Correlation of L-type amino acid transporter 1 and CD98 expression with triple negative breast cancer prognosis

Targeting LAT1 with JPH203 to reduce TNBC proliferation and reshape suppressive immune microenvironment by blocking essential amino acid uptake

The competitive uptake of essential amino acids (EAAs) by breast cancer cells is associated with poor patient prognosis and the development of an immunosuppressive tumor microenvironment. L-type amino acid transporters, LAT1 (SLC7 A5) and LAT2 (SLC7 A8) are major mediators of EAAs transmembrane uptake and are overexpressed in some tumor tissues. However, the distribution and functional roles of these transporters across breast cancer subtypes have not been fully elucidated. This study aims to investigate the therapeutic potential of targeting EAA transporters, particularly LAT1, in triple-negative breast cancer (TNBC) and its role in remodeling the tumor immune microenvironment. The distribution of EAA transporters across breast cancer subtypes was analyzed using multi-omics data. The effects of LAT1 targeting on TNBC cell proliferation and EAA uptake were evaluated using SLC7 A5 knockout and LAT1 inhibitors in vitro experiments. A 4T1-BALB/c tumor-bearing mouse model with normal immune function was constructed to investigate the effects of LAT1 targeting on tumor growth and immune microenvironment remodeling in vivo. TNBC demonstrated a strong dependence on LAT1-mediated EAAs uptake. Targeting LAT1 limited the exogenous supply of EAAs, leading to amino acid starvation, cell cycle arrest, and increased apoptosis in TNBC cells. The in vivo experiments, using a 4T1-BALB/c tumor-bearing mouse model, showed that LAT1 targeting inhibited tumor growth and remodeled the immunosuppressive tumor microenvironment. Targeting LAT1 improved PD-L1-associated immune suppression and improved the efficacy of PD-1 antibody treatment, producing synergistic anti-tumor effects. This study highlights the therapeutic potential of targeting LAT1 in TNBC, particularly in remodeling the tumor immune microenvironment. The findings provide a promising strategy for immune combination therapy in TNBC.

The R-RAS2 GTPase is a signaling hub in triple-negative breast cancer cell metabolism and metastatic behavior

BACKGROUND

Recent research from our group has shown that the overexpression of the wild-type RAS-family GTPase RRAS2 drives the onset of triple-negative breast cancer (TNBC) in mice following one or more pregnancies. This phenomenon mirrors human TNBC, where RRAS2 is overexpressed in approximately 75% of cases, particularly in tumors associated with the postpartum period. These findings underscore the relevance of R-RAS2 in TNBC development and progression.

METHODS

We conducted RNA sequencing on tumors derived from conditional knock-in mice overexpressing human wild-type RRAS2 to identify the somatic mutation landscape associated with TNBC development in these mice. Additionally, we developed a TNBC cell line from RRAS2-overexpressing mice, enabling loss-of-function studies to investigate the role of R-RAS2 in various pathobiological parameters of TNBC cells, including cell migration, invasiveness, metabolic activity, and metastatic spread. Furthermore, proteomic analysis of a freshly isolated tumor identified plasma membrane receptors interacting with R-RAS2.

RESULTS

Our findings demonstrate that TNBC driven by RRAS2 overexpression exhibits a pattern of somatic mutations similar to those observed in human breast cancer, particularly in genes involved in stemness, extracellular matrix interactions, and actin cytoskeleton regulation. Proteomic analysis revealed that wild-type R-RAS2 interacts with 245 membrane-associated proteins, including key solute carriers involved in cell metabolism (CD98/LAT1, GLUT1, and basigin), adhesion and matrix interaction proteins (CD44, EpCAM, MCAM, ICAM1, integrin-α6, and integrin-β1), and stem cell markers (β1-catenin, α1-catenin, PTK7, and CD44). We show that R-RAS2 regulates CD98/LAT1 transporter-mediated mTOR pathway activation and mediates CD44-dependent cancer cell migration and invasion, thus providing a mechanism by which R-RAS2 promotes breast cancer cell metastasis.

CONCLUSIONS

R-RAS2 associates with CD44, CD98/LAT1, and other plasma membrane receptors to regulate metabolic activity, actin cytoskeleton reorganization, cell migration, invasion, and distant metastasis formation in TNBC. These findings establish R-RAS2 as a central driver of TNBC malignancy and highlight its potential as a promising therapeutic target, particularly in aggressive, postpartum-associated breast cancers.

Exploring tumor microenvironment interactions and apoptosis pathways in NSCLC through spatial transcriptomics and machine learning

BACKGROUND

The most common type of lung cancer is non-small cell lung cancer (NSCLC), accounting for 85% of all cases. Programmed cell death (PCD), an important regulatory mechanism for cell survival and homeostasis, has become increasingly prominent in cancer research in recent years. As such, exploring the role of PCD in NSCLC may help uncover new mechanisms for therapeutic targets.

METHODS

We utilized the GEO database and TCGA NSCLC gene data to screen for co-expressed genes. To delve deeper, single-cell sequencing combined with spatial transcriptomics was employed to study the intrinsic mechanisms of programmed cell death in cells and their interaction with the tumor microenvironment. Furthermore, Mendelian randomization was applied to screen for causally related genes. Prognostic models were constructed using various machine learning algorithms, and multi-cohort multi-omics analyses were conducted to screen for genes. In vitro experiments were then carried out to reveal the biological functions of the genes and their relationship with apoptosis.

RESULTS

Cells with high programmed cell death activity primarily activate pathways related to apoptosis, cell migration, and hypoxia, while also exhibiting strong interactions with smooth muscle cells in the tumor microenvironment. Based on a set of programmed cell death genes, the prognostic model NSCLCPCD demonstrates strong predictive capabilities. Moreover, laboratory experiments confirm that SLC7A5 promotes the proliferation of NSCLC cells, and the knockout of SLC7A5 significantly increases tumor cell apoptosis.

CONCLUSIONS

Our data indicate that programmed cell death is predominantly associated with pathways related to apoptosis, tumor metastasis, and hypoxia. Additionally, it suggests that SLC7A5 is a significant risk indicator for the prognosis of non-small cell lung cancer (NSCLC) and may serve as an effective target for enhancing apoptosis in NSCLC tumor cells.

A Bioinspired Photosensitizer Performs Tumor Thermoresistance Reversion to Optimize the Atraumatic Mild-Hyperthermia Photothermal Therapy for Breast Cancer

Mild-hyperthermia photothermal therapy (mPTT) has therapeutic potential with minimized damage to normal tissues. However, the poorly vascularized tumor area severely hampers the penetration of photothermal agents (PTAs), resulting in their heterogeneous distribution and the subsequent heterogeneous local temperature during mPTT. The presence of regions below the therapeutic 42 °C threshold can lead to incomplete tumor ablation and potential recurrence. Additionally, tumor anti-apoptosis and cytoprotection pathways, particularly activated thermoresistance, can nullify mild hyperthermia-induced tumor damage. Therefore, a bioinspired photosensitizer decorated with leucine to form biomimetic nanoclusters (CP-PLeu nanoparticles (NPs)) aimed at achieving rapid and homogeneous accumulation in tumors, is introduced. Moreover, CP-PLeu exhibits photodynamic effects that reverse tumor thermoresistance and physiological repair mechanisms, thereby inhibiting tumor resistance to hyperthermia. With the addition of NIR-II laser irradiation, CP-PLeu optimizes the therapeutic efficacy of mPTT and contributes to a minimally invasive therapeutic process for breast cancer. This therapeutic strategy, utilizing a biomimetic photosensitizer for homogeneous distribution of therapeutic temperature and photoactivated reversal of tumor thermoresistance, successfully achieves efficient breast tumor inhibition through an atraumatic mPTT process.

Prognostic value of large amino acid transporter type 1 (LAT1) expression in pulmonary adenocarcinoma: A tissue microarray study

BACKGROUND

Large amino acid transporter type 1 (LAT1) provides cancer cells with essential amino acids for both protein synthesis and cell growth and may predict patient prognosis. Additionally, LAT1 inhibition can be a therapeutic target. This study aimed to examine the prognostic significance of LAT1 expression in lung cancer, paying special attention to adenocarcinoma subtypes.

METHODS

Tissue microarrays (TMA) of 1,560 total cores obtained from surgically resected lung cancer specimens between 1995 and 2008 at our hospital were used. Overall, 795 cases of adenocarcinoma were identified, and 717 underwent further evaluation. Immunohistochemical staining of whole slides and TMA cores were assessed to set H-score cutoff value.. Immunohistochemical expression of LAT1 was examined based on the subtypes of adenocarcinoma. Statistical analyses explored the prognostic significance of LAT1.

