The amino acid transporter SLC7A5 is required for efficient growth of KRAS-mutant colorectal cancer

Barriers to Immunotherapy in Ovarian Cancer: Metabolic, Genomic, and Immune Perturbations in the Tumour Microenvironment

A lack of explicit early clinical signs and effective screening measures mean that ovarian cancer (OC) often presents as advanced, incurable disease. While conventional treatment combines maximal cytoreductive surgery and platinum-based chemotherapy, patients frequently develop chemoresistance and disease recurrence. The clinical application of immune checkpoint blockade (ICB) aims to restore anti-cancer T-cell function in the tumour microenvironment (TME). Disappointingly, even though tumour infiltrating lymphocytes are associated with superior survival in OC, ICB has offered limited therapeutic benefits. Herein, we discuss specific TME features that prevent ICB from reaching its full potential, focussing in particular on the challenges created by immune, genomic and metabolic alterations. We explore both recent and current therapeutic strategies aiming to overcome these hurdles, including the synergistic effect of combination treatments with immune-based strategies and review the status quo of current clinical trials aiming to maximise the success of immunotherapy in OC.

Targeting cancer metabolism in the era of precision oncology

One hundred years have passed since Warburg discovered alterations in cancer metabolism, more than 70 years since Sidney Farber introduced anti-folates that transformed the treatment of childhood leukaemia, and 20 years since metabolism was linked to oncogenes. However, progress in targeting cancer metabolism therapeutically in the past decade has been limited. Only a few metabolism-based drugs for cancer have been successfully developed, some of which are in - or en route to - clinical trials. Strategies for targeting the intrinsic metabolism of cancer cells often did not account for the metabolism of non-cancer stromal and immune cells, which have pivotal roles in tumour progression and maintenance. By considering immune cell metabolism and the clinical manifestations of inborn errors of metabolism, it may be possible to isolate undesirable off-tumour, on-target effects of metabolic drugs during their development. Hence, the conceptual framework for drug design must consider the metabolic vulnerabilities of non-cancer cells in the tumour immune microenvironment, as well as those of cancer cells. In this Review, we cover the recent developments, notable milestones and setbacks in targeting cancer metabolism, and discuss the way forward for the field.

Pancreatic cancer: branched-chain amino acids as putative key metabolic regulators?

Branched-chain amino acids (BCAA) are essential amino acids utilized in anabolic and catabolic metabolism. While extensively studied in obesity and diabetes, recent evidence suggests an important role for BCAA metabolism in cancer. Elevated plasma levels of BCAA are associated with an increased risk of developing pancreatic cancer, namely pancreatic ductal adenocarcinoma (PDAC), a tumor with one of the highest 1-year mortality rates. The dreadful prognosis for PDAC patients could be attributable also to the early and frequent development of cancer cachexia, a fatal host metabolic reprogramming leading to muscle and adipose wasting. We propose that BCAA dysmetabolism is a unifying component of several pathological conditions, i.e., obesity, insulin resistance, and PDAC. These conditions are mutually dependent since PDAC ranks among cancers tightly associated with obesity and insulin resistance. It is also well-established that PDAC itself can trigger insulin resistance and new-onset diabetes. However, the exact link between BCAA metabolism, development of PDAC, and tissue wasting is still unclear. Although tissue-specific intracellular and systemic metabolism of BCAA is being intensively studied, unresolved questions related to PDAC and cancer cachexia remain, namely, whether elevated circulating BCAA contribute to PDAC etiology, what is the biological background of BCAA elevation, and what is the role of adipose tissue relative to BCAA metabolism during cancer cachexia. To cover those issues, we provide our view on BCAA metabolism at the intracellular, tissue, and whole-body level, with special emphasis on different metabolic links to BCAA intermediates and the role of insulin in substrate handling.

A novel PDX modeling strategy and its application in metabolomics study for malignant pleural mesothelioma

BACKGROUND

Malignant pleural mesothelioma (MPM) is a rare and aggressive carcinoma located in pleural cavity. Due to lack of effective diagnostic biomarkers and therapeutic targets in MPM, the prognosis is extremely poor. Because of difficulties in sample extraction, and the high rate of misdiagnosis, MPM is rarely studied. Therefore, novel modeling methodology is crucially needed to facilitate MPM research.

