Cancer stem-like cell: a novel target for nasopharyngeal carcinoma therapy

The strategies to cure cancer patients by eradicating cancer stem-like cells

Cancer stem-like cells (CSCs), a subpopulation of cancer cells, possess remarkable capability in proliferation, self-renewal, and differentiation. Their presence is recognized as a crucial factor contributing to tumor progression and metastasis. CSCs have garnered significant attention as a therapeutic focus and an etiologic root of treatment-resistant cells. Increasing evidence indicated that specific biomarkers, aberrant activated pathways, immunosuppressive tumor microenvironment (TME), and immunoevasion are considered the culprits in the occurrence of CSCs and the maintenance of CSCs properties including multi-directional differentiation. Targeting CSC biomarkers, stemness-associated pathways, TME, immunoevasion and inducing CSCs differentiation improve CSCs eradication and, therefore, cancer treatment. This review comprehensively summarized these targeted therapies, along with their current status in clinical trials. By exploring and implementing strategies aimed at eradicating CSCs, researchers aim to improve cancer treatment outcomes and overcome the challenges posed by CSC-mediated therapy resistance.

Ferroptosis regulators related scoring system by Gaussian finite mixture model to predict prognosis and immunotherapy efficacy in nasopharyngeal carcinoma

The role of ferroptosis in tumor progression and metastasis has been demonstrated. Nonetheless, potential biological function of ferroptosis regulatory pattern in nasopharyngeal carcinoma (NPC) remains unknown. Ferroptosis regulatory patterns of nasopharyngeal carcinoma samples were evaluated based on 113 ferroptosis regulators and three distinct ferroptosis subtypes were determined by unsupervised clustering. The ferroptosis score (FEP score) was identified to quantify ferroptosis patterns within individual tumors by Gaussian finite mixture model and systematically correlated with representative tumor characteristics. Subtype 1 and subtype 3 were consistent with immune activated phenotype, while subtype 2 was consistent with immune suppressed phenotype. High ferroptosis score, characterized by immune activation and suppression of mRNA based stemness index (mRNAsi) and Epstein-Barr virus (EBV) genes, indicated an immune activated tumor microenvironment (TME) phenotype, with better progression free survival (PFS) and lower risk of recurrence and metastasis. Low ferroptosis score, characterized by activation of Wnt and NF-κB signaling pathways and lack of effective immune infiltration, indicated an immune suppressed tumor microenvironment phenotype and poorer survival. High ferroptosis score was also correlated to enhanced response to immunotherapy, and was confirmed to correlate with therapeutic advantages and clinical benefits in an anti-programmed cell death 1 ligand 1 (PD-L1) immunotherapy cohort. As ferroptosis played a crucial role in the tumor microenvironment’s diversity, assessing the ferroptosis pattern within individual tumor with ferroptosis score could enhance our understanding of tumor microenvironment infiltration characterization and help develop more effective immunotherapy.

m6A Regulators Mediated Methylation Modification Patterns and Tumor Microenvironment Infiltration Characterization In Nasopharyngeal Carcinoma

Background

The role of RNA N6-methyladenosine (m6A) modification in tumor progression and metastasis has been demonstrated. Nonetheless, potential biological function of m6A modification patterns in nasopharyngeal carcinoma (NPC) remains unknown.

Methods

The m6A modification patterns were comprehensively evaluated based on 26 m6A regulators in NPC, and m6A subtype and also m6A score were identified and systematically correlated with representative tumor characteristics.

Results

Two distinct m6A subtypes were determined and were highly consistent with immune activated and immune suppressed phenotypes, respectively. More representative m6A scores of individual tumors could predict tumor microenvironment (TME) infiltration, mRNA based stemness index (mRNAsi), EBV gene expression, genetic variation, and prognosis of NPC patients. Low m6A score, characterized by activation of immunity and suppression of mRNAsi and EBV gene, indicated an activated TME phenotype and better PFS and also lower risk of recurrence and metastasis. High m6A score, characterized by activation of Wnt and NF-κB signaling pathway and lack of effective immune infiltration, indicated an immune suppressed TME phenotype and poorer survival. Low m6A score was also correlated with increased tumor mutation burden (TMB) and better response to immunotherapy, and vice versa. A significant therapeutic advantage in patients with low m6A score was confirmed with an anti-PDL1 immunotherapy cohort.

