Divergent expression of L-type amino acid transporter 1 during uterine cervical carcinogenesis

A Review on the Role of Human Solute Carriers Transporters in Cancer

Background and Aim

The high rate of tumor growth results in an increased need for amino acids. As solute carriers (SLC) transporters are capable of transporting different amino acids, cancer may develop as a result of these transporters' over-expression due to their complex formation with other biological molecules. Therefore, this review investigated the role of SLC transporters in the progression of cancer.

Methods

We retrieved data from Google Scholar, Web of Science, PubMed, Cochrane Library, and EMBASE regarding the influence of human SLCs on the development of cancer. Articles published in English before August 2024 were included in the study.

Results

The overexpression of SLCs is strongly related to tumor cell proliferation and angiogenesis in a number of cancer types including thyroid, pancreatic, lung, hepatocellular, and colon cancers. They are crucial for the stimulation of several biological signaling pathways, particularly mTOR kinase activity, which starts a signaling cascade, protein synthesis, cell growth, and proliferation, and inhibits apoptosis of cancerous cells. Furthermore, they contribute to the activation of PI3K/AKT signaling, which has an impact on the growth, invasion, and death of cancer cells. Thus, SLC transporters become a potential therapeutic target that plays a crucial role in drug resistance, tumor microenvironment regulation, and modulation of immune response.

Conclusion

The review recognized the crucial role of SLC transporters in different types of cancer progression. Therefore, to confirm our findings, a case-control study is required to investigate the role of amino acid transporters in cancer development.

Construction of a ferroptosis and hypoxia-related gene signature in cervical cancer to assess tumour immune microenvironment and predict prognosis

BACKGROUND

This study aimed to investigate the potential role of ferroptosis/hypoxia-related genes in cervical cancer to improve early management and treatment of cervical cancer.

METHODS

All data were downloaded from public databases. Ferroptosis/hypoxia-related genes associated with cervical cancer prognosis were selected to construct a risk score model. The relationship between risk score and clinical features, immune microenvironment and prognosis were analysed.

RESULTS

Risk score model was constructed based on eight signature genes. Drug prediction analysis showed that bevacizumab and cisplatin were related to vascular endothelial growth factor A. Risk score, as an independent prognostic factor of cervical cancer, had a good survival prediction effect. The two groups differed significantly in degree of immune cell infiltration, gene expression, tumour mutation burden and somatic variation.

CONCLUSIONS

We developed a novel prognostic gene signature combining ferroptosis/hypoxia-related genes, which provides new ideas for individual treatment of cervical cancer.

Boron uptake of boronophenylalanine and the effect of boron neutron capture therapy in cervical cancer cells

There are few studies about boron neutron capture therapy (BNCT) for cervical cancer. The present study evaluated the biodistribution of boronophenylalanine (BPA) and the effect of BNCT on cervical cancer cell lines. BPA exposure and neutron irradiation of cervical cancer cell lines resulted in decreased survival fraction compared to irradiation only. In vivo cervical cancer tumor boron concentration was highest at 2.5 h after BPA intraperitoneal administration, and higher than in the other organs. BNCT may be effective against cervical carcinoma.

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.

Correlation of high LAT1 expression with the prognosis of endometrioid carcinoma of the uterine corpus

The expression of L-type amino acid transporter 1 (LAT1) has been described to play essential roles in cancer cell growth and survival. To determine the significance of LAT1 in the prognosis of endometrial endometrioid carcinoma, we investigated LAT1 expression in 353 endometrioid carcinoma patients by immunohistochemical analysis using tissue microarray. The tumors in which stained tumor cells made up more than 25% of the tumor were graded as high expression. High expression of LAT1 was detected in 29 (8.2%) of patients. The ratio of high LAT1 expression did not significantly differ by age (< 60 vs. ≥ 60), FIGO stage (stage I/II vs. III/IV), histological grade (grade 1 vs. grade 2/3), or lymph node metastasis (positive vs. negative). However, high LAT1 expression in endometrioid carcinoma was associated with a poorer progression-free survival and overall survival, as per the results of the log-rank test (P = 0.0263 and 0.0404, respectively). Cox univariate and multivariate analyses revealed that high LAT1 expression is an independent marker of poor progression-free survival (hazard ratio = 2.598, P = 0.0137), in addition to a higher age (≥ 60 years vs. < 60 years), FIGO stage (stage III/IV vs. I/II), and histological grade (grade 2/3 vs. grade 1). In conclusion, we demonstrate that LAT1 is associated with a poor prognosis of endometrioid carcinoma of the uterine corpus.