METHODS

A novel patient-derived xenograft (PDX) modeling strategy was designed, which included preliminary screening of patients with pleural thickening using computerized tomography (CT) scan, further reviewing history of disease and imaging by a senior sonographer as well as histopathological analysis by a senior pathologist, and PDX model construction using ultrasound-guided pleural biopsy from MPM patients. Gas chromatography-mass spectrometry-based metabolomics was further utilized for investigating circulating metabolic features of the PDX models. Univariate and multivariate analysis, and pathway analysis were performed to explore the differential metabolites, enriched metabolism pathways and potential metabolic targets.

RESULTS

After screening using our strategy, 5 out of 116 patients were confirmed to be MPM, and their specimens were used for modeling. Two PDX models were established successfully. Metabolomics analysis revealed significant metabolic shifts in PDX models, such as dysregulations in amino acid metabolism, TCA cycle and glycolysis, and nucleotide metabolism.

CONCLUSIONS

To sum up, we suggested a novel modeling strategy that may facilitate specimen availability for MM research, and by applying metabolomics in this model, several metabolic features were identified, whereas future studies with large sample size are needed.

Establishment of non-small-cell lung cancer risk prediction model based on prognosis-associated ADME genes

PURPOSE

ADME genes are those involved in the absorption, distribution, metabolism, and excretion (ADME) of drugs. In the present study, a non-small-cell lung cancer (NSCLC) risk prediction model was established using prognosis-associated ADME genes, and the predictive performance of this model was evaluated and verified. In addition, multifaceted difference analysis was performed on groups with high and low risk scores.

METHODS

An NSCLC sample transcriptome and clinical data were obtained from public databases. The prognosis-associated ADME genes were obtained by univariate Cox and lasso regression analyses to build a risk model. Tumor samples were divided into high-risk and low-risk score groups according to the risk score. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses of the differentially expressed genes and the differences in the immune infiltration, mutation, and medication reactions in the two groups were studied in detail.

RESULTS

A risk prediction model was established with seven prognosis-associated ADME genes. Its good predictive ability was confirmed by studies of the model's effectiveness. Univariate and multivariate Cox regression analyses showed that the model's risk score was an independent prognostic factor for patients with NSCLC. The study also showed that the risk score closely correlated with immune infiltration, mutations, and medication reactions.

CONCLUSION

The risk prediction model established with seven ADME genes in the present study can predict the prognosis of patients with NSCLC. In addition, significant differences in immune infiltration, mutations, and therapeutic efficacy exist between the high- and low-risk score groups.

Supply and demand: Cellular nutrient uptake and exchange in cancer

Nutrient supply and demand delineate cell behavior in health and disease. Mammalian cells have developed multiple strategies to secure the necessary nutrients that fuel their metabolic needs. This is more evident upon disruption of homeostasis in conditions such as cancer, when cells display high proliferation rates in energetically challenging conditions where nutritional sources may be scarce. Here, we summarize the main routes of nutrient acquisition that fuel mammalian cells and their implications in tumorigenesis. We argue that the molecular mechanisms of nutrient acquisition not only tip the balance between nutrient supply and demand but also determine cell behavior upon nutrient limitation and energetic stress and contribute to nutrient partitioning and metabolic coordination between different cell types in inflamed or tumorigenic environments.

HIST2H2BF Potentiates the Propagation of Cancer Stem Cells via Notch Signaling to Promote Malignancy and Liver Metastasis in Colorectal Carcinoma

Background

Growing evidence demonstrates that the initiation and progression of colorectal carcinoma (CRC) is related to the presence of cancer stem cells (CSCs). However, the mechanism through which the stem cell features of CRC cells are maintained is poorly understood. In this study, we identified the oncogenic histone cluster 2 H2B family member F (HIST2H2BF) and aimed to investigate the function of upregulated HIST2H2BF expression in maintaining the stem cell features of CRC cells, which accelerate the progression of CRC.