Conclusions

m6A patterns played an important role in the diversity and complexity of TME. m6A score could be used to evaluate the m6A pattern of individual tumor to enhance our understanding of TME infiltration and guide more effective immunotherapy strategies.

Increased MCL-1 synthesis promotes irradiation-induced nasopharyngeal carcinoma radioresistance via regulation of the ROS/AKT loop

Worldwide, nasopharyngeal carcinoma (NPC) is a rare head and neck cancer; however, it is a common malignancy in southern China. Radiotherapy is the most important treatment strategy for NPC. However, although radiotherapy is a strong tool to kill cancer cells, paradoxically it also promotes aggressive phenotypes. Therefore, we mimicked the treatment process in NPC cells in vitro. Upon exposure to radiation, a subpopulation of NPC cells gradually developed resistance to radiation and displayed cancer stem-cell characteristics. Radiation-induced stemness largely depends on the accumulation of the antiapoptotic myeloid cell leukemia 1 (MCL-1) protein. Upregulated MCL-1 levels were caused by increased stability and more importantly, enhanced protein synthesis. We showed that repeated ionizing radiation resulted in persistently enhanced reactive oxygen species (ROS) production at a higher basal level, further promoting protein kinase B (AKT) signaling activation. Intracellular ROS and AKT activation form a positive feedback loop in the process of MCL-1 protein synthesis, which in turn induces stemness and radioresistance. AKT/MCL-1 axis inhibition attenuated radiation-induced resistance, providing a potential target to reverse radiation therapy-induced radioresistance.

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.

Long non-coding RNA FOXD3-AS1 silencing exerts tumor suppressive effects in nasopharyngeal carcinoma by downregulating FOXD3 expression via microRNA-185-3p upregulation

Emerging evidence indicates that the incidence of nasopharyngeal carcinoma (NPC) remains high in endemic regions despite changing environmental factors, suggesting that genetic traits contribute to its development. Recently, long non-coding RNA-microRNA-messenger RNA (lncRNA-miRNA-mRNA) axis has been reported to be implicated in the pathophysiological processes of malignancies. Moreover, initial bioinformatic analysis revealed a highly expressed lncRNA Forkhead box D3 antisense RNA1 (FOXD3-AS1) for mechanistic network underlying NPC in this present study. Therefore, this study aims to delineate the ability of lncRNA FOXD3-AS1 to influence the NPC progression. The relationship among lncRNA FOXD3-AS1, miR-185-3p, and FOXD3 was identified with bioinformatics prediction, dual-luciferase reporter gene assays, RNA-binding protein immunoprecipitation, and RNA pull-down assays. Furthermore, effects of lncRNA FOXD3-AS1 on malignant phenotypes in vitro, alongside tumor formation in vivo, of transfected NPC stem-like cells were examined with gain- and loss-of-function experiments. Our findings revealed that lncRNA FOXD3-AS1 and FOXD3 exhibited increased expression levels, while miR-185-3p exhibited diminished levels in NPC. The levels of lncRNA FOXD3-AS1 and FOXD3 were further correlated with tumor node metastasis stage and pathological type of patients with NPC. LncRNA FOXD3-AS1 was also confirmed to negatively regulate the miR-185-3p expression, which further targeted the downstream gene FOXD3. In addition, lncRNA FOXD3-AS1 knockdown repressed cell stemness, colony formation, viability, invasion, migration, and in vivo tumor growth, and accelerated cell apoptosis. Moreover, FOXD3 silencing or miR-185-3p overexpression reversed the effects of lncRNA FOXD3-AS1. Our findings provide evidence indicating that lncRNA FOXD3-AS1 could bind to miR-185-3p to upregulate the FOXD3 expression, thereby promoting the development of NPC.

