Dynamic association of the intramembrane proteases SPPL2a/b and their substrates with tetraspanin-enriched microdomains

Signal peptide peptidase-like 2a and b (SPPL2a/b) are aspartyl intramembrane proteases and cleave tail-anchored proteins as well as N-terminal fragments (NTFs) derived from type II-oriented transmembrane proteins. How these proteases recruit substrates and cleavage is regulated, is still incompletely understood. We found that SPPL2a/b localize to detergent-resistant membrane (DRM) domains with the characteristics of tetraspanin-enriched microdomains (TEMs). Based on this, association with several tetraspanins was evaluated. We demonstrate that not only SPPL2a/b but also their substrates tumor necrosis factor (TNF) and CD74 associate with tetraspanins like CD9, CD81, and CD82 and/or TEMs and analyze the stability of these complexes in different detergents. CD9 and CD81 deficiency has protease- and substrate-selective effects on SPPL2a/b function. Our findings suggest that reciprocal interactions with tetraspanins may assist protease-substrate encounters of SPPL2a/b within the membrane. Beyond SPP/SPPL proteases, this supports previous concepts that tetraspanins facilitate membrane-embedded proteolytic processes.

Identification and tracking of HTLV-1-infected T cell clones in virus-associated neurologic disease

Human T lymphotropic virus type 1-assoicated (HTLV-1-associated) myelopathy/tropical spastic paraparesis (HAM/TSP) is a neuroinflammatory disease caused by the persistent proliferation of HTLV-1-infected T cells. Here, we performed a T cell receptor (TCR) repertoire analysis focused on HTLV-1-infected cells to identify and track the infected T cell clones that are preserved in patients with HAM/TSP and migrate to the CNS. TCRβ repertoire analysis revealed higher clonal expansion in HTLV-1-infected cells compared with noninfected cells from patients with HAM/TSP and asymptomatic carriers (ACs). TCR clonality in HTLV-1-infected cells was similar in patients with HAM/TSP and ACs. Longitudinal analysis showed that the TCR repertoire signature in HTLV-1-infected cells remained stable, and highly expanded infected clones were preserved within each patient with HAM/TSP over years. Expanded HTLV-1-infected clones revealed different distributions between cerebrospinal fluid (CSF) and peripheral blood and were enriched in the CSF of patients with HAM/TSP. Cluster analysis showed similarity in TCRβ sequences in HTLV-1-infected cells, suggesting that they proliferate after common antigen stimulation. Our results indicate that exploring TCR repertoires of HTLV-1-infected cells can elucidate individual clonal dynamics and identify potential pathogenic clones expanded in the CNS.

HAM/TSP Pathogenesis: The Transmigration Activity of HTLV-1-Infected T Cells into Tissues

Slowly progressive spastic paraparesis with bladder dysfunction, the main clinical feature of human T-cell leukemia virus-1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), is induced by chronic inflammation in the spinal cord, mainly the lower thoracic cord. A long-standing bystander mechanism, such as the destruction of surrounding tissues by inflammatory cytokines, etc., induced under the interaction between infiltrated HTLV-1-infected CD4⁺ T cells and HTLV-1-specific CD8⁺ cytotoxic T cells, has been considered implicated for the induction of chronic inflammation. As this bystander mechanism is triggered conceivably by the transmigration of HTLV-1-infected CD4⁺ T cells to the spinal cord, heightened transmigrating activity of HTLV-1-infected CD4⁺ T cells to the spinal cord might play a crucial role as the first responder in the development of HAM/TSP. This review evaluated the functions of HTLV-1-infected CD4⁺ T cells in HAM/TSP patients as the prerequisite for the acquisition of the activity such as adhesion molecule expression changes, small GTPases activation, and expression of mediators involved in basement membrane disruption. The findings suggest that HTLV-1-infected CD4⁺ T cells in HAM/TSP patients have enough potential to facilitate transmigration into the tissues. Future HAM/TSP research should clarify the molecular mechanisms leading to the establishment of HTLV-1-infected CD4⁺ T cells as the first responder in HAM/TSP patients. In addition, a regimen with an inhibitory activity against the transmigration of HTLV-1-infected CD4⁺ T cells into the spinal cord might be recommended as one of the therapeutic strategies against HAM/TSP patients.

Impact of anti-diabetic sodium-glucose cotransporter 2 inhibitors on tumor growth of intractable hematological malignancy in humans

Under the dysfunction of mitochondria, cancer cells preferentially utilize both glycolytic and pentose phosphate pathways rather than electron transport chains to desperately generate adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH), classically recognized as the Warburg effect. Based on this background, the present study tested the hypothesis that anti-diabetic sodium-glucose cotransporter 2 (SGLT2) inhibitors would exert a tumor-suppressive impact on intractable human hematological malignancies via the modulation of glucose metabolism within cells and cell cycles. The level of mRNA for SGLT2 was remarkably elevated in leukemic cells from patients with adult T-cell leukemia (ATL), one of the most intractable blood cancers in humans, and as well as in two kinds of ATL cell lines (MT-1 and MT-2). Two kinds of SGLT2 inhibitors, Luseogliflozin and Tofogliflozin substantially suppressed the proliferation of MT-1 and MT-2 cells in both adherent and anchorage-independent culture conditions. Such a suppressive effect on tumor cell growth was reproduced by Luseogliflozin in leukemic cells in peripheral blood from patients with ATL. In MT-2 cells, both of SGLT2 inhibitors considerably attenuated glucose uptake, intracellular ATP levels, and NADPH production, resultantly enhancing cell cycle arrest at the G0/G1 phase. From the standpoint of metabolic oncology, the present study suggests that SGLT2 inhibitors would be a promising adjunctive option for the treatment of the most intractable human hematological malignancies like ATL.