RESULTS

Adenocarcinoma accounted for 71.8% of all cases (n = 795), and 216 cases (27.1%) expressed LAT1. The 795 cases were categorized into five subtypes: lepidic (n = 29, 3.6%), papillary (n = 601, 75.6%), acinar (n = 58, 7.3%), and solid (n = 9, 1.1%); 717 of the 795 cases were further assessed according to the exclusion criteria. The LAT1-positive ratio increased as the architectural grade increased. Notably, in papillary adenocarcinoma, the LAT1-positive group had significantly lower overall survival compared to the negative group (10-year survival: 45.6% vs. 60.8%, p < 0.001).

CONCLUSION

LAT1 expression was higher in high-grade subtypes of pulmonary adenocarcinoma. Moreover, LAT1 expression is useful for predicting prognosis, particularly in papillary adenocarcinoma, facilitating prognostic stratification of papillary adenocarcinoma.

ALYREF-JunD-SLC7A5 axis promotes pancreatic ductal adenocarcinoma progression through epitranscriptome-metabolism reprogramming and immune evasion

Pancreatic ductal adenocarcinoma (PDAC) is a kind of tumor lacking nutrients due to its poor vascularity and desmoplasia. Recent studies have shown that cancer cells might achieve growth advantage through epitranscriptome reprogramming. However, the role of m5C in PDAC was not fully understood. We found that Aly/REF export factor (ALYREF), a reader of m5C modification, was overexpressed in PDAC, and associated with bad prognosis. In addition, the ALYREF expression was negatively related to CD8+ T cells infiltration in clinical samples. ALYREF knockdown decreased tumor growth in vivo partly dependent of immunity. ALYREF silencing decreased SLC7A5 expression and subsequently inactivated mTORC1 pathway, resulting in decreased tumor proliferation. Mechanically, ALYREF specifically recognized m5C sites in JunD mRNA, maintained the stabilization of JunD mRNA and subsequently upregulated transcription of SLC7A5. Since SLC7A5 was a key transporter of large neutral amino acids (LNAAs), overexpression of SLC7A5 on tumor cells depleted amino acid in microenvironment and restricted CD8+ T cells function. Moreover, ALYREF-JunD-SLC7A5 axis was overexpressed and negatively related with survival through TMA assays. In conclusion, this research revealed the relationship between m5C modification, amino acid transportation and immune microenvironment. ALYREF might be a novel target for PDAC metabolic vulnerability and immune surveillance.

m6A modification mediates SLC3A2/SLC7A5 translation in 3-methylcholanthrene-induced uroepithelial transformation

3-Methylcholanthracene (3-MC) is one of the most carcinogenic polycyclic aromatic hydrocarbons (PAHs). Long-term exposure to PAHs has been thought of as an important factor in urothelial tumorigenesis. N6-methyladenosine (m6A) exists widely in eukaryotic organisms and regulates the expression level of specific genes by regulating mRNA stability, translation efficiency, and nuclear export efficiency. Currently, the potential molecular mechanisms that regulate m6A modification for 3-MC carcinogenesis remain unclear. Here, we profiled mRNA, m6A, translation and protein level using "-omics" methodologies, including transcriptomes, m6A profile, translatomes, and proteomics in 3-MC-transformed urothelial cells and control cells. The key molecules SLC3A2/SLC7A5 were screened and identified in 3-MC-induced uroepithelial transformation. Moreover, SLC7A5/SLC3A2 promoted uroepithelial cells malignant phenotype in vitro and in vivo. Mechanically, METTL3 and ALKBH5 mediated m6A modification of SLC3A2/SLC7A5 mRNA in 3-MC-induced uroepithelial transformation by upregulating the translation of SLC3A2/SLC7A5. Furthermore, programmable m6A modification of SLC3A2/SLC7A5 mRNA affected the expression of its proteins. Taken together, our results revealed that the m6A modification-mediated SLC3A2/SLC7A5 translation promoted 3-MC-induced uroepithelial transformation, suggesting that targeting m6A modification of SLC3A2/SLC7A5 may be a potential therapeutic strategy for bladder cancer related to PAHs.

Hsa_circ_0050900 affects ferroptosis in intrahepatic cholangiocarcinoma cells by targeting hsa‑miR-605‑3p to regulate SLC3A2

Intrahepatic cholangiocarcinoma (ICC) is a highly lethal hepatobiliary tumor with high aggressiveness. The role of circular RNA (circRNA) in ICC remains to be explored. The present study aimed to investigate whether hsa_circ_0050900 affected ferroptosis in ICC cells by regulating hsa-microRNA (miR)-605-3p/solute carrier family 3 member 2 (SLC3A2). Human ICC cells were cultured and hsa_circ_0050900 expression was evaluated by reverse transcription-quantitative PCR. hsa_circ_0050900 was knocked down and ferroptosis inhibitor ferrostatin-1 was added to HuCCT-1 cells. Following knockdown or overexpression of hsa-miR-605-3p, Fe2+, reactive oxygen species (ROS), glutathione peroxidase 4 and SLC3A2 levels were assessed using iron and ROS assay kit or RT-qPCR and western blotting, respectively. Cell function experiments were performed to examine proliferation and migration abilities. Dual-luciferase reporter gene and argonaute2-RNA immunoprecipitation assay verified the relationship among hsa_circ_0050900, hsa-miR-605-3p, and SLC3A2. hsa_circ_0050900 was derived from actinin alpha 4 gene and was elevated in ICC cells. Among HuCCT-1, QBC-939, HCCC-9810, and RBE cell lines, the highest expression was in HuCCT-1 cells. Inhibition of hsa_circ_0050900 inhibited proliferation and migration by facilitating ICC cell ferroptosis. hsa-miR-605-3p expression was elevated after knocking down hsa_circ_0050900 and hsa-miR-605-3p was negatively regulated by hsa_circ_0050900. In addition, hsa-miR-605-3p targeted SLC3A2. Overexpression of hsa-miR-605-3p regulated SLC3A2 to promote ICC cell ferroptosis and inhibit proliferation and migration. Taken together, knockdown of hsa_circ_0050900 inhibited SLC3A2 expression via sponging hsa-miR-605-3p to promote ICC cell ferroptosis, and finally suppressed proliferation and migration. The present study suggested that hsa_circ_0050900 was a potential therapeutic target for ICC.

L-Type Amino Acid Transporter 1 (LAT1) Promotes PMA-Induced Cell Migration through mTORC2 Activation at the Lysosome

The mTOR signaling pathway integrates signaling inputs from nutrients, including glucose and amino acids, which are precisely regulated by transporters depending on nutrient levels. The L-type amino acid transporter 1 (LAT1) affects the activity of mTORC1 through upstream regulators that sense intracellular amino acid levels. While mTORC1 activation by LAT1 has been thoroughly investigated in cultured cells, the effects of LAT1 expression on the activity of mTORC2 has scarcely been studied. Here, we provide evidence that LAT1 recruits and activates mTORC2 on the lysosome for PMA-induced cell migration. LAT1 is translocated to the lysosomes in cells treated with PMA in a dose- and time-dependent manner. Lysosomal LAT1 interacted with mTORC2 through a direct interaction with Rictor, leading to the lysosomal localization of mTORC2. Furthermore, the depletion of LAT1 reduced PMA-induced cell migration in a wound-healing assay. Consistent with these results, the LAT1 N3KR mutant, which is defective in PMA-induced endocytosis and lysosomal localization, did not induce mTORC2 recruitment to the lysosome, with the activation of mTORC2 determined via Akt phosphorylation or the LAT1-mediated promotion of cell migration. Taken together, lysosomal LAT1 recruits and activates the mTORC2 complex and downstream Akt for PMA-mediated cell migration. These results provide insights into the development of therapeutic drugs targeting the LAT1 amino acid transporter to block metastasis, as well as disease progression in various types of cancer.

Evaluation of LAT1 Expression in Patients With Lung Cancer and Mediastinal Tumors: 18F-FBPA PET Study With Immunohistological Comparison

PURPOSE OF THE REPORT

L-type amino acid transporter-1 (LAT1) is a tumor-specific transporter expressed in various tumor types, with minimal expression in normal organs. We previously demonstrated 18F-fluoro-borono-phenylalanine (18F-FBPA) as a selective PET probe for LAT1 in a preclinical study. Herein, we evaluated LAT1 expression in preoperative patients with lung or mediastinal tumors using 18F-FBPA PET and immunofluorescence staining.