Programmed death protein 1 is essential for maintaining the anti-inflammatory function of infiltrating regulatory T cells in a murine spinal cord injury model

Excessive neuroinflammation exacerbates neuronal impairment after spinal cord injury (SCI). Thymic regulatory T cells (Tregs), macrophages, and microglia play significant roles in the process of post-SCI neuroinflammation. However, the mechanisms by which these cells were modulated in the injured spinal cord remain unclear. In the current research, we applied a murine SCI model to demonstrate the upregulation of programmed death protein 1(PD-1) in infiltrating Tregs and significant expression of programmed death-ligand 1 (PD-L1) on post-SCI macrophages/microglia. Furthermore, through using an inducible shRNA lentivirus system, we showed that Treg-specific PD-1 knockdown impairs the anti-inflammatory function of infiltrating Tregs. PD-1 is crucial for the maintenance of Treg identity and function under the influence of pro-inflammatory macrophages/microglia, and PD-1-deficient Tregs are less competent to inhibit pro-inflammatory macrophages/microglia. Besides, in a murine SCI model using T-and-B-cell-deficient Rag1^-/- mice, Treg-specific PD-1 knockdown impairs Treg-mediated neuroprotection in vivo, as evidenced by enlarged lesion area. Taken together, our study revealed that PD-1, which is upregulated on infiltrating Tregs in the subacute phase of SCI, is essential for Tregs to maintain Foxp3 expression and anti-inflammatory activity to counteract the effect of pro-inflammatory macrophages and microglia. Novel therapies targeting Treg PD-1 might benefit SCI treatment.

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.

Advances in targeted therapy mainly based on signal pathways for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant epithelial carcinoma of the head and neck region which mainly distributes in southern China and Southeast Asia and has a crucial association with the Epstein-Barr virus. Based on epidemiological data, both incidence and mortality of NPC have significantly declined in recent decades grounded on the improvement of living standard and medical level in an endemic region, in particular, with the clinical use of individualized chemotherapy and intensity-modulated radiotherapy (IMRT) which profoundly contributes to the cure rate of NPC patients. To tackle the challenges including local recurrence and distant metastasis in the current NPC treatment, we discussed the implication of using targeted therapy against critical molecules in various signal pathways, and how they synergize with chemoradiotherapy in the NPC treatment. Combination treatment including targeted therapy and IMRT or concurrent chemoradiotherapy is presumably to be future options, which may reduce radiation or chemotherapy toxicities and open new avenues for the improvement of the expected functional outcome for patients with advanced NPC.

RASSF1A inhibits PDGFB-driven malignant phenotypes of nasopharyngeal carcinoma cells in a YAP1-dependent manner

Nasopharyngeal carcinoma (NPC) is a highly aggressive tumor characterized by distant metastasis. Deletion or down-regulation of the tumor suppressor protein ras-association domain family protein1 isoform A (RASSF1A) has been confirmed to be a key event in NPC progression; however, little is known about the effects or underlying mechanism of RASSF1A on the malignant phenotype. In the present study, we observed that RASSF1A expression inhibited the malignant phenotypes of NPC cells. Stable silencing of RASSF1A in NPC cell lines induced self-renewal properties and tumorigenicity in vivo/in vitro and the acquisition of an invasive phenotype in vitro. Mechanistically, RASSF1A inactivated Yes-associated Protein 1 (YAP1), a transcriptional coactivator, through actin remodeling, which further contributed to Platelet Derived Growth Factor Subunit B (PDGFB) transcription inhibition. Treatment with ectopic PDGFB partially increased the malignancy of NPC cells with transient knockdown of YAP1. Collectively, these findings suggest that RASSF1A inhibits malignant phenotypes by repressing PDGFB expression in a YAP1-dependent manner. PDGFB may serve as a potential interest of therapeutic regulators in patients with metastatic NPC.