Analysis of the key ligand receptor CADM1_CADM1 in the regulation of thyroid cancer based on scRNA-seq and bulk RNA-seq data

INTRODUCTION

Advanced papillary thyroid cancer (PTC) has a poor prognosis, 60~70% of which become radio iodine refractory (RAI-R), but the molecular markers that assess PTC progress to advanced PTC remain unclear. Meanwhile, current targeted therapies are badly effective due to drug resistance and adverse side effects. Ligand-receptor pairs (L/R pairs) play an important role in the interactions between tumor cells and other cells in the tumor microenvironment (TME). Nowadays, therapies targeting ligand-receptor pairs in the TME are advancing rapidly in the treatment of advanced cancers. However, therapies targeting L/R pairs applied to advanced PTC remains challenging because of limited knowledge about L/R pairs in PTC.

METHODS

We screened the critical L/R pair: CADM1-CADM1 using 65311 single-cell RNA sequencing (scRNA-seq) samples from 7 patients in different stage of PTC and bulk RNA-seq datasets containing data from 487 tumor samples and 58 para-carcinoma samples. Moreover, the expression levels of CADM1-CADM1 was assessed by quantitative real time polymerase chain reaction (qRT-PCR) and the function was analyzed using Transwell immigration assay.

RESULTS

We found that CADM1_CADM1 could be regarded as a biomarker representing a good prognosis of PTC. In addition, the high expression of CADM1_CADM1 can strongly increase the sensitivity of many targeted drugs, which can alleviate drug resistance. And the results of qRT-PCR showed us that the expression of CADM1_CADM1 in PTC was down-regulated and overexpression of CADM1 could suppresses tumor cell invasion migration.

CONCLUSION

Our study identified that CADM1_CADM1 played an essential role in the progression of PTC for the first time and our findings provide a new potential prognostic and therapeutic ligand-receptor pair for advanced PTC.

CCR4 as a Therapeutic Target for Cancer Immunotherapy

Simple Summary

CCR4 is a chemokine receptor selectively expressed on normal T cell subsets such as type 2 helper T cells, skin-homing T cells and regulatory T cells, and on skin-associated T cell malignancies such as adult T cell leukemia/lymphoma (ATLL), which is etiologically associated with human T lymphocyte virus type 1 (HTLV-1), and cutaneous T cell lymphomas (CTCLs). Mogamulizumab is a fully humanized and glyco-engineered monoclonal anti-CCR4 antibody used for the treatment of refractory/relapsed ATLL and CTCLs, often resulting in complete remission. The clinical applications of Mogamulizumab are now being extended to solid tumors, exploring the therapeutic effect of regulatory T cell depletion. This review overviews the expression of CCR4 in various T cell subsets, HTLV-1-infected T cells, ATLL and CTCLs, and the clinical applications of Mogamulizumab.

Abstract

CCR4 is a chemokine receptor mainly expressed by T cells. It is the receptor for two CC chemokine ligands, CCL17 and CCL22. Originally, the expression of CCR4 was described as highly selective for helper T type 2 (Th2) cells. Later, its expression was extended to other T cell subsets such as regulatory T (Treg) cells and Th17 cells. CCR4 has long been regarded as a potential therapeutic target for allergic diseases such as atopic dermatitis and bronchial asthma. Furthermore, the findings showing that CCR4 is strongly expressed by T cell malignancies such as adult T cell leukemia/lymphoma (ATLL) and cutaneous T cell lymphomas (CTCLs) have led to the development and clinical application of the fully humanized and glyco-engineered monoclonal anti-CCR4 Mogamulizumab in refractory/relapsed ATLL and CTCLs with remarkable successes. However, Mogamulizumab often induces severe adverse events in the skin possibly because of its efficient depletion of Treg cells. In particular, treatment with Mogamulizumab prior to allogenic hematopoietic stem cell transplantation (allo-HSCT), the only curative option of these T cell malignancies, often leads to severe glucocorticoid-refractory graft-versus-host diseases. The efficient depletion of Treg cells by Mogamulizumab has also led to its clinical trials in advanced solid tumors singly or in combination with immune checkpoint inhibitors. The main focus of this review is CCR4; its expression on normal and malignant T cells and its significance as a therapeutic target in cancer immunotherapy.

Diagnosis of Early Mycosis Fungoides

Mycosis fungoides (MF), the most common type of cutaneous T-cell lymphomas, generally has a favorable clinical course. Early MF typically presents erythematous patches and/or plaques and lasts for many years without affecting the life expectancy. Only limited cases progress to develop skin tumors, with subsequent lymph nodes and rarely visceral organ involvement. One of the clinical problems in early MF is the difficulty in differentiating the disease from benign inflammatory disorders (BIDs), such as atopic dermatitis, chronic eczema, and psoriasis. In some MF cases, clinical and pathological findings are similar to those of BIDs. However, the accurate diagnosis of early MF is quite important, as inappropriate treatment including immunosuppressants can cause unfavorable or even fatal outcomes. This article focuses on general methods and novel tools for diagnosis of early MF.