PATIENTS AND METHODS

The study population included patients with histopathological diagnosis (n = 55): primary lung cancers (n = 21), lung metastases (n = 6), mediastinal tumors (n = 15), and benign lesion (n = 13). PET scanning was performed 1 hour after the injection of 18F-FBPA (232 ± 32 MBq). Immunofluorescence staining was performed on the resected tumor sections using LAT1 antibody. LAT1 staining was graded on a 4-grade scale and compared with the SUVmax on 18F-FBPA PET.

RESULTS

A positive correlation was observed between the SUVmax of 18F-FBPA PET and LAT1 expression by immunofluorescence staining (r = 0.611, P < 0.001). The SUVmax of 18F-FBPA was 3.92 ± 1.46 in grade 3, 3.21 ± 1.82 in grade 2, 2.33 ± 0.93 in grade 1, and 1.50 ± 0.39 in grade 0 of LAT1 expression. Although 18F-FBPA PET showed variable uptake in lung cancers and mediastinal tumors, benign lesions showed significantly lower SUVmax than those in malignant lesions (P < 0.01).

CONCLUSIONS

Uptake on 18F-FBPA PET reflected the expression level of LAT1 in lung and mediastinal tumors. It was suggested that 18F-FBPA PET can be used for the precise characterization of the tumor in pretreatment evaluation.

Inhibition of cancer-type amino acid transporter LAT1 suppresses B16-F10 melanoma metastasis in mouse models

Metastasis is the leading cause of mortality in cancer patients. L-type amino acid transporter 1 (LAT1, SLC7A5) is a Na+-independent neutral amino acid transporter highly expressed in various cancers to support their growth. Although high LAT1 expression is closely associated with cancer metastasis, its role in this process remains unclear. This study aimed to investigate the effect of LAT1 inhibition on cancer metastasis using B16-F10 melanoma mouse models. Our results demonstrated that nanvuranlat (JPH203), a high-affinity LAT1-selective inhibitor, suppressed B16-F10 cell proliferation, migration, and invasion. Similarly, LAT1 knockdown reduced cell proliferation, migration, and invasion. LAT1 inhibitors and LAT1 knockdown diminished B16-F10 lung metastasis in a lung metastasis model. Furthermore, nanvuranlat and LAT1 knockdown suppressed lung, spleen, and lymph node metastasis in an orthotopic metastasis model. We discovered that the LAT1 inhibitor reduced the cell surface expression of integrin αvβ3. Our findings revealed that the downregulation of the mTOR signaling pathway, induced by LAT1 inhibitors, decreased the expression of integrin αvβ3, contributing to the suppression of metastasis. These results highlight the critical role of LAT1 in cancer metastasis and suggest that LAT1 inhibition may serve as a potential target for anti-metastasis cancer therapy.

Omics Technologies Improving Breast Cancer Research and Diagnostics

Breast cancer (BC) has yielded approximately 2.26 million new cases and has caused nearly 685,000 deaths worldwide in the last two years, making it the most common diagnosed cancer type in the world. BC is an intricate ecosystem formed by both the tumor microenvironment and malignant cells, and its heterogeneity impacts the response to treatment. Biomedical research has entered the era of massive omics data thanks to the high-throughput sequencing revolution, quick progress and widespread adoption. These technologies-liquid biopsy, transcriptomics, epigenomics, proteomics, metabolomics, pharmaco-omics and artificial intelligence imaging-could help researchers and clinicians to better understand the formation and evolution of BC. This review focuses on the findings of recent multi-omics-based research that has been applied to BC research, with an introduction to every omics technique and their applications for the different BC phenotypes, biomarkers, target therapies, diagnosis, treatment and prognosis, to provide a comprehensive overview of the possibilities of BC research.

An amino acid transporter subunit as an antibody-drug conjugate target in colorectal cancer

BACKGROUND

Advanced colorectal cancer (CRC) is difficult to treat. For that reason, the development of novel therapeutics is necessary. Here we describe a potentially actionable plasma membrane target, the amino acid transporter protein subunit CD98hc.

METHODS

Western blot and immunohistochemical analyses of CD98hc protein expression were carried out on paired normal and tumoral tissues from patients with CRC. Immunofluorescence and western studies were used to characterize the action of a DM1-based CD98hc-directed antibody-drug conjugate (ADC). MTT and Annexin V studies were performed to evaluate the effect of the anti-CD98hc-ADC on cell proliferation and apoptosis. CRISPR/Cas9 and shRNA were used to explore the specificity of the ADC. In vitro analyses of the antitumoral activity of the anti-CD98hc-ADC on 3D patient-derived normal as well as tumoral organoids were also carried out. Xenografted CRC cells and a PDX were used to analyze the antitumoral properties of the anti-CD98hc-ADC.

RESULTS

Genomic as well proteomic analyses of paired normal and tumoral samples showed that CD98hc expression was significantly higher in tumoral tissues as compared to levels of CD98hc present in the normal colonic tissue. In human CRC cell lines, an ADC that recognized the CD98hc ectodomain, reached the lysosomes and exerted potent antitumoral activity. The specificity of the CD98hc-directed ADC was demonstrated using CRC cells in which CD98hc was decreased by shRNA or deleted using CRISPR/Cas9. Studies in patient-derived organoids verified the antitumoral action of the anti-CD98hc-ADC, which largely spared normal tissue-derived colon organoids. In vivo studies using xenografted CRC cells or patient-derived xenografts confirmed the antitumoral activity of the anti-CD98hc-ADC.

CONCLUSIONS

The studies herewith reported indicate that CD98hc may represent a novel ADC target that, upon well-designed clinical trials, could be used to increase the therapeutic armamentarium against CRC.

LAT1 expression influences Paneth cell number and tumor development in ApcMin/+ mice

BACKGROUND

Amino acid transporters play an important role in supplying nutrition to cells and are associated with cell proliferation. L-type amino acid transporter 1 (LAT1) is highly expressed in many types of cancers and promotes tumor growth; however, how LAT1 affects tumor development is not fully understood.

METHODS

To investigate the role of LAT1 in intestinal tumorigenesis, mice carrying LAT1 floxed alleles that also expressed Cre recombinase from the promoter of gene encoding Villin were crossed to an ApcMin/+ background (LAT1fl/fl; vil-cre; ApcMin/+), which were subject to analysis; organoids derived from those mice were also analyzed.

RESULTS

This study showed that LAT1 was constitutively expressed in normal crypt base cells, and its conditional deletion in the intestinal epithelium resulted in fewer Paneth cells. LAT1 deletion reduced tumor size and number in the small intestine of ApcMin/+ mice. Organoids derived from LAT1-deleted ApcMin/+ intestinal crypts displayed fewer spherical organoids with reduced Wnt/β-catenin target gene expression, suggesting a low tumor-initiation capacity. Wnt3 expression was decreased in the absence of LAT1 in the intestinal epithelium, suggesting that loss of Paneth cells due to LAT1 deficiency reduced the risk of tumor initiation by decreasing Wnt3 production.

CONCLUSIONS

LAT1 affects intestinal tumor development in a cell-extrinsic manner through reduced Wnt3 expression in Paneth cells. Our findings may partly explain how nutrient availability can affect the risk of tumor development in the intestines.

Neuropilin-1 Knockout and Rescue Confirms Its Role to Promote Metastasis in MDA-MB-231 Breast Cancer Cells

Breast cancer (BC) metastasis remains a leading cause of female mortality. Neuropilin-1 (NRP-1) is a glycoprotein receptor that plays ligand-dependent roles in BC. Clinical studies indicate its correlation with metastatic disease; however, its functional role in BC metastasis remains uncertain. CRISPR-Cas9 was used to knockout the NRP-1 gene in MDA-MB-231 BC cells, and the effects on metastasis were determined using an orthotopic mouse engraftment model. NRP-1 expression in knockout cells was rescued using a recombinant cDNA with a silent mutation in the sgRNA target-adjacent PAM sequence. Differentially expressed genes between NRP-1 knockout and control cells were determined using whole-transcriptome sequencing and validated using real-time PCR. NRP-1KO cells showed a pronounced reduction in the metastasis to the lungs. KEGG pathway analysis of the transcriptome data revealed that PI3K and ECM receptor interactions were among the top altered pathways in the NRP-1KO cells. In addition, reduction in metastasis enhancers proteins, Integrin-β3 and Tenascin-C, and genes CCL20 and FN1 and upregulation of metastasis suppressor genes, ACVRL and GPX3 in NRP-1KO were detected. These findings provide evidence for a functional role for NRP-1 in BC metastasis, supporting further exploration of NRP-1 and the identified genes as targets in treating metastatic BC.