Rac1: A potential radiosensitization target of human nasopharyngeal carcinoma CNE2 cells

Radiotherapy has a high cure rate for early nasopharyngeal carcinoma(NPC). However, the radiation resistance of poorly differentiated NPC cells impacts the effectiveness of treatment of early-stage NPC patients. Here, we explored the relationship between Ras-related C3 botulinum toxin substrate 1(Rac1) expression and NPC radiosensitivity. In vitro and in vivo studies revealed that upregulation of Rac1, when combined with X-ray treatment, increased growth inhibition and induced remarkable morphological changes and apoptosis in CNE2 cells. Furthermore, rupturing of the cell and nuclear membranes, degeneration of the cristae and significant swelling of the mitochondria were observed, which were consistent with the high apoptotic rate. The Rac1(+) cells exhibited approximately 50% more migration compared with that of the NC and Rac1(-) cells. The overexpression of Rac1 can increase the radiation sensitivity of NPC CNE2 cells, and the mechanism may be closely related to the oxidative damage of mitochondria. Rac1 might be a potential target for radiosensitization in poorly differentiated NPC.

The tumor-suppressive role of microRNA-873 in nasopharyngeal carcinoma correlates with downregulation of ZIC2 and inhibition of AKT signaling pathway

Cancer stem cells (CSCs) are responsible for tumor initiation, relapse, and metastasis. Thus, residual CSCs after chemotherapy may result in poor prognosis for nasopharyngeal carcinoma (NPC). Emerging evidence suggests that differentially expressed microRNAs (miRNAs) regulate genes that carry out important functions in CSCs. Here we investigate the interaction of microRNA-873 (miR-873) with the Zic family member 2 (ZIC2) and the effects on downstream serine-threonine protein kinase (AKT) signaling pathway in CSCs in the context of NPC. Initially, microarray-based gene expression profiling identified ZIC2 as a key differentially expressed gene in NPC, which was subsequently confirmed to be upregulated in clinical NPC tissue samples. NPC cells were subjected to sphere-formation conditions in low-attachment plates, followed by sorting of CD133⁺ cells, which were selected as NPC stem cells after further characterization of stem cell biomarkers. ZIC2 was then shown to be enriched in NPC stem cells at both mRNA and protein levels. However, loss of ZIC2 was associated with the self-renewal, proliferative and tumorigenic properties of NPC stem cells. Next, miRNAs potentially able to target ZIC2 were predicted by the intersection of mirDIP and TargetScan database results, and miRNA miR-873 was found to be downregulated in NPC tissues in general but especially in NPC stem cells. Upregulation of miR-873 inhibited the stem-like properties and tumorigenicity of NPC stem cells, which was found to take place through downregulation of ZIC2 and disruption of the AKT signaling pathway. Collectively, the results obtained suggest that overexpression of miR-873 could aid NPC tumor suppression through reduction of the malignant potential of CSCs.

Multiple Mechanisms Involving in Radioresistance of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is the malignant tumor with ethnic and geographical distribution preference. Although intensity-modulated radiotherapy (IMRT)-based radiotherapy combined with chemotherapy and targeted therapy has dramatically improved the overall survival of NPC patients, there are still some patients suffering from recurrent tumors and the prognosis is poor. Multiple mechanisms may be responsible for radioresistance of NPC, such as cancer stem cells (CSCs) existence, gene mutation or aberrant expression of genes, epigenetic modification of genes, abnormal activation of certain signaling pathways, alteration of tumor microenvironment, stress granules (SGs) formation, etc. We conduct a comprehensive review of the published literatures focusing on the causes of radioresistance, retrospect the regulation mechanisms following radiation, and discuss future directions of overcoming the resistance to radiation.