Brucella melitensis UGPase inhibits the activation of NF-κB by modulating the ubiquitination of NEMO

BACKGROUND

UTP-glucose-1-phosphoryl transferase (UGPase) catalyzes the synthesis of UDP-glucose, which is essential for generating the glycogen needed for the synthesis of bacterial lipopolysaccharide (LPS) and capsular polysaccharide, which play important roles in bacterial virulence. However, the molecular function of UGPase in Brucella is still unknown.

RESULTS

In this study, the ubiquitination modification of host immune-related protein in cells infected with UGPase-deleted or wild-type Brucella was analyzed using ubiquitination proteomics technology. The ubiquitination modification level and type of NF-κB Essential Modulator (NEMO or Ikbkg), a molecule necessary for NF-κB signal activation, was evaluated using Coimmunoprecipitation, Western blot, and dual-Luciferase Assay. We found 80 ubiquitin proteins were upregulated and 203 ubiquitin proteins were downregulated in cells infected with B. melitensis 16 M compared with those of B. melitensis UGPase-deleted strain (16 M-UGPase^-). Moreover, the ubiquitin-modified proteins were mostly enriched in the categories of regulation of kinase/NF-κB signaling and response to a bacterium, suggesting Brucella UGPase inhibits ubiquitin modification of related proteins in the host NF-κB signaling pathway. Further analysis showed that the ubiquitination levels of NEMO K63 (K63-Ub) and Met1 (Met1-Ub) were significantly increased in the 16 M-UGPase^--infected cells compared with that of the 16 M-infected cells, further confirming that the ubiquitination levels of NF-κB signaling-related proteins were regulated by the bacterial UGPase. Besides, the expression level of IκBα was decreased, but the level of p-P65 was significantly increased in the 16 M-UGPase^--infected cells compared with that of the 16 M- and mock-infected cells, demonstrating that B. melitensis UGPase can significantly inhibit the degradation of IκBα and the phosphorylation of p65, and thus suppressing the NF-κB pathway.

CONCLUSIONS

The results of this study showed that Brucella melitensis UGPase inhibits the activation of NF-κB by modulating the ubiquitination of NEMO, which will provide a new scientific basis for the study of immune mechanisms induced by Brucella.

Functional and Clinical Characteristics of Cell Adhesion Molecule CADM1 in Cancer

The cell adhesion molecule CADM1, which participates in cell adhesion and signal transduction, has a regulatory effect on the development of tumors. CADM1 is often involved in malignant tumors of multiple organ systems, such as the respiratory and digestive systems. Upregulated CADM1 promotes tumor cell apoptosis and inhibits malignant proliferation. Along with cell cycle-related proteins, it participates in regulating signaling pathways, such as EMT, STAT3, and AKT, and plays an important role in inhibiting invasion and migration. Considering clinical characteristics, low CADM1 expression is associated with aggressive tumors and poor prognosis. In addition, some long non-coding RNAs (lncRNAs) or miRNAs directly or indirectly act on CADM1 to regulate tumor growth and motility. Interestingly, CADM1 function differs in adult T-cell leukemia/lymphoma (ATLL), and NF-κB is thought to be involved in this process. Taken together, CADM1 could be a potential biomarker for early diagnosis and a target for cancer treatment in future clinical practices.

Activation of PERK-ATF4-CHOP pathway as a novel therapeutic approach for efficient elimination of HTLV-1-infected cells

Patients with adult T-cell leukemia (ATL) exhibit a poor prognosis and overall survival rate when treated with standard chemotherapy, highlighting the continued requirement for the development of novel safe and effective therapies for human T-cell leukemia virus type 1 (HTLV-1)-related diseases. In this study, we demonstrated that MK-2048, a second-generation HIV-1 integrase (IN) inhibitor, potently and selectively kills HTLV-1-infected cells. Differential transcriptome profiling revealed significantly elevated levels of gene expression of the unfolded protein response (UPR) PKR-like ER kinase (PERK) signaling pathway in ATL cell lines following MK-2048 treatment. We also identified a significant downregulation in glucose regulated protein 78 (GRP78), a master regulator of the UPR in the CD4+CADM1+ HTLV-1-infected cell population of primary HTLV-1 carrier peripheral blood mononuclear cells (PBMCs) (n = 9), suggesting that HTLV-1-infected cells are hypersensitive to endoplasmic reticulum (ER) stress-mediated apoptosis. MK-2048 efficiently reduced proviral loads in primary HTLV-1 carrier PBMCs (n = 4), but had no effect on the total numbers of these cells, indicating that MK-2048 does not affect the proliferation of HTLV-1-uninfected PBMCs. MK-2048 specifically activated the ER stress-related proapoptotic gene, DNA damage-inducible transcript 3 protein (DDIT3), also known as C/EBP homologous protein (CHOP), in HTLV-1-infected but not uninfected cells of HTLV-1-carrier PBMCs. Our findings demonstrated that MK-2048 selectively induces HTLV-1-infected cell apoptosis via the activation of the UPR. This novel regulatory mechanism of the HIV IN inhibitor MK-2048 in HTLV-1-infected cells provides a promising prophylactic and therapeutic target for HTLV-1-related diseases including ATL.