Glutamine metabolism in breast cancer and possible therapeutic targets

Cancer is characterized by metabolic reprogramming, which is a hot topic in tumor treatment research. Cancer cells alter metabolic pathways to promote their growth, and the common purpose of these altered metabolic pathways is to adapt the metabolic state to the uncontrolled proliferation of cancer cells. Most cancer cells in a state of nonhypoxia will increase the uptake of glucose and produce lactate, called the Warburg effect. Increased glucose consumption is used as a carbon source to support cell proliferation, including nucleotide, lipid and protein synthesis. In the Warburg effect, pyruvate dehydrogenase activity decreases, thereby disrupting the TCA cycle. In addition to glucose, glutamine is also an important nutrient for the growth and proliferation of cancer cells, an important carbon bank and nitrogen bank for the growth and proliferation of cancer cells, providing ribose, nonessential amino acids, citrate, and glycerin necessary for cancer cell growth and proliferation and compensating for the reduction in oxidative phosphorylation pathways in cancer cells caused by the Warburg effect. In human plasma, glutamine is the most abundant amino acid. Normal cells produce glutamine via glutamine synthase (GLS), but the glutamine synthesized by tumor cells is insufficient to meet their high growth needs, resulting in a "glutamine-dependent phenomenon." Most cancers have an increased glutamine demand, including breast cancer. Metabolic reprogramming not only enables tumor cells to maintain the reduction-oxidation (redox) balance and commit resources to biosynthesis but also establishes heterogeneous metabolic phenotypes of tumor cells that are distinct from those of nontumor cells. Thus, targeting the metabolic differences between tumor and nontumor cells may be a promising and novel anticancer strategy. Glutamine metabolic compartments have emerged as promising candidates, especially in TNBC and drug-resistant breast cancer. In this review, the latest discoveries of breast cancer and glutamine metabolism are discussed, novel treatment methods based on amino acid transporters and glutaminase are discussed, and the relationship between glutamine metabolism and breast cancer metastasis, drug resistance, tumor immunity and ferroptosis are explained, which provides new ideas for the clinical treatment of breast cancer.

LAT1 is associated with poor prognosis and radioresistance in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) has been identified as the sixth most common disease in the world, and its prognosis remains poor. The basic treatment of HNSCC includes a combination of chemoradiation and surgery. With the advent of immune checkpoint inhibitors, the prognosis has improved; however, the efficacy of checkpoint inhibitors is limited. L-type amino acid transporter 1 (LAT1), an amino acid transporter, is highly expressed in a cancer-specific manner. However, to the best of our knowledge, LAT1 expression in HNSCC has not been determined. Therefore, the present study aimed to examine the role of LAT1 expression in HNSCC. A total of three HNSCC cell lines (Sa3, HSC2 and HSC4) were used to investigate the characteristics of LAT1-positive cells, including their ability to form spheroids, and their invasion and migration. The present study also examined LAT1 by immunostaining of biopsy specimens from 174 patients diagnosed, treated and followed-up at Akita University (Akita, Japan) between January 2010 and December 2019, and overall survival, progression-free survival and multivariate analyses were performed. The results demonstrated that LAT1-positive cells in HNSCC were an independent prognostic factor for overall survival and progression-free survival, and were resistant to chemoradiation. Therefore, JPH203, a LAT1 inhibitor, may be effective in treating chemoradiotherapy-resistant HNSCC and may improve the prognosis of patients with HNSCC.

Contribution of the L-Type Amino Acid Transporter Family in the Diagnosis and Treatment of Prostate Cancer

The L-type amino acid transporter (LAT) family contains four members, LAT1~4, which are important amino acid transporters. They mainly transport specific amino acids through cell membranes, provide nutrients to cells, and are involved in a variety of metabolic pathways. They regulate the mTOR signaling pathway which has been found to be strongly linked to cancer in recent years. However, in the field of prostate cancer (PCa), the LAT family is still in the nascent stage of research, and the importance of LATs in the diagnosis and treatment of prostate cancer is still unknown. Therefore, this article aims to report the role of LATs in prostate cancer and their clinical significance and application. LATs promote the progression of prostate cancer by increasing amino acid uptake, activating the mammalian target of rapamycin (mTOR) pathway and downstream signals, mediating castration-resistance, promoting tumor angiogenesis, and enhancing chemotherapy resistance. The importance of LATs as diagnostic and therapeutic targets for prostate cancer was emphasized and the latest research results were introduced. In addition, we introduced selective LAT1 inhibitors, including JPH203 and OKY034, which showed excellent inhibitory effects on the proliferation of various tumor cells. This is the future direction of amino acid transporter targeting therapy drugs.

An anti-CD98 antibody displaying pH-dependent Fc-mediated tumour-specific activity against multiple cancers in CD98-humanized mice

The cell-surface glycoprotein CD98-a subunit of the LAT1/CD98 amino acid transporter-is an attractive target for cancer immunotherapies, but its widespread expression has hampered the development of CD98-targeting antibody therapeutics. Here we report that an anti-CD98 antibody, identified via the screening of phage-display libraries of CD98 single-chain variable fragments with mutated complementarity-determining regions, preserves the physiological function of CD98 and elicits broad-spectrum crystallizable-fragment (Fc)-mediated anti-tumour activity (requiring Fcγ receptors for immunoglobulins, macrophages, dendritic cells and CD8⁺ T cells, as well as other components of the innate and adaptive immune systems) in multiple xenograft and syngeneic tumour models established in CD98-humanized mice. We also show that a variant of the anti-CD98 antibody with pH-dependent binding, generated by solving the structure of the antibody-CD98 complex, displayed enhanced tumour-specific activity and pharmacokinetics. pH-dependent antibody variants targeting widely expressed antigens may lead to superior therapeutic outcomes.

In Vitro and In Vivo Comparative Analysis of Differentially Expressed Genes and Signaling Pathways in Breast Cancer Cells on Interaction with Mesenchymal Stem Cells

The interaction of breast cancer cells (BCC) with mesenchymal stem cells (MSC) plays a vital role in influencing the gene expression in breast cancer cells and thereby its uncontrolled proliferation, metastasis, and drug resistance. The extent of MSC governing the BCC or the extent of BCC influencing the MSC is a complex process, and the interaction strongly depends upon conditions such as the presence or absence of other cell types and in vivo tumor microenvironment or simple in vitro conditions. Hence, understanding this interaction through gene expression profiling may provide key insights about potential genes which can be targeted for breast cancer treatment. In the current study, in vitro microarray dataset and in vivo RNA-seq dataset of BCC on interaction with the MSC were downloaded from NCBI GEO database and analyzed for differentially expressed genes (DEGs), gene ontology (GO) term enrichment, and Reactome pathway analysis. To target the genes which have similar effect on both in vitro and in vivo, a comparative analysis was performed, 24 genes were commonly upregulated in both in vitro and in vivo datasets, while no common downregulated genes were observed. Out of which, 16 significant genes based upon fold change (logFC > 2) are identified for manipulating the interactions between MSC and BCC. Among them, 6 of the identified genes (FSTL1, LOX, SERPINE1, INHBA, FN1, and VEGFA) have already been reported to be upregulated in BCC on interaction with MSC by various studies. Further experiments need to be conducted to understand the role of remaining 10 identified genes (EFEMP1, IGFBP3, EDIL3, IFITM1, IGFBP4, ITGA5, SLC3A2, HRH1, PPP1R15A, and NNMT) in MSC-BCC interaction. In addition to the reported significant genes and its associated pathways, the expression of long non-coding RNA identified in this study may increase our understanding about the way MSC interacts with BCC and accelerate MSC-based treatment strategies for breast cancer.

Tryptophan and its metabolites in normal physiology and cancer etiology

Within the growing field of amino acid metabolism, tryptophan (Trp) catabolism is an area of increasing interest. Trp is essential for protein synthesis, and its metabolism gives rise to biologically active catabolites including serotonin and numerous metabolites in the kynurenine (Kyn) pathway. In normal tissues, the production of Trp metabolites is directly regulated by the tissue-specific expression of Trp-metabolizing enzymes. Alterations of these enzymes in cancers can shift the balance and lead to an increased production of specific byproducts that can function as oncometabolites. For example, increased expression of the enzyme indoleamine 2,3-dioxygenase, which converts Trp into Kyn, leads to an increase in Kyn levels in numerous cancers. Kyn functions as an oncometabolite in cancer cells by promoting the activity of the transcription factor aryl hydrocarbon receptor, which regulates progrowth genes. Moreover, Kyn also inhibits T-cell activity and thus allows cancer cells to evade clearance by the immune system. Therefore, targeting the Kyn pathway has become a therapeutic focus as a novel means to abrogate tumor growth and immune resistance. This review summarizes the biological role and regulation of Trp metabolism and its catabolites with an emphasis on tumor cell growth and immune evasion and outlines areas for future research focus.