Radiosensitization of Clioquinol Combined with Zinc in the Nasopharyngeal Cancer Stem-like Cells by Inhibiting Autophagy in Vitro and in Vivo

Loco-regional recurrence of nasopharyngeal carcinoma (NPC) after radiation therapy is one of the main types of treatment failure. This study is aimed to explore the possible causes of inside-field recurrence of NPC patients in order to develop effective treatment methods. Our study indicated that CD44 and autophagy proteins in tumor tissues of patients with recurrent NPC are higher than that of the relapse free patients. The in vitro experiments further confirmed that cancer stem cells (CSCs) were more radioresistant with enhanced autophagy activity. Treatment with clioquinol (CQ) combined with zinc could obviously enhance the radiosensitivity of CNE-2s cells through autophagy inhibition, activation of the caspase system and impairment of DNA damage repair. The in vivo experiments have further consolidated our findings. Our results suggest that CSCs and enhanced autophagy activity may be involved in the inside-field recurrence of NPC, and CQ combined with zinc could be an important therapeutic approach for recurrent NPC.

Ovatodiolide suppresses nasopharyngeal cancer by targeting stem cell-like population, inducing apoptosis, inhibiting EMT and dysregulating JAK/STAT signaling pathway

BACKGROUND

Treatment for metastatic nasopharyngeal carcinoma (NPC) is challenging. Till now, a truly effective chemotherapy regimen for NPC has not yet been identified. These clinical observations prompted us to investigate a potential drug as alternative option for treating.

PURPOSE

This study evaluated the inhibitory effects of Ovatodiolide (Ova), on tumorigenic and cancer stem cell characteristics of NPC cells.

METHODS

Two NPC cell lines (NPC-BM1 and NPC-BM2) were used to examine the anticancer effects of Ova and the molecular mechanism underlying these activities by using sulforhodamine B cytotoxicity assay, western blot, immunofluorescence, migration, colony and tumorsphere formation assays.

RESULTS

Ova significantly inhibited the viability of BM1 and BM2 cells, downregulated Bcl-xL and Puma, and upregulated Bax/Bad expression levels. Ova dose-dependent suppressed migratory/invasive potential of NPC cells, and reduced ability to form colonies. Ova-induced apoptosis correlated with increased Bax/Bcl-xL ratio while NPC motility and colony formation inhibition were associated with reduced expression of p-FAK, p-PXN, F-actin, and Slug proteins and increased E-cadherin. Furthermore, ova inhibited NPC tumorsphere formation, associated with decreased SOX2, OCT4 and JAK-STAT signaling pathway. Ova also attenuated NPC stem cell tumorigenicity, inhibited tumor growth, and enhanced the sensitivity of NPC cells to cisplatin treatment, in vivo.

CONCLUSIONS

Our results demonstrated the anticancer efficacy of Ova in NPC and its potential as a putative inhibitor of JAK2 and STAT3, which are essential in tumorigenesis of NPC. Further development of Ova is encouraged.

Triptolide inhibits cell growth and GRP78 protein expression but induces cell apoptosis in original and radioresistant NPC cells

The radioresistance is the key factor to hamper curative effect and survival of nasopharyngeal carcinoma (NPC) patients. Nature triptolide (TPL) has been found to circumvent drug-resistant effect of cancer, but its effect on NPC radioresistance has been rarely studied. In the present study, the 10 Gy-resistant CNE2 subclones (CNE2-SR) were used as a NPC radioresistant model. The IC₅₀ of TPL in CNE2 and CNE2-SR cells was measured by MTT assay, cell cycle was analyzed by flow cytometry, and protein expression was examined by western blot. Our data showed that TPL treatment decreased the percentage of viable cells, and IC50 value in CNE2 and CNE2-SR cells was 23.6 ± 1.41 nmol/L and 31.2 ± 1.16 nmol/L, respectively. Six Gy was a moderate dosage of X-ray for CNE2, and 25 nM TPL was close to IC50 value of CNE2 and CNE2-SR. Six Gy X-ray and/or 25 nM TPL significantly inhibited tumor growth in nude mice. Furthermore, 6 Gy X-ray and/or 25 nM TPL significantly inhibited cell growth and induced cell apoptosis and M/G2 phase arrest in CNE2 and CNE2-SR cells. Moreover, TPL treatment significantly inhibited the expression of GRP78 protein in CNE2 and CNE2-SR cells. These results suggest that TPL may serve as a potential radiosensitizer agent for NPC treatment.