Novel targeted therapies of T cell lymphomas

T cell lymphomas (TCL) comprise a heterogeneous group of non-Hodgkin lymphomas (NHL) that often present at an advanced stage at the time of diagnosis and that most commonly have an aggressive clinical course. Treatment in the front-line setting is most often cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or CHOP-like regimens, which are effective in B cell lymphomas, but in TCL are associated with a high failure rate and frequent relapses. Furthermore, in contrast to B cell NHL, in which substantial clinical progress has been made with the introduction of monoclonal antibodies, no comparable advances have been seen in TCL. To change this situation and improve the prognosis in TCL, new gene-targeted therapies must be developed. This is now possible due to enormous progress that has been made in the last years in the understanding of the biology and molecular pathogenesis of TCL, which enables the implementation of the research findings in clinical practice. In this review, we present new therapies and current clinical and preclinical trials on targeted treatments for TCL using histone deacetylase inhibitors (HDACi), antibodies, chimeric antigen receptor T cells (CARTs), phosphatidylinositol 3-kinase inhibitors (PI3Ki), anaplastic lymphoma kinase inhibitors (ALKi), and antibiotics, used alone or in combinations. The recent clinical success of ALKi and conjugated anti-CD30 antibody (brentuximab-vedotin) suggests that novel therapies for TCL can significantly improve outcomes when properly targeted.

Role of exosomes in malignant glioma: microRNAs and proteins in pathogenesis and diagnosis

Malignant gliomas are the most common and deadly type of central nervous system tumors. Despite some advances in treatment, the mean survival time remains only about 1.25 years. Even after surgery, radiotherapy and chemotherapy, gliomas still have a poor prognosis. Exosomes are the most common type of extracellular vesicles with a size range of 30 to 100 nm, and can act as carriers of proteins, RNAs, and other bioactive molecules. Exosomes play a key role in tumorigenesis and resistance to chemotherapy or radiation. Recent evidence has shown that exosomal microRNAs (miRNAs) can be detected in the extracellular microenvironment, and can also be transferred from cell to cell via exosome secretion and uptake. Therefore, many recent studies have focused on exosomal miRNAs as important cellular regulators in various physiological and pathological conditions. A variety of exosomal miRNAs have been implicated in the initiation and progression of gliomas, by activating and/or inhibiting different signaling pathways. Exosomal miRNAs could be used as therapeutic agents to modulate different biological processes in gliomas. Exosomal miRNAs derived from mesenchymal stem cells could also be used for glioma treatment. The present review summarizes the exosomal miRNAs that have been implicated in the pathogenesis, diagnosis and treatment of gliomas. Moreover, exosomal proteins could also be involved in glioma pathogenesis. Exosomal miRNAs and proteins could also serve as non-invasive biomarkers for prognosis and disease monitoring. Video Abstract.

CADM1 inhibits ovarian cancer cell proliferation and migration by potentially regulating the PI3K/Akt/mTOR pathway

Previous studies have shown that cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member, is frequently inactivated but functions as a tumor suppressor in many solid tumors. However, the characterization of CADM1 expression in ovarian cancer cells and the mechanisms of its tumor suppressor function are not fully understood. We generated ovarian cancer cell lines in which CADM1 was stably upregulated or downregulated. CADM1 expression was significantly decreased in ovarian cancer tissue and cells lines. Functionally, knockdown of CADM1 promoted the growth, migration and invasion of ovarian cancer cells. Conversely, further experimental evidence indicated that overexpression of CADM1 inhibited the migration and invasion of ovarian cancer cells potentially through inhibition of the PI3K/Akt/mTOR signaling pathway by regulating upstream regulators (LXR/RXR, IGF1, IFI44L and C4BPA) and downstream effectors (APP, EDN1, TGFBI and Rap1A). In conclusion, CADM1 inhibits ovarian cancer cell proliferation and migration by potentially regulating the PI3K/Akt/mTOR signaling pathway. CADM1 could be a potential therapeutic target for ovarian cancer.

NF-κB and MicroRNA Deregulation Mediated by HTLV-1 Tax and HBZ

The risk of developing adult T-cell leukemia/lymphoma (ATLL) in individuals infected with human T-cell lymphotropic virus 1 (HTLV-1) is about 3–5%. The mechanisms by which the virus triggers this aggressive cancer are still an area of intensive investigation. The viral protein Tax-1, together with additional regulatory proteins, in particular HTLV-1 basic leucine zipper factor (HBZ), are recognized as relevant viral factors required for both viral replication and transformation of infected cells. Tax-1 deregulates several cellular pathways affecting the cell cycle, survival, and proliferation. The effects of Tax-1 on the NF-κB pathway have been thoroughly studied. Recent studies also revealed the impact of Tax-1 and HBZ on microRNA expression. In this review, we summarize the recent progress in understanding the contribution of HTLV-1 Tax- and HBZ-mediated deregulation of NF-κB and the microRNA regulatory network to HTLV-1 pathogenesis.

MicroRNA-155-3p promotes breast cancer progression through down-regulating CADM1

BACKGROUND/PURPOSE

Cell adhesion molecule 1 (CADM1) functions as a tumor suppressor and has been identified to be frequently inactivated in breast cancer, and closely associated with patients' poor prognosis and advanced TNM stage. However, the mechanisms underlying CADM1 in breast cancer progression remains incompletely clear. miR-155, a predicted modulator of CADM1 was reported to be overexpressed in breast cancer, and its high expression level was closely related to the malignant progression of breast cancer. The present study aimed to explore whether miR-155-3p could modulate CADM1 expression and then involved in the progression of breast cancer.

METHODS

The expression patterns of miR-155-3p in breast cancer tissues and cell lines were determined by RT-PCR technology. The relationship between CADM1 and miR-155-3p were determined by the luciferase gene reporter and Western Blot (WB) assays. Cell proliferation, apoptosis rates and tumorigenesis were determined by CCK-8, flow cytometry and in vivo xenotransplanation experiments, respectively.

RESULTS

miR-155-3p was up-regulated in breast cancer tissues and cells when compared to the adjacent normal tissues and normal breast MCF 10A cells. The mRNA and protein levels of CADM1 showed opposite expression patterns to that of miR-155-3p expression detected, and miR-155-3p could negatively regulate CADM1 expression in breast cancer MCF-7 cells. Moreover, gain-of function assay showed that overexpression of miR-155-3p promoted cell proliferation, tumorigenesis and repressed cell apoptosis, but these effects were all significantly impaired when the cells were simultaneously transfected with OE-CADM1, the overexpressing vector of CADM1.

CONCLUSION

This study revealed that miR-155-3p could accelerate the progression of breast cancer via down-regulation of CADM1 expression.

Phenotypic characterisation of regulatory T cells in dogs reveals signature transcripts conserved in humans and mice

Regulatory T cells (Tregs) are a double-edged regulator of the immune system. Aberrations of Tregs correlate with pathogenesis of inflammatory, autoimmune and neoplastic disorders. Phenotypically and functionally distinct subsets of Tregs have been identified in humans and mice on the basis of their extensive portfolios of monoclonal antibodies (mAb) against Treg surface antigens. As an important veterinary species, dogs are increasingly recognised as an excellent model for many human diseases. However, insightful study of canine Tregs has been restrained by the limited availability of mAb. We therefore set out to characterise CD4⁺CD25^high T cells isolated ex vivo from healthy dogs and showed that they possess a regulatory phenotype, function, and transcriptomic signature that resembles those of human and murine Tregs. By launching a cross-species comparison, we unveiled a conserved transcriptomic signature of Tregs and identified that transcript hip1 may have implications in Treg function.

Sleeping Beauty Mouse Models of Cancer: Microenvironmental Influences on Cancer Genetics

The Sleeping Beauty (SB) transposon insertional mutagenesis system offers a streamlined approach to identify genetic drivers of cancer. With a relatively random insertion profile, SB is uniquely positioned for conducting unbiased forward genetic screens. Indeed, SB mouse models of cancer have revealed insights into the genetics of tumorigenesis. In this review, we highlight experiments that have exploited the SB system to interrogate the genetics of cancer in distinct biological contexts. We also propose experimental designs that could further our understanding of the relationship between tumor microenvironment and tumor progression.

Metabolic abnormalities in adult T-cell leukemia/lymphoma and induction of specific leukemic cell death using photodynamic therapy

Adult T-cell leukemia/lymphoma (ATL) is an aggressive T-cell neoplasm caused by human T-cell leukemia virus type I (HTLV-I). Therapeutic interventions have not been associated with satisfactory outcomes. We showed that the porphyrin metabolic pathway preferentially accumulates the endogenous photosensitive metabolite, protoporphyrin IX (PpIX) in ATL, after a short-term culture with 5-aminolevulinic acid (ALA). PpIX accumulated 10-100-fold more in ATL leukemic cells when compared to healthy peripheral blood mononuclear cells (PBMCs). Patient specimens showed dynamic changes in flow cytometry profiles during the onset and progression of ATL. Furthermore, 98.7% of ATL leukemic cell death in the ATL patient specimens could be induced with 10 min of visible light exposure, while 77.5% of normal PBMCs survived. Metabolomics analyses revealed that a specific stage of the metabolic pathway progressively deteriorated with HTLV-I infection and at the onset of ATL. Therefore, this method will be useful in diagnosing and identifying high-risk HTLV-I carriers with single cell resolutions. Photodynamic therapy in the circulatory system may be a potential treatment due to its highly-specific, non-invasive, safe, simultaneous, and repeatedly-treatable modalities.

Exosomes of glioma cells deliver miR-148a to promote proliferation and metastasis of glioblastoma via targeting CADM1

Exosomes are now considered to be involved in mediating cell-to-cell communication to promote or inhibit tumor progression. However, the role and molecular mechanism of exosomes in promoting glioblastoma (GBM) metastasis remains elusive. Here, we found that circulating exosomal miR-148a levels were significantly higher in serum from GBM patients compared with serum from healthy volunteers. In T98G cells, inhibition of miR-148a suppressed cell proliferation and metastasis. In addition, we identified Cell adhesion molecule 1 (CADM1) as a target gene of miR-148a using luciferase reporter assay. Both protein and mRNA levels of CADM1 were decreased in tissues from GBM patients. There was a strong negative correlation between exosomal miR-148a and CADM1 mRNA levels in samples of patients. Moreover, miR-148a antagonist increased p-STAT3 protein level to activate STAT3 pathway. In conclusion, our findings indicated that miR-148a delivered by exosomes may promote cancer cell proliferation and metastasis via targeting CADM1 to activate STAT3 pathway, suggesting a predictor and therapeutic target role of exosomal miR-148a in GBM patients.

CADM1 is essential for KSHV-encoded vGPCR-and vFLIP-mediated chronic NF-κB activation

Approximately 12% of all human cancers worldwide are caused by infections with oncogenic viruses. Kaposi's sarcoma herpesvirus/human herpesvirus 8 (KSHV/HHV8) is one of the oncogenic viruses responsible for human cancers, including Kaposi's sarcoma (KS), Primary Effusion Lymphoma (PEL), and the lymphoproliferative disorder multicentric Castleman's disease (MCD). Chronic inflammation mediated by KSHV infection plays a decisive role in the development and survival of these cancers. NF-κB, a family of transcription factors regulating inflammation, cell survival, and proliferation, is persistently activated in KSHV-infected cells. The KSHV latent and lytic expressing oncogenes involved in NF-κB activation are vFLIP/K13 and vGPCR, respectively. However, the mechanisms by which NF-κB is activated by vFLIP and vGPCR are poorly understood. In this study, we have found that a host molecule, Cell Adhesion Molecule 1 (CADM1), is robustly upregulated in KSHV-infected PBMCs and KSHV-associated PEL cells. Further investigation determined that both vFLIP and vGPCR interacted with CADM1. The PDZ binding motif localized at the carboxyl terminus of CADM1 is essential for both vGPCR and vFLIP to maintain chronic NF-κB activation. Membrane lipid raft associated CADM1 interaction with vFLIP is critical for the initiation of IKK kinase complex and NF-κB activation in the PEL cells. In addition, CADM1 played essential roles in the survival of KSHV-associated PEL cells. These data indicate that CADM1 plays key roles in the activation of NF-κB pathways during latent and lytic phases of the KSHV life cycle and the survival of KSHV-infected cells.

HTLV-1, the Other Pathogenic Yet Neglected Human Retrovirus: From Transmission to Therapeutic Treatment

Going back to their discovery in the early 1980s, both the Human T-cell Leukemia virus type-1 (HTLV-1) and the Human Immunodeficiency Virus type-1 (HIV-1) greatly fascinated the virology scene, not only because they were the first human retroviruses discovered, but also because they were associated with fatal diseases in the human population. In almost four decades of scientific research, both viruses have had different fates, HTLV-1 being often upstaged by HIV-1. However, although being very close in terms of genome organization, cellular tropism, and viral replication, HIV-1 and HTLV-1 are not completely commutable in terms of treatment, especially because of the opposite fate of the cells they infect: death versus immortalization, respectively. Nowadays, the antiretroviral therapies developed to treat HIV-1 infected individuals and to limit HIV-1 spread among the human population have a poor or no effect on HTLV-1 infected individuals, and thus, do not prevent the development of HTLV-1-associated diseases, which still lack highly efficient treatments. The present review mainly focuses on the course of HTLV-1 infection, from the initial infection of the host to diseases development and associated treatments, but also investigates HIV-1/HTLV-1 co-infection events and their impact on diseases development.

Cell adhesion molecule-1 (CADM1) expressed on adult T-cell leukemia/lymphoma cells is not involved in the interaction with macrophages

Cell adhesion molecule 1 (CADM1) is a cell adhesion molecule that is expressed in brain, liver, lung, testis, and some kinds of cancer cells including adult T-cell leukemia/lymphoma (ATLL). Recent studies have indicated the involvement of CADM1 in cell-cell contact between cytotoxic T-lymphocytes and virus infected cells. We previously reported that cell-cell interaction between lymphoma cells and macrophages induces lymphoma cell proliferation. In the present study, we investigated whether CADM1 is associated with cell-cell interaction between several human lymphoma cell lines and macrophages.CADM1 expression was observed in the ATLL cell lines, ATN-1, ATL-T, and ATL-35T, and in the B cell lymphoma cell lines, TL-1, DAUDI, and SLVL, using western blotting. Significant cell-cell interaction between macrophages and ATN-1, ATL-T, ATL-35T and MT-2, DAUDI, and SLVL cells, as assessed by induction of cell proliferation, was observed. Immunohistochemical analysis of human biopsy samples indicated CADM1 expression in 10 of 14 ATLL cases; however, no case of follicular lymphoma or diffuse large B-cell lymphoma was positive for CADM1. Finally, the interaction of macrophages with cells of the CADM1-negative ED ATLL cell line and CADM1-transfected ED cells was tested. However, significant cell-cell interaction between macrophage and CADM1-transfected ED cells was not observed. We conclude that CADM1 was not associated with cell-cell interaction between lymphoma cells and macrophages, although CADM1 may be a useful marker of ATLL for diagnostic procedures.

Tumor Necrosis Factor α Regulates Endothelial Progenitor Cell Migration via CADM1 and NF-kB

Shortly after the discovery of endothelial progenitor cells (EPCs) in 1997, many clinical trials were conducted using EPCs as a cellular based therapy with the goal of restoring damaged organ function by inducing growth of new blood vessels (angiogenesis). Results were disappointing, largely because the cellular and molecular mechanisms of EPC-induced angiogenesis were not clearly understood. Following injection, EPCs must migrate to the target tissue and engraft prior to induction of angiogenesis. In this study EPC migration was investigated in response to tumor necrosis factor α (TNFα), a pro-inflammatory cytokine, to test the hypothesis that organ damage observed in ischemic diseases induces an inflammatory signal that is important for EPC homing. In this study, EPC migration and incorporation were modeled in vitro using a coculture assay where TNFα treated EPCs were tracked while migrating toward vessel-like structures. It was found that TNFα treatment of EPCs increased migration and incorporation into vessel-like structures. Using a combination of genomic and proteomic approaches, NF-kB mediated upregulation of CADM1 was identified as a mechanism of TNFα induced migration. Inhibition of NF-kB or CADM1 significantly decreased migration of EPCs in vitro suggesting a role for TNFα signaling in EPC homing during tissue repair. Stem Cells 2016;34:1922-1933.