The Involvement of Long Non-Coding RNAs in Glutamine-Metabolic Reprogramming and Therapeutic Resistance in Cancer

Metabolic alterations that support the supply of biosynthetic molecules necessary for rapid and sustained proliferation are characteristic of cancer. Some cancer cells rely on glutamine to maintain their energy requirements for growth. Glutamine is an important metabolite in cells because it not only links to the tricarboxylic acid cycle by producing α-ketoglutarate by glutaminase and glutamate dehydrogenase but also supplies other non-essential amino acids, fatty acids, and components of nucleotide synthesis. Altered glutamine metabolism is associated with cancer cell survival, proliferation, metastasis, and aggression. Furthermore, altered glutamine metabolism is known to be involved in therapeutic resistance. In recent studies, lncRNAs were shown to act on amino acid transporters and glutamine-metabolic enzymes, resulting in the regulation of glutamine metabolism. The lncRNAs involved in the expression of the transporters include the abhydrolase domain containing 11 antisense RNA 1, LINC00857, plasmacytoma variant translocation 1, Myc-induced long non-coding RNA, and opa interacting protein 5 antisense RNA 1, all of which play oncogenic roles. When it comes to the regulation of glutamine-metabolic enzymes, several lncRNAs, including nuclear paraspeckle assembly transcript 1, XLOC_006390, urothelial cancer associated 1, and thymopoietin antisense RNA 1, show oncogenic activities, and others such as antisense lncRNA of glutaminase, lincRNA-p21, and ataxin 8 opposite strand serve as tumor suppressors. In addition, glutamine-dependent cancer cells with lncRNA dysregulation promote cell survival, proliferation, and metastasis by increasing chemo- and radio-resistance. Therefore, understanding the roles of lncRNAs in glutamine metabolism will be helpful for the establishment of therapeutic strategies for glutamine-dependent cancer patients.

Spatial multi-omics analyses of the tumor immune microenvironment

In the past decade, single-cell technologies have revealed the heterogeneity of the tumor-immune microenvironment at the genomic, transcriptomic, and proteomic levels and have furthered our understanding of the mechanisms of tumor development. Single-cell technologies have also been used to identify potential biomarkers. However, spatial information about the tumor-immune microenvironment such as cell locations and cell-cell interactomes is lost in these approaches. Recently, spatial multi-omics technologies have been used to study transcriptomes, proteomes, and metabolomes of tumor-immune microenvironments in several types of cancer, and the data obtained from these methods has been combined with immunohistochemistry and multiparameter analysis to yield markers of cancer progression. Here, we review numerous cutting-edge spatial 'omics techniques, their application to study of the tumor-immune microenvironment, and remaining technical challenges.

The Evaluation of L-Tryptophan Derivatives as Inhibitors of the LType Amino Acid Transporter LAT1 (SLC7A5)

A series of derivatives of the substrate amino acid l‐tryptophan have been investigated for inhibition of the L‐type amino acid transporter LAT1 (SLC7A5), which is an emerging target in anticancer drug discovery. Of the four isomeric 4‐, 5‐, 6‐, or 7‐benzyloxy‐l‐tryptophans, the 5‐substituted derivative was the most potent, with an IC₅₀ of 19 μM for inhibition of [³H]‐l‐leucine uptake into HT‐29 human colon carcinoma cells. The replacement of the carboxy group in 5‐benzyloxy‐l‐tryptophan by a bioisosteric tetrazole moiety led to a complete loss in potency. Likewise, the corresponding tetrazolide derived from l‐tryptophan itself was found to be neither a substrate nor an inhibitor of the transporter. Increasing the steric bulk at the 5‐position, while reasonably well tolerated in some cases, did not result in an improvement in potency. At the same time, none of these derivatives was found to be a substrate for LAT1‐mediated transport.

Transport of Biologically Active Ultrashort Peptides Using POT and LAT Carriers

Ultrashort peptides (USPs), consisting of 2–7 amino-acid residues, are a group of signaling molecules that regulate gene expression and protein synthesis under normal conditions in various diseases and ageing. USPs serve as a basis for the development of drugs with a targeted mechanism of action. The purpose of this review is to systematize the available data on USP transport involving POT and LAT transporters in various organs and tissues under normal, pathological and ageing conditions. The carriers of the POT family (PEPT1, PEPT2, PHT1, PHT2) transport predominantly di- and tripeptides into the cell. Methods of molecular modeling and physicochemistry have demonstrated the ability of LAT1 to transfer not only amino acids but also some di- and tripeptides into the cell and out of it. LAT1 and 2 are involved in the regulation of the antioxidant, endocrine, immune and nervous systems’ functions. Analysis of the above data allows us to conclude that, depending on their structure, di- and tripeptides can be transported into the cells of various tissues by POT and LAT transporters. This mechanism is likely to underlie the tissue specificity of peptides, their geroprotective action and effectiveness in the case of neuroimmunoendocrine system disorders.

Increased/Targeted Brain (Pro)Drug Delivery via Utilization of Solute Carriers (SLCs)

Membrane transporters have a crucial role in compounds’ brain drug delivery. They allow not only the penetration of a wide variety of different compounds to cross the endothelial cells of the blood–brain barrier (BBB), but also the accumulation of them into the brain parenchymal cells. Solute carriers (SLCs), with nearly 500 family members, are the largest group of membrane transporters. Unfortunately, not all SLCs are fully characterized and used in rational drug design. However, if the structural features for transporter interactions (binding and translocation) are known, a prodrug approach can be utilized to temporarily change the pharmacokinetics and brain delivery properties of almost any compound. In this review, main transporter subtypes that are participating in brain drug disposition or have been used to improve brain drug delivery across the BBB via the prodrug approach, are introduced. Moreover, the ability of selected transporters to be utilized in intrabrain drug delivery is discussed. Thus, this comprehensive review will give insights into the methods, such as computational drug design, that should be utilized more effectively to understand the detailed transport mechanisms. Moreover, factors, such as transporter expression modulation pathways in diseases that should be taken into account in rational (pro)drug development, are considered to achieve successful clinical applications in the future.

Surfaceome analyses uncover CD98hc as an antibody drug-conjugate target in triple negative breast cancer

Background

Despite the incorporation of novel therapeutics, advanced triple negative breast cancer (TNBC) still represents a relevant clinical problem. Considering this, as well as the clinical efficacy of antibody-drug conjugates (ADCs), we aimed at identifying novel ADC targets that could be used to treat TNBC.

Methods

Transcriptomic analyses were performed on TNBC and normal samples from three different studies. Plasma membrane proteins of three cell lines representative of the TNBC subtype were identified by cell surface biotinylation or plasma membrane isolation, followed by analyses of cell surface proteins using the Surfaceome online tool. Immunofluorescence and western studies were used to characterize the action of a CD98hc-directed ADC, which was prepared by in house coupling of emtansine to an antibody that recognized the ectodomain of CD98hc. Xenografted TNBC cells were used to analyze the antitumoral properties of the anti-CD98hc ADC.

Results

Comparative genomic studies between normal breast and TNBC tissues, together with proteomic and bioinformatic analyses resulted in the elaboration of a catalog of potential ADC targets. One of them, the CD98hc transmembrane protein, was validated as an ADC target. An antibody recognizing the ectodomain of CD98hc efficiently internalized and reached the lysosomal compartment. An emtansine-based ADC derived from such antibody was prepared and showed antitumoral properties in TNBC in vitro and in vivo models. Mechanistically, the anti-CD98hc ADC blocked cell cycle progression, that was followed by cell death caused by mitotic catastrophe.

Conclusions

This work describes a list of potential ADC targets in TNBC and validates one of them, the transmembrane protein CD98hc. The studies presented here also demonstrate the robustness of the multiomic approach herewith described to identify novel potential ADC targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02330-4.

miR-126 Decreases Proliferation and Mammosphere Formation of MCF-7 and Predicts Prognosis of ER+ Breast Cancer

Breast cancer (BC) is a major health burden that affects over one million women each year. It is the most prevalent cancer in women and the number one cancer killer of them worldwide. Of all BC subtypes, estrogen receptor-positive (ER+) BC is the most commonly diagnosed. The objective of this study is to investigate the contribution of miR-126 in the tumorigenesis of ER+ BC. miR-126 was downregulated in ER+ BC tissues from young breast cancer patients, as shown through miRNA microarray analysis and RT-qPCR. Subsequently, the effect of the modulation of miR-126 levels on the proliferation, cell cycle progression, and spheres formation of the ER+ BC cell line, MCF-7, was assessed by MTT assay, PI analysis, and mammosphere formation assay, respectively. miR-126 overexpression significantly decreased MCF-7 proliferation and mammosphere-forming ability, but did not affect cell cycle progression. Then, in silico analysis determined SLC7A5, PLXNB2, CRK, PLK2, SPRED1, and IRS1 as potential targets of miR-126. RT-qPCR data showed that miR-126 overexpression significantly downregulated SLC7A5 and PLXNB2 mRNA levels in MCF-7. Finally, in silico survival analysis showed that high expression of miR-126 or low expression of SLC7A5 correlated with better overall survival (OS) of ER+ BC patients. Overall, our study suggests that miR-126 might play a tumor suppressor role in ER+ BC. miR-126 and SLC7A5 might also be considered potential prognostic biomarkers in ER+ BC.

Association of L-type amino acid transporter 1 (LAT1) with the immune system and prognosis in invasive breast cancer

L-type amino acid transporter 1 (LAT1), also referred to as SLC7A5, is believed to regulate tumor metabolism and be associated with tumor proliferation. In invasive breast cancer, we clinicopathologically investigated the utility of LAT1 expression. LAT1 expression was evaluated via immunohistochemistry analyses in 250 breast cancer patients undergoing long-term follow-up. We assessed the relationships between LAT1 expression and patient outcomes and clinicopathological factors. Breast cancer-specific survival stratified by LAT1 expression was assessed. Human epidermal growth factor receptor 2 (HER2)-positive patients with metastasis received trastuzumab therapy. The density of tumor-infiltrating lymphocytes (TILs) was evaluated according to the International Working Group guidelines. In the current study, high LAT1 expression was significantly correlated with estrogen receptor (ER) negativity, progesterone receptor negativity, high histological grade, increased TILs, and programmed death ligand 1 positivity. Among the ER-positive and HER2-negative patients, high LAT1 was an independent indicator of poor outcomes (hazard ratio (HR) = 2.97; 95% confidence interval (CI), 1.16-7.62; p = 0.023). Moreover, high LAT1 expression was an independent poor prognostic factor in luminal B-like breast cancer with aggressive features (HR = 3.39; 95% CI 1.35-8.52; p = 0.0094). In conclusion, high LAT1 expression could be used to identify a subgroup of invasive breast cancer characterized by aggressive behavior and high tumor immunoreaction. Our findings suggest that LAT1 might be a candidate therapeutic target for breast cancer patients, particularly those with luminal B-like type breast cancer.

Amino Acid and Proliferation PET/CT for the Diagnosis of Multiple Myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by infiltration of monoclonal plasma cells in the bone marrow (BM). The standard examination performed for the assessment of bone lesions has progressed from radiographic skeletal survey to the more advanced imaging modalities of computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT). The Durie-Salmon PLUS staging system (upgraded from the Durie-Salmon staging system) applies 2-[18F]-fluoro-2-deoxy-glucose (18F-FDG) PET/CT, and MRI findings to the staging of MM, and 18F-FDG PET/CT has been incorporated into the International Myeloma Working Group (IMWG) guidelines for the diagnosis and staging of MM. However, 18F-FDG PET/CT has significant limitations in the assessment of diffuse BM infiltration and in the differentiation of MM lesions from inflammatory or infectious lesions. The potential of several new PET tracers that exploit the underlying disease mechanism of MM has been evaluated in terms of improving the diagnosis. L-type amino acid transporter 1 (LAT1), a membrane protein that transports neutral amino acids, is associated with cell proliferation and has strong ability to represent the status of MM. This review evaluates the potential of amino acid and proliferation PET tracers for diagnosis and compares the characteristics and accuracy of non-FDG tracers in the management of patients with MM.

Contribution of LAT1-4F2hc in Urological Cancers via Toll-like Receptor and Other Vital Pathways

Simple Summary

LAT1-4F2hc complex is an important amino acid transporter. It mainly transports specific amino acids through the cell membrane, provides nutrition for cells, and participates in a variety of metabolic pathways. LAT1 plays a role in transporting essential amino acids including leucine, which regulates the mTOR signaling pathway. However, the importance of SLCs is still not well known in the field of urological cancer. Therefore, the purpose of this review is to report the role of the LAT1-4F2hc complex in urological cancers, as well as their clinical significance and application. Moreover, the inhibitor of LAT1-4F2hc complex is a promising direction as a targeted therapy to improve the treatment and prognosis of urological cancers.

Abstract

Tumor cells are known for their ability to proliferate. Nutrients are essential for rapidly growing tumor cells. In particular, essential amino acids are essential for tumor cell growth. Tumor cell growth nutrition requires the regulation of membrane transport proteins. Nutritional processes require amino acid uptake across the cell membrane. Leucine, one of the essential amino acids, has recently been found to be closely associated with cancer, which activate mTOR signaling pathway. The transport of leucine into cells requires an L-type amino acid transporter protein 1, LAT1 (SLC7A5), which requires the 4F2 cell surface antigen heavy chain (4F2hc, SLC3A2) to form a heterodimeric amino acid transporter protein complex. Recent evidence identified 4F2hc as a specific downstream target of the androgen receptor splice variant 7 (AR-V7). We stressed the importance of the LAT1-4F2hc complex as a diagnostic and therapeutic target in urological cancers in this review, which covered the recent achievements in research on the involvement of the LAT1-4F2hc complex in urinary system tumors. In addition, JPH203, which is a selective LAT1 inhibitor, has shown excellent inhibitory effects on the proliferation in a variety of tumor cells. The current phase I clinical trials of JPH203 in patients with biliary tract cancer have also achieved good results, which is the future research direction for LAT1 targeted therapy drugs.

Novel strategies to improve tumour therapy by targeting the proteins MCT1, MCT4 and LAT1

Poor selectivity, potential systemic toxicity and drug resistance are the main challenges associated with chemotherapeutic drugs. MCT1 and MCT4 and LAT1 play vital roles in tumour metabolism and growth by taking up nutrients and are thus potential targets for tumour therapy. An increasing number of studies have shown the feasibility of including these transporters as components of tumour-targeting therapy. Here, we summarize the recent progress in MCT1-, MCT4-and LAT1-based therapeutic strategies. First, protein structures, expression, relationships with cancer, and substrate characteristics are introduced. Then, different drug targeting and delivery strategies using these proteins have been reviewed, including designing protein inhibitors, prodrugs and nanoparticles. Finally, a dual targeted strategy is discussed because these proteins exert a synergistic effect on tumour proliferation. This article concentrates on tumour treatments targeting MCT1, MCT4 and LAT1 and delivery techniques for improving the antitumour effect. These innovative tactics represent current state-of-the-art developments in transporter-based antitumour drugs.

Expression of L-type amino acid transporter 1 is a poor prognostic factor for Non-Hodgkin's lymphoma

L-type neutral amino acid transporter 1 (LAT1) is a heterodimeric membrane transport protein involved in neutral amino acid transport. LAT1 is highly expressed in various malignant solid tumors and plays an essential role in cell proliferation. However, its role in malignant lymphoma remains unknown. Here, we evaluated LAT1 expression level in tissues from 138 patients with Non-Hodgkin lymphoma (NHL). Overexpression of LAT1 was confirmed in all types of NHL and we found that there is a significant correlation between the level of LAT1 expression and lymphoma grade. The LAT1 expression was higher in aggressive types of lymphomas when compared with static types of lymphomas, suggesting that active tumor proliferation requires nutrient uptake via LAT1. The expression level of LAT1 was inversely correlated with patients’ survival span. Furthermore, pharmacological inhibition of LAT1 by a specific inhibitor JPH203 inhibits lymphoma cell growth. In conclusion, our study demonstrated that LAT1 expression can be used as a prognostic marker for patients with NHL and targeting LAT1 by JPH203 can be a novel therapeutic modality for NHL.

A Novel Brain-Permeant Chemotherapeutic Agent for the Treatment of Brain Metastasis in Triple-Negative Breast Cancer

Development of metastases to central nervous system (CNS) is an increasing clinical issue following the diagnosis of advanced breast cancer. The propensity to metastasize to CNS varies by breast cancer subtype. Of the four breast cancer subtypes, triple-negative breast cancers (TNBC) have the highest rates of both parenchymal brain metastasis and leptomeningeal metastasis (LM). LM is rapidly fatal due to poor detection and limited therapeutic options. Therapy of TNBC brain metastasis and LM is challenged by multifocal brain metastasis and diffuse spread of LM, and must balance brain penetration, tumor cytotoxicity, and the avoidance of neurotoxicity. Thus, there is an urgent need for novel therapeutic options in TNBCs CNS metastasis. QBS10072S is a novel chemotherapeutic that leverages TNBC-specific defects in DNA repair and LAT1 (L-amino acid transporter type 1)-dependent transport into the brain. In our study, activity of QBS10072S was investigated in vitro with various cell lines including the human TNBC cell line MDA-MB-231 and its brain-tropic derivative MDA-MB-231-BR3. QBS10072S was preferentially toxic to TNBC cells. The efficacy of QBS10072S against brain metastasis and LM was tested using a model of brain metastasis based on the internal carotid injection of luciferase-expressing tumor cells into NuNu mice. The compound was well tolerated, delayed tumor growth and reduced leptomeningeal dissemination, resulting in significant extension of survival. Given that current treatments for LM are palliative with only few studies reporting a survival benefit, QBS10072S is planned to be investigated in clinical trials as a therapeutic for TNBC LM. SIGNIFICANCE: TNBC brain metastasis often involves dissemination into leptomeninges. Treatment options for TNBC leptomeningeal metastasis are limited and are mostly palliative. Our study demonstrates significant efficacy of the brain-penetrating agent QBS10072S against TNBC brain metastasis and leptomeningeal spread.

Targeting Amino Acid Metabolic Reprogramming via L-Type Amino Acid Transporter 1 (LAT1) for Endocrine-Resistant Breast Cancer

The PI3K/Akt/mTOR pathway has been well known to interact with the estrogen receptor (ER)-pathway and to be also frequently upregulated in aromatase inhibitor (AI)-resistant breast cancer patients. Intracellular levels of free amino acids, especially leucine, regulate the mammalian target of rapamycin complex 1 (mTORC1) activation. L-type amino acid transporters such as LAT1 and LAT3 are associated with the uptake of essential amino acids. LAT1 expression could mediate leucine uptake, mTORC1 signaling, and cell proliferation. Therefore, in this study, we explored amino acid metabolism, including LAT1, in breast cancer and clarified the potential roles of LAT1 in the development of therapeutic resistance and the eventual clinical outcome of the patients. We evaluated LAT1 and LAT3 expression before and after neoadjuvant hormone therapy (NAH) and examined LAT1 function and expression in estrogen deprivation-resistant (EDR) breast carcinoma cell lines. Tumors tended to be in advanced stages in the cases whose LAT1 expression was high. LAT1 expression in the EDR cell lines was upregulated. JPH203, a selective LAT1 inhibitor, demonstrated inhibitory effects on cell proliferation in EDR cells. Hormone therapy changed the tumor microenvironment and resulted in metabolic reprogramming through inducing LAT1 expression. LAT1 expression then mediated leucine uptake, enhanced mTORC1 signaling, and eventually resulted in AI resistance. Therefore, LAT1 could be the potential therapeutic target in AI-resistant breast cancer patients.

High L-Type Amino Acid Transporter 1 Levels Are Associated with Chemotherapeutic Resistance in Gastric Cancer Patients

INTRODUCTION

We investigated whether the expression of L-type amino acid transporter 1 (LAT-1) in clinical gastric cancer (GC) patients could predict patient therapeutic response to postoperative adjuvant chemotherapy.

METHODS

Immunohistochemistry was used to investigate LAT-1, CD98, and phosphorylated-mammalian target of rapamycin (p-mTOR) expression in 111 GC patients. To clarify whether LAT-1 influences the therapeutic effects of chemotherapy, the correlation between disease-free survival rates and LAT-1 was determined in 2 groups: 59 patients who did not undergo postoperative adjuvant chemotherapy and 52 patients who did undergo postoperative adjuvant chemotherapy.

RESULTS

LAT-1 was significantly correlated with CD98 and p-mTOR expressions. We did not find any statistically significant correlation between LAT-1 and recurrence in the nontreated group. In contrast, a significant association was found between LAT-1 expression and disease-free survival in the chemotherapy group. Moreover, multivariate regression analysis demonstrated that LAT-1 was an independent predictor of disease-free survival in the postoperative adjuvant chemotherapy group (p = 0.012).

CONCLUSION

Our findings demonstrate that LAT-1 is a useful predictive marker for a successful postoperative adjuvant chemotherapy treatment.

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.

Prognostic Value of L-Type Amino Acid Transporter 1 (LAT1) in Various Cancers: A Meta-Analysis

BACKGROUND AND OBJECTIVE

The L-type amino acid transporter 1 (LAT1, SLC7A5) is overexpressed in various types of cancer and has been thought to assist cancer progression through its uptake of neutral amino acids. However, the prognostic role of LAT1 in human cancers remains uncharacterized. Therefore, we conducted this meta-analysis to determine the prognostic significance of LAT1 in various cancers.

METHODS

We systematically searched the PubMed, Web of Science, EMBASE, Chinese National Knowledge Infrastructure, and WanFang databases to collect relevant cohort studies investigating the prognostic value of LAT1 expression in patients with cancer. Hazard ratios (HRs) with corresponding 95% confidence intervals (CIs) were pooled to clarify the association between the LAT1 expression and the survival of patients with cancer. Odds ratios (ORs) with 95% CIs were calculated to appraise the correlation between LAT1 and the clinicopathological characteristics in patients with cancer.

RESULTS

A total of 32 eligible articles, including 34 cohorts and 6410 patients, were enrolled in this meta-analysis. Our results demonstrated that high LAT1 expression was significantly associated with poor overall survival (HR = 1.66, 95% CI 1.41-1.96, P < 0.001), cancer-specific survival (HR = 1.64, 95% CI 1.31-2.05, P < 0.001), disease-free survival (HR = 1.55, 95% CI 1.31-1.83, P < 0.001), and progression-free survival (HR = 1.18, 95% CI 1.02-1.37, P = 0.026) in patients with cancer. In addition, we found that the elevated expression level of LAT1 was significantly related to certain phenotypes of tumor aggressiveness, such as tumor size, clinical stage, T stage, lymphatic invasion, vascular invasion, tumor differentiation, Ki-67, CD34, CD98, p53, and system ASC amino acid transporter-2.

CONCLUSIONS

Elevated expression of LAT1 is associated with poor prognosis in human cancers and may serve as a potential prognostic marker and therapeutic target for patients with malignancies.

Highly Specific L-Type Amino Acid Transporter 1 Inhibition by JPH203 as a Potential Pan-Cancer Treatment

Accelerated cancer cell growth requires a massive intake of amino acids. Overexpression of L-type (large) amino acid transporter 1 (LAT1) on the cancer cell membrane facilitates such a demand, which is limited in normal organs. Therefore, LAT1 overexpression is ideal as a molecular cancer therapeutic target. JPH203, a LAT1-selective non-transportable blocker, had demonstrated LAT1 inhibition in <10 µM IC50 values and effectively suppressed cancer cell growth in studies involving several types of cancer cell lines and tumor xenograft models. A limited phase I clinical trial was performed on five different solid tumors and showed that JPH203 is well-tolerated and has a promising activity for the treatment of bile duct cancer. This review details the development and prospect of JPH203 as a LAT1-targeting cancer therapy.

Expression of LAT1 and 4F2hc in Gastroenteropancreatic Neuroendocrine Neoplasms

BACKGROUND/AIM

Little is known about the expression of L-type amino acid transporter 1 (LAT1) and 4F2hc in gastroenteropancreatic-neuroendocrine neoplasms (GEP-NENs). Hence, we conducted a study to verify the clinicopathological significance of LAT1 and 4F2hc.

PATIENTS AND METHODS

Tissues from 126 patients with GEP-NENs were collected between August 2007 and August 2019 at our institution. We evaluated LAT1 and 4F2hc expression by immunohistochemistry, and examined their clinical significance.

RESULTS

No statistically significant associations were observed between LAT1 expression and the different NENs. Expression of 4F2hc was significantly different between neuroendocrine tumour (NET)-G1, NET-G2, and NET-G3 (p=0.029), and was significantly associated with vascular invasion (p=0.044) and the Ki-67 index (p=0.042).

CONCLUSION

No association between LAT1 expression and malignant features in GEP-NENs was observed. However, an association between 4F2hc expression and the potential of malignancy in GEP-NENs was evident.

