolysis. However, lipidomic technologies have matured considerably over the last decade and broadened our understanding of how lipid metabolism is relevant to cancer biology [1-3]. Studies now suggest that the reprogramming of cellular lipid metabolism contributes directly to malignant transformation and progression [4, 5]. For example, de novo lipid synthesis can supply proliferating tumor cells with phospholipid components that comprise the plasma and organelle membranes of new daughter cells [6, 7]. Moreover, the upregulation of mitochondrial β-oxidation can support tumor cell energetics and redox homeostasis [8], while lipid-derived messengers can regulate major signaling pathways or coordinate immunosuppressive mechanisms [9-11]. Lipid metabolism has, therefore, become implicated in a variety of oncogenic processes, including metastatic colonization, drug resistance, and cell differentiation [10, 12-16]. However, whether we can safely and effectively modulate the underlying mechanisms of lipid metabolism for cancer therapy is still an open question.

Upregulation of fatty acid synthase in MYC and BCL-2 double-expressor lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common and heterogeneous lymphoid malignancy. The subtype with MYC and BCL-2 double-expressor lymphoma (DEL) was defined by its aggressive nature and poor survival outcome. Therefore, the development of effective therapies for the DEL subtype is imperative. Fatty acid synthase (FASN) activity is associated with altered lipid metabolism and aberrant protein translation in DLBCL. However, the inter-regulation of these key processes is not fully determined in DEL. In the present study, the clinical and biological impact of FASN was investigated in the DEL subtype. Initially, FASN expression levels were analyzed from a patient cohort and the data indicated that the highest FASN expression was noted in DEL tissues compared with that noted in the DLBCL and reactive lymphoid hyperplasia tissues. Patients with DEL with combined high-FASN expression indicated poorer EFS outcomes than the rest of the patients. In vitro data indicated that FASN was overexpressed in SU-DHL-2 and U2932 cells. Silencing FASN decreased cell growth and promoted cell apoptosis by modulating the pERK/BCL-2 signaling pathway. In conclusion, the present study indicated that FASN was overexpressed in DEL and that its expression was associated with poor survival outcomes. Furthermore, the data demonstrated that FASN regulated the biological function via the pERK/BCL-2 signaling pathway. FASN serves a critical role in the progression of DEL and its expression may be associated with the development to a more aggressive phenotype of DLBCL. Therefore, it may be considered a potential therapeutic target for DLBCL.

Fatty Acid Synthase: An Emerging Target in Cancer

In recent years, lipid metabolism has garnered significant attention as it provides the necessary building blocks required to sustain tumor growth and serves as an alternative fuel source for ATP generation. Fatty acid synthase (FASN) functions as a central regulator of lipid metabolism and plays a critical role in the growth and survival of tumors with lipogenic phenotypes. Accumulating evidence has shown that it is capable of rewiring tumor cells for greater energy flexibility to attain their high energy requirements. This multi-enzyme protein is capable of modulating the function of subcellular organelles for optimal function under different conditions. Apart from lipid metabolism, FASN has functional roles in other cellular processes such as glycolysis and amino acid metabolism. These pivotal roles of FASN in lipid metabolism make it an attractive target in the clinic with several new inhibitors currently being tested in early clinical trials. This article aims to present the current evidence on the emergence of FASN as a target in human malignancies.

Function and regulation of lipid signaling in lymphomagenesis: A novel target in cancer research and therapy

To survive under the challenging conditions, cancer cells adapt their own metabolic mechanism(s) to be able steady supplying energy and metabolites for synthesis of new biomass. Aberrant lipid metabolism in cancer cells becomes a hall marker of carcinogenesis. Epidemiologic evidence indicates that fat intake, in particular saturated or animal fat, may increase the risk of lymphoma. Understanding the specific alterations of lymphoma metabolism becomes essential to address malignant transformation, progression, and therapeutic approaches. This review is focused on the lipid metabolism, with emphasis on fatty acid synthase, lipid rafts, exosomes, and metabolic diseases, in distinct lymphoma entities.