CADM1/TSLC1 Identifies HTLV-1-Infected Cells and Determines Their Susceptibility to CTL-Mediated Lysis

Human T cell lymphotropic virus-1 (HTLV-1) primarily infects CD4⁺ T cells, causing inflammatory disorders or a T cell malignancy in 5% to 10% of carriers. The cytotoxic T lymphocyte (CTL) response is a key factor that controls the viral load and thus the risk of disease. The ability to detect the viral protein Tax in primary cells has made it possible to estimate the rate at which Tax-expressing infected cells are eliminated by CTLs in persistently infected people. However, most HTLV-1-infected cells are Tax^–at a given time, and their immunophenotype is poorly defined. Here, we aimed to identify a cell-surface molecule expressed by both Tax⁺ and Tax^–HTLV-1-infected cells and use it to analyse the CTL response in fresh peripheral blood mononuclear cells. Cell adhesion molecule 1 (CADM1/TSLC1) was the best single marker of HTLV-1 infection, identifying HTLV-1-infected cells with greater sensitivity and specificity than CD25, CCR4 or ICAM-1. CADM1⁺CD4⁺ T cells carried a median of 65% of proviral copies in peripheral blood. In a cohort of 23 individuals, we quantified the rate of CTL-mediated killing of Tax⁺ and Tax⁻CADM1⁺ cells. We show that CADM1 expression is associated with enhanced susceptibility of infected cells to CTL lysis: despite the immunodominance of Tax in the CTL response, Tax⁺CADM1^– cells were inefficiently lysed by CTLs. Upregulation of the CADM1 ligand CRTAM on CD8⁺ T cells correlated with efficient lysis of infected cells. Tax^–CADM1⁺ cells were lysed at a very low rate by autologous CTLs, however, were efficiently killed when loaded with exogenous peptide antigen. High expression of CADM1 on most HTLV-1-infected cells in the face of enhanced CTL counterselection implies that CADM1 confers a strong benefit on the virus.

Human T cell lymphotropic virus-1 (HTLV-1) infects white blood cells (CD4⁺ T cells) for the lifetime of the host. The immune response limits viral spread, and people with a weak immune response have a high risk of developing an aggressive blood cancer, or a condition involving irreversible spinal cord damage. Virus and host are engaged in a constant battle: virus proteins drive the host cell to divide or infect new cells. We know that the viral protein Tax is an important target of the immune response, and cells which produce Tax are killed quickly. Infected cells which do not produce Tax are difficult to detect, so we have no idea how quickly they are killed. In this paper we show that most infected cells have a host protein ‘CADM1’ on their surface. We measured killing of CADM1 cells and saw that Tax⁺CADM1⁺ cells are the only infected cells which are strongly targeted by the immune response. We also found that infected cells which did not have CADM1 on the surface escaped killing, showing that CADM1 aids in immune control of HTLV-1. These findings are an important step forward in our understanding of cellular turnover and immune control in chronic infection.

Human T-cell leukemia virus type 1 (HTLV-1) tax requires CADM1/TSLC1 for inactivation of the NF-κB inhibitor A20 and constitutive NF-κB signaling

Persistent activation of NF-κB by the Human T-cell leukemia virus type 1 (HTLV-1) oncoprotein, Tax, is vital for the development and pathogenesis of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). K63-linked polyubiquitinated Tax activates the IKK complex in the plasma membrane-associated lipid raft microdomain. Tax also interacts with TAX1BP1 to inactivate the NF-κB negative regulatory ubiquitin-editing A20 enzyme complex. However, the molecular mechanisms of Tax-mediated IKK activation and A20 protein complex inactivation are poorly understood. Here, we demonstrated that membrane associated CADM1 (Cell adhesion molecule1) recruits Ubc13 to Tax, causing K63-linked polyubiquitination of Tax, and IKK complex activation in the membrane lipid raft. The c-terminal cytoplasmic tail containing PDZ binding motif of CADM1 is critical for Tax to maintain persistent NF-κB activation. Finally, Tax failed to inactivate the NF-κB negative regulator ubiquitin-editing enzyme A20 complex, and activate the IKK complex in the lipid raft in absence of CADM1. Our results thus indicate that CADM1 functions as a critical scaffold molecule for Tax and Ubc13 to form a cellular complex with NEMO, TAX1BP1 and NRP, to activate the IKK complex in the plasma membrane-associated lipid rafts, to inactivate NF-κB negative regulators, and maintain persistent NF-κB activation in HTLV-1 infected cells.

HTLV-1 infection leads to the development of Adult T-cell Leukemia (ATL) or HTLV-1 associated myelopathy/ tropical spastic paraparesis (HAM/TSP). One of the major causes responsible for the development of HTLV-1 associated diseases is chronic inflammation directed by NF-kappaB (NF-κB). NF-κB activation in response to a wide variety of signals is transient and tightly controlled by ubiquitin-editing enzyme A20. One of the mechanisms of persistent NF-κB activation in HTLV-1 infected cells is inactivation of NF-κB negative regulators; however, the precise mechanism is unknown. Here, we focused on host tumor suppressor Cell adhesion molecule 1 (CADM1) that is robustly upregulated in HTLV-1 infected cells. The expression of CADM1 is frequently silenced in several cancers; however, it is critical for HTLV-1 associated ATL tumor cell survival. We characterized the role of CADM1 in persistent NF-κB activation in HTLV-1 infected cells. We found that CADM1 is required for the HTLV-1 oncoprotein, Tax, to form a cellular complex with Ubc13, TAX1BP1, NRP and NEMO in the membrane lipid rafts micorodomain. We further demonstrated that Tax requires CADM1 to inactivate NF-κB negative regulator and maintain persistent NF-κB activation. Our study reveals a novel mechanism of chronic NF-κB activation by CADM1 in HTLV-1 infected cells.