Rediscovery of NF-κB signaling in nasopharyngeal carcinoma: How genetic defects of NF-κB pathway interplay with EBV in driving oncogenesis?

Nasopharyngeal carcinoma (NPC) is a unique EBV-associated subtype of head and neck cancer, which has the highest incidence in Southern China and eastern South Asia. The interaction between genetic risk factors and environmental challenge, have been considered to contribute to the development of nasopharyngeal carcinogenesis. Constitutive activation of NF-κB signaling has been seen in NPC tissues and is associated with unfavorable prognosis. Recently, several whole exome sequencing study consistently revealed that high frequency mutations of NF-κB pathway negative regulators is common in nasopharyngeal carcinoma, which reinforce the importance of NF-κB driving oncogenesis. This review focuses on the current state of research in role of NF-κB in NPC carcinogenesis. We summarized the newly identified loss of function (LOF) mutations on NF-κB negative regulators leading to it's activation bypass LMP-1 stimulation. We discussed the critical role of NF-κB activation in immortalization and transformation of nasopharygeal epithelium. We also depicted how NF-κB signaling mediated chronic inflammation contribute to persistent EBV infection, immune evasion of EBV infected cells, metabolic reprogramming, and cancer stem cells (CSCs) formation in NPC. Lastly, we discussed the clinical resonance of targeting NF-κB for NPC precise therapy.

Cancer Stem Cell Hypothesis for Therapeutic Innovation in Clinical Oncology? Taking the Root Out, Not Chopping the Leaf

Clinical oncology is in need of therapeutic innovation. New hypotheses and concepts for translation of basic research to novel diagnostics and therapeutics are called for. In this context, the cancer stem cell (CSC) hypothesis rests on the premise that tumors comprise tumor cells and a subset of tumor-initiating cells, CSCs, in a quiescent state characterized by slow cell cycling and expression of specific stem cell surface markers with the capability to maintain a tumor in vivo. The CSCs have unlimited self-renewal abilities and propagate tumors through division into asymmetric daughter cells. This differentiation is induced by both genetic and environmental factors. Another characteristic of CSCs is their therapeutic resistance, which is due to their quiescent state and slow dividing. Notably, the CSC phenotype differs greatly between patients and different cancer types. The CSCs may differ genetically and phenotypically and may include primary CSCs and metastatic stem cells circulating within the blood system. Targeting CSCs will require the knowledge of distinct stem cells within the tumor. CSCs can differentiate into nontumorigenic cells and this has been touted as the source of heterogeneity observed in many solid tumors. The latter cannot be fully explained by epigenetic regulation or by the clonal evolution theory. This heterogeneity markedly influences how tumors respond to therapy and prognosis. The present expert review offers an analysis and synthesis of the latest research and concepts on CSCs, with a view to truly disruptive innovation for future diagnostics and therapeutics in clinical oncology.