The L-Type Amino Acid Transporter LAT1-An Emerging Target in Cancer

Chronic proliferation is a major hallmark of tumor cells. Rapidly proliferating cancer cells are highly dependent on nutrients in order to duplicate their cell mass during each cell division. In particular, essential amino acids are indispensable for proliferating cancer cells. Their uptake across the cell membrane is tightly controlled by membrane transporters. Among those, the L-type amino acid transporter LAT1 (SLC7A5) has been repeatedly found overexpressed in a vast variety of cancers. In this review, we summarize the most recent advances in our understanding of the role of LAT1 in cancer and highlight preclinical studies and drug developments underlying the potential of LAT1 as therapeutic target.

Significant relationship between the LAT1 expression pattern and chemoresistance in ovarian clear cell carcinoma

L-type amino acid transporter 1 (LAT1) is a Na⁺-independent neutral amino acid transporter that plays a key role in cancer cell growth and survival. To determine the significance of LAT1 in prognosis and resistance to chemotherapy in ovarian carcinoma, we investigated the LAT1 expression in 245 ovarian carcinoma patients by immunohistochemistry using tissue microarray. High expression of LAT1 was detected in 85 (34.7%) patients. The ratio of high expression of LAT1 was significantly high in clear cell carcinoma and low in serous carcinoma compared to other histological types (P < 0.0001). High expression of LAT1 in ovarian carcinoma was associated with poorer prognosis as per log-rank test (P = 0.008). Cox's univariate and multivariate analysis revealed that high expression of LAT1 is an independent marker indicating poor prognosis (hazard ratio = 2.810, P < 0.0001) as well as the FIGO stage III/IV (vs. I/II) and suboptimal surgery. High LAT1 expression was also found to be associated with resistance to chemotherapy (P = 0.016) notably in clear cell carcinoma. In conclusion, we demonstrate that LAT1 is not only associated with poor prognosis of ovarian carcinoma, but also associated with chemoresistance in ovarian carcinoma.

False-positive findings on 6-[18F]fluor-l-3,4-dihydroxyphenylalanine PET (18F-FDOPA-PET) performed for imaging of neuroendocrine tumors

BACKGROUND/AIM

PET with 6-[18F]fluor-l-3,4-dihydroxyphenylalanine (¹⁸F-FDOPA) has been shown to be a useful imaging tool with a high sensitivity for the visualization of neuroendocrine tumors (NETs). ¹⁸F-FDOPA uptake in tumors other than NETs has been suggested previously, but data on this phenomenon are limited. We therefore studied the non-physiological, false-positive uptake of ¹⁸F-FDOPA in a large population of patients with a NET or with a high clinical suspicion of harboring a NET.

PATIENTS AND METHODS

Retrospective single-center study among adult patients in whom ¹⁸F-FDOPA PET scintigraphy was performed between January 2004 and December 2014. The original scan report was compared with the original pathology report corresponding with the ¹⁸F-FDOPA PET-positive lesion. In case this was inconsistent with the diagnosis of a NET, both the scan and the pathology slides were reassessed. Specimens of these non-NET tissues were immunohistochemically stained for AADC.

RESULTS

1070 ¹⁸F-FDOPA PET scans from 705 patients were evaluated. Focal or multiple ¹⁸F-FDOPA-avid lesions were described in 709 ¹⁸F-FDOPA PET scans (66%). Histology of these ¹⁸F-FDOPA PET-positive lesions was present in 508 (72%) cases. In seven cases, the histopathology was not compatible with NET but showed squamous cell carcinoma of the cervix, multiple myeloma (two cases), hepatocellular carcinoma, Schwannoma, adrenocortical carcinoma and a skeletal myxoid chondrosarcoma, with positive immunohistochemical staining for AADC in 67%.

CONCLUSIONS

Pathological uptake of ¹⁸F-FDOPA does not always indicate the presence of a NET. The possibility of ¹⁸F-FDOPA uptake by tumor types other than NETs, although rare, should be considered.

Ultrastructural immunohistochemical study of L-type amino acid transporter 1-4F2 heavy chain in tumor microvasculatures of N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) induced rat bladder carcinoma

Angiogenesis is essential for tumor growth, and an enhanced vasculature supplying nutrients and oxygen might reflect malignant potential. L-type amino acid transporter 1 (LAT1/4F2hc) comprises a major nutrient transport system responsible for the Na+-independent transport of large neutral amino acids. Seventy five to seventy eight percent N-butyl-N-(4-hydroxybutyl) nitrosamine-induced rat bladder carcinoma cells showed high LAT1/4F2hc expression. While the intracarcinoma microvasculatures of fenestrated endothelial cells highly expressing LAT1/4F2hc might progressively transport essential amino acids from the microvasculatures to the extracellular matrix, non-fenestrated endothelial cells and pericytes did not. The present study revealed that the tumor angiogenesis is one of target anti-L-type amino acid transporter 1 drug.

Metformin enhances anti-tumor effect of L-type amino acid transporter 1 (LAT1) inhibitor

BACKGROUND

In many cancer cells, L-type amino acid transporter 1 (LAT1) transports neutral amino acids with bulky side chain, which activate mammalian target of rapamycin (mTOR) to cause cell proliferation. An anti-diabetic drug, metformin, has been shown to activate AMP-activated protein kinase (AMPK), which leads to inhibition of mTOR. LAT1 inhibition in combination with metformin could result in more prominent suppression of mTOR activity.

PURPOSE

Anti-proliferative effect of a newly developed LAT1 specific inhibitor JPH203 in combination with metformin is evaluated in 2 head and neck cancer cell lines, Ca9-22 and HEp-2 cells and in nude mice inoculated with Ca9-22 cells.

RESULTS AND DISCUSSION

By MTT assay, 0.5 mM metformin inhibited proliferation of Ca9-22 cells to 70% of control. In the presence of 100 μM JPH203, proliferation of Ca9-22 cells was inhibited to 60% of control. By combining these 2 drugs, proliferation of Ca9-22 was significantly inhibited to 40% of control. However, this regimen was not very effective against HEp-2 cells. This combination also suppressed in vivo growth of Ca9-22 cells in a xenotransplant model. A combination of anti-LAT1 drug with metformin may be an effective anti-proliferative therapy for certain subsets of cancers.

The role of L-type amino acid transporter 1 in human tumors

L-type amino acid transporter 1 (LAT1) is an L-type amino acid transporter and transports large neutral amino acids such as leucine, isoleucine, valine, phenylalanine, tyrosine, tryptophan, methionine, and histidine. LAT1 was found to be highly expressed especially in human cancer tissues, and up-regulated LAT1 can lead to dysfunction in human tumor cells. These findings suggest that LAT1 plays an important role in human tumors. This review provides an overview of the current understanding of LAT1 expression and its clinical significance and function in tumors.

L-Type amino acid transporter 1 (LAT1) expression in lymph node metastasis of gastric carcinoma: Its correlation with size of metastatic lesion and Ki-67 labeling

L-Type amino acid transporter 1 (LAT1) is one of the major amino acid transporters. High levels of LAT1 expression have been reported in various tumors, which can act as a novel prognostic marker. Previously, we demonstrated that LAT1 is highly expressed in advanced gastric carcinoma with lymph node metastasis, and proposed that LAT1 is an independent prognostic factor in non-scirrhous gastric carcinoma. The aim of the present study was to investigate the relationship between LAT1 expression and the size of lymph node metastatic lesions in gastric carcinoma. LAT1 and Ki-67 expression was immunohistochemically analyzed in 64 cases of advanced gastric carcinoma with lymph node metastasis. LAT1 expression in the metastatic lymph nodes was correlated with that in the primary lesions. The high LAT1 expression group showed a larger size of metastatic lesion and a higher Ki-67 labeling index than the low LAT1 expression group. LAT1 expression had a weak association with Ki-67 labeling index and tumor diameter of lymph nodes. These results suggest that LAT1 expression is associated with disease progression in gastric carcinoma. We proposed that LAT1 could be a potential therapeutic target for gastric carcinoma cases with large lymph node metastasis.