Hemocompatible LAT1-inhibitor can induce apoptosis in cancer cells without affecting brain amino acid homeostasis

Increased amounts of amino acids are essential for cancer cells to support their sustained growth and survival. Therefore, inhibitors of amino acid transporters, such as l-type amino acid transporter 1 (LAT1) have been developed. In this study, a previously reported LAT1-inhibitor (KMH-233) was studied for its hemocompatibility and toxicity towards human umbilical vein endothelial cells (HUVEC) and human aortic smooth muscle cells (AoSMCs). Furthermore, the cytotoxic effects against human breast adenocarcinoma cells (MCF-7) and its ability to affect mammalian (or mechanistic) target of rapamycin (mTOR) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling were evaluated. Moreover, the effects of this inhibitor to modulate LAT1 function on the cell surface and the brain amino acid homeostasis were evaluated after intraperitoneal (i.p.) administration of LAT1-inhibitor (23 µmol/kg) in mice. The results showed that LAT1-inhibitor (KMH-233) is hemocompatible at concentrations below 25 µM and it does not affect coagulation in plasma. However, it can reduce the total protein amount of mTOR and NF-κB, resulting in increased apoptosis in LAT1-expressing cancer cells. Most importantly, the inhibitor did not affect mouse brain levels of l-Leu, l-Tyr or l-Trp or modulate the function of LAT1 on the MCF-7 cell surface. Therefore, this inhibitor can be considered as a safe but effective anti-cancer agent. However, due to the compensative mechanism of cancer cells for their increased amino acid demand, this compound is most effective inducing apoptosis when used in combinations with other chemotherapeutics, such as protease inhibitor, bestatin, as demonstrated in this study.

The heavy chain of 4F2 antigen promote prostate cancer progression via SKP-2

The 4F2 cell-surface antigen heavy chain (4F2hc) forms a heterodimeric complex with L-type amino acid transporter 1 (LAT1) and transports large neutral essential amino acids. However, in contrast to the traditional role of LAT1 in various cancers, the role of 4F2hc has largely remained unknown. The role of 4F2hc in prostate cancer was studied. Treatment of C4-2 cells with si4F2hc was found to suppress cellular growth, migratory and invasive abilities, with this effect occurring through the cell cycle, with a significant decrease in S phase and a significant increase in G0/G1 phase, suggesting cell cycle arrest. In addition, it was proven by RNA seq that the key to 4F2hc's impact on cancer is SKP2. si4F2hc upregulates the protein expression of cyclin-dependent kinase inhibitors (P21cip1, P27kip1) through the downstream target SKP2. Furthermore, the expression of 4F2hc and LAT1 in prostate cancer cells suggests the importance of 4F2hc. Multivariate analysis showed that high 4F2hc expression was an independent prognostic factor for progression-free survival (HR 11.54, p = 0.0357). High 4F2hc was related to the clinical tumour stage (p = 0.0255) and Gleason score (p = 0.0035). Collectively, 4F2hc contributed significantly to prostate cancer (PC) progression. 4F2hc may be a novel marker and therapeutic target in PC.

Molecular characteristics supporting l-Type amino acid transporter 1 (LAT1)-mediated translocation

l-Type amino acid transporter 1 (LAT1) is an interesting protein due to its peculiar expression profile. It can be utilized not only as a carrier for improved or targeted drug delivery, e.g., into the brain but also as a target protein by which amino acid supply can be restricted, e.g., from the cancer cells. The recognition and binding processes of LAT1-ligands, such as amino acids and clinically used small molecules, including l-dopa, gabapentin, and melphalan, are today well-known. Binding to LAT1 is crucial, particularly when designing the LAT1-inhibitors. However, it will not guarantee effective translocation across the cell membrane via LAT1, which is a definite requirement for LAT1-substrates, such as drugs that elicit their pharmacological effects inside the cells. Therefore, in the present study, the accumulation of known LAT1-utilizing compounds into the selected LAT1-expressing cancer cells (MCF-7) was explored experimentally over a time period. The differences found among the transport efficiency and affinity of the studied compounds for LAT1 were subsequently explained by docking the ligands into the human LAT1 model (based on the recent cryo-electron microscopy structure). Thus, the findings of this study clarify the favorable structural requirements of the size, shape, and polarity of the ligands that support the translocation and effective transport across the cell membrane via LAT1. This knowledge can be applied in future drug design to attain improved or targeted drug delivery and hence, successful LAT1-utilizing drugs with increased therapeutic effects.

Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology

Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H⁺ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b^0,+AT-rBAT and the SLC6 family heteromer B⁰AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.

Heteromeric Amino Acid Transporters in Brain: from Physiology to Pathology

In humans, more than 50 transporters are responsible for the traffic and balance of amino acids within and between cells and tissues, and half of them have been associated with disease [1]. Covering all common amino acids, Heteromeric Amino acid Transporters (HATs) are one class of such transporters. This review first highlights structural and functional studies that solved the atomic structure of HATs and revealed molecular clues on substrate interaction. Moreover, this review focuses on HATs that have a role in the central nervous system (CNS) and that are related to neurological diseases, including: (i) LAT1/CD98hc and its role in the uptake of branched chain amino acids trough the blood brain barrier and autism. (ii) LAT2/CD98hc and its potential role in the transport of glutamine between plasma and cerebrospinal fluid. (iii) y⁺LAT2/CD98hc that is emerging as a key player in hepatic encephalopathy. xCT/CD98hc as a potential therapeutic target in glioblastoma, and (iv) Asc-1/CD98hc as a potential therapeutic target in pathologies with alterations in NMDA glutamate receptors.

L-type amino acid transporter 1 is associated with chemoresistance in breast cancer via the promotion of amino acid metabolism

¹⁸F-FDG PET/CT has been used as an indicator of chemotherapy effects, but cancer cells can remain even when no FDG uptake is detected, indicating the importance of exploring other metabolomic pathways. Therefore, we explored the amino acid metabolism, including L-type amino acid transporter-1 (LAT1), in breast cancer tissues and clarified the role of LAT1 in therapeutic resistance and clinical outcomes of patients. We evaluated LAT1 expression before and after neoadjuvant chemotherapy and examined the correlation of glucose uptake using FDG-PET with the pathological response of patients. It revealed that LAT1 levels correlated with proliferation after chemotherapy, and amino acid and glucose metabolism were closely correlated. In addition, LAT1 was considered to be involved in treatment resistance and sensitivity only in luminal type breast cancer. Results of in vitro analyses revealed that LAT1 promoted amino acid uptake, which contributed to energy production by supplying amino acids to the TCA cycle. However, in MCF-7 cells treated with chemotherapeutic agents, oncometabolites and branched-chain amino acids also played a pivotal role in energy production and drug resistance, despite decreased glucose metabolism. In conclusion, LAT1 was involved in drug resistance and could be a novel therapeutic target against chemotherapy resistance in luminal type breast cancer.

ASCT2 and LAT1 Contribution to the Hallmarks of Cancer: From a Molecular Perspective to Clinical Translation

The role of the amino acid transporters ASCT2 and LAT1 in cancer has been explored throughout the years. In this review, we report their impact on the hallmarks of cancer, as well as their clinical significance. Overall, both proteins have been associated with cell death resistance through dysregulation of caspases and sustainment of proliferative signaling through mTOR activation. Furthermore, ASCT2 appears to play an important role in cellular energetics regulation, whereas LAT1 expression is associated with angiogenesis and invasion and metastasis activation. The molecular impact of these proteins on the hallmarks of cancer translates into various clinical applications and both transporters have been identified as prognostic factors in many types of cancer. Concerning their role as therapeutic targets, efforts have been undertaken to synthesize competitive or irreversible ASCT2 and LAT1 inhibitors. However, JHP203, a selective inhibitor of the latter, is, to the best of our knowledge, the only compound included in a Phase 1 clinical trial. In conclusion, considering the usefulness of ASCT2 and LAT1 in a variety of cancer-related pathways and cancer therapy/diagnosis, the development and testing of novel inhibitors for these transporters that could be evaluated in clinical trials represents a promising approach to cancer prognosis improvement.

Amino Acid Transporters on the Guard of Cell Genome and Epigenome

Tumorigenesis is driven by metabolic reprogramming. Oncogenic mutations and epigenetic alterations that cause metabolic rewiring may also upregulate the reactive oxygen species (ROS). Precise regulation of the intracellular ROS levels is critical for tumor cell growth and survival. High ROS production leads to the damage of vital macromolecules, such as DNA, proteins, and lipids, causing genomic instability and further tumor evolution. One of the hallmarks of cancer metabolism is deregulated amino acid uptake. In fast-growing tumors, amino acids are not only the source of energy and building intermediates but also critical regulators of redox homeostasis. Amino acid uptake regulates the intracellular glutathione (GSH) levels, endoplasmic reticulum stress, unfolded protein response signaling, mTOR-mediated antioxidant defense, and epigenetic adaptations of tumor cells to oxidative stress. This review summarizes the role of amino acid transporters as the defender of tumor antioxidant system and genome integrity and discusses them as promising therapeutic targets and tumor imaging tools.