CD44+ cancer stem-like cells in EBV-associated nasopharyngeal carcinoma

Characterizing resistant cellular states in nasopharyngeal carcinoma during EBV lytic induction

The pervasive occurrence of nasopharyngeal carcinoma (NPC) is intricately linked to Epstein-Barr virus (EBV) infection, making EBV and its associated pathways promising therapeutic targets for NPC and other EBV-related cancers. Lytic induction therapy, an emerging virus-targeted therapeutic strategy, capitalizes on the presence of EBV in tumor cells to specifically induce cytotoxicity against EBV-associated malignancies. Despite the expanding repertoire of compounds developed to induce EBV lytic reactivation, achieving universal induction across all infected cells remains elusive. The inherent heterogeneity of tumor cells likely contributes to this variability. In this study, we used the NPC43 cell line, an EBV-positive NPC in vitro model, and single-cell transcriptomics to characterize the diverse cellular responses to EBV lytic induction. Our longitudinal monitoring revealed a distinctive lytic induction non-responsive cellular state characterized by elevated expression of SOX2 and NTRK2. Cells in this state exhibit phenotypic similarities to cancer stem cells (CSCs), and we verified the roles of SOX2 and NTRK2 in manifesting these phenotypes. Our findings reveal a significant challenge for lytic induction therapy, as not all tumor cells are equally susceptible. These insights highlight the importance of combining lytic induction with therapies targeting CSC-like properties to enhance treatment efficacy for NPC and other EBV-associated cancers.

Prion protein regulates invasiveness in glioblastoma stem cells

BACKGROUND

Glioblastoma (GBM) is an aggressive brain tumor driven by glioblastoma stem cells (GSCs), which represent an appealing target for therapeutic interventions. The cellular prion protein (PrPC), a scaffold protein involved in diverse cellular processes, interacts with various membrane and extracellular matrix molecules, influencing tumor biology. Herein, we investigate the impact of PrPC expression on GBM.

METHODS

To address this goal, we employed CRISPR-Cas9 technology to generate PrPC knockout (KO) glioblastoma cell lines, enabling detailed loss-of-function studies. Bulk RNA sequencing followed by differentially expressed gene and pathway enrichment analyses between U87 or U251 PrPC-wild-type (WT) cells and PrPC-knockout (KO) cells were used to identify pathways regulated by PrPC. Immunofluorescence assays were used to evaluate cellular morphology and protein distribution. For assessment of protein levels, Western blot and flow cytometry assays were employed. Transwell and growth curve assays were used to determine the impact of loss-of-PrPC in GBM invasiveness and proliferation, respectively. Single-cell RNA sequencing analysis of data from patient tumors from The Cancer Genome Atlas (TCGA) and the Broad Institute of Single-Cell Data Portal were used to evaluate the correspondence between our in vitro results and patient samples.

RESULTS

Transcriptome analysis of PrPC-KO GBM cell lines revealed altered expression of genes associated with crucial tumor progression pathways, including migration, proliferation, and stemness. These findings were corroborated by assays that revealed impaired invasion, migration, proliferation, and self-renewal in PrPC-KO GBM cells, highlighting its critical role in sustaining tumor growth. Notably, loss-of-PrPC disrupted the expression and localization of key stemness markers, particularly CD44. Additionally, the modulation of PrPC levels through CD44 overexpression further emphasizes their regulatory role in these processes.

CONCLUSIONS

These findings establish PrPC as a modulator of essential molecules on the cell surface of GSCs, highlighting its potential as a therapeutic target for GBM.

Epstein-Barr virus reactivation induces divergent abortive, reprogrammed, and host shutoff states by lytic progression

Viral infection leads to heterogeneous cellular outcomes ranging from refractory to abortive and fully productive states. Single cell transcriptomics enables a high resolution view of these distinct post-infection states. Here, we have interrogated the host-pathogen dynamics following reactivation of Epstein-Barr virus (EBV). While benign in most people, EBV is responsible for infectious mononucleosis, up to 2% of human cancers, and is a trigger for the development of multiple sclerosis. Following latency establishment in B cells, EBV reactivates and is shed in saliva to enable infection of new hosts. Beyond its importance for transmission, the lytic cycle is also implicated in EBV-associated oncogenesis. Conversely, induction of lytic reactivation in latent EBV-positive tumors presents a novel therapeutic opportunity. Therefore, defining the dynamics and heterogeneity of EBV lytic reactivation is a high priority to better understand pathogenesis and therapeutic potential. In this study, we applied single-cell techniques to analyze diverse fate trajectories during lytic reactivation in three B cell models. Consistent with prior work, we find that cell cycle and MYC expression correlate with cells refractory to lytic reactivation. We further found that lytic induction yields a continuum from abortive to complete reactivation. Abortive lytic cells upregulate NFκB and IRF3 pathway target genes, while cells that proceed through the full lytic cycle exhibit unexpected expression of genes associated with cellular reprogramming. Distinct subpopulations of lytic cells further displayed variable profiles for transcripts known to escape virus-mediated host shutoff. These data reveal previously unknown and promiscuous outcomes of lytic reactivation with broad implications for viral replication and EBV-associated oncogenesis.

LncRNA HOTAIRM1 promotes radioresistance in nasopharyngeal carcinoma by modulating FTO acetylation-dependent alternative splicing of CD44

BACKGROUND

Radiotherapy is the primary treatment for patients with nasopharyngeal carcinoma (NPC); however, almost 20% of patients experience treatment failure due to radioresistance. Therefore, understanding the mechanisms of radioresistance is imperative. HOTAIRM1 is deregulated in various human cancers, yet its role in NPC radioresistance are largely unclear.

METHODS

This study investigated the association between HOTAIRM1 and radioresistance using CCK8, flow cytometry, and comet assays. Additionally, xenograft mice and patient-derived xenografts (PDX) models were employed to elucidate the biological functions of HOTAIRM1, and transcriptomic RNA sequencing was utilized to identify its target genes.

RESULTS

Our study revealed an upregulation of HOTAIRM1 levels in radioresistant NPC cell lines and tissues. Furthermore, a positive correlation was noted between high HOTAIRM1 expression and increased NPC cell proliferation, reduced apoptosis, G2/M cell cycle arrest, and diminished cellular DNA damage following radiotherapy. HOTAIRM1 modulates the acetylation and stability of the FTO protein, and inhibiting FTO elevates the m6A methylation level of CD44 precursor transcripts in NPC cells. Additionally, silencing the m6A reading protein YTHDC1 was found to increase the expression of CD44V. HOTAIRM1 enhances NPC cell resistance to ferroptosis and irradiation through the HOTAIRM1-FTO-YTHDC1-CD44 axis. Mechanistically, HOTAIRM1 interacts with the FTO protein and induces m6A demethylation of the CD44 transcript. The absence of m6A modification in the CD44 transcript prevents its recognition by YTHDC1, resulting in the transition from CD44S to CD44V. An abundance of CD44V suppresses ferroptosis induced by irradiation and contributes to NPC radioresistance.

CONCLUSIONS

In conclusion, the results in this study support the idea that HOTAIRM1 stimulates CD44 alternative splicing via FTO-mediated demethylation, thereby attenuating ferroptosis induced by irradiation and promoting NPC radioresistance.

Global trends in research of nasopharyngeal carcinoma: a bibliometric and visualization analysis

Objective

This study aims to assess the current research status, focus areas, and developmental trends in nasopharyngeal carcinoma (NPC) through a bibliometric analysis.

Methods

Articles focusing on NPC published from 2000 to 2023 were retrieved from the Web of Science database. VOSviewer and CiteSpace were used for bibliometric and visual analysis.

Results

A total of 14516 related publications were retrieved. There has been a steady increase in the number of NPC-related publications from 2000 to 2023. China was the dominant country in this field with 8948 papers (61.64%), followed by the USA (2234, 15.39%). Sun Yat-sen University was the most influential institution, while Ma J was the most prolific author. Furthermore, Head And Neck-journal For The Sciences And Specialties Of The Head And Neck was the most prolific journal. International Journal of Radiation Oncology Biology Physics had the highest total citation counts. "Introduction chemotherapy", "Concurrent chemotherapy", "Epithelial-mesenchymal transition", "Cancer stem cells", "MicroRNAs", "LncRNA", "Exosomes", and "Biomarker" were the most common keywords. The reference "Chen YP, 2019, Lancet" had the highest citations and strong outbreak value.

Conclusion

The past two decades have witnessed a significant increase in research on NPC. The optimization of treatment mode is the most widely studied aspect at present. The mechanism of occurrence and development and the most favorable diagnostic and therapeutic targets are the research hotspots in the future.