Methods

HIST2H2BF expression was quantified using real-time polymerase chain reaction, immunohistochemistry, and western blotting. The correlation between CpG island methylation status and HIST2H2BF re-expression was assessed through bisulfite sequencing polymerase chain reaction, methylation-specific polymerase chain reaction, and 5-Aza-dC treatment. Functional assays were performed on CRC cells and mice to investigate the HIST2H2BF-induced stem cell-like and cancer properties of CRC. Using the Notch pathway inhibitor FLI-06, the regulatory effect of HIST2H2BF on downstream Notch signaling was confirmed.

Results

HIST2H2BF was highly expressed in CRC tissues and cell lines. The reactivation of HIST2H2BF in CRC stems at least in part from the hypomethylated CpG islands. CRC patients with high HIST2H2BF expression have poor survival outcomes. Functional studies have shown that HIST2H2BF promotes CSC phenotype, malignancy, and liver metastasis through the activation of Notch signaling in CRC. Blockage of the Notch pathway reduced the stem cell-like and cancer properties.

Conclusion

Our study suggests that HIST2H2BF upregulation enhances the CSC phenotype, malignancy, and liver metastasis through the activation of Notch signaling in CRC. These results identified a new perspective on the mechanism by which the stem cell features of CRC cells are maintained and highlighted the potential novel therapeutic targets for CRC.

Amino acid transporter LAT1 (SLC7A5) as a molecular target for cancer diagnosis and therapeutics

Cancer cells require a massive supply of nutrients, including sugars and amino acids-the upregulation of transporters for each nutrient contributes to meet the demand. Distinct from glucose transporters, amino acid transporters include ones whose expression is specific to cancer cells. For example, LAT1 (SLC7A5) displays protein expression mostly limited to the plasma membrane of cancer cells. The exceptions are the placental barrier and the blood-brain barrier, where immunohistochemical and mass spectrometric studies have shown LAT1 expression, although their levels are supposed to be lower than those in cancers. The expression of LAT1 has been reported in cancers from various tissue origins, where high LAT1 expression is related to the poor prognosis of patients. LAT1 is essential for cancer cell growth because the pharmacologic inhibition and knockdown/knockout of LAT1 suppress the proliferation of cancer cells and the growth of xenograft tumors. The inhibition of LAT1 suppresses protein synthesis by downregulating the mTORC1 signaling pathway and mobilizing the general amino acid control (GAAC) pathway in cancer cells. LAT1 is, thus, a candidate molecular target for the diagnosis and therapeutics of cancers. ¹⁸F-labeled 3-fluoro-l-α-methyl-tyrosine (FAMT) is used as a LAT1-specific PET probe for cancer detection due to the LAT1 specificity of α-methyl aromatic amino acids. FAMT accumulation is cancer-specific and avoids non-cancer lesions, including inflammation, confirming the cancer-specific expression of LAT1 in humans. Due to the cancer-specific nature, LAT1 can also be used for cancer-specific delivery of anti-tumor agents such as l-para-boronophenylalanine used for boron neutron capture therapy and α-emitting nuclide-labeled LAT1 substrates developed for nuclear medicine treatment. Based on the importance of LAT1 in cancer progression, high-affinity LAT1-specific inhibitors have been developed for anti-tumor drugs. JPH203 (KYT0353) is such a compound designed based on the structure-activity relationship of LAT1 ligands. It is one of the highest-affinity inhibitors with less affecting other transporters. It suppresses tumor growth in vivo without significant toxicity in preclinical studies at doses enough to suppress tumor growth. In the phase-I clinical trial, JPH203 appeared to provide promising activity. Because the mechanisms of action of LAT1 inhibitors are novel, with or without combination with other anti-tumor drugs, they could contribute to the treatment of cancers that do not respond to current therapy. The LAT1-specific PET probe could also be used as companion diagnostics of the LAT1-targeting therapies to select patients to whom therapeutic benefits could be expected. Recently, the cryo-EM structure of LAT1 has been solved, which would facilitate the understanding of the mechanisms of the dynamic interaction of ligands and the binding site, and further designing new compounds with higher activity.

Cellular feedback dynamics and multilevel regulation driven by the hippo pathway

The Hippo pathway is a dynamic cellular signalling nexus that regulates differentiation and controls cell proliferation and death. If the Hippo pathway is not precisely regulated, the functionality of the upstream kinase module is impaired, which increases nuclear localisation and activity of the central effectors, the transcriptional co-regulators YAP and TAZ. Pathological YAP and TAZ hyperactivity consequently cause cancer, fibrosis and developmental defects. The Hippo pathway controls an array of fundamental cellular processes, including adhesion, migration, mitosis, polarity and secretion of a range of biologically active components. Recent studies highlight that spatio-temporal regulation of Hippo pathway components are central to precisely controlling its context-dependent dynamic activity. Several levels of feedback are integrated into the Hippo pathway, which is further synergized with interactors outside of the pathway that directly regulate specific Hippo pathway components. Likewise, Hippo core kinases also ‘moonlight’ by phosphorylating multiple substrates beyond the Hippo pathway and thereby integrates further flexibility and robustness in the cellular decision-making process. This topic is still in its infancy but promises to reveal new fundamental insights into the cellular regulation of this therapeutically important pathway. We here highlight recent advances emphasising feedback dynamics and multilevel regulation of the Hippo pathway with a focus on mitosis and cell migration, as well as discuss potential productive future research avenues that might reveal novel insights into the overall dynamics of the pathway.

Metabolic Alterations in Preneoplastic Development Revealed by Untargeted Metabolomic Analysis

Metabolic rewiring is a critical hallmark of tumorigenesis and is essential for the development of cancer. Although many key features of metabolic alteration that are crucial for tumor cell survival, proliferation and progression have been identified, these are obtained from studies with established tumors and cancer cell lines. However, information on the essential metabolic changes that occur during pre-neoplastic cell (PNC) development that enables its progression to full blown tumor is still lacking. Here, we present an untargeted metabolomics analysis of human oncogene HRASG12V induced PNC development, using a transgenic inducible zebrafish larval skin development model. By comparison with normal sibling controls, we identified six metabolic pathways that are significantly altered during PNC development in the skin. Amongst these altered pathways are pyrimidine, purine and amino acid metabolism that are common to the cancer metabolic changes that support rapid cell proliferation and growth. Our data also suggest alterations in post transcriptional modification of RNAs that might play a role in PNC development. Our study provides a proof of principle work flow for identifying metabolic alterations during PNC development driven by an oncogenic mutation. In the future, this approach could be combined with transcriptomic or proteomic approaches to establish the detailed interaction between signaling networks and cellular metabolic pathways that occur at the onset of tumor progression.

Combination of Plasma-Based Metabolomics and Machine Learning Algorithm Provides a Novel Diagnostic Strategy for Malignant Mesothelioma

BACKGROUND

Malignant mesothelioma (MM) is an aggressive and incurable carcinoma that is primarily caused by asbestos exposure. However, the current diagnostic tool for MM is still under-developed. Therefore, the aim of this study is to explore the diagnostic significance of a strategy that combined plasma-based metabolomics with machine learning algorithms for MM.

METHODS

Plasma samples collected from 25 MM patients and 32 healthy controls (HCs) were randomly divided into train set and test set, after which analyzation was performed by liquid chromatography-mass spectrometry-based metabolomics. Differential metabolites were screened out from the samples of the train set. Subsequently, metabolite-based diagnostic models, including receiver operating characteristic (ROC) curves and Random Forest model (RF), were established, and their prediction accuracies were calculated for the test set samples.

