Prognostic significance of L-type amino acid transporter 1 (LAT1) and 4F2 heavy chain (CD98) expression in early stage squamous cell carcinoma of the lung

CD98 heavy chain protein is overexpressed in non-small cell lung cancer and is a potential target for CAR T-cell therapy

Chimeric antigen receptor (CAR) T cells are effective against hematological cancers, but are less effective against solid tumors such as non-small cell lung cancer (NSCLC). One of the reasons is that only a few cell surface targets specific for NSCLC cells have been identified. Here, we report that CD98 heavy chain (hc) protein is overexpressed on the surface of NSCLC cells and is a potential target for CAR T cells against NSCLC. Screening of over 10,000 mAb clones raised against NSCLC cell lines showed that mAb H2A011 bound to NSCLC cells but not normal lung epithelial cells. H2A011 recognized CD98hc. Although CAR T cells derived from H2A011 could not be established presumably due to the high level of H2A011 reactivity in activated T cells, those derived from the anti-CD98hc mAb R8H283, which had been shown to lack reactivity with CD98hc glycoforms expressed on normal hematopoietic cells and some normal tissues, were successfully developed. R8H283 specifically reacted with NSCLC cells in six of 15 patients. R8H283-derived CAR T cells exerted significant anti-tumor effects in a xenograft NSCLC model in vivo. These results suggest that R8H283 CAR T cells may become a new therapeutic tool for NSCLC, although careful testing for off-tumor reactivity should be performed in the future.

Protein expression of the amino acid transporter SLC7A5 in tumor tissue is prognostic in early-stage colorectal cancer

Proteins overexpressed in early-stage cancers may serve as early diagnosis and prognosis markers as well as targets for cancer therapies. In this study, we examined the expression of an essential amino acid carrier SLC7A5 (LAT1, CD98, or 4F2 light chain) in cancer tissue from two well-annotated cohorts of 575 cases of early-stage and 106 cases of late-stage colorectal cancer patients. Immunohistochemistry showed SLC7A5 overexpression in 72.0% of early-stage and 56.6% of late-stage cases. SLC7A5 expression was not influenced by patient gender, age, location, or mismatch repair status, although it appeared to be slightly less prevalent in tumors of mucinous differentiation or with lymphovascular invasion. Statistical analyses revealed a positive correlation between SLC7A5 overexpression and both overall survival and disease-free survival in early-stage but not late-stage cancers. Co-expression analyses of the TCGA and CPTAC colorectal cancer cohorts identified a network of gene transcripts positively related to SLC7A5, with its heterodimer partner SLC3A2 having the highest co-expression score. Network analysis uncovered the SLC7A network to be significantly associated with ncRNA such as tRNA processing and the mitotic cell cycle. Since SLC7A5 is also a marker of activated lymphocytes such as NK, T, and B lymphocytes, SLC7A5 overexpression in early colorectal cancers might trigger a strong anti-tumor immune response which could results in better clinical outcome. Overall, our study provides clear evidence of differential SLC7A5 expression and its prognostic value for early-stage colorectal cancer, although the understanding of its functions in colorectal tumorigenesis and cancer immunity is currently rather limited and awaits further characterization.

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.

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.

Induction of CTH expression in response to amino acid starvation confers resistance to anti-LAT1 therapy in MDA-MB-231 cells

L type amino acid transporter 1 (LAT1) is an attractive molecular target for cancer therapy because of its overexpression in many cancer cells. JPH203, a selective LAT1 inhibitor, causes amino acid deprivation and suppresses cancer cell proliferation. However, several cancer cells showed resistance to amino acid deprivation. In this study, we aimed to elucidate the molecular mechanism of different sensitivity between 2 breast cancer cells to anti-LAT1 therapy. MDA-MB-231 cells were more resistant to growth suppression effect of JPH203 than T-47D cells (IC50 was 200 ± 12.5 μM for MDA-MB-231, and 5 ± 1.1 μM for T-47D cells; p < 0.05). Transcriptome and biochemical analysis were done in these cells in the presence/absence of JPH203. JPH203 induced intracellular amino acid deprivation stress in both cells, but it upregulated cystathionine γ lyase (CTH), an enzyme for synthesis of antioxidants, only in MDA-MB-231 cells. Moreover, siRNA-mediated CTH knockdown induced oxidative stress in response to JPH203 leading to decreased cell viability in MDA-MB-231 cells. These results suggest that activation of anti-oxidation pathways in response to amino acid deprivation confers resistance to anti-LAT1 therapy.

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.

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.

Physiological and Pathophysiological Roles of Ion Transporter-Mediated Metabolism in the Thyroid Gland and in Thyroid Cancer

Thyroid cancer is the most common type of endocrine tumor and has shown an increasing annual incidence, especially among women. Patients with thyroid cancer have a good prognosis, with a high five-year survival rate; however, the recurrence rate and disease status of thyroid cancer remain a burden for patients, which compels us to further elucidate the pathogenesis of this disease. Recently, ion transporters have gradually become a hot topic in the field of thyroid gland biology and cancer research. Additionally, alterations in the metabolic state of tumor cells and protein molecules have gradually become the focus of scientific research. This review focuses on the progress in understanding the physiological and pathophysiological roles of ion transporter-mediated metabolism in both the thyroid gland and thyroid cancer. We also hope to shed light on new targets for the treatment and prognosis of thyroid cancer.

Preparation and assessment of a new radiotracer technetium-99m-6-hydrazinonicotinic acid-tyrosine as a targeting agent in tumor detecting through single photon emission tomography

The goal of investigation was to bring up an impressive way to synthesize technetium-99 m-6-hydrazinonicotinic acid-tyrosine (^99mTc-HYNIC-Tyr), a newfound radiotracer, and to assess the capacity of being as a tumor scintigraphy agent. The conjugate was prepared by solid phase method using tritely chloride resin. The precursor HYNIC-Tyr was labeled with ^99mTc which was accomplished at 100 °C through the coligands tricine and EDDA. Furthermore, the serum albumin binding, cellular attachment, organs uptake and tumor accumulation were measured. C6 glioma cells were used for cellular and tumor uptake studies. ^99mTc-HYNIC-Tyr was prepared with labeling yield of >99% (n = 3). Radiotracer showed stability in serum proteins in incubates temperature. Specific cellular attachment of radiotracer was noticeable in C6 glioma cells with dissociation constant in nano molar range (21.03 ± 1.54 nM). The amount of uptake in C6 rat glioma xenograft was 2.61 ± 0.12 percent of injection dose per gram after 30 min. In whole-body scintigraphy, C6 glioma tumor was easy to be traced and interpreted at 1 h after administration of radiotracer. Our data suggest that ^99mTc-HYNIC-Tyr, a new radiotracer based on amino acid, efficiently differentiates the tumor cells and goes into them. Our results indicate that this radiotracer has excellent capacity to detect tumor cells in rat and to be included as a radiopharmaceutical for detecting cancer tumors.

Oncology Therapeutics Targeting the Metabolism of Amino Acids

Amino acid metabolism promotes cancer cell proliferation and survival by supporting building block synthesis, producing reducing agents to mitigate oxidative stress, and generating immunosuppressive metabolites for immune evasion. Malignant cells rewire amino acid metabolism to maximize their access to nutrients. Amino acid transporter expression is upregulated to acquire amino acids from the extracellular environment. Under nutrient depleted conditions, macropinocytosis can be activated where proteins from the extracellular environment are engulfed and degraded into the constituent amino acids. The demand for non-essential amino acids (NEAAs) can be met through de novo synthesis pathways. Cancer cells can alter various signaling pathways to boost amino acid usage for the generation of nucleotides, reactive oxygen species (ROS) scavenging molecules, and oncometabolites. The importance of amino acid metabolism in cancer proliferation makes it a potential target for therapeutic intervention, including via small molecules and antibodies. In this review, we will delineate the targets related to amino acid metabolism and promising therapeutic approaches.

Prognostic value of LAT-1 status in solid cancer: A systematic review and meta-analysis

Background

The expression of the L-type amino acid transporter 1 (LAT1) plays a significant role in tumor progression. However, it remains unclear whether high LAT1 expression correlates with poor prognosis of solid tumor patients. Here, we conducted a meta-analysis to assess the potential of LAT1 in predicting the prognosis of tumor patients.

Methods and findings

A total of 4,579 cases were analyzed from 35 qualified studies. In patients with solid tumors, elevated expression of LAT1 is associated with poor prognosis (overall survival [OS]: pooled hazard ratio (HR) = 1.848, 95% confidence interval (CI) = 1.620–2.108, P < 0.001; disease free survival [DFS]: pooled HR = 1.923, 95% CI = 1.585–2.333, P < 0.001; progression free survival [PFS]: pooled HR = 1.345, 95% CI = 1.133–1.597, P = 0.001). Furthermore, in subgroup analysis, we found an association between high LAT1 expression and poor OS in non-small cell lung cancer (HR = 1.554, 95% CI = 1.345–1.794, P < 0.001), pancreatic cancer (HR = 2.052, 95% CI = 1.613–2.724, P < 0.001) and biliary tract cancer (HR = 2.253, 95% CI = 1.562–3.227, P < 0.001).

Conclusion

The results of this meta-analysis indicate the reliability and potential of using LAT1 expression as a predictive biomarker in solid cancers prior to treatment. However, further studies with larger sample sizes would be beneficial for fully evaluating the predictive value of LAT1 expression for clinical applications.

Extraprostatic Uptake of 18F-Fluciclovine: Differentiation of Nonprostatic Neoplasms From Metastatic Prostate Cancer

OBJECTIVE. Fluciclovine is a synthetic radiolabeled amino acid analog used for imaging of biochemical recurrent prostate cancer. Uptake of fluciclovine is mediated by several amino acid transporters, including alanine-serine-cysteine transporter 2 and large neutral amino acid transporters, which are known to be overexpressed in other malignancies. CONCLUSION. Knowledge of the common patterns of prostate cancer recurrence, in addition to what other neoplasms can show uptake, is critical for accurate study interpretation.

Development of a high affinity Anticalin® directed against human CD98hc for theranostic applications

Enhanced amino acid supply and dysregulated integrin signaling constitute two hallmarks of cancer and are pivotal for metastatic transformation of cells. In line with its function at the crossroads of both processes, overexpression of CD98hc is clinically observed in various cancer malignancies, thus rendering it a promising tumor target.

Methods: We describe the development of Anticalin proteins based on the lipocalin 2 (Lcn2) scaffold against the human CD98hc ectodomain (hCD98hcED) using directed evolution and protein design. X-ray structural analysis was performed to identify the epitope recognized by the lead Anticalin candidate. The Anticalin - with a tuned plasma half-life using PASylation^® technology - was labeled with ⁸⁹Zr and investigated by positron emission tomography (PET) of CD98-positive tumor xenograft mice.

Results: The Anticalin P3D11 binds CD98hc with picomolar affinity and recognizes a protruding loop structure surrounded by several glycosylation sites within the solvent exposed membrane-distal part of the hCD98hcED. In vitro studies revealed specific binding activity of the Anticalin towards various CD98hc-expressing human tumor cell lines, suggesting broader applicability in cancer research. PET/CT imaging of mice bearing human prostate carcinoma xenografts using the optimized and ⁸⁹Zr-labeled Anticalin demonstrated strong and specific tracer accumulation (8.6 ± 1.1 %ID/g) as well as a favorable tumor-to-blood ratio of 11.8.

Conclusion: Our findings provide a first proof of concept to exploit CD98hc for non-invasive biomedical imaging. The novel Anticalin-based αhCD98hc radiopharmaceutical constitutes a promising tool for preclinical and, potentially, clinical applications in oncology.

The Role of Large Neutral Amino Acid Transporter (LAT1) in Cancer

Background:

The solute carrier family 7 (SLC7) can be categorically divided into two subfamilies, the L-type amino acid transporters (LATs) including SLC7A5-13, and SLC7A15, and the cationic amino acid transporters (CATs) including SLC7A1-4 and SLC7A14. Members of the CAT family transport predominantly cationic amino acids by facilitating diffusion with intracellular substrates. LAT1 (also known as SLC7A5), is defined as a heteromeric amino acid transporter (HAT) interacting with the glycoprotein CD98 (SLC3A2) through a conserved disulfide to uptake not only large neutral amino acids, but also several pharmaceutical drugs to cells.

Methods:

In this review, we provide an overview of the interaction of the structure-function of LAT1 and its essential role in cancer, specifically, its role at the blood-brain barrier (BBB) to facilitate the transport of thyroid hormones, pharmaceuticals (e.g., I-DOPA, gabapentin), and metabolites into the brain.

Results:

LAT1 expression increases as cancers progress, leading to higher expression levels in highgrade tumors and metastases. In addition, LAT1 plays a crucial role in cancer-associated reprogrammed metabolic networks by supplying tumor cells with essential amino acids.

Conclusion:

The increasing understanding of the role of LAT1 in cancer has led to an increase in interest surrounding its potential as a drug target for cancer treatment.

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.

The combined expression of solute carriers is associated with a poor prognosis in highly proliferative ER+ breast cancer

PURPOSE

Breast cancer (BC) is a heterogeneous disease characterised by variant biology, metabolic activity, and patient outcome. Glutamine availability for growth and progression of BC is important in several BC subtypes. This study aimed to evaluate the biological and prognostic role of the combined expression of key glutamine transporters, SLC1A5, SLC7A5, and SLC3A2 in BC with emphasis on the intrinsic molecular subtypes.

METHODS

SLC1A5, SLC7A5, and SLC3A2 were assessed at the protein level, using immunohistochemistry on tissue microarrays constructed from a large well-characterised BC cohort (n = 2248). Patients were stratified into accredited clusters based on protein expression and correlated with clinicopathological parameters, molecular subtypes, and patient outcome.

RESULTS

Clustering analysis of SLC1A5, SLC7A5, and SLC3A2 identified three clusters low SLCs (SLC1A5-/SLC7A5-/SLC3A2-), high SLC1A5 (SLC1A5+/SLC7A5-/SLC3A2-), and high SLCs (SLC1A5+/SLC7A5+/SLC3A2+) which had distinct correlations to known prognostic factors and patient outcome (p < 0.001). The key regulator of tumour cell metabolism, c-MYC, was significantly expressed in tumours in the high SLC cluster (p < 0.001). When different BC subtypes were considered, the association with the poor outcome was observed in the ER+ high proliferation/luminal B class only (p = 0.003). In multivariate analysis, SLC clusters were independent risk factor for shorter BC-specific survival (p = 0.001).

CONCLUSION

The co-operative expression of SLC1A5, SLC7A5, and SLC3A2 appears to play a role in the aggressive subclass of ER+ high proliferation/luminal BC, driven by c-MYC, and therefore have the potential to act as therapeutic targets, particularly in synergism.

CD44 variant 9 expression as a predictor for gastric cancer recurrence: immunohistochemical and metabolomic analysis of surgically resected tissues

CD44 variant 9 (CD44v9) and the heavy chain of 4F2 cell-surface antigen (CD98hc) appear important for regulation of reactive oxygen species defence and tumor growth in gastric cancer. This study examined the roles of CD44v9 and CD98hc as markers of gastric cancer recurrence, and investigated associations with energy metabolism. We applied capillary electrophoresis time-of-flight mass spectrometry to metabolome profiling of gastric cancer specimens from 103 patients who underwent resection with no residual tumor or microscopic residual tumor, and compared metabolite levels to immunohistochemical staining for CD44v9 and CD98hc. Positive expression rates were 40.7% for CD44v9 and 42.7% for CD98hc. Various tumor characteristics were significantly associated with CD44v9 expression. Five-year recurrence-free survival rate was significantly lower for CD44v9-positive tumors (39.1%) than for CD44v9-negative tumors (73.5%; P < 0.0001), but no significant differences in recurrence-free survival were seen according to CD98hc expression. Uni- and multivariate analyses identified positive CD44v9 expression as an independent predictor of poorer recurrence-free survival. Metabolome analysis of 110 metabolites found that levels of glutathione disulfide were significantly lower and reduced glutathione (GSH)/ glutathione disulfide (GSSG) ratio was significantly higher in CD44v9-positive tumors than in CD44v9-negative tumors, suggesting that CD44v9 may enhance pentose phosphate pathway flux and maintain GSH levels in cancer cells.

Novel therapeutic approaches targeting L-type amino acid transporters for cancer treatment

L-type amino acid transporters (LATs) mainly assist the uptake of neutral amino acids into cells. Four LATs (LAT1, LAT2, LAT3 and LAT4) have so far been identified. LAT1 (SLC7A5) has been attracting much attention in the field of cancer research since it is commonly up-regulated in various cancers. Basic research has made it increasingly clear that LAT1 plays a predominant role in malignancy. The functional significance of LAT1 in cancer and the potential therapeutic application of the features of LAT1 to cancer management are described in this review.

MicroRNA-126 inhibits cell proliferation in gastric cancer by targeting LAT-1

MicroRNA-126 (miR-126) is a pivotal post-transcriptional regulator, which has been validated as a suppressor in gastric cancer (GC). However, the downstream of its tumor inhibiting function has not been totally clear. L-type amino-acid transporter 1 (LAT-1) is a novel member of system L-type transporters involving in cell proliferation, and we have previously validated that LAT-1 played a role of promotor in GC. In this study, we further detected and confirmed that LAT-1 was exactly targeted by miR-126 in GC. We found LAT-1 was significantly downregulated in GC MKN-45 cell lines by using miR-126 mimics, along with an impairment on cell proliferation and cell cycle. Additionally, by overexpressing LAT-1 in MKN-45 cells which was firstly treated with miR-126 mimics, the ability of cell proliferation in MKN-45 cells was definitely rescued. Thus, our results suggests and consolidates the standpoint that miR-126 plays a pivotal role in GC suppressing the process of GC cell, and this function is at least partly taken to implement by miR-126s's post-transcriptional effect on LAT-1. This might provide us likely potential biomarkers and targets for GC prevention, diagnosis and therapeutic treatment.

Cell surface marker profiling of human tracheal basal cells reveals distinct subpopulations, identifies MST1/MSP as a mitogenic signal, and identifies new biomarkers for lung squamous cell carcinomas

BACKGROUND

The large airways of the lungs (trachea and bronchi) are lined with a pseudostratified mucociliary epithelium, which is maintained by stem cells/progenitors within the basal cell compartment. Alterations in basal cell behavior can contribute to large airway diseases including squamous cell carcinomas (SQCCs). Basal cells have traditionally been thought of as a uniform population defined by basolateral position, cuboidal cell shape, and expression of pan-basal cell lineage markers like KRT5 and TP63. While some evidence suggests that basal cells are not all functionally equivalent, few heterogeneously expressed markers have been identified to purify and study subpopulations. In addition, few signaling pathways have been identified that regulate their cell behavior. The goals of this work were to investigate tracheal basal cell diversity and to identify new signaling pathways that regulate basal cell behavior.

METHODS

We used flow cytometry (FACS) to profile cell surface marker expression at a single cell level in primary human tracheal basal cell cultures that maintain stem cell/progenitor activity. FACS results were validated with tissue staining, in silico comparisons with normal basal cell and lung cancer datasets, and an in vitro proliferation assay.

RESULTS

We identified 105 surface markers, with 47 markers identifying potential subpopulations. These subpopulations generally fell into more (~ > 13%) or less abundant (~ < 6%) groups. Microarray gene expression profiling supported the heterogeneous expression of these markers in the total population, and immunostaining of large airway tissue suggested that some of these markers are relevant in vivo. 24 markers were enriched in lung SQCCs relative to adenocarcinomas, with four markers having prognostic significance in SQCCs. We also identified 33 signaling receptors, including the MST1R/RON growth factor receptor, whose ligand MST1/MSP was mitogenic for basal cells.

CONCLUSION

This work provides the largest description to date of molecular diversity among human large airway basal cells. Furthermore, these markers can be used to further study basal cell function in repair and disease, and may aid in the classification and study of SQCCs.

Genetic variations in SLC3A2/CD98 gene as prognosis predictors in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is characterized by poor prognosis and only a few molecular markers may be potentially used to predict the risk of progression. This study aims to assess the effects of single nucleotide polymorphisms (SNPs) in the CD98 gene on prognosis of NSCLC patients. We genotyped three potential functional SNPs in CD98 gene using Sequenom iPLEX genotyping system in a cohort of 482 NSCLC patients. Multivariate cox proportional hazards model and Kaplan-Meier curve were used for the survival analysis. The variant-containing genotypes of rs1059292 in 5'-flanking region of CD98 gene were significantly associated with an increased risk of death in the multivariate analysis (Hazard ratio [HR], 1.49; 95% confidence interval [95% CI]: 1.04-2.14 in a dominant model). In stratified analysis, the association remained significant in patients with poor differentiation (HR=1.81, 95% CI=1.01-3.25). In addition, rs1059292 also showed a borderline significant association with T stage (OR=1.49; 95% CI: 0.96-2.35) and N stage (OR=1.53; 95% CI: 0.98-2.39). Functional analysis demonstrated that variant genotype of SNP rs1059292 significantly enhanced the transcription activity of CD98 gene promoter. Our data suggest that genetic variation of rs1059292 in CD98 gene may affect clinical outcome of NSCLC in Chinese population.

Cancer stem cell enrichment marker CD98: a prognostic factor for survival in patients with human papillomavirus-positive oropharyngeal cancer

PURPOSE

Several hypotheses have been proposed to explain the relatively good prognosis of patients with a human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (OPSCC) and one of these is a higher sensitivity to (chemo)radiation. Previous studies have suggested that treatment failure in OPSCC patients is caused by resistance of cancer stem cells (CSCs). The purpose of this study was to evaluate the association between the number of CSCs and prognosis in HPV-positive OPSCC patients.

EXPERIMENTAL DESIGN

All OPSCC patients (n=711) treated between 2000 and 2006 in two Dutch university hospitals were included. Presence of HPV in a tumour tissue specimen was tested by p16-immunostaining followed by HPV DNA GP5+/6+polymerase chain reaction (PCR). The presence and intensity of tumour CSC markers CD44 and CD98 were determined by immunohistochemistry and semiquantitative scoring was performed. Overall survival (OS) and progression-free survival (PFS) rates were compared between patients with low and high CD44/CD98 expression in relation to HPV status.

RESULTS

HPV-positive tumours showed a lower percentage of cells with CD44 and CD98 expression than HPV-negative tumours (p<0.001, χ(2)-test). Within the group of patients with HPV-positive OPSCC, a high percentage of CD98-positive tumour cells was associated with a significantly worse 5-year OS and PFS (OS: 36.4% and PFS: 27.3%) compared to patients with a low percentage of CD98-positive cells (OS: 71.9% and PFS: 70.5%, respectively) (p<0.001).

CONCLUSIONS

HPV-positive OPSCCs harbour fewer cells expressing the CSC enrichment markers CD44 and CD98. Furthermore, OS and PFS were significantly worse for patients with HPV-positive OPSCC with a high percentage of CD98-positive cells.

Imaging the L-type amino acid transporter-1 (LAT1) with Zr-89 immunoPET

The L-type amino acid transporter-1 (LAT1, SLC7A5) is upregulated in a wide range of human cancers, positively correlated with the biological aggressiveness of tumors, and a promising target for both imaging and therapy. Radiolabeled amino acids such as O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET) that are transport substrates for system L amino acid transporters including LAT1 have met limited success for oncologic imaging outside of the brain, and thus new strategies are needed for imaging LAT1 in systemic cancers. Here, we describe the development and biological evaluation of a novel zirconium-89 labeled antibody, [⁸⁹Zr]DFO-Ab2, targeting the extracellular domain of LAT1 in a preclinical model of colorectal cancer. This tracer demonstrated specificity for LAT1 in vitro and in vivo with excellent tumor imaging properties in mice with xenograft tumors. PET imaging studies showed high tumor uptake, with optimal tumor-to-non target contrast achieved at 7 days post administration. Biodistribution studies demonstrated tumor uptake of 10.5 ± 1.8 percent injected dose per gram (%ID/g) at 7 days with a tumor to muscle ratio of 13 to 1. In contrast, the peak tumor uptake of the radiolabeled amino acid [¹⁸F]FET was 4.4 ± 0.5 %ID/g at 30 min after injection with a tumor to muscle ratio of 1.4 to 1. Blocking studies with unlabeled anti-LAT1 antibody demonstrated a 55% reduction of [⁸⁹Zr]DFO-Ab2 accumulation in the tumor at 7 days. These results are the first report of direct PET imaging of LAT1 and demonstrate the potential of immunoPET agents for imaging specific amino acid transporters.

[An efficient method for producing monoclonal antibodies against multi-pass membrane proteins]

Antibodies have greatly contributed to the development of medical science and pharmacology, because of their high specificity. The cell fusion method has developed monoclonal antibodies (mAb) technology, such that massive amounts of mAb with a uniform structure can be produced. Although mAb have been produced against many proteins so far, the production of mAb against multi-pass transmembrane proteins, such as G-protein coupled receptor (GPCR) and various transporter proteins has been extremely difficult. The complicated structures, poorly extracellular regions, and high hydrophobicity of multiple-transmembrane proteins make it difficult to produce mAb against them. Production of mAb that recognize the extracellular region of living cells is thought to be important in determining the ability of a protein. Based on these findings, we tried to produce mAb against a multi-pass transmembrane transporter using green fluorescent protein (GFP)-fused full-length target proteins as immunogens. Furthermore, the immunizing method has proved to be important in generating functional mAb. We succeeded in producing functional mAb that react against the extracellular region of a 12-pass transmembrane transporter in a living cell. Based on this success, we began to produce mAb against seven-transmembrane GPCR. In this symposium, we report on the results of producing mAb against S1P receptors, a type of GPCR.

Development of (99m)Tc-EC-tyrosine for early detection of breast cancer tumor response to the anticancer drug melphalan

RATIONALE AND OBJECTIVES

Radiolabeled tyrosine analogues that have been successfully used in tumor imaging accumulate in tumor cells via an upregulated L-type amino acid transporter system. The anticancer drug melphalan is an L-type amino acid transporter substrate. Therefore, radiolabeled tyrosine analogues may have great potential in evaluating treatment responses to melphalan. In this study, a (99m)Tc-labeled tyrosine analogue, (99m)Tc tyrosine using N,N'-ethylene-di-L-cysteine (EC) as a chelator, was developed and its potential for noninvasively assessing tumors' early response to melphalan determined.

MATERIALS AND METHODS

EC-tyrosine was synthesized in a three-step procedure and labeled with (99m)Tc. To assess cellular uptake kinetics, the percentage uptake of (99m)Tc-EC-tyrosine in the rat breast cancer cell line 13762 was measured. Planar imaging was performed in rats with 13762 cell-derived tumors. To determine the transport mechanisms of (99m)Tc-EC-tyrosine, a competitive inhibition study using L-tyrosine as an inhibitor was performed in vitro and in vivo. To assess tumors' response to melphalan, tumor-bearing rats were treated with different doses of melphalan, and planar imaging was performed 0 and 3 days after treatment. Immunohistochemical analyses were conducted to determine expressions of L-type amino acid transporter 1 and cellular proliferation marker Ki-67.

RESULTS

L-tyrosine significantly inhibited (99m)Tc-EC-tyrosine uptake in vitro and in vivo. Tumor volume decreased in a dose-dependent manner with melphalan, and tumor/muscle ratios of (99m)Tc-EC-tyrosine were significantly reduced in treated groups. Immunohistochemical data indicated that about 70% of tumor cells in the melphalan-treated groups underwent apoptosis, and the changes in tumor/muscle ratios reflected the decreased percentage of viable cells in treated tumors.

CONCLUSIONS

These findings suggest that (99m)Tc-EC-tyrosine has great potential for monitoring tumor response to melphalan in breast tumor-bearing rats.

CD98 increases renal epithelial cell proliferation by activating MAPKs

CD98 heavy chain (CD98hc) is a multifunctional transmembrane spanning scaffolding protein whose extracellular domain binds with light chain amino acid transporters (Lats) to form the heterodimeric amino acid transporters (HATs). It also interacts with β1 and β3 integrins by its transmembrane and cytoplasmic domains. This interaction is proposed to be the mechanism whereby CD98 mediates cell survival and growth via currently undefined signaling pathways. In this study, we determined whether the critical function of CD98-dependent amino acid transport also plays a role in cell proliferation and defined the signaling pathways that mediate CD98-dependent proliferation of murine renal inner medullary collecting duct (IMCD) cells. We demonstrate that downregulating CD98hc expression resulted in IMCD cell death. Utilizing overexpression studies of CD98hc mutants that either lacked a cytoplasmic tail or were unable to bind to Lats we showed that CD98 increases serum-dependent cell proliferation by a mechanism that requires the CD98hc cytoplasmic tail. We further demonstrated that CD98-dependent amino acid transport increased renal tubular epithelial cell proliferation by a mechanism that does not require the CD98hc cytoplasmic tail. Both these mechanisms of increased renal tubular epithelial cell proliferation are mediated by Erk and p38 MAPK signaling. Although increased amino transport markedly activated mTor signaling, this pathway did not alter cell proliferation. Thus, these studies demonstrate that in IMCD cells, the cytoplasmic and extracellular domains of CD98hc regulate cell proliferation by distinct mechanisms that are mediated by common MAPK signaling pathways.

c-Myc is crucial for the expression of LAT1 in MIA Paca-2 human pancreatic cancer cells

Tumor cells take up a massive amount of nutrition compared to normal cells for increased metabolism. Therefore, special transporters for organic materials are required to satisfy the powerful consumption of nutrition in tumor cells. L-type amino acid transporter 1 (LAT1) incorporates large neutral amino acids, most of which are also categorized as essential amino acids, into cells in a Na+-independent manner. Because of its high expression levels in a variety of cancer cells, it is speculated that LAT1 functions as a key transporter for highly effective delivery of essential amino acids into cancer cells. In this regard, LAT1 inhibitor is expected to have clinical benefit for cancer therapy. However, the molecular mechanism of enrichment of LAT1 in cancer cells remains poorly understood. Here, we show that a proto-oncogene, c-Myc, is a critical positive regulator of LAT1 expression in MIA Paca-2 human pancreatic cancer cells. The uptake of leucine, a representative neutral amino acid, was strictly dependent on LAT1 in MIA Paca-2 cells, and siRNA-mediated knockdown of LAT1 inhibited cell proliferation. Diminished c-Myc expression with siRNA resulted in severe reduction of LAT1 protein levels as well as mRNA levels, which, in turn, led to a significant defect of leucine incorporation. The LAT1 promoter has a canonical c-Myc binding sequence and overexpression of c-Myc increased LAT1 promoter activity, whereas mutation of c-Myc binding site diminished this effect. Our results suggest biological significance of LAT1 in tumor growth and molecular machinery that could explain why LAT1 is preferentially expressed in cancer cells.

Homeostatic and innate immune responses: role of the transmembrane glycoprotein CD98

The transmembrane glycoprotein CD98 is a potential regulator of multiple functions, including integrin signaling and amino acid transport. Abnormal expression or function of CD98 and disruption of the interactions between CD98 and its binding partners result in defects in cell homeostasis and immune responses. Indeed, expression of CD98 has been correlated with diseases such as inflammation and tumor metastasis. Modulation of CD98 expression and/or function therefore represents a promising therapeutic strategy for the treatment and prevention of such pathologies. Herein, we review the role of CD98 with focus on its functional importance in homeostasis and immune responses, which could help to better understand the pathogenesis of CD98-associated diseases.

Dysplasia-carcinoma transition specific transcripts in colonic biopsy samples

BACKGROUND

The early molecular detection of the dysplasia-carcinoma transition may enhance the strength of diagnosis in the case of colonic biopsies. Our aims were to identify characteristic transcript sets in order to develop diagnostic mRNA expression patterns for objective classification of benign and malignant colorectal diseases and to test the classificatory power of these markers on an independent sample set.

METHODOLOGY/PRINCIPAL FINDINGS

Colorectal cancer (CRC) and adenoma specific transcript sets were identified using HGU133plus2 microarrays and 53 biopsies (22 CRC, 20 adenoma and 11 normal). Ninety-four independent biopsies (27 CRC, 29 adenoma and 38 normal) were analyzed on microarrays for testing the classificatory power of the discriminatory genes. Array real-time PCR validation was done on 68 independent samples (24 CRC, 24 adenoma and 20 normal). A set of 11 transcripts (including CXCL1, CHI3L1 and GREM1) was determined which could correctly discriminate between high-grade dysplastic adenoma and CRC samples by 100% sensitivity and 88.9% specificity. The discriminatory power of the marker set was proved to be high on independent samples in both microarray and RT-PCR analyses. 95.6% of original and 94.1% of cross-validated samples was correctly classified in discriminant analysis.

CONCLUSIONS/SIGNIFICANCE

The identified transcripts could correctly characterize the dysplasia-carcinoma transition in biopsy samples, also on a large independent sample set. These markers can establish the basis of gene expression based diagnostic classification of colorectal cancer. Diagnostic RT-PCR cards can become part of the automated routine procedure.

Androgen receptor and nutrient signaling pathways coordinate the demand for increased amino acid transport during prostate cancer progression

L-Type amino acid transporters such as LAT1 and LAT3 mediate the uptake of essential amino acids. Here, we report that prostate cancer cells coordinate the expression of LAT1 and LAT3 to maintain sufficient levels of leucine needed for mTORC1 signaling and cell growth. Inhibiting LAT function was sufficient to decrease cell growth and mTORC1 signaling in prostate cancer cells. These cells maintained levels of amino acid influx through androgen receptor-mediated regulation of LAT3 expression and ATF4 regulation of LAT1 expression after amino acid deprivation. These responses remained intact in primary prostate cancer, as indicated by high levels of LAT3 in primary disease, and by increased levels of LAT1 after hormone ablation and in metastatic lesions. Taken together, our results show how prostate cancer cells respond to demands for increased essential amino acids by coordinately activating amino acid transporter pathways vital for tumor outgrowth.

Global molecular dysfunctions in gastric cancer revealed by an integrated analysis of the phosphoproteome and transcriptome

We integrated LC-MS/MS-based and protein antibody array-based proteomics with genomics approaches to investigate the phosphoproteome and transcriptome of gastric cancer cell lines and endoscopic gastric biopsies from normal subjects and patients with benign gastritis or gastric cancer. More than 3,000 non-redundant phosphorylation sites in over 1,200 proteins were identified in gastric cancer cells. We correlated phosphoproteome data with transcriptome data sets and reported the expression of 41 protein kinases, 5 phosphatases and 65 phosphorylated mitochondrial proteins in gastric cancer cells. Transcriptional expression levels of 190 phosphorylated proteins were >2-fold higher in gastric cancer cells compared to normal stomach tissue. Pathway analysis demonstrated over-presentation of DNA damage response pathway and underscored critical roles of phosphorylated p53 in gastric cancer. This is the first study to comprehensively report the gastric cancer phosphoproteome. Integrative analysis of the phosphoproteome and transcriptome provided an expansive view of molecular signaling pathways in gastric cancer.

Assessment of therapy response in lung cancer with ¹⁸F-α-methyl tyrosine PET

OBJECTIVE

PET with a novel tracer, L-[3-¹⁸F]-α-methyl tyrosine (¹⁸F-FMT), has been studied in lung cancer. We evaluated ¹⁸F-FMT PET for therapy response in comparison with ¹⁸F-FDG PET.

SUBJECTS AND METHODS

Eighteen patients with lung cancer underwent PET studies with ¹⁸F-FMT and FDG before and after chemoradiotherapy. Uptake of tracers was measured by standardized uptake value (SUV) in the primary tumor and the mediastinal lymph node. The ratio of the lymph node maximum SUV (SUV(max)) to that of the primary tumor and the SUV(max) of the primary tumor itself were correlated with the survival time estimated by Kaplan-Meier method. Metabolic response, as determined by the changes in the tracer uptake, was compared with Response Evaluation Criteria in Solid Tumors (RECIST) for therapy response.

RESULTS

Agreement of therapeutic response evaluated by RECIST was noted in 10 (56%) of 18 patients evaluated with FDG PET and in 16 (89%) of 18 patients evaluated with ¹⁸F-FMT PET (p = 0.025). In nine patients with partial response, partial metabolic response was observed in eight (89%) by use of FDG PET and in nine (100%) by use of ¹⁸F-FMT PET. In nine patients with stable disease, stable metabolic disease was observed in two (22%) by use of FDG PET and in seven (78%) by use of ¹⁸F-FMT PET (p = 0.056). Fluorine-18-FMT PET revealed that the prognosis of the group with a lymph node-to-primary tumor SUV(max) ratio greater than or equal to 1 was significantly better than that in the group with a ratio of less than 1.

CONCLUSION

Fluorine-18-FMT is a promising PET tracer for monitoring response to chemoradiotherapy and for predicting the prognosis of patients with lung cancer.

Comparison of L-type amino acid transporter 1 expression and L-[3-18F]-α-methyl tyrosine uptake in outcome of non-small cell lung cancer

OBJECTIVE

L-Type amino acid transporter 1 (LAT1) has associated with tumor growth and poor outcome of patients with non-small cell lung cancer (NSCLC). L-[3-(18)F]-α-methyl tyrosine ((18)F-FAMT) is an amino acid tracer for positron emission tomography (PET) imaging, and (18)F-FAMT uptake is mediated by LAT1. The purpose of this study is to compare the prognostic significance of (18)F-FAMT uptake in the primary tumors with that of LAT1 expression in patients with NSCLC.

METHODS

Fifty-nine patients with NSCLC were enrolled in this study. All patients underwent (18)F-FAMT PET prior to resection of the tumor, and immunohistochemical staining of the resected tumors were performed to compare the (18)F-FAMT uptake and LAT1 expression. Uptake of (18)F-FAMT was evaluated using semiquantitative standardized uptake value (SUV(max)), and the cutoff value was determined to discriminate patients with high SUV(max) from those with low SUV(max). Expression of LAT1 was evaluated by the score of staining intensity through 1 to 4. SUV(max) and LAT1 expression were compared according to the clinicopathological variables.

RESULTS

The best discriminative cutoff value of (18)F-FAMT SUV(max) within the primary tumors was 1.6. The high SUV(max) (>1.6) in (18)F-FAMT PET was significantly associated with male, and positive LAT1 expression was significantly associated with male and nonadenocarcinoma. In the univariate analysis, high SUV(max) (>1.6) in (18)F-FAMT PET and positive LAT1 expression were significant predictor of the poor outcome. Multivariate analysis confirmed that positive LAT1 expression was an independent and significant factor for predicting poor prognosis in NSCLC (P=.035).

CONCLUSION

LAT1 expression is a stronger prognostic factor than (18)F-FAMT uptake in surgically resected NSCLC.

CD98 expression is associated with poor prognosis in resected non-small-cell lung cancer with lymph node metastases

BACKGROUND

The purpose of this study was to evaluate the prognostic value of L-type amino acid transporter 1 (LAT1) and 4F2 heavy chain (CD98) expression in resectable non-small-cell lung cancer (NSCLC) patients with N1 and N2 nodal involvement.

METHODS

A total of 220 consecutive patients were retrospectively reviewed. Immunohistochemical expression of LAT1, CD98, Ki-67 labeling index, vascular endothelial growth factor (VEGF), and microvessel density (MVD) was correlated with clinical features and prognosis of patients after complete resection of the tumor.

RESULTS

Positive expression of LAT1 and CD98 was recognized in 60% (132/220) and 47% (103/220), respectively (P = 0.021). A positive rate of LAT1 expression was significantly higher in squamous cell carcinoma (SQC) (91%; 65/71) and large cell carcinoma (LCC) (82%; 9/11) than in adenocarcinoma (AC) (42%; 58/138). Moreover, a positive rate of CD98 expression was also significantly higher in SQC (76%; 54/71) and LCC (73%; 8/11) than in AC (30%; 42/138). LAT1 expression was significantly correlated with CD98, Ki-67 labeling index, VEGF, and MVD. The 5-year survival rates of LAT1-positive and LAT1-negative patients and CD98-positive and CD98-negative patients, were 43% and 48% (P = 0.1043), respectively and 39% and 50% (P = 0.0239), respectively. Multivariate analysis confirmed that positive expression of CD98 was an independent factor for predicting a poor prognosis.

CONCLUSIONS

In our limited series, CD98 is a pathological factor that predicts prognosis in resectable adenocarcinoma patients with N2 disease.