Loss of CADM1 expression is associated with poor prognosis and brain metastasis in breast cancer patients

Breast cancer brain metastases (BCBM) are detected with increasing incidence. In order to detect potential genes involved in BCBM, we first screened for genes down-regulated by methylation in cell lines with site-specific metastatic ability. The expression of five genes, CADM1, SPARC, RECK, TNFAIP3 and CXCL14, which were also found down-regulated in gene expression profiling analyses of BCBM tissue samples, was verified by qRT-PCR in a larger patient cohort. CADM1 was chosen for further down-stream analyses. A higher incidence of CADM1 methylation, correlating with lower expression levels, was found in BCBM as compared to primary BC. Loss of CADM1 protein expression was detected most commonly among BCBM samples as well as among primary tumors with subsequent brain relapse. The prognostic role of CADM1 expression was finally verified in four large independent breast cancer cohorts (n=2136). Loss of CADM1 protein expression was associated with disease stage, lymph node status, and tumor size in primary BC. Furthermore, all analyses revealed a significant association between loss of CADM1 and shorter survival. In multivariate analyses, survival was significantly shorter among patients with CADM1-negative tumors. Loss of CADM1 expression is an independent prognostic factor especially associated with the development of brain metastases in breast cancer patients.

[Nectins and nectin-like receptors DNAM-1 and CRTAM: new ways for tumor escape]

Nectin and nectin-like (Necl) are cell adhesion molecules expressed in various tumors. They were alternatively reported as involved in tumor suppressor or oncogenic functions that led to their use as histological or serological cancer markers. Gene inactivation in lung carcinoma but overexpression in leukemia were reported for Necl-2. DNAM-1 and CRTAM are emerging NK receptors of immune cells that were described to interact with nectin and Necl. DNAM-1, constitutively expressed by CD8(+) T cells, NK or γδ T lymphocytes, is a ligand of Necl-5. It participates to tumor immunosurveillance promoting Necl-5 expressing tumor cell lysis. CRTAM, only expressed after lymphocyte activation, is a ligand of Necl-2. Engagement of CRTAM with Necl-2 has opposite effects depending on the type of lymphocyte. For NK or CD8(+) T cells, it promotes cytotoxicity and IFNγ secretion favoring immunosurveillance. By contrast, CRTAM/Necl-2 interaction triggers cell death of activated TVg9Vd2 γδ T cells favoring immune escape. Nectin and Necl-mediated interactions appear to be crucial for the delicate balance between tumor escape and antitumor response.

Biological evaluation of 131I- and CF750-labeled Dmab(scFv)-Fc antibodies for xenograft imaging of CD25-positive tumors

A Dmab(scFv)-Fc antibody containing the single chain variable fragment of a humanized daclizumab antibody and the Fc fragment of a human IgG1 antibody was produced via recombinant expression in Pichia pastoris. The Dmab(scFv)-Fc antibody forms a dimer in solution, and it specifically binds CD25-positive tumor cells and tumor tissues. For tumor imaging, the Dmab(scFv)-Fc antibody was labeled with the 131I isotope and CF750 fluorescent dye, respectively. After intravenous injection of mice bearing CD25-positive tumor xenografts, tumor uptake of the (131)I-Dmab(scFv)-Fc antibody was visible at 1 h, and clear images were obtained at 5 h using SPECT/CT. After systemic administration of the CF750-Dmab(scFv)-Fc antibody, tumor uptake was present as early as 1 h, and tumor xenografts could be kinetically imaged within 9 h after injection. These results indicate that the Dmab(scFv)-Fc antibody rapidly and specifically targets CD25-positive tumor cells, suggesting the potential of this antibody as an imaging agent for the diagnosis of lymphomatous-type ATLL.

CADM1 expression and stepwise downregulation of CD7 are closely associated with clonal expansion of HTLV-I-infected cells in adult T-cell leukemia/lymphoma

PURPOSE

Cell adhesion molecule 1 (CADM1), initially identified as a tumor suppressor gene, has recently been reported to be ectopically expressed in primary adult T-cell leukemia-lymphoma (ATL) cells. We incorporated CADM1 into flow-cytometric analysis to reveal oncogenic mechanisms in human T-cell lymphotrophic virus type I (HTLV-I) infection by purifying cells from the intermediate stages of ATL development.

EXPERIMENTAL DESIGN

We isolated CADM1- and CD7-expressing peripheral blood mononuclear cells of asymptomatic carriers and ATLs using multicolor flow cytometry. Fluorescence-activated cell sorted (FACS) subpopulations were subjected to clonal expansion and gene expression analysis.

RESULTS

HTLV-I-infected cells were efficiently enriched in CADM1(+) subpopulations (D, CADM1(pos)CD7(dim) and N, CADM1(pos)CD7(neg)). Clonally expanding cells were detected exclusively in these subpopulations in asymptomatic carriers with high proviral load, suggesting that the appearance of D and N could be a surrogate marker of progression from asymptomatic carrier to early ATL. Further disease progression was accompanied by an increase in N with a reciprocal decrease in D, indicating clonal evolution from D to N. The gene expression profiles of D and N in asymptomatic carriers showed similarities to those of indolent ATLs, suggesting that these subpopulations represent premalignant cells. This is further supported by the molecular hallmarks of ATL, that is, drastic downregulation of miR-31 and upregulation of abnormal Helios transcripts.

CONCLUSION

The CADM1 versus CD7 plot accurately reflects disease progression in HTLV-I infection, and CADM1(+) cells with downregulated CD7 in asymptomatic carriers have common properties with those in indolent ATLs.