Epstein-Barr virus reactivation induces divergent abortive, reprogrammed, and host shutoff states by lytic progression

Viral infection leads to heterogeneous cellular outcomes ranging from refractory to abortive and fully productive states. Single cell transcriptomics enables a high resolution view of these distinct post-infection states. Here, we have interrogated the host-pathogen dynamics following reactivation of Epstein-Barr virus (EBV). While benign in most people, EBV is responsible for infectious mononucleosis, up to 2% of human cancers, and is a trigger for the development of multiple sclerosis. Following latency establishment in B cells, EBV reactivates and is shed in saliva to enable infection of new hosts. Beyond its importance for transmission, the lytic cycle is also implicated in EBV-associated oncogenesis. Conversely, induction of lytic reactivation in latent EBV-positive tumors presents a novel therapeutic opportunity. Therefore, defining the dynamics and heterogeneity of EBV lytic reactivation is a high priority to better understand pathogenesis and therapeutic potential. In this study, we applied single-cell techniques to analyze diverse fate trajectories during lytic reactivation in two B cell models. Consistent with prior work, we find that cell cycle and MYC expression correlate with cells refractory to lytic reactivation. We further found that lytic induction yields a continuum from abortive to complete reactivation. Abortive lytic cells upregulate NFκB and IRF3 pathway target genes, while cells that proceed through the full lytic cycle exhibit unexpected expression of genes associated with cellular reprogramming. Distinct subpopulations of lytic cells further displayed variable profiles for transcripts known to escape virus-mediated host shutoff. These data reveal previously unknown and promiscuous outcomes of lytic reactivation with broad implications for viral replication and EBV-associated oncogenesis.

Linking ABC transporters to the hallmarks of cancer

Human ATP-binding cassette (ABC) transporters are ubiquitously expressed and transport a broad range of endogenous and xenobiotic substrates across extra- and intracellular membranes. Mutations in ABC genes cause 21 monogenic diseases, and polymorphisms in these genes are associated with susceptibility to complex diseases. ABC transporters also play a major role in drug bioavailability, and they mediate multidrug resistance in cancer. At least 13 ABC transporters were shown to be involved in drug resistance in vitro. In the past decade, efforts have been made to elucidate their roles in tumor biology. Herein, we explore their involvement in tumorigenesis, focusing on the hallmarks of cells as they make their way from normalcy to neoplastic growth states.

Integrated analysis of miRNA-mRNA expression of newly emerging swine H3N2 influenza virus cross-species infection with tree shrews

BACKGROUND

Cross-species transmission of zoonotic IAVs to humans is potentially widespread and lethal, posing a great threat to human health, and their cross-species transmission mechanism has attracted much attention. miRNAs have been shown to be involved in the regulation of IAVs infection and immunity, however, few studies have focused on the molecular mechanisms underlying miRNAs and mRNAs expression after IAVs cross-species infection.

METHODS

We used tree shrews, a close relative of primates, as a model and used RNA-Seq and bioinformatics tools to analyze the expression profiles of DEMs and DEGs in the nasal turbinate tissue at different time points after the newly emerged swine influenza A virus SW2783 cross-species infection with tree shrews, and miRNA-mRNA interaction maps were constructed and verified by RT-qPCR, miRNA transfection and luciferase reporter assay.

RESULTS

14 DEMs were screened based on functional analysis and interaction map, miR-760-3p, miR-449b-2, miR-30e-3p, and miR-429 were involved in the signal transduction process of replication and proliferation after infection, miR-324-3p, miR-1301-1, miR-103-1, miR-134-5p, miR-29a, miR-31, miR-16b, miR-34a, and miR-125b participate in negative feedback regulation of genes related to the immune function of the body to activate the antiviral immune response, and miR-106b-3p may be related to the cross-species infection potential of SW2783, and the expression level of these miRNAs varies in different days after infection.

CONCLUSIONS

The miRNA regulatory networks were constructed and 14 DEMs were identified, some of them can affect the replication and proliferation of viruses by regulating signal transduction, while others can play an antiviral role by regulating the immune response. It indicates that abnormal expression of miRNAs plays a crucial role in the regulation of cross-species IAVs infection, which lays a solid foundation for further exploration of the molecular regulatory mechanism of miRNAs in IAVs cross-species infection and anti-influenza virus targets.

The efficacy of natural products for the treatment of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor originating in the nasopharyngeal epithelium with a high incidence in southern China and parts of Southeast Asia. The current treatment methods are mainly radiotherapy and chemotherapy. However, they often have side effects and are not suitable for long-term exposure. Natural products have received more and more attention in cancer prevention and treatment because of their its high efficiency, low toxic side effects, and low toxicity. Natural products can serve as a viable alternative, and this study aimed to review the efficacy and mechanisms of natural products in the treatment of NPC by examining previous literature. Most natural products act by inhibiting cell proliferation, metastasis, inducing cell cycle arrest, and apoptosis. Although further research is needed to verify their effectiveness and safety, natural products can significantly improve the treatment of NPC.

Epstein-Barr Virus Promotes Oral Squamous Cell Carcinoma Stemness through the Warburg Effect

Epstein-Barr virus (EBV) is associated with various human malignancies. An association between EBV infection and oral squamous cell carcinoma (OSCC) has recently been reported. We established EBV-positive OSCC cells and demonstrated that EBV infection promoted OSCC progression. However, the mechanisms by which EBV promotes OSCC progression remain poorly understood. Therefore, we performed metabolic analyses of EBV-positive OSCC cells and established a xenograft model to investigate the viral contribution to OSCC progression. Here, we demonstrated that EBV infection induced mitochondrial stress by reducing the number of mitochondrial DNA (mtDNA) copies. Microarray data from EBV-positive OSCC cells showed altered expression of glycolysis-related genes, particularly the upregulation of key genes involved in the Warburg effect, including LDHA, GLUT1, and PDK1. Furthermore, lactate production and LDH activity were elevated in EBV-positive OSCC cells. EBV infection significantly upregulated the expression levels of cancer stem cell (CSC) markers such as CD44 and CD133 in the xenograft model. In this model, tumor growth was significantly increased in EBV-positive SCC25 cells compared with that in uninfected cells. Furthermore, tumorigenicity increased after serial passages of EBV-positive SCC25 tumors. This study revealed the oncogenic role of EBV in OSCC progression by inducing the Warburg effect and cancer stemness.

Identity matters: cancer stem cells and tumour plasticity in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) represents frequent yet aggressive tumours that encompass complex ecosystems of stromal and neoplastic components including a dynamic population of cancer stem cells (CSCs). Recently, research in the field of CSCs has gained increased momentum owing in part to their role in tumourigenicity, metastasis, therapy resistance and relapse. We provide herein a comprehensive assessment of the latest progress in comprehending CSC plasticity, including newly discovered influencing factors and their possible application in HNSCC. We further discuss the dynamic interplay of CSCs within tumour microenvironment considering our evolving appreciation of the contribution of oral microbiota and the pressing need for relevant models depicting their features. In sum, CSCs and tumour plasticity represent an exciting and expanding battleground with great implications for cancer therapy that are only beginning to be appreciated in head and neck oncology.

EBV promotes vascular mimicry of dormant cancer cells by potentiating stemness and EMT

Vascular mimicry (VM) is defined as a vascular channel-like structure composed of tumor cells that correlates with the growth of cancer cells by providing blood circulation. However, whether VM can be formed in dormant cancer cells remains unclear. Our previous research revealed that polyploid giant cancer cells (PGCCs) are specific dormant cells related to the poor prognosis of head and neck cancer. Here, we demonstrated that EBV could promote VM formation by PGCCs in vivo and in vitro. Furthermore, we revealed that the activation of the ERK pathway partly mediated by LMP2A is responsible for stemness, and the acquisition of the stemness phenotype is crucial to the malignant biological behavior of PGCCs. The epithelial-to-mesenchymal transition (EMT) process plays a considerable role in PGCCs, and EMT progression is vital for EBV-positive PGCCs to form VM. This is the first study to reveal that EBV creates plasticity in PGCC-VM and provide a new strategy for targeted anti-tumor therapy.

Exosomes derived from γδ-T cells synergize with radiotherapy and preserve antitumor activities against nasopharyngeal carcinoma in immunosuppressive microenvironment

Background

Radiotherapy is the first-line treatment for patients nasopharyngeal carcinoma (NPC), but its therapeutic efficacy is poor in some patients due to radioresistance. Adoptive T cell-based immunotherapy has also shown promise to control NPC; however, its antitumor efficacy may be attenuated by an immunosuppressive tumor microenvironment. Exosomes derived from γδ-T cells (γδ-T-Exos) have potent antitumor potentials. However, it remains unknown whether γδ-T-Exos have synergistic effect with radiotherapy and preserve their antitumor activities against NPC in an immunosuppressive tumor microenvironment.

Methods

γδ-T-Exos were stained with fluorescent membrane dye, and their interactions with NPC were determined both in vitro and in vivo. NPC cell deaths were detected after treatment with γδ-T-Exos and/or irradiation. Moreover, effects of γδ-T-Exos on radioresistant cancer stem-like cells (CSCs) were determined. The therapeutic efficacy of combination therapy using γδ-T-Exos and irradiation on NPC tumor progression was also monitored in vivo. Finally, the tumor-killing and T cell-promoting activities of γδ-T-Exos were determined under the culture in immunosuppressive NPC supernatant.

Results

γδ-T-Exos effectively interacted with NPC tumor cells in vitro and in vivo. γδ-T-Exos not only killed NPC cells in vitro, which was mainly mediated by Fas/Fas ligand (FasL) and death receptor 5 (DR5)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathways, but also controlled NPC tumor growth and prolonged tumor-bearing mice survival in vivo. Furthermore, γδ-T-Exos selectively targeted the radioresistant CD44^+/high CSCs and induced profound cell apoptosis. The combination of γδ-T-Exos with radiotherapy overcame the radioresistance of CD44^+/high NPC cells and significantly improved its therapeutic efficacy against NPC in vitro and in vivo. In addition, γδ-T-Exos promoted T-cell migration into NPC tumors by upregulating CCR5 on T cells that were chemoattracted by CCR5 ligands in the NPC tumor microenvironment. Although NPC tumor cells secreted abundant tumor growth factor beta to suppress T-cell responses, γδ-T-Exos preserved their direct antitumor activities and overcame the immunosuppressive NPC microenvironment to amplify T-cell antitumor immunity.

Conclusions

γδ-T-Exos synergized with radiotherapy to control NPC by overcoming the radioresistance of NPC CSCs. Moreover, γδ-T-Exos preserved their tumor-killing and T cell-promoting activities in the immunosuppressive NPC microenvironment. This study provides a proof of concept for a novel and potent strategy by combining γδ-T-Exos with radiotherapy in the control of NPC.

Downregulation of SLC27A6 by DNA Hypermethylation Promotes Proliferation but Suppresses Metastasis of Nasopharyngeal Carcinoma Through Modulating Lipid Metabolism

Lipid is the building block and an important source of energy, contributing to the malignant behavior of tumor cells. Recent studies suggested that lipid droplets (LDs) accumulations were associated with nasopharyngeal carcinoma (NPC) progression. Solute carrier family 27 member 6 (SLC27A6) mediates the cellular uptake of long-chain fatty acid (LCFA), a necessary lipid component. However, the functions of SLC27A6 in NPC remain unknown. Here, we found a significant reduction of SLC27A6 mRNA in NPC tissues compared with normal nasopharyngeal epithelia (NNE). The promoter methylation ratio of SLC27A6 was greater in NPC than in non-cancerous tissues. The demethylation reagent 5-aza-2'-deoxycytidine (5-aza-dC) remarkably restored the mRNA expression of SLC27A6, suggesting that this gene was downregulated in NPC owing to DNA promoter hypermethylation. Furthermore, SLC27A6 overexpression level in NPC cell lines led to significant suppression of cell proliferation, clonogenicity in vitro, and tumorigenesis in vivo. Higher SLC27A6 expression, on the other hand, promoted NPC cell migration and invasion. In particular, re-expression of SLC27A6 faciliated epithelial-mesenchymal transition (EMT) signals in xenograft tumors. Furthermore, we observed that SLC27A6 enhanced the intracellular amount of triglyceride (TG) and total cholesterol (T-CHO) in NPC cells, contributing to lipid biosynthesis and increasing metastatic potential. Notably, the mRNA level of SLC27A6 was positively correlated with cancer stem cell (CSC) markers, CD24 and CD44. In summary, DNA promoter hypermethylation downregulated the expression of SLC27A6. Furthermore, re-expression of SLC27A6 inhibited the growth capacity of NPC cells but strengthened the CSC markers. Our findings revealed the dual role of SLC27A6 in NPC and shed novel light on the link between lipid metabolism and CSC maintenance.

The Stromal and Immune Landscape of Nasopharyngeal Carcinoma and Its Implications for Precision Medicine Targeting the Tumor Microenvironment

The evolution of the tumor microenvironment (TME) is a cancer-dependent and dynamic process. The TME is often a complex ecosystem with immunosuppressive and tumor-promoting functions. Conventional chemotherapy and radiotherapy, primarily focus on inducing tumor apoptosis and hijacking tumor growth, whereas the tumor-protective microenvironment cannot be altered or destructed. Thus, tumor cells can quickly escape from extraneous attack and develop therapeutic resistance, eventually leading to treatment failure. As an Epstein Barr virus (EBV)-associated malignancy, nasopharyngeal carcinoma (NPC) is frequently infiltrated with varied stromal cells, making its microenvironment a highly heterogeneous and suppressive harbor protecting tumor cells from drug penetration, immune attack, and facilitating tumor development. In the last decade, targeted therapy and immunotherapy have emerged as promising options to treat advanced, metastatic, recurrent, and resistant NPC, but lack of understanding of the TME had hindered the therapeutic development and optimization. Single-cell sequencing of NPC-infiltrating cells has recently deciphered stromal composition and functional dynamics in the TME and non-malignant counterpart. In this review, we aim to depict the stromal landscape of NPC in detail based on recent advances, and propose various microenvironment-based approaches for precision therapy.

EBV latent membrane proteins promote hybrid epithelial-mesenchymal and extreme mesenchymal states of nasopharyngeal carcinoma cells for tumorigenicity

EBV-encoded LMPs are consistently detected in nasopharyngeal carcinoma (NPC). Recent evidence suggests potential roles of LMP1 and LMP2A in Epithelial-to-mesenchymal transition (EMT) process in NPC. EMT engages in the generation and maintenance of cancer stem cells (CSCs) and confers on cancer cells increased tumor-initiating and metastatic potential, and higher resistance to anticancer therapies. However, how LMP1 and LMP2A regulate the EMT process to generate cells with different EMT states and its implications for tumor progression remain unclear. Here we report that LMP1 and LMP2A promote EMT that drives NPC cells from the epithelial-like state (E) (CD104⁺, CD44^low) to epithelial-mesenchymal hybrid (E/M) state (CD104⁺, CD44^high). Furthermore, LMP2A possesses an additional function in stabilizing LMP1 and increasing the level of LMP1 in NPC cells. The elevated LMP1 further forces the EMT to generate extreme-mesenchymal (xM) state cells (CD104^-, CD44^high). To define the tumorigenic features of cancer stem cells at different states in the EMT spectrum, E, E/M and xM subpopulations were isolated and tested for tumorigenic capability in a tumor xenograft animal model. We found that the cells with E/M phenotypes possess the highest tumor initiating capacity. However, the xM subpopulation exhibits increased vasculogenic mimicry, a hallmark of metastatic cancers. Taken together, coordinated action of LMP1 and LMP2A generates an array of intermediate subpopulations in the EMT spectrum that are responsible for distinct tumorigenic features of NPC such as tumor-initiation, vasculogenesis, and metastasis.

Intratumoral heterogeneity, characterized by the existence of distinct cellular populations within tumor lesions, poses a significant challenge for the treatment of high-grade cancers. Using an EBV-associated nasopharyngeal carcinoma (NPC) model, we sought to elucidate how a virus or its oncoproteins promote the establishment of cancer stem cells that comprises heterogeneous subpopulations. We found that the coordinated action of EBV membrane proteins LMP1 and LMP2A generates heterogeneous subpopulations of cancer stem cells in nasopharyngeal carcinoma by activating the epithelial-to-mesenchymal transition (EMT). Furthermore, the contributions of the different subpopulations to NPC oncogenesis were investigated. Results showed that cells with an epithelial/mesenchymal hybrid state (E/M) possess the highest tumor initiating capacity; and a highly mesenchymal state (xM) subpopulation exhibits increased vasculogenic mimicry. These finding suggest that cancer stem cells residing at various EMT states are responsible for distinct tumorigenic features such as tumor-initiation, vasculogenesis, and metastasis.

Correlation between CD44+ cancer stem cell expression and histopathological types of nasopharyngeal carcinoma

Background: Nasopharyngeal carcinoma (NPC) recurrency rate is still high despite patients receiving complete treatment. The response to treatment may vary depending on the type of histopathology and Epstein-Barr virus, however the mechanism remains unclear. Recent studies have found that there is a relationship between response to treatment and the presence of cancer stem cells (CSCs). CD44+ cancer stem cells may cause cancer cells to be resistant to treatment. Therefore, this cross-sectional study aims to determine the correlation between CD44 + cancer stem cell expression and the histopathological types of NPC. Method: Samples were obtained from NPC biopsies of type I, II, III patients (based on WHO histopathology criteria), who had not received prior treatment. CD44+ expression was examined using immunohistochemistry methods by staining CD44+ monoclonal antibodies. The degree of CD44+ cell membrane expression was based on the immunoreactive score scale or the Remmele index scale. Results: Most histopathological types were WHO type III (21 patients, 50%), followed by type II (18 patients, 42.86%), and type I (3 patients, 7.14%). CD44 + expression on type I showed one patient had moderate positive and two patients had a high-positive expression. In type II, 10 were moderate positive and eight were high-positive. In type III, one patient was low-positive, 11 were moderate positive and nine patients were high-positive. Statistical analysis showed that the CD44+ expression difference between the three histopathology types were not statistically significant. Conclusion: There were no correlations between CD44 + expression and histopathological type of NPC.

Correlation between CD44+ cancer stem cell expression and histopathological types of nasopharyngeal carcinoma

Background: Nasopharyngeal carcinoma (NPC) recurrency rate is still high despite patients receiving complete treatment. The response to treatment may vary depending on the type of histopathology and Epstein-Barr virus, however the mechanism remains unclear. Recent studies have found that there is a relationship between response to treatment and the presence of cancer stem cells (CSCs). CD44+ cancer stem cells may cause cancer cells to be resistant to treatment. Therefore, this cross-sectional study aims to determine the correlation between CD44 + cancer stem cell expression and the histopathological types of NPC. Method: Samples were obtained from NPC biopsies of type I, II, III patients (based on WHO histopathology criteria), who had not received prior treatment. CD44+ expression was examined using immunohistochemistry methods by staining CD44+ monoclonal antibodies. The degree of CD44+ cell membrane expression was based on the immunoreactive score scale or the Remmele index scale. Results: Most histopathological types were WHO type III (21 patients, 50%), followed by type II (18 patients, 42.86%), and type I (3 patients, 7.14%). CD44 + expression on type I showed one patient had moderate positive and two patients had a high-positive expression. In type II, 10 were moderate positive and eight were high-positive. In type III, one patient was low-positive, 11 were moderate positive and nine patients were high-positive. Statistical analysis showed that the CD44+ expression difference between the three histopathology types were not statistically significant. Conclusion: There were no correlations between CD44 + expression and histopathological type of NPC.

Stem Cell Theory of Cancer: Implications of a Viral Etiology in Certain Malignancies

Simple Summary

We postulate that a virus is more likely to cause cancer when it infects a progenitor stem-like cell rather than a progeny differentiated cell. We propose that the virus may turn out to be a surreptitious agent and a serendipitous model in our quest to investigate the origin of cancer. When it pertains, oncology recapitulates ontogeny, although genetic makeup is king. Cellular context may be the key to elucidating a stem cell origin of cancer.

Abstract

In 1911, Peyton Rous (Nobel Prize winner in 1966) demonstrated that a virus (i.e., RSV) caused cancer in chickens. In 1976, Bishop and Varmus (Nobel Prize winners in 1989) showed that the cellular origin of retroviral oncogenes was actually normal cellular genes (i.e., proto-oncogenes). In this article, we revisit the role viruses play in the genetic origin of cancer. We review a link between viruses or cancer and autoimmunity in an alternative stem cell origin of cancer. We propose that a virus is more likely to cause cancer when it infects a progenitor stem-like cell rather than a progeny differentiated cell. We postulate that both known (e.g., HBV and HPV) and novel viruses (e.g., SARS-CoV-2) pose an imminent threat in the emergence of chronic viral diseases as well as virally induced malignancies. Knowing the origin of cancer has profound implications on our current conception and perception of cancer. It affects our conduct in cancer research and our delivery of cancer care. It would be ironic if viruses turn out to be a useful tool and an ideal means in our quest to verify a genetic versus stem cell origin of cancer. When it pertains, oncology recapitulates ontogeny; although genetic makeup is pivotal, cellular context may be paramount to elucidating a stem cell origin of cancer.

Alteration in stemness causes exclusivity between Epstein-Barr virus-positivity and microsatellite instability status in gastric cancer

BACKGROUND

Gastric cancer (GC) is a leading cause of cancer morbidity and mortality worldwide. This is due to the heterogeneous features of GC, which consist of a diverse molecular phenotype. Epstein-Barr virus (EBV)-positive GC and microsatellite instability (MSI)-high GC encompass similar epigenetic traits, including high levels of DNA methylation in CpG islands; however, EBV-positive and MSI-high GCs are mutually exclusive. We aimed to elucidate the underlying mechanism of this exclusivity.

METHODS

We knocked out MLH1 in EBV-positive GC cell lines SNU-719 and NCC24 via CRISPR-Cas9, and evaluated the modified cellular properties in vitro and in vivo. The MSI status of each cell line was screened with two marker capillary electrophoresis, and further diagnosed with five marker capillary electrophoresis and parallel sequencing using 21 markers.

RESULTS

Initial evaluation showed that cell growth, migration, invasion, and MSI status were not affected by MLH1 silencing. However, with prolonged passage, GC cell lines gradually gained MSI and NCC24 cells were transformed to EBV-positive/MSI-high GC cells after 12 months. Furthermore, MLH1 silencing reduced tumor stemness in SNU-719 and NCC24 regardless of the MSI status in vitro and in vivo.

CONCLUSIONS

Our findings suggest that EBV-positivity and MSI-high status are mutually exclusive due to the immediate disadvantage in tumor stemness when MLH1 is silenced, whereas the establishment of MSI-high status in EBV-positive GCs required a longer period.

Identification of Four Genes as Prognosis Signatures in Lung Adenocarcinoma Microenvironment

Background

Tumor microenvironment (TME) cells constitute a vital element of tumor tissues. Increasing evidence has shown that immune response in the microenvironment plays an active role in tumor invasion, metastasis, and recurrence, and is an important factor affecting tumor prognosis. Our study aimed to identify the gene signatures in lung adenocarcinoma (LUAD) microenvironment for prognosis and immunotherapy.

Methods

In this study, we evaluated, for the first time, the stromal and immune scores of 594 patients from The Cancer Genome Atlas (TCGA) database with LUAD using the ESTIMATE algorithm. Three hundred and sixty-seven dysregulated immune-related genes were identified. Then, we performed functional enrichment analysis of these genes, and found the best gene model and construct the signature through univariate, Lasso and multivariate COX regression analysis. To assess the independently prognostic ability of the signature, the Kaplan–Meier survival analysis and Cox’s proportional hazards model were performed.

Results

Functional enrichment analysis and protein–protein interaction networks showed that the immune-related genes mainly played a role in immune response, activation/proliferation of immune-related cells, and chemokine activity. A prognostic model involving 6 genes was constructed and the signature was identified as an independent prognostic factor and significantly associated with the overall survival (OS) of LUAD. The area under curve (AUC) of the receiver operating characteristic curve (ROC curve) for the 6 genes signature in predicting the 3-year survival rate was 0.708. Finally, four genes (FOXN4, KLHL4, FAM83F and CCR2) can be used as candidate prognostic biomarkers for LUAD.

Conclusion

Our findings will help evaluate the prognosis of LUAD and provide new ideas for exploring the potential relationship between TME and LUAD treatment and prognosis.

Reversal of cisplatin sensitization and abrogation of cisplatin-enriched cancer stem cells in 5-8F nasopharyngeal carcinoma cell line through a suppression of Wnt/β-catenin-signaling pathway

Nasopharyngeal carcinoma (NPC) is one of the rare cancers in western countries but predominant in Southeast Asian countries including Thailand. One major cause for failure of NPC chemotherapeutic treatments is reportedly correlated with the elevation of cancer stem cell (CSC) fractions. Thus, this present study aims to investigate the effect of cisplatin (CDDP) treatment on the enrichment of cancer stem-like cells (CSCs) and its associated signaling pathway in EBV-negative NPC cells. Cisplatin-pretreated 5-8F NPC cells (5-8F CDDP) were first generated by treating the cells with 0.5 μM cisplatin for 48 h. After the instant treatment, 5-8F CDDP showed increased IC₅₀ values, demonstrating a decrease in CDDP sensitization. Besides, the proportion of NPC cells with cancer stem-like phenotypes comprising side population (SP), key stemness-related gene expressions including SOX2, ALDH1, CD24 was significantly enhanced. Additionally, 5-8F CDDP displayed the upregulation of β-catenin gene, suggesting its association with the CSC-initiating mechanism. Furthermore, a tankyrase inhibitor for Wnt/β-catenin pathway, XAV939, substantially reduced CSCs and retrieved the cisplatin sensitivity in 5-8F CDDP. This confirms that the Wnt/β-catenin signaling is accountable for rising of the CSC population in EBV-negative NPC. Finally, the combined treatment of CDDP and XAV939 exhibited lower 5-8F CDDP cell viability compared to the treatment of CDDP alone, suggesting the reversal of cisplatin sensitization. In conclusion, the enhancement of CSCs in 5-8F NPC cells caused by the instant cisplatin treatment is initially mediated through the upregulation of β-catenin and activation of Wnt/β-catenin signaling pathway. As a result, a primary chemotherapeutic treatment with closely monitoring the targeted Wnt/β-catenin signaling pathway could potentially prevent the development of CSCs and improve the treatment efficiency in NPC.

Epstein-Barr virus-associated gastric cancer: A distinct subtype

Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) is a common malignant tumor associated with EBV infection. The molecular classification of gastric carcinoma indicates that EBVaGC is a distinct subtype in terms of oncogenesis and molecular features. Viral proteins, Bam-HI-A rightward transcripts (BART) miRNAs, and Bam-HI A rightward frame 1 (BARF1) promote oncogenesis after EBV infection via the induction of methylation, regulation of host gene expression, and malignant transformation. Together with abnormal mutations and amplification of the host genome as driving factors, interactions between the EBV genome and host genome accelerate carcinogenesis. The molecular profile of EBVaGC is that of EBV driving DNA hypermethylation, frequent phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) mutations, and the overexpression of Janus kinase 2 (JAK2), programmed death ligand-1 (PD-L1), and PD-L2. Clinically, the frequency of lymph node metastasis is lower, and the prognosis is better for EBVaGC than EBV-negative gastric cancer (EBVnGC). Pathologically, EBVaGC is a gastric adenocarcinoma with lymphoid stroma. This review interprets how the EBV genome is involved in the oncogenesis of gastric cancer and describes the molecular and clinicopathological features of EBVaGC.

Lgr5 maintains stemness and regulates cell property in nasopharyngeal carcinoma through Wnt/β-catenin signaling pathway

Nasopharyngeal carcinoma (NPC) is a common malignant tumor in Southern China and Southeast Asia. In this study, we found that Leucine rich repeat containing G protein-coupled receptor 5 (Lgr5) was highly expressed in NPC tissues and marked NPC stem cells. Lgr5high tumors showed differential transcriptional landscape compared to Lgr5not high tumors. Lgr5 expression was associated with the clinicopathologic features in NPC and was able to regulate the stemness and viability of NPC cell line CNE1 and HNE1. Meanwhile, the migration, invasion and epithelial-mesenchymal transition (EMT) was modulated by Lgr5 via Wnt/β-catenin signaling pathway. Furthermore, Lgr5 could regulate the sensitivity of NPC cells to chemotherapy drugs. Xenografted tumors from Lgr5-overexpressed CNE1 cells showed stronger tumor forming capacity and higher expression level of stem cell markers. Thus, we characterized previously unidentified role of Lgr5 in NPC cells, potential serving as a NPC stem cell biomarker and a therapeutic target against NPC.

The deubiquitylase UCHL3 maintains cancer stem-like properties by stabilizing the aryl hydrocarbon receptor

Cancer stem cells (CSCs) exhibit highly aggressive and metastatic features and resistance to chemotherapy and radiotherapy. Aryl hydrocarbon receptor (AhR) expression varies among non-small cell lung cancers (NSCLCs), and the mechanisms that support abnormal AhR expression in CSCs remain elusive. Here, we identified ubiquitin carboxyl terminal hydrolase L3 (UCHL3), a DUB enzyme in the UCH protease family, as a bona fide deubiquitylase of the AhR in NSCLC. UCHL3 was shown to interact with, deubiquitylate, and stabilize AhR in a manner dependent on its deubiquitylation activity. Moreover, we showed that UCHL3 promotes the stem-like characteristics and potent tumorigenic capacity of NSCLC cells. UCHL3 increased AhR stability and the binding of AhR to the promoter regions of the “stemness” genes ATP-binding cassette subfamily G member 2 (ABCG2), KLF4, and c-Myc. Depletion of UCHL3 markedly downregulated the “stemness” genes ABCG2, KLF4, and c-Myc, leading to the loss of self-renewal and tumorigenesis in NSCLCs. Furthermore, the UCHL3 inhibitor TCID induced AhR degradation and exhibited significantly attenuated efficacy in NSCLC cells with stem cell-like properties. Additionally, UCHL3 was shown to indicate poor prognosis in patients with lung adenocarcinoma. In general, our results reveal that the UCHL3 deubiquitylase is pivotal for AhR protein stability and a potential target for NSCLC-targeted therapy.

Cancer stem cells in Epstein-Barr virus-associated gastric carcinoma

Cancer stem cells (CSCs) play a decisive role in the development and progression of cancer. To investigate CSCs in Epstein-Barr virus (EBV)-associated carcinoma (EBVaGC), we screened previously reported stem cell markers of gastric cancer in EBV-infected gastric cancer cell lines (TMK1 and NUGC3) and identified CD44v6v9 double positive cells as candidate CSCs. CD44v6/v9^+/+ cells were sorted from EBVaGC cell line (SNU719) cells and EBV-infected TMK1 cells and these cell populations showed high spheroid-forming ability and tumor formation in SCID mice compared with the respective CD44v6/v9^-/- cells. Sphere-forming ability was dependent on the nuclear factor-κB (NF-κB) signaling pathway, which was confirmed by decrease of sphere formation ability under BAY 11-7082. Small interfering RNA knockdown of latent membrane protein 2A (LMP2A), one of the latent gene products of EBV infection, decreased spheroid formation in SNU719 cells. Transfection of the LMP2A gene increased the sphere-forming ability of TMK1 cells, which was mediated through NF-κB signaling. Together, these results indicate that CD44v6v9^+/+ cells are CSCs in EBVaGC that are maintained through the LMP2A/NF-κB pathway. Future studies should investigate CD44v6/v9^+/+ cells in normal and neoplastic gastric epithelium to prevent and treat this specific subtype of gastric cancer infected with EBV.

CD44+CD24-/low sphere-forming cells of EBV-associated gastric carcinomas show immunosuppressive effects and induce Tregs partially through production of PGE2

EBV-associated gastric carcinoma (EBVaGC) is accompanied by massive lymphocyte infiltration, but therapy resistance and tumor progression still occur in patients with EBVaGC. Cancer stem cells (CSCs) are reported to possess immunomodulatory ability that allows them to resist immune-mediated rejection for many tumor types. However, whether and how CSCs in EBVaGC exhibit immunosuppression has not yet been elucidated. We isolated CSC-like sphere-forming cells (SFCs) from EBVaGC cell line SNU-719 using the cancer sphere method. We validated their CSC-associated properties in the expression of the epithelial-mesenchymal transition (EMT)-related genes, the ability to form colonies, and resistance to chemotherapy drug-induced apoptosis and explored their immunomodulatory ability using the coculture system with PBMC (peripheral blood mononuclear cell). These CSC-like SFCs were CD44⁺CD24^-/low and were more tumorigenic than the parental SNU-719 cells in the xenograft mouse model. Remarkably, in the tumor-PBMC co-culturing experiments, these EBVaGC SFCs demonstrated profound immunosuppression by inhibiting the proliferation of PBMCs and T cell activation as well as inducing the generation of regulatory T cells (Tregs). Furthermore, the induction of Tregs was partially dependent on prostaglandin E2 (PGE2) produced from SFCs. Moreover, the presence of high CD44⁺CD24^-/low cells in tumor tissues predicted a decreased disease-free survival in patients with EBVaGC. Our study collectively confirmed the existence and immune resistance of CSCs in EBVaGC and offers new insights into the development of novel anti-EBVaGC strategies by targeting CSCs.

Cancer stem-like cells with hybrid epithelial/mesenchymal phenotype leading the collective invasion

Collective invasion of cancer cells is the key process of circulating tumor cell (CTC) cluster formation, and greatly contributes to metastasis. Cancer stem-like cells (CSC) have a distinct advantage of motility for metastatic dissemination. To verify the role of CSC in the collective invasion, we performed 3D assays to investigate the collective invasion from cancer cell spheroids. The results demonstrated that CSC can significantly promote both collective and single-cell invasion. Further study showed that CSC prefer to move outside and lead the collective invasion. More interestingly, approximately 60% of the leader CSC in collective invasion co-expressed both epithelial and mesenchymal genes, while only 4% co-expressed in single invasive CSC, indicating that CSC with hybrid epithelial/mesenchymal phenotype play a key role in cancer cell collective invasion.

Patient-derived tumor models for human nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is one of the most common head and neck tumors in Southern China. At present, the interaction of genetic susceptibility, Epstein-Barr virus (EBV) infection and environmental factors has been considered to be the main cause of NPC. However, the detailed molecular mechanisms of tumorigenesis and tumor metastasis have not been fully understood. The effective therapeutic drugs targeting NPC are still being developed and discovered. NPC cell lines and normal nasopharyngeal epithelial cell lines were frequently used by researchers, but not represent the complex situation in vivo. Establishing an ideal animal model of NPC is one of the keys to solving the above problems. Here, we introduce the development of in vitro and in vivo models of NPC.

Crucifera sulforaphane (SFN) inhibits the growth of nasopharyngeal carcinoma through DNA methyltransferase 1 (DNMT1)/Wnt inhibitory factor 1 (WIF1) axis

BACKGROUND

Sulforaphane (SFN), a natural compound present in cruciferous vegetable, has been shown to possess anti-cancer activities. Cancer stem cell (CSC) in bulk tumor is generally considered as treatment resistant cell and involved in cancer recurrence. The effects of SFN on nasopharyngeal carcinoma (NPC) CSCs have not yet been explored.

PURPOSE

The present study aims to examine the anti-tumor activities of SFN on NPC cells with CSC-like properties and the underlying mechanisms.

METHODS

NPC cells growing in monolayer culture, CSCs-enriched NPC tumor spheres, and also the NPC nude mice xenograft were used to study the anti-tumor activities of SFN on NPC. The population of cells expressing CSC-associated markers was evaluated using flow cytometry and aldehyde dehydrogenase (ALDH) activity assay. The effect of DNA methyltransferase 1 (DNMT1) on the growth of NPC cells was analyzed by using small interfering RNA (siRNA)-mediated silencing method.

RESULTS

SFN was found to inhibit the formation of CSC-enriched NPC tumor spheres and reduce the population of cells with CSC-associated properties (SRY (Sex determining Region Y)-box 2 (SOX2) and ALDH). In the functional study, SFN was found to restore the expression of Wnt inhibitory factor 1 (WIF1) and the effect was accompanied with the downregulation of DNMT1. The functional activities of WIF1 and DNMT1 were confirmed using exogenously added recombinant WIF1 and siRNA knockdown of DNMT1. Moreover, SFN was found to inhibit the in vivo growth of C666-1 cells and enhance the anti-tumor effects of cisplatin.

CONCLUSION

Taken together, we demonstrated that SFN could suppress the growth of NPC cells via the DNMT1/WIF1 axis.

Genistein inhibits nasopharyngeal cancer stem cells through sonic hedgehog signaling

Genistein, a soy derived isoflavanoid compound, exerts anticancer effects in various cancers. Nasopharyngeal cancer stem cells (NCSCs) are a small subpopulation of cancer cells which are responsible for initiation, progression, metastasis, and recurrence of nasopharyngeal cancer. The present study aimed to investigate the suppressive effects of genistein on NCSCs and its underlying mechanism. NCSCs were enriched from human nasopharyngeal cancer cell lines CNE2 and HONE1 through tumorsphere-forming assay. It was shown that genistein inhibited the tumorsphere formation capacity, decreased the number of EpCAM+ cells, downregulated the expression of NCSCs markers, suppressed cell proliferation, and induced apoptosis of NCSCs. Genistein suppressed the activity of Sonic hedgehog (SHH) signaling, which was important for the maintenance of NCSCs, while activation of SHH signaling by purmorphamine diminished the inhibitory effects of genistein on NCSCs. Our data suggested that genistein inhibited NCSCs through the suppression of SHH signaling. These findings support the use of genistein for targeting NCSCs.

Array expression meta-analysis of cancer stem cell genes identifies upregulation of PODXL especially in DCC low expression meningiomas

BACKGROUND

Meningiomas are the most common intracranial tumors, with a subset of cases bearing a progressive phenotype. The DCC netrin 1 receptor (DCC) is a candidate gene for early meningioma progression. Cancer stem cell (CSC) genes are emerging as cancer therapeutic targets, as their expression is frequently associated with aggressive tumor phenotypes. The main objective of the study was to identify deregulated CSC genes in meningiomas.

MATERIALS AND METHODS

Interrogating two expression data repositories, significantly differentially expressed genes (DEGs) were determined using DCC low vs. DCC high expression groups and WHO grade I (GI) vs. grade II + grade III (GII + GIII) comparison groups. Human stem cell (SC) genes were compiled from two published data sets and were extracted from the DEG lists. Biofunctional analysis was performed to assess associations between genes or molecules.

RESULTS

In the DCC low vs. DCC high expression groups, we assessed seven studies representing each between seven and 58 samples. The type I transmembrane protein podocalyxin like (PODXL) was markedly upregulated in DCC low expression meningiomas in six studies. Other CSC genes repeatedly deregulated included, e.g., BMP/retinoic acid inducible neural specific 1 (BRINP1), prominin 1 (PROM1), solute carrier family 24 member 3 (SLC24A3), rRho GTPase activating protein 28 (ARHGAP28), Kruppel like factor 5 (KLF5), and leucine rich repeat containing G protein-coupled receptor 4 (LGR4). In the GI vs. GII + GIII comparison groups, we assessed six studies representing each between nine and 68 samples. DNA topoisomerase 2-alpha (TOP2A) was markedly upregulated in GII + GIII meningiomas in four studies. Other CSC genes repeatedly deregulated included, e.g., ARHGAP28 and PODXL. Network analysis revealed associations of molecules with, e.g., cellular development and movement; nervous system development and function; and cancer.

CONCLUSIONS

This meta-analysis on meningiomas identified a comprehensive list of deregulated CSC genes across different array expression studies. Especially, PODXL is of interest for functional assessment in progressive meningiomas.

The Wnt modulator ICG‑001 mediates the inhibition of nasopharyngeal carcinoma cell migration in vitro via the miR‑150/CD44 axis

The Wnt signaling pathway is known to serve an important role in the control of cell migration. The present study analyzed the mechanisms underlying the in vitro modulation of the migration of nasopharyngeal carcinoma (NPC) cells by the CREB‑binding protein/catenin antagonist and Wnt modulator ICG‑001. The results revealed that ICG‑001‑mediated inhibition of tumor cell migration involved downregulated mRNA and protein expression of the Wnt target gene cluster of differentiation (CD)44. It was also demonstrated that ICG‑001 downregulated the expression of CD44, and this effect was accompanied by restored expression of microRNA (miRNA)‑150 in various NPC cell lines. Using a CD44 3'‑untranslated region luciferase reporter assay, miR‑150 was confirmed to be a novel CD44‑targeting miRNA, which could directly target CD44 and subsequently regulate the migration of NPC cells. The present study provides further insight into the inhibition of tumor cell migration through the modulation of miRNA expression by the Wnt modulator ICG‑001.

MicroRNA-328 inhibits migration and epithelial-mesenchymal transition by targeting CD44 in nasopharyngeal carcinoma cells

Background

MicroRNAs (miRNAs) play crucial roles in various types of cancers, particularly in tumor development, migration, and progression. Dysregulation of miR-328 was reported to occur in some types of human malignancies, however, the role of miR-328 in nasopharyngeal carcinoma (NPC) and its potential involvement in metastasis remain undetermined.

Methods

The invasion capacity of NPC sphere-forming cells was evaluated by in vitro cell migration assays. Differential miRNAs expression was examined in NPC sphere-forming cells compared to parental monolayer cells using miRNA array analysis. The role of miR-328 in regulating NPC cells migratory properties was analyzed after miR-328 mimics transfection. The expression of E-cadherin and CD44 was analyzed by flow cytometry. CD44 was examined as a target of miR-328 through luciferase reporter assays and Western blotting.

Results

Here, we report that NPC TW01 and TW06 sphere-forming cells exhibited increased migratory ability in comparison with parental monolayer cells. Sphere-forming cells had significantly lower levels of miR-328, as observed using miRNA arrays and confirmed through real-time polymerase chain reaction. Overexpression of miR-328 induced by transfection with synthetic miR-328 mimics decreased the migration of NPC sphere-forming cells. The inhibitory effects were associated with increased expression of E-cadherin and the downregulated expression of mesenchymal markers such as N-cadherin, Snail, and vimentin. Moreover, our results demonstrated that miR-328 suppressed NPC cell migration and inhibited the epithelial–mesenchymal transition process directly through a binding site on the CD44 3′ untranslated region.

Conclusion

miR-328, a previously unrecognized miRNA, may serve as a potential prognostic marker and therapeutic target for NPC.

Epstein-Barr virus infection and nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is associated with multiple types of human cancer, including lymphoid and epithelial cancers. The closest association with EBV infection is seen in undifferentiated nasopharyngeal carcinoma (NPC), which is endemic in the southern Chinese population. A strong association between NPC risk and the HLA locus at chromosome 6p has been identified, indicating a link between the presentation of EBV antigens to host immune cells and NPC risk. EBV infection in NPC is clonal in origin, strongly suggesting that NPC develops from the clonal expansion of a single EBV-infected cell. In epithelial cells, the default program of EBV infection is lytic replication. However, latent infection is the predominant mode of EBV infection in NPC. The establishment of latent EBV infection in pre-invasive nasopharyngeal epithelium is believed to be an early stage of NPC pathogenesis. Recent genomic study of NPC has identified multiple somatic mutations in the upstream negative regulators of NF-κB signalling. Dysregulated NF-κB signalling may contribute to the establishment of latent EBV infection in NPC. Stable EBV infection and the expression of latent EBV genes are postulated to drive the transformation of pre-invasive nasopharyngeal epithelial cells to cancer cells through multiple pathways.This article is part of the themed issue 'Human oncogenic viruses'.

XIAP Limits Autophagic Degradation of Sox2 and Is A Therapeutic Target in Nasopharyngeal Carcinoma Stem Cells

Rationale: Nasopharyngeal carcinoma (NPC) is the most frequent head and neck tumor in South China. The presence of cancer stem cells (CSCs) in NPC contributes to tumor maintenance and therapeutic resistance, while the ability of CSCs to escape from the apoptosis pathway may render them the resistant property to the therapies. Inhibitor of apoptosis proteins family proteins (IAPs), which are overexpressed in nasopharyngeal carcinoma stem cells, may play an important role in maintaining nasopharyngeal cancer stem cell properties. Here, we develop a novel CSC-targeting strategy to treat NPC through inhibiting IAPs.

Methods: Human NPC S-18 and S-26 cell lines were used as the model system in vitro and in vivo. Fluorescence activated cell sorting (FACS) assay was used to detect nasopharyngeal SP cells and CD44+ cells. The characteristics of CSCs were defined by sphere suspension culture, colony formation assay and cell migration. The role of XIAP on the regulation of Sox2 protein stability and ERK1-mediated phosphorylation of Sox2 signaling pathway were analyzed using immunoblotting, immunoprecipitation, immunofluorescence, phosphorylation mass spectrometry, siRNA silencing and plasmid overexpression. The correlation between XIAP and Sox2 in NPC biopsies and their role in prognosis was performed by immunohistochemistry. APG-1387 or chemotherapies-induced cell death and apoptosis in S-18 and S-26 were determined by WST, immunoblotting and flow cytometry assay.

Results: IAPs, especially X chromosome-linked IAP (XIAP), were elevated in CSCs of NPC, and these proteins were critically involved in the maintenance of CSCs properties by enhancing the stability of Sox2. Mechanistically, ERK1 kinase promoted autophagic degradation of Sox2 via phosphorylation of Sox2 at Ser251 and further SUMOylation of Sox2 at Lys245 in non-CSCs. However, XIAP blocked autophagic degradation of Sox2 by inhibiting ERK1 activation in CSCs. Additionally, XIAP was positively correlated with Sox2 expression in NPC tissues, which were associated with NPC progression. Finally, we discovered that a novel antagonist of IAPs, APG-1387, exerted antitumor effect on CSCs. Also, the combination of APG-1387 with CDDP /5-FU has a synergistic effect on NPC.

Conclusion: Our study highlights the importance of IAPs in the maintenance of CSCs in NPC. Thus, XIAP is a promising therapeutic target in CSCs and suggests that NPC patients may benefit from a combination treatment of APG-1387 with conventional chemotherapy.

Modulation of the tumor microenvironment by Epstein-Barr virus latent membrane protein 1 in nasopharyngeal carcinoma

Latent membrane protein 1 (LMP1) is a primary oncogene encoded by the Epstein‐Barr virus, and various portions of LMP1 are detected in nasopharyngeal carcinoma (NPC) tumor cells. LMP1 has been extensively studied since the discovery of its transforming property in 1985. LMP1 promotes cancer cell growth during NPC development and facilitates the interaction of cancer cells with surrounding stromal cells for invasion, angiogenesis, and immune modulation. LMP1 is detected in 100% of pre‐invasive NPC tumors and in approximately 50% of advanced NPC tumors. Moreover, a small population of LMP1‐expressing cells in advanced NPC tumor tissue is proposed to orchestrate NPC tumor tissue maintenance and development through cancer stem cells and progenitor cells. Recent studies suggest that LMP1 activity shifts according to tumor development stage, but it still has a pivotal role during all stages of NPC development.

Suppression of Epstein-Barr virus DNA load in latently infected nasopharyngeal carcinoma cells by CRISPR/Cas9

Epstein-Barr virus (EBV) infects more than 90% of the world's adult population. Once established, latent infection of nasopharyngeal epithelial cells with EBV is difficult to eradicate and might lead to the development of nasopharyngeal carcinoma (NPC) in a small subset of individuals. In this study we explored the anti-EBV potential of CRISPR/Cas9 targeting of EBV genome in infected NPC cells. We designed gRNAs to target different regions of the EBV genome and transfected them into C666-1 cells. The levels of EBV DNA in transfected cells were decreased by about 50%. The suppressive effect on EBV DNA load lasted for weeks but could not be further enhanced by re-transfection of gRNA. Suppression of EBV by CRISPR/Cas9 did not affect survival of C666-1 cells but sensitized them to chemotherapeutic killing by cisplatin and 5-fluorouracil. Our work provides the proof-of-principle for suppressing EBV DNA load with CRISPR/Cas9 and a potential new strategy to sensitize EBV-infected NPC cells to chemotherapy.

Will a mAb-Based Immunotherapy Directed against Cancer Stem Cells Be Feasible?

The cancer stem cell (CSC) hypothesis suggests that within a tumor, there is a small subpopulation of cells with stem cell properties responsible for tumor maintenance and metastasis generation. This hypothesis also implies that new antitumor drugs, rather than targeting the bulk of the tumor mass, would be more effective if they directly targeted the CSC subpopulation. The CSCs from several types of tumors have been identified with mAbs recognizing surface antigens in these cells; however, antigens specifically or exclusively expressed in the CSC population have not yet been identified. Thus, questioning the possibility of using therapeutic antibodies directed against the CSCs. Here, we review the possibilities of using antibodies directly targeting the CSCs as therapeutic agents in the form of naked antibodies, antibodies conjugated to nanoparticles, or antibody cocktails.

CD24, CD44 and EpCAM enrich for tumour-initiating cells in a newly established patient-derived xenograft of nasopharyngeal carcinoma

Subpopulations of nasopharyngeal carcinoma (NPC) contain cells with differential tumourigenic properties. Our study evaluates the tumourigenic potential of CD24, CD44, EpCAM and combination of EpCAM/CD44 cells in NPC. CD44br and EpCAMbr cells enriched for higher S-phase cell content, faster-growing tumourigenic cells leading to tumours with larger volume and higher mitotic figures. Although CD44br and EpCAMbr cells significantly enriched for tumour-initiating cells (TICs), all cells could retain self-renewal property for at least four generations. Compared to CD44 marker alone, EpCAM/CD44dbr marker did not enhance for cells with faster-growing ability or higher TIC frequency. Cells expressing high CD44 or EpCAM had lower KLF4 and p21 in NPC subpopulations. KLF4-overexpressed EpCAMbr cells had slower growth while Kenpaullone inhibition of KLF4 transcription increased in vitro cell proliferation. Compared to non-NPC, NPC specimens had increased expression of EPCAM, of which tumours from advanced stage of NPC had higher expression. Together, our study provides evidence that EpCAM is a potentially important marker in NPC.

5T4-specific chimeric antigen receptor modification promotes the immune efficacy of cytokine-induced killer cells against nasopharyngeal carcinoma stem cell-like cells

Relapse and metastasis of nasopharyngeal carcinoma (NPC) are presumably attributed to cancer stem cells (CSCs). In recent years, chimeric antigen receptor (CAR)-modified immune effector cells have been shown to have impressive antitumour efficacy. In this study, we aimed to identify appropriate tumour-associated antigens predominantly expressed on NPC stem cells (NPCSCs) and determine their suitability for CAR-engineered cytokine-induced killer (CIK) cell therapy against NPC. By investigating the expression patterns of potential target antigens (ROR1, 5T4 and CAIX) in NPC, we found that the oncofetal antigen 5T4 was predominately expressed in NPC cell lines and tissues but absent in non-cancerous nasopharyngeal tissues. Moreover, significantly enhanced expression of 5T4 in NPC spheroids revealed its relationship with putative NPCSCs. Hence, we designed a CAR construct (5T4-28Z) specific for 5T4 and generated CAR-transduced CIK cells. Our results showed that the artificial CAR was efficiently expressed on the surface of CIK cells and that no native phenotypes were altered by the gene transduction. Functional assays revealed that 5T4-28Z-CIK cells possessed both CAR-mediated and CAR-independent anti-NPC activity and were capable of efficiently attacking NPC cells, especially NPCSC-like cells in vitro, suggesting that they might serve as an attractive tool for developing efficient therapies against NPC.