Cancer stratification by molecular imaging

The lack of specificity of traditional cytotoxic drugs has triggered the development of anticancer agents that selectively address specific molecular targets. An intrinsic property of these specialized drugs is their limited applicability for specific patient subgroups. Consequently, the generation of information about tumor characteristics is the key to exploit the potential of these drugs. Currently, cancer stratification relies on three approaches: Gene expression analysis and cancer proteomics, immunohistochemistry and molecular imaging. In order to enable the precise localization of functionally expressed targets, molecular imaging combines highly selective biomarkers and intense signal sources. Thus, cancer stratification and localization are performed simultaneously. Many cancer types are characterized by altered receptor expression, such as somatostatin receptors, folate receptors or Her2 (human epidermal growth factor receptor 2). Similar correlations are also known for a multitude of transporters, such as glucose transporters, amino acid transporters or hNIS (human sodium iodide symporter), as well as cell specific proteins, such as the prostate specific membrane antigen, integrins, and CD20. This review provides a comprehensive description of the methods, targets and agents used in molecular imaging, to outline their application for cancer stratification. Emphasis is placed on radiotracers which are used to identify altered expression patterns of cancer associated markers.

Evolutionary origin of amino acid transporter families SLC32, SLC36 and SLC38 and physiological, pathological and therapeutic aspects

About 25% of all solute carriers (SLCs) are likely to transport amino acids as their primary substrate. One of the major phylogenetic clusters of amino acid transporters from the SLC family is the β-family, which is part of the PFAM APC clan. The β-family includes three SLC families, SLC32, SLC36 and SLC38 with one, four and eleven members in humans, respectively. The most well characterized genes within these families are the vesicular inhibitory amino acid transporter (VIAAT, SLC32A1), PAT1 (SLC36A1), PAT2 (SLC36A2), PAT4 (SLC36A4), SNAT1 (SLC38A1), SNAT2 (SLC38A2), SNAT3 (SLC38A3), and SNAT4 (SLC38A4). Here we review the structural characteristics and functional role of these transporters. We also mined the complete protein sequence datasets for nine different genomes to clarify the evolutionary history of the β-family of transporters. We show that all three main branches of the this family are found as far back as green algae suggesting that genes from these families existed in the early eukaryote before the split of animals and plants and that they are present in most animal species. We also address the potential of further drug development within this field highlighting the important role of these transporters in neurotransmission and transport of amino acids as nutrients.

Relation of LAT1/4F2hc expression with pathological grade, proliferation and angiogenesis in human gliomas

Background

LAT1/4F2hc heterodimeric complex is a major route for the transport of large neutral essential amino acids through the plasma membrane. Although it has been shown that LAT1/4F2hc is highly expressed in a variety of human tumors including gliomas, and LAT1 over-expression is associated with glioma grade and poor prognosis of glioma patients, the precise tissue location of LAT1/4F2hc in gliomas and the precise role of LAT1/4F2hc in glioma biological features remain unclear.

Methods

In the current study, the expressions of LAT1, 4F2hc, CD34 and Ki-67 were investigated by immunohistochemistry in 62 cases of human brain glioma; LAT1/4F2hc expression level, Ki-67 labeling index (Ki-67 LI) and microvessel density (MVD) were measured semi-quantitatively; and the correlation of LAT1/4F2hc expression with histopathological features, Ki-67 LI and MVD in gliomas was further analyzed.

Results

The results showed that both LAT1 and 4F2hc were expressed in all examined specimens. LAT1 but 4F2hc expression levels significantly correlated with the pathological grade and both expression levels significantly correlated with Ki-67 LI of gliomas. We also demonstrated that both LAT1 and 4F2hc immunoreactivity were observed in tumor cells as well as vascular endothelia; furthermore, the LAT1 expression level was markedly associated with glioma MVD as well.

Conclusion

LAT1/4F2hc over-expression is closely correlates with the malignant phenotype and proliferation of gliomas, and LAT1 was associates with glioma angiogenesis. LAT1/4F2hc, especially LAT1, may become a novel potential molecular target for glioma biological therapy.