Fatty acid synthase and adenosine monophosphate-activated protein kinase regulate cell survival and drug sensitivity in diffuse large B-cell lymphoma

Fatty acid synthesis is crucial in supporting the survival and proliferation of multiple forms of cancer. The high metabolic demands of fatty acid synthesis are regulated by the AMP-activated kinase and activity of the fatty acid synthase enzyme. In this study, the roles of these enzymes in diffuse large B-cell lymphoma (DLBCL) were investigated by genetic knock-down and pharmacological activation of AMP-activated kinase by metformin, and selective inhibition of fatty acid synthase using the novel drug Fasnall. We observed distinct heterogeneity and adaptive plasticity of lipid metabolism in a panel of DLBCL cell lines and demonstrate the therapeutic potential of inhibiting fatty acid synthesis in a subset of DLBCL cells. The translational relevance of these in vitro data is supported by the strong correlation between AMP-activated protein kinase expression in primary DLBCL samples and disease relapse. Inhibition of fatty acid synthase with Fasnall may represent a therapeutic option for DLBCL that preferentially subverts to de novo fatty acid synthesis.

Genomics, Morphoproteomics, and Treatment Patterns of Patients with Alveolar Soft Part Sarcoma and Response to Multiple Experimental Therapies

Overexpression of transcription factor 3 in alveolar soft part sarcoma(ASPS) results in upregulation of cell proliferation pathways. No standard treatment algorithm exists for ASPS; multikinase inhibitors[tyrosine kinase inhibitor (TKI)] and immune checkpoint inhibitors (ICI) have shown clinical benefit. To date, no studies have reported on management strategies or sequencing of therapy. We evaluated ASPS treatment patterns and responses in an experimental therapeutics clinic. Genomic and morphoproteomic analysis was performed to further elucidate novel targets. We retrospectively reviewed patients with ASPS treated on clinical trials. Demographic and clinical next-generation sequencing (NGS) profiles were collected. AACR GENIE database was queried to further evaluate aberrations in ASPS. Morphoproteomic analysis was carried out to better define the biology of ASPS with integration of genomic and proteomic findings. Eleven patients with ASPS were identified; 7 received NGS testing and mutations in CDKN2A (n = 1) and hepatocyte growth factor (n = 1) were present. Ten patients were treated with TKIs with stable disease as best response and 4 patients with ICI (three partial responses). Within GENIE, 20 patients were identified harboring 3 called pathogenic mutations. Tumor mutation burden was low in all samples. Morphoproteomic analysis confirmed the expression of phosphorylated c-Met. In addition, fatty acid synthase and phosphorylated-STAT3 were detected in tumor cell cytoplasm and nuclei. Patients with ASPS have a quiescent genome and derive clinical benefit from VEGF-targeting TKIs. Morphoproteomic analysis has provided both additional correlative pathways and angiogenic mechanisms that are targetable for patients with ASPS. Our study suggests that sequential therapy with TKIs and immune checkpoint inhibitors is a reasonable management strategy.

Verticillin A suppresses HGF-induced migration and invasion via repression of the c-Met/FAK/Src pathway in human gastric and cervical cancer cells

Background and purpose: Verticillin A is a fungal epipolythiodioxopiperazine (ETP) metabolite that was isolated from Amanita flavorubescens Alk infected by Verticillium sp. It was previously proven to possess potent anti-tumor cell growth activity, and we have recently determined that verticillin A is a selective inhibitor of H3K9me3-specific histone methyltransferase. The objective of this study was to find out whether verticillin A is an effective agent for suppression of gastric and cervical tumor progression. Materials and methods: Wound healing and transwell assays was performed to evaluate the effect of verticillin A on hepatocyte growth factor (HGF)-induced AGS and HeLa cells migration and invasion in vitro. Western blot was used to detect signaling proteins verticillin A affected. Results: We determined that verticillin A effectively suppressed hepatocyte growth factor (HGF)-induced AGS and HeLa cells migration and invasion in vitro. At the molecular level, we demonstrated that verticillin A inhibited HGF-induced c-Met phosphorylation and repressed the expression of total c-Met protein in AGS and HeLa cells, resulting from reduced expression of fatty acid synthase. In addition, verticillin A could suppress c-Met downstream FAK/Src signaling pathways by impairing c-Met phosphorylation induced by HGF. Conclusion: Our study demonstrated verticillin A inhibits the migration ability of human gastric cancer (AGS) cells and cervical cancer (HeLa) cells by targeting c-Met and its downstream FAK/Src signaling pathways, and suggested that verticillin A acts as a novel HGF/c-Met inhibitor by reducing expression of this receptor.

Downregulation of long non-coding RNA TUG1 suppresses tumor growth by promoting ubiquitination of MET in diffuse large B-cell lymphoma

Long non-coding RNAs (lncRNAs) can modulate gene expression through different mechanisms, but the fundamental molecular mechanism between lncRNAs and MET protein in diffuse large B-cell lymphoma (DLBCL) was poorly understood. The expression of lncRNA TUG1 and MET in DLBCL tissues and cell lines was determined by quantitative real-time PCR and western blotting. Cell proliferation, invasion and apoptosis were determined by cell counting kit-8 assay, transwell assay and flow cytometer. The animal xenograft model was established by the injection of DLBCL cells carrying si-TUG1. The expression of TUG1 and MET was upregulated in DLBCL tissues and cells. We demonstrated that MET was altered in the TUG1 knockdown DLBCL cells, and confirmed the interaction between TUG1 and MET by RNA pull-down and RNA immunoprecipitation. Furthermore, knockdown of TUG1 reduced MET protein level by promoting ubiquitination, and suppressed tumor growth in vitro and in vivo. Our findings demonstrated that TUG1 exerted its oncogenic function in DLBCL by inhibiting the ubiquitination and the subsequent degradation of MET. Knockdown of TUG1 through MET downregulation suppressed DLBCL cell proliferation and tumor growth.

Fatty Acid Synthase induced S6Kinase facilitates USP11-eIF4B complex formation for sustained oncogenic translation in DLBCL

Altered lipid metabolism and aberrant protein translation are strongly associated with cancerous outgrowth; however, the inter-regulation of these key processes is still underexplored in diffuse large B-cell lymphoma (DLBCL). Although fatty acid synthase (FASN) activity is reported to positively correlate with PI3K-Akt-mTOR pathway that can modulate protein synthesis, the precise impact of FASN inhibition on this process is still unknown. Herein, we demonstrate that attenuating FASN expression or its activity significantly reduces eIF4B (eukaryotic initiation factor 4B) levels and consequently overall protein translation. Through biochemical studies, we identified eIF4B as a bonafide substrate of USP11, which stabilizes and enhances eIF4B activity. Employing both pharmacological and genetic approaches, we establish that FASN-induced PI3K-S6Kinase signaling phosphorylates USP11 enhancing its interaction with eIF4B and thereby promoting oncogenic translation.

Interacting Cancer Machineries: Cell Signaling, Lipid Metabolism, and Epigenetics

Cancer-specific perturbations of signaling, metabolism, and epigenetics can be a cause and/or consequence of malignant transformation. Evidence indicates that these regulatory systems interact with each other to form highly flexible and robust cybernetic networks that promote malignant growth and confer treatment resistance. Deciphering these plexuses using holistic approaches known from systems biology can be instructive for the future design of novel anticancer strategies. In this review, I discuss novel findings elucidating the multiple molecular interdependence among cancer-specific signaling, cell metabolism, and epigenetics to provide an insightful understanding of how major cancer machineries interact with each other during cancer development and progression, and how this knowledge may be used for future co-targeting strategies.

Palmitoylation regulates the intracellular trafficking and stability of c-Met

c-Met is a receptor tyrosine kinase whose activity can promote both mitogenic and motogenic phenotypes involved in tissue development and cancer progression. Herein, we report the first evidence that c-Met is palmitoylated and that palmitoylation facilitates its trafficking and stability. Inhibition of palmitoylation reduced the expression of c-Met in multiple cancer cell lines post-transcriptionally. Using surface biotinylation, confocal microscopy, and metabolic labeling we determined that inhibition of palmitoylation reduces the stability of newly synthesized c-Met and causes accumulation at the Golgi. Acyl-biotin exchange and click chemistry-based palmitate labeling indicated the c-Met β-chain is palmitoylated, and site-directed mutagenesis revealed two likely cysteine palmitoylation sites. Moreover, by monitoring palmitoylation kinetics during the biosynthesis and trafficking of c-Met, we revealed that stable palmitoylation occurs in the endoplasmic reticulum prior to cleavage of the 170 kDa c-Met precursor to the mature 140 kDa form. Our data suggest palmitoylation is required for egress from the Golgi for transport to the plasma membrane. These findings introduce palmitoylation as a critical modification of c-Met, providing a novel therapeutic target for c-Met-driven cancers.

FASN Inhibition and Taxane Treatment Combine to Enhance Anti-tumor Efficacy in Diverse Xenograft Tumor Models through Disruption of Tubulin Palmitoylation and Microtubule Organization and FASN Inhibition-Mediated Effects on Oncogenic Signaling and Gene Expression

Palmitate, the enzymatic product of FASN, and palmitate-derived lipids support cell metabolism, membrane architecture, protein localization, and intracellular signaling. Tubulins are among many proteins that are modified post-translationally by acylation with palmitate. We show that FASN inhibition with TVB-3166 or TVB-3664 significantly reduces tubulin palmitoylation and mRNA expression. Disrupted microtubule organization in tumor cells is an additional consequence of FASN inhibition. FASN inhibition combined with taxane treatment enhances inhibition of in vitro tumor cell growth compared to treatment with either agent alone. In lung, ovarian, prostate, and pancreatic tumor xenograft studies, FASN inhibition and paclitaxel or docetaxel combine to inhibit xenograft tumor growth with significantly enhanced anti-tumor activity. Tumor regression was observed in 3 of 6 tumor xenograft models. FASN inhibition does not affect cellular taxane concentration in vitro. Our data suggest a mechanism of enhanced anti-tumor activity of the FASN and taxane drug combination that includes inhibition of tubulin palmitoylation and disruption of microtubule organization in tumor cells, as well as a sensitization of tumor cells to FASN inhibition-mediated effects that include gene expression changes and inhibition of β-catenin. Together, the results strongly support investigation of combined FASN inhibition and taxane treatment as a therapy for a variety of human cancers.

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FASN inhibition decreases tubulin palmitoylation and disrupts microtubules in tumor cells but not non-tumor cells

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Combined FASN inhibition and taxane treatment increases inhibition of in vitro tumor cell colony growth

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FASN inhibition does not affect intracellular paclitaxel concentrations

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Combined FASN inhibition and taxane treatment significantly increases inhibition of tumor growth or causes regression of diverse xenograft tumors

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Taxane treatment sensitizes xenograft tumors to FASN inhibition-mediated beta-catenin blockade and gene expression changes

Fatty acid synthase (FASN) is a vital enzyme in tumor cell biology; the over-expression of FASN is associated with diminished patient prognosis and resistance to many cancer therapies. Our data demonstrate that selective and potent FASN inhibition combines with taxane treatment to enhance tumor growth inhibition and induce tumor regression in varied preclinical tumor models. Mechanism-of-action studies indicate that the increased activity of the combination results from the effects of both drugs. The results support clinical investigation of combined FASN inhibition and taxane treatment as an anti-cancer therapy.

The role of HGF/c-MET signaling pathway in lymphoma

Inappropriate activation of c-mesenchymal-epithelial transition (MET), the receptor tyrosine kinase (RTK) for hepatocyte growth factor (HGF), has been implicated in tumorigenesis and represented a promising therapeutic target for developing anticancer agents. In contrast to other solid tumors, there are limited data describing the functional role of HGF/c-MET signaling pathway in lymphoma. In the current review, we summarize recent findings about the expression, cellular mechanisms/functions, and therapeutic application of HGF/c-MET in different types of lymphoma, especially B cell lymphoma, T and NK cell lymphoma, and Hodgkin lymphoma. We also discuss the existing problems and future directions about studying the HGF/c-MET pathway in lymphoma cells.

Co-activation of AKT and c-Met triggers rapid hepatocellular carcinoma development via the mTORC1/FASN pathway in mice

Activation of the AKT/mTOR cascade and overexpression of c-Met have been implicated in the development of human hepatocellular carcinoma (HCC). To elucidate the functional crosstalk between the two pathways, we generated a model characterized by the combined expression of activated AKT and c-Met in the mouse liver. Co-expression of AKT and c-Met triggered rapid liver tumor development and mice required to be euthanized within 8 weeks after hydrodynamic injection. At the molecular level, liver tumors induced by AKT/c-Met display activation of AKT/mTOR and Ras/MAPK cascades as well as increased lipogenesis and glycolysis. Since a remarkable lipogenic phenotype characterizes liver lesions from AKT/c-Met mice, we determined the requirement of lipogenesis in AKT/c-Met driven hepatocarcinogenesis using conditional Fatty Acid Synthase (FASN) knockout mice. Of note, hepatocarcinogenesis induced by AKT/c-Met was fully inhibited by FASN ablation. In human HCC samples, coordinated expression of FASN, activated AKT, and c-Met proteins was detected in a subgroup of biologically aggressive tumors. Altogether, our study demonstrates that co-activation of AKT and c-Met induces HCC development that depends on the mTORC1/FASN pathway. Suppression of mTORC1 and/or FASN might be highly detrimental for the growth of human HCC subsets characterized by concomitant induction of the AKT and c-Met cascades.

Quercetin inhibits HGF/c-Met signaling and HGF-stimulated melanoma cell migration and invasion

Background

Melanoma is notorious for its propensity to metastasize, which makes treatment extremely difficult. Receptor tyrosine kinase c-Met is activated in human melanoma and is involved in melanoma progression and metastasis. Hepatocyte growth factor (HGF)-mediated activation of c-Met signaling has been suggested as a therapeutic target for melanoma metastasis. Quercetin is a dietary flavonoid that exerts anti-metastatic effect in various types of cancer including melanoma. In a previous report, we demonstrated that quercetin inhibited melanoma cell migration and invasion in vitro, and prevented melanoma cell lung metastasis in vivo. In this study, we sought to determine the involvement of HGF/c-Met signaling in the anti-metastatic action of quercetin in melanoma.

Methods

Transwell chamber assay was conducted to determine the cell migratory and invasive abilities. Western blotting was performed to determine the expression levels and activities of c-Met and its downstream molecules. And immunoblotting was performed in BS³ cross-linked cells to examine the homo-dimerization of c-Met. Quantitative real-time PCR analysis was carried out to evaluate the mRNA expression level of HGF. Transient transfection was used to overexpress PAK or FAK in cell models. Student’s t-test was used in analyzing differences between two groups.

Results

Quercetin dose-dependently suppressed HGF-stimulated melanoma cell migration and invasion. Further study indicated that quercetin inhibited c-Met phosphorylation, reduced c-Met homo-dimerization and decreased c-Met protein expression. The effect of quercetin on c-Met expression was associated with a reduced expression of fatty acid synthase. In addition, quercetin suppressed the phosphorylation of c-Met downstream molecules including Gab1 (GRB2-associated-binding protein 1), FAK (Focal Adhesion Kinase) and PAK (p21-activated kinases). More importantly, overexpression of FAK or PAK significantly reduced the inhibitory effect of quercetin on the migration of the melanoma cells.

Conclusions

Our findings suggest that suppression of the HGF/c-Met signaling pathway contributes to the anti-metastatic action of quercetin in melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0367-4) contains supplementary material, which is available to authorized users.

Individualized medicine enabled by genomics in Saudi Arabia

The biomedical research sector in Saudi Arabia has recently received special attention from the government, which is currently supporting research aimed at improving the understanding and treatment of common diseases afflicting Saudi Arabian society. To build capacity for research and training, a number of centres of excellence were established in different areas of the country. Among these, is the Centre of Excellence in Genomic Medicine Research (CEGMR) at King Abdulaziz University, Jeddah, with its internationally ranked and highly productive team performing translational research in the area of individualized medicine. Here, we present a panorama of the recent trends in different areas of biomedical research in Saudi Arabia drawing from our vision of where genomics will have maximal impact in the Kingdom of Saudi Arabia. We describe advances in a number of research areas including; congenital malformations, infertility, consanguinity and pre-implantation genetic diagnosis, cancer and genomic classifications in Saudi Arabia, epigenetic explanations of idiopathic disease, and pharmacogenomics and personalized medicine. We conclude that CEGMR will continue to play a pivotal role in advances in the field of genomics and research in this area is facing a number of challenges including generating high quality control data from Saudi population and policies for using these data need to comply with the international set up.

Role of abnormal lipid metabolism in development, progression, diagnosis and therapy of pancreatic cancer

There is growing evidence that metabolic alterations play an important role in cancer development and progression. The metabolism of cancer cells is reprogrammed in order to support their rapid proliferation. Elevated fatty acid synthesis is one of the most important aberrations of cancer cell metabolism. An enhancement of fatty acids synthesis is required both for carcinogenesis and cancer cell survival, as inhibition of key lipogenic enzymes slows down the growth of tumor cells and impairs their survival. Based on the data that serum fatty acid synthase (FASN), also known as oncoantigen 519, is elevated in patients with certain types of cancer, its serum level was proposed as a marker of neoplasia. This review aims to demonstrate the changes in lipid metabolism and other metabolic processes associated with lipid metabolism in pancreatic ductal adenocarcinoma (PDAC), the most common pancreatic neoplasm, characterized by high mortality. We also addressed the influence of some oncogenic factors and tumor suppressors on pancreatic cancer cell metabolism. Additionally the review discusses the potential role of elevated lipid synthesis in diagnosis and treatment of pancreatic cancer. In particular, FASN is a viable candidate for indicator of pathologic state, marker of neoplasia, as well as, pharmacological treatment target in pancreatic cancer. Recent research showed that, in addition to lipogenesis, certain cancer cells can use fatty acids from circulation, derived from diet (chylomicrons), synthesized in liver, or released from adipose tissue for their growth. Thus, the interactions between de novo lipogenesis and uptake of fatty acids from circulation by PDAC cells require further investigation.

Receptor tyrosine kinases MET and RON as prognostic factors in diffuse large B-cell lymphoma patients receiving R-CHOP

Receptor tyrosine kinases MET and RON (MST1R) form non-covalent complexes on the cell surface, a critical step in tumor progression. A recent study suggested a prognostic role for MET expression in diffuse large B-cell lymphoma (DLBCL). The aim of this study was to examine the impact of MET and RON expression in uniformly treated DLBCL patients. The expression of MET and RON was retrospectively examined by immunohistochemistry in 120 DLBCL patients treated with rituximab combined with a CHOP regimen (cyclophosphamide, doxorubicin, vincristine, and prednisone). The median follow-up time was 42.5 months (range, 1-89 months). Thirty-two (26%) and 30 patients (25%) expressed MET or RON, respectively. Seventy-five patients (62.5%) were negative for both MET and RON (MET(-) RON(-) ). MET negativity was associated with worse overall survival (P = 0.029). In multivariate analysis, negativity for both MET and RON (MET(-) RON(-) ) was strongly associated with inferior overall survival (P = 0.008). Interestingly, the MET(-) RON(-) phenotype retained its prognostic impact after subgroup analysis according to the international prognostic index or by the cell of origin by immunohistochemical algorithm by Choi et al. This study suggests that the MET(-) RON(-) phenotype is an independent prognostic factor in DLBCL patients receiving R-CHOP, and may identify a subgroup of DLBCL patients who require more intensive therapy.

Extranodal Nasal NK/T-Cell Lymphoma: A Rare Oral Presentation and FASN, CD44 and GLUT-1 Expression

Extranodal natural killer (NK)/T-cell lymphoma is an aggressive malignant tumor with distinctive clinicopathological features, characterized by vascular invasion and destruction, prominent necrosis, cytotoxic lymphocyte phenotype and a strong association with Epstein-Barr virus. Here is reported an extranodal nasal NK/T-cell lymphoma case, involving the maxillary sinus, floor of the orbit, and interestingly extending to the oral cavity through the alveolar bone and buccal mucosa, preserving the palate, leading to a primary misdiagnosis of aggressive periodontal disease. Moreover, this work investigated for the first time the immunohistochemical expression of fatty acid synthase (FASN) and glucose transporter 1 (GLUT-1) proteins in this neoplasia. FASN showed strong cytoplasmatic expression in the neoplastic cells, whereas GLUT-1 and CD44 were negative. These findings suggest that the expression of FASN and the loss of CD44 might be involved in the pathogenesis of the extranodal nasal NK/T-cell lymphoma, and that GLUT-1 may not participate in the survival adaptation of the tumor cells to the hypoxic environment. Further studies with larger series are required to confirm these initial results.

Proteomics of genetically engineered mouse mammary tumors identifies fatty acid metabolism members as potential predictive markers for cisplatin resistance

In contrast to various signatures that predict the prognosis of breast cancer patients, markers that predict chemotherapy response are still elusive. To detect such predictive biomarkers, we investigated early changes in protein expression using two mouse models for distinct breast cancer subtypes who have a differential knock-out status for the breast cancer 1, early onset (Brca1) gene. The proteome of cisplatin-sensitive BRCA1-deficient mammary tumors was compared with that of cisplatin-resistant mammary tumors resembling pleomorphic invasive lobular carcinoma. The analyses were performed 24 h after administration of the maximum tolerable dose of cisplatin. At this time point, drug-sensitive BRCA1-deficient tumors showed DNA damage, but cells were largely viable. By applying paired statistics and quantitative filtering, we identified highly discriminatory markers for the sensitive and resistant model. Proteins up-regulated in the sensitive model are involved in centrosome organization, chromosome condensation, homology-directed DNA repair, and nucleotide metabolism. Major discriminatory markers that were up-regulated in the resistant model were predominantly involved in fatty acid metabolism, such as fatty-acid synthase. Specific inhibition of fatty-acid synthase sensitized resistant cells to cisplatin. Our data suggest that exploring the functional link between the DNA damage response and cancer metabolism shortly after the initial treatment may be a useful strategy to predict the efficacy of cisplatin.

High MET gene copy number predicted poor prognosis in primary intestinal diffuse large B-cell lymphoma

BACKGROUND

MET is a proto-oncogene with its copy number (CN) alterations been reported in some cancers, but not in primary intestinal diffuse large B-cell lymphoma (PI-DLBL) yet.

METHODS

In this retrospective study, we performed histology and chart reviews, immunohistochemistry and quantitative polymerase chain reaction for MET CN alterations on 28 surgically resected PI-DLBLs.

RESULTS

There were 12 men and 16 women with a median age of 70 and a mean follow-up of 32 months. The median MET CN was 2.20 (range, 1.04 to 3.35). CN gain was observed in 11 cases, including 5 with CN greater than 3. Nine patients (32%) had diploid CN and eight (29%) with CN loss. Patients with gain or diploid CN showed significantly worse prognosis (P = 0.046) than those with CN loss. Furthermore, MET CN greater than 3 was associated with an adverse outcome (P = 0.003). Intestinal perforation at presentation was the sole clinicopathological factor associated with a poor prognosis (P = 0.004) and perforation was correlated with CN greater than 3 (P = 0.002).

CONCLUSIONS

Our finding of MET CN gain as a poor prognostic factor in PI-DLBL patients might serve as the rationale for targeting MET signaling pathway in the treatment of these patients.

FASN and CD36 predict survival in rituximab-treated diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma is the most common lymphoid malignancy, as it accounts for approximately one third of all patient cases of non-Hodgkin's lymphoma. Patients with diffuse large B-cell lymphoma have markedly different treatment outcomes, suggesting a need for reliable prognostic factors and novel therapeutic approaches. De novo fatty acid synthesis is an important metabolic driver of tumor in multiple malignancies. In this retrospective study, we analyzed expression of fatty acid synthase (a key enzyme in de novo fatty acid synthesis), Spot 14 (thyroid hormone responsive Spot 14, a nuclear protein that promotes expression of genes involved in fatty acid synthesis), and CD36 (the cell surface channel for exogenous fatty acid uptake) in patients with diffuse large B-cell lymphoma and their clinical significance. We observed that overexpression of fatty acid synthase is negatively associated with overall survival (p=0.001) and progression-free period (p=0.004) in patients with diffuse large B-cell lymphoma. Multivariate analysis showed that fatty acid synthase overexpression is an independent prognostic marker of aggressive clinical course. For the first time, we report CD36 as an independent protective factor in patients treated with rituximab. Thus, fatty acid synthase and CD36 expression may serve as prognostic markers to predict response to treatment and survival in diffuse large B-cell lymphoma patients. Fatty acid synthase may also be a potential therapeutic target in lymphoid malignancies.

Blockade of fatty acid synthase triggers significant apoptosis in mantle cell lymphoma

Fatty acid synthase (FASN), a key player in the de novo synthetic pathway of long-chain fatty acids, has been shown to contribute to the tumorigenesis in various types of solid tumors. We here report that FASN is highly and consistently expressed in mantle cell lymphoma (MCL), an aggressive form of B-cell lymphoid malignancy. Specifically, the expression of FASN was detectable in all four MCL cell lines and 15 tumors examined. In contrast, benign lymphoid tissues and peripheral blood mononuclear cells from normal donors were negative. Treatment of MCL cell lines with orlistat, a FASN inhibitor, resulted in significant apoptosis. Knockdown of FASN expression using siRNA, which also significantly decreased the growth of MCL cells, led to a dramatic decrease in the cyclin D1 level. β-catenin, which has been previously reported to be upregulated in a subset of MCL tumors, contributed to the high level of FASN in MCL cells, Interesting, siRNA knock-down of FASN in turn down-regulated β-catenin. In conclusion, our data supports the concept that FASN contributes to the pathogenesis of MCL, by collaborating with β-catenin. In view of its high and consistent expression in MCL, FASN inhibitors may hold promises for treating MCL.

Inhibition of fatty acid synthase attenuates CD44-associated signaling and reduces metastasis in colorectal cancer

Fatty acid synthase (FASN) and ATP-citrate lyase, key enzymes of de novo lipogenesis, are significantly upregulated and activated in many cancers and portend poor prognosis. Even though the role of lipogenesis in providing proliferative and survival advantages to cancer cells has been described, the impact of aberrant activation of lipogenic enzymes on cancer progression remains unknown. In this study, we found that elevated expression of FASN is associated with advanced stages of colorectal cancer (CRC) and liver metastasis, suggesting that it may play a role in progression of CRC to metastatic disease. Targeted inhibition of lipogenic enzymes abolished expression of CD44, a transmembrane protein associated with metastases in several cancers including CRC. In addition, inhibition of lipogenic enzymes and reduced expression of CD44 attenuated the activation of MET, Akt, FAK, and paxillin, which are known to regulate adhesion, migration, and invasion. These changes were consistent with an observed decrease in migration and adhesion of CRC cells in functional assays and with reorganization of actin cytoskeleton upon FASN inhibition. Despite the modest effect of FASN inhibition on tumor growth in xenografts, attenuation of lipogenesis completely abolished establishment of hepatic metastasis and formation of secondary metastasis. Together, our findings suggest that targeting de novo lipogenesis may be a potential treatment strategy for advanced CRC.

Met degradation: more than one stone to shoot a receptor down

The receptor tyrosine kinase Met and its high-affinity ligand, the hepatocyte growth factor/scatter factor (HGF/SF), are essential to embryonic development. Deregulation of their signaling is associated with tumorigenesis and metastasis, notably through receptor overexpression. It is thus important to understand the mechanisms controlling Met expression. The ligand-dependent internalization of Met and its subsequent degradation in the lysosomal compartment are well described. This process is known to attenuate downstream Met signaling pathways. Yet internalized Met takes part directly in intracellular signaling by chaperoning signaling factors in the course of its trafficking. Furthermore, recent studies describe various new degradation mechanisms of membrane-anchored Met, involving proteolytic cleavages or association with novel partners. Although all these degradations are ligand-independent, they share, to different extents, some common features with canonical HGF/SF-dependent degradation. Interestingly, activated Met variants display resistance to degradation, suggesting defective degradation is involved in tumorigenesis. Conversely, forced degradation of Met through reinduction of one or more degradation pathways is a promising therapeutic strategy.

Differentiation of breast cancer stem cells by knockdown of CD44: promising differentiation therapy

BACKGROUND

Breast cancer stem cells (BCSCs) are the source of breast tumors. Compared with other cancer cells, cancer stem cells show high resistance to both chemotherapy and radiotherapy. Targeting of BCSCs is thus a potentially promising and effective strategy for breast cancer treatment. Differentiation therapy represents one type of cancer stem-cell-targeting therapy, aimed at attacking the stemness of cancer stem cells, thus reducing their chemo- and radioresistance. In a previous study, we showed that down-regulation of CD44 sensitized BCSCs to the anti-tumor agent doxorubicin. This study aimed to determine if CD44 knockdown caused BCSCs to differentiate into breast cancer non-stem cells (non-BCSCs).

METHODS

We isolated a breast cancer cell population (CD44+CD24- cells) from primary cultures of malignant breast tumors. These cells were sorted into four sub-populations based on their expression of CD44 and CD24 surface markers. CD44 knockdown in the BCSC population was achieved using small hairpin RNA lentivirus particles. The differentiated status of CD44 knock-down BCSCs was evaluated on the basis of changes in CD44+CD24- phenotype, tumorigenesis in NOD/SCID mice, and gene expression in relation to renewal status, metastasis, and cell cycle in comparison with BCSCs and non-BCSCs.

RESULTS

Knockdown of CD44 caused BCSCs to differentiate into non-BCSCs with lower tumorigenic potential, and altered the cell cycle and expression profiles of some stem cell-related genes, making them more similar to those seen in non-BCSCs.

CONCLUSIONS

Knockdown of CD44 is an effective strategy for attacking the stemness of BCSCs, resulting in a loss of stemness and an increase in susceptibility to chemotherapy or radiation. The results of this study highlight a potential new strategy for breast cancer treatment through the targeting of BCSCs.