RESULTS

Twenty differential plasma metabolites were annotated in the train set; 10 of these metabolites were validated in the test set. The seven most prevalent diagnostic metabolites were taurocholic acid), 0.7142 (uracil), 0.7142 (biliverdin), 0.8571 (histidine), 0.5000 (tauroursodeoxycholic acid), 0.8571 (pyrroline hydroxycarboxylic acid), and 0.7857 (phenylalanine). Furthermore, RF based on 20 annotated metabolites showed a prediction accuracy of 0.9286, and its optimized version achieved 1.0000 in the test set. Moreover, the comparison between the samples of peritoneal MM (n = 8) and pleural MM (n = 17) illustrated a significant increase in levels of taurocholic acid and tauroursodeoxycholic acid, as well as an evident decrease in biliverdin.

CONCLUSIONS

Our results revealed the potential diagnostic value of plasma-based metabolomics combined with machine learning for MM. Further research with large sample size is worthy conducting. Moreover, our data demonstrated dysregulated metabolism pathways in MM, which aids in better understanding of molecular mechanisms related to the initiation and development of MM.

Neutrophil Extracellular Traps in Colorectal Cancer Progression and Metastasis

Neutrophils form sticky web-like structures known as neutrophil extracellular traps (NETs) as part of innate immune response. NETs are decondensed extracellular chromatin filaments comprising nuclear and cytoplasmic proteins. NETs have been implicated in many gastrointestinal diseases including colorectal cancer (CRC). However, the regulatory mechanisms of NET formation and potential pharmacological inhibitors in the context of CRC have not been thoroughly discussed. In this review, we intend to highlight roles of NETs in CRC progression and metastasis as well as the potential of targeting NETs during colon cancer therapy.

Metabolic Reprogramming: A Friend or Foe to Cancer Therapy?

Drug resistance is a major cause of cancer treatment failure, effectively driven by processes that promote escape from therapy-induced cell death. The mechanisms driving evasion of apoptosis have been widely studied across multiple cancer types, and have facilitated new and exciting therapeutic discoveries with the potential to improve cancer patient care. However, an increasing understanding of the crosstalk between cancer hallmarks has highlighted the complexity of the mechanisms of drug resistance, co-opting pathways outside of the canonical "cell death" machinery to facilitate cell survival in the face of cytotoxic stress. Rewiring of cellular metabolism is vital to drive and support increased proliferative demands in cancer cells, and recent discoveries in the field of cancer metabolism have uncovered a novel role for these programs in facilitating drug resistance. As a key organelle in both metabolic and apoptotic homeostasis, the mitochondria are at the forefront of these mechanisms of resistance, coordinating crosstalk in the event of cellular stress, and promoting cellular survival. Importantly, the appreciation of this role metabolism plays in the cytotoxic response to therapy, and the ability to profile metabolic adaptions in response to treatment, has encouraged new avenues of investigation into the potential of exploiting metabolic addictions to improve therapeutic efficacy and overcome drug resistance in cancer. Here, we review the role cancer metabolism can play in mediating drug resistance, and the exciting opportunities presented by imposed metabolic vulnerabilities.

Amino acid transporters as emerging therapeutic targets in cancer

Amino acids are indispensable nutrients for both normal and cancer cells. Cancer cells are unable to synthesize essential amino acids as well as some non‐essential amino acids adequately to support rapid proliferation, and must take up amino acids from the surroundings. To meet the increased demand for the amino acid needed for proliferation, high levels of amino acid transporters are expressed on the surface of cancer cells. Cancer cells utilize amino acids to synthesize proteins and nucleotides, as well as to obtain energy. In addition, amino acids are known to play pathological roles in cancer cells. Interestingly, breast cancer cells limit the use of amino acids for cell proliferation based on amino acid availability, which depends on estrogen receptor status. Here, we present a summarized literature review of novel amino acid functions in cancer cells. This review organizes the available knowledge on 2 amino acid transporters, SLC7A5 and SLC7A11, which are considered essential for breast cancer cell growth in a cell‐dependent manner. In particular, we propose the glutamine recycling model to clarify the mechanism underlying aberrant SLC7A5 activation. Finally, we overview the pathological significances of SLC7A5 and SLC7A11 in cancer tissues.

Oncogenic transformation of NIH/3T3 cells by the overexpression of L-type amino acid transporter 1, a promising anti-cancer target

L-type amino acid transporter 1 (LAT1)/SLC7A5 is the first identified CD98 light chain disulfide linked to the CD98 heavy chain (CD98hc/SLC3A2). LAT1 transports large neutral amino acids, including leucine, which activates mTOR, and is highly expressed in human cancers. We investigated the oncogenicity of human LAT1 introduced to NIH/3T3 cells by retrovirus infection. NIH/3T3 cell lines stably expressing human native (164C) or mutant (164S) LAT1 (naLAT1/3T3 or muLAT1/3T3, respectively) were established. We confirmed that endogenous mouse CD98hc forms a disulfide bond with exogenous human LAT1 in naLAT1/3T3, but not in muLAT1/3T3. Endogenous mouse CD98hc mRNA increased in both naNIH/3T3 and muLAT1/3T3, and a similar amount of exogenous human LAT1 protein was detected in both cell lines. Furthermore, naLAT1/3T3 and muLAT1/3T3 cell lines were evaluated for cell growth-related phenotypes (phosphorylation of ERK, cell-cycle progression) and cell malignancy-related phenotypes (anchorage-independent cell growth, tumor formation in nude mice). naLAT1/3T3 had stronger growth- and malignancy- related phenotypes than NIH/3T3 and muLAT1/3T3, suggesting the oncogenicity of native LAT1 through its interaction with CD98hc. Anti-LAT1 monoclonal antibodies significantly inhibited in vitro cell proliferation and in vivo tumor growth of naLAT1/3T3 cells in nude mice, demonstrating LAT1 to be a promising anti-cancer target.

Amino Acid Depletion Therapies: Starving Cancer Cells to Death

Targeting tumor cell metabolism is an attractive form of therapy, as it may enhance treatment response in therapy resistant cancers as well as mitigate treatment-related toxicities by reducing the need for genotoxic agents. To meet their increased demand for biomass accumulation and energy production and to maintain redox homeostasis, tumor cells undergo profound changes in their metabolism. In addition to the diversion of glucose metabolism, this is achieved by upregulation of amino acid metabolism. Interfering with amino acid availability can be selectively lethal to tumor cells and has proven to be a cancer specific Achilles' heel. Here we review the biology behind such cancer specific amino acid dependencies and discuss how these vulnerabilities can be exploited to improve cancer therapies.

Immunometabolism of Tissue-Resident Macrophages - An Appraisal of the Current Knowledge and Cutting-Edge Methods and Technologies

Tissue-resident macrophages exist in unique environments, or niches, that inform their identity and function. There is an emerging body of literature suggesting that the qualities of this environment, such as the types of cells and debris they eat, the intercellular interactions they form, and the length of time spent in residence, collectively what we call habitare, directly inform their metabolic state. In turn, a tissue-resident macrophage’s metabolic state can inform their function, including whether they resolve inflammation and protect the host from excessive perturbations of homeostasis. In this review, we summarize recent work that seeks to understand the metabolic requirements for tissue-resident macrophage identity and maintenance, for how they respond to inflammatory challenges, and for how they perform homeostatic functions or resolve inflammatory insults. We end with a discussion of the emerging technologies that are enabling, or will enable, in situ study of tissue-resident macrophage metabolism.

Transporters at the Interface between Cytosolic and Mitochondrial Amino Acid Metabolism

Mitochondria are central organelles that coordinate a vast array of metabolic and biologic functions important for cellular health. Amino acids are intricately linked to the bioenergetic, biosynthetic, and homeostatic function of the mitochondrion and require specific transporters to facilitate their import, export, and exchange across the inner mitochondrial membrane. Here we review key cellular metabolic outputs of eukaryotic mitochondrial amino acid metabolism and discuss both known and unknown transporters involved. Furthermore, we discuss how utilization of compartmentalized amino acid metabolism functions in disease and physiological contexts. We examine how improved methods to study mitochondrial metabolism, define organelle metabolite composition, and visualize cellular gradients allow for a more comprehensive understanding of how transporters facilitate compartmentalized metabolism.