Targeting Lung Cancer Stem Cells: Research and Clinical Impacts

Lung cancer is the most common cancer worldwide, accounting for 1.8 million new cases and 1.6 million deaths in 2012. Non-small cell lung cancer (NSCLC), which is one of two types of lung cancer, accounts for 85–90% of all lung cancers. Despite advances in therapy, lung cancer still remains a leading cause of death. Cancer relapse and dissemination after treatment indicates the existence of a niche of cancer cells that are not fully eradicated by current therapies. These chemoresistant populations of cancer cells are called cancer stem cells (CSCs) because they possess the self-renewal and differentiation capabilities similar to those of normal stem cells. Targeting the niche of CSCs in combination with chemotherapy might provide a promising strategy to eradicate these cells. Thus, understanding the characteristics of CSCs has become a focus of studies of NSCLC therapies.

Modeling nasopharyngeal carcinoma in three dimensions

Nasopharyngeal carcinoma (NPC) is a type of cancer endemic in Asia, including Malaysia, Southern China, Hong Kong and Taiwan. Treatment resistance, particularly in recurring cases, remains a challenge. Thus, studies to develop novel therapeutic agents are important. Potential therapeutic compounds may be effectively examined using two-dimensional (2D) cell culture models, three-dimensional (3D) spheroid models or in vivo animal models. The majority of drug assessments for cancers, including for NPC, are currently performed with 2D cell culture models. This model offers economical and high-throughput screening advantages. However, 2D cell culture models cannot recapitulate the architecture and the microenvironment of a tumor. In vivo models may recapitulate certain architectural and microenvironmental conditions of a tumor, however, these are not feasible for the screening of large numbers of compounds. By contrast, 3D spheroid models may be able to recapitulate a physiological microenvironment not observed in 2D cell culture models, in addition to avoiding the impediments of in vivo animal models. Thus, the 3D spheroid model offers a more representative model for the study of NPC growth, invasion and drug response, which may be cost-effective without forgoing quality.

BEX3 contributes to cisplatin chemoresistance in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) can develop cisplatin‐resistant phenotype. Research has revealed that enriched in cancer stem cell population is involved in developing cisplatin‐resistant phenotype. CD271 is a candidate stem cell maker in head and neck cancers. The CD receptor does not possess any enzymatic property. Signal transduction function of CD271 is mediated by the cellular receptor‐associated protein. Our data showed that Brain‐expressed X‐linked 3 (BEX3), a CD271 receptor‐associated protein, was overexpressed in NPC. BEX3 overexpression was a unique event in cancer developed in the head and neck regions, especially NPC. BEX3 expression was inducible by cisplatin in NPC. In cisplatin‐resistant NPC xenograft, treatment with nontoxic level of cisplatin led to a remarkable increase in BEX3 level. High BEX3 expression was accompanied with high octamer‐binding transcription factor 4 (OCT4) expression in cisplatin‐resistant NPC. To confirm the inducing role of BEX3 on OCT4 expression, we knockdown BEX3 using siRNA and compared the expression of OCT4 with mock transfectants. Suppressing BEX3 transcripts led to a significant reduction in OCT4. In addition, targeting BEX3 using shRNA could increase the sensitivity of NPC cells to cisplatin. In summary, our results indicated a unique functional role of BEX3 in mediating the sensitivity of NPC cells to cisplatin. Targeting or blocking BEX3 activity might be useful in reversing the cisplatin‐resistant phenotype in NPC.

Proteoglycan expression correlates with the phenotype of malignant and non-malignant EBV-positive B-cell lines

The involvement of proteoglycans (PGs) in EBV-host interactions and lymphomagenesis remains poorly investigated. In this study, expression of major proteoglycans (syndecan-1, glypican-1, perlecan, versican, brevican, aggrecan, NG2, serglycin, decorin, biglycan, lumican, CD44), heparan sulphate (HS) metabolic system (EXT1/2, NDST1/2, GLCE, HS2ST1, HS3ST1/2, HS6ST1/2, SULF1/2, HPSE) and extracellular matrix (ECM) components (collagen 1A1, fibronectin, elastin) in primary B cells and EBV carrying cell lines with different phenotypes, patterns of EBV-host cell interaction and viral latency stages (type I-III) was investigated. Primary B cells expressed a wide repertoire of PGs (dominated by serglycin and CD44) and ECM components. Lymphoblastoid EBV+ B cell lines (LCLs) showed specific PG expression with down-regulation of CD44 and ECM components and up-regulation of serglycin and perlecan/HSPG2. For Burkitt's lymphoma cells (BL), serglycin was down-regulated in BL type III cells and perlecan in type I BL cells. The biosynthetic machinery for HS was active in all cell lines, with some tendency to be down-regulated in BL cells. 5'-aza-dC and/or Trichostatin A resulted in transcriptional upregulation of the genes, suggesting that low expression of ECM components, proteoglycan core proteins and HS biosynthetic system is due to epigenetic suppression in type I cells. Taken together, our data show that proteoglycans are expressed in primary B lymphocytes whereas they are not or only partly expressed in EBV-carrying cell lines, depending on their latency type program.

MicroRNA-183 suppresses cancer stem-like cell properties in EBV-associated nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated epithelial malignancy that exhibits distinct geographical and ethnic prevalence. Although the contemporary therapeutic approach of radio-/chemotherapy provides excellent results for patients with early-stage disease, it is far from satisfactory for those with disease remission and distant metastasis. Promising therapeutic strategies for advanced and relapsed NPC are still lacking. We recently identified and characterized a cancer stem-like cell (CSC) subpopulation in NPC that appeared to play an important role in tumor progression. Microarray analysis revealed downregulation of several stemness-inhibiting miRNAs in these CSC cells. Among these miRNAs, miR-96 and miR-183 showed the highest fold change and were selected to elucidate their role in repressing NPC CSC properties.

METHODS

MiR-96 and miR-183 expression in NPC CSCs was detected by qRT-PCR. Transient and stable transfection was performed in EBV-positive NPC C666-1 cells to examine the effects of ectopic expression of miR-96 and miR-183 on repressing cell growth and CSC properties. Anchorage-dependent (colony formation) and anchorage-independent (tumor sphere formation) growths of these miR-96 and miR-183 expressing cells were determined. Expression of multiple CSC markers and related molecules were accessed by flow cytometry and Western blotting. The tumorigenicity of the stable miR-96- and miR-183-transfected NPC cells was examined in an in vivo nude mice model.

RESULTS

Downregulation of miR-96 and miR-183 was confirmed in NPC spheroids. Using transient or stable transfection, we showed that ectopic expression of miR-96 and miR-183 suppressed cell growth and tumor sphere formation in NPC. Reduced NICD3 and NICD4 in miR-96- and miR-183-expressing NPC cells suggests the involvement of the NOTCH signaling pathway in their tumor suppressive function. Finally, we showed that the tumorigenicity of cells stably expressing miR-183 was significantly inhibited in the in vivo nude mice model.

CONCLUSIONS

miR-183 is a tumor-suppressive miRNA in EBV-associated NPC. Its abilities to suppress CSC properties in vitro and effectively reduce tumor growth in vivo shed light on its role as a potential therapeutic target.

DC120, a novel AKT inhibitor, preferentially suppresses nasopharyngeal carcinoma cancer stem-like cells by downregulating Sox2

Side population (SP) contains cancer stem-like cells (CSLCs). In this study, we characterized SP cells from nasopharyngeal carcinoma (NPC) cell lines and found that SP cells had a higher self-renewal ability in vitro and greater tumorigenicity in vivo. The AKT pathway was activated in NPC SP cells. DC120, a 2-pyrimidyl-5-amidothiazole inhibitor of the ATP binding site of AKT, inhibited phosphorylation of FKHRL1 and GSK-3β. DC120 inhibited SP fraction, the sphere-forming ability in vitro and growth of primary xenografts as well as secondary xenografts’ tumor recurrence. This inhibition was accompanied by reduced expression of stem-related gene Sox2 due to induction of p27 and miR-30a. A combination of DC120 and CDDP more effectively inhibited NPC cells compared with monotherapy in vitro and in vivo. Clinical evaluation of DC120 is warranted.