NOR1 Suppresses Cancer Stem-Like Cells Properties of Tumor Cells via the Inhibition of the AKT-GSK-3β-Wnt/β-catenin-ALDH1A1 Signal Circuit

Cancer stem cells (CSCs) play a key role in tumor radiotherapy and chemotherapy resistance, relapse, and metastasis, and are primarily maintained in a resting state in vivo. The failure of conventional therapies to target CSCs is the main cause of treatment failure. The discovery of CSCs in nasopharyngeal carcinoma (NPC) tumors is becoming more prevalent; however, the understanding of the mechanisms underlying the maintenance of tumor stemness is still limited. We previously cloned NOR1, a tumor suppressor gene downregulated in NPC cell lines and tissues. In this study, we demonstrate that Wnt/β-catenin and ALDH1A1 form a signal circuit and that NOR1 antagonizes the tumor stem cell-like phenotype in NPC cell lines: the ectopic overexpression of NOR1 reduced β-catenin and ALDH1A1 expression; β-catenin/TCF4 targeted the regulation of ALDH1A1 transcription in NPC cells; silencing ALDH1A1 reduced AKT (total and phosphorylated) and GSK-3β (phosphorylated) expression; and eventually feedback decreased β-catenin expression levels. We also found that NOR1 expression decreased cancer stem-like cell properties of NPC cells, reduced their ability to form tumor spheroids in vitro, reduced tumorigenicity in nude mice in vivo, and increased sensitivity to chemotherapy agents. Taken together, our findings illustrated a new function of NOR1 that suppresses cancer stem-like cell properties in tumor cells by inhibiting the AKT-GSK-3β-Wnt/β-catenin-ALDH1A1 signal circuit. The study suggests that NOR1 deletion expression in NPC cells may be a potential molecular target for cancer stem cell therapy. J. Cell. Physiol. 232: 2829-2840, 2017. © 2016 Wiley Periodicals, Inc.

Downregulation of mitochondrial cyclooxygenase-2 inhibits the stemness of nasopharyngeal carcinoma by decreasing the activity of dynamin-related protein 1

Cancer stem cells (CSCs) are a small subset of malignant cells, possessing stemness, with strong tumorigenic capability, conferring resistance to therapy and leading to the relapse of nasopharyngeal carcinoma (NPC). Our previous study suggested that cyclooxygenase-2 (COX-2) would be a novel target for the CSCs-like side population (SP) cells in NPC. In the present study, we further found that COX-2 maintained the stemness of NPC by enhancing the activity of mitochondrial dynamin-related protein 1 (Drp1), a mitochondrial fission mediator, by studying both sorted SP cells from NPC cell lines and gene expression analyses in NPC tissues. Using both overexpression and knockdown of COX-2, we demonstrated that the localization of COX-2 at mitochondria promotes the stemness of NPC by recruiting the mitochondrial translocation of p53, increasing the activity of Drp1 and inducing mitochondrial fisson. Inhibition of the expression or the activity of Drp1 by siRNA or Mdivi-1 downregulates the stemness of NPC. The present study also found that inhibition of mitochondrial COX-2 with resveratrol (RSV), a natural phytochemical, increased the sensitivity of NPC to 5-fluorouracil (5-FU), a classical chemotherapy drug for NPC. The underlying mechanism is that RSV suppresses mitochondrial COX-2, thereby reducing NPC stemness by inhibiting Drp1 activity as demonstrated in both the in vitro and the in vivo studies. Taken together, the results of this study suggest that mitochondrial COX-2 is a potential theranostic target for the CSCs in NPC. Inhibition of mitochondrial COX-2 could be an attractive therapeutic option for the effective clinical treatment of therapy-resistant NPC.

Longikaurin A, a natural ent-kaurane, suppresses stemness in nasopharyngeal carcinoma cells

Cancer stem cells (CSCs) are a small proportion of tumor cells that may be responsible for tumor metastasis and recurrence. Our recent research indicated that longikaurin A (LK-A) exhibited anti-tumor activity in nasopharyngeal carcinoma (NPC) both in vitro and in vivo. Here, we further investigated whether LK-A could suppress the stemness of NPC cells. Sphere formation assay was used to assess the self-renewal ability of the cells treated with LK-A. Side population (SP) was determined by flow cytometry to measure the influence of LK-A on NPC SPs. The expression of the c-myc and fibronectin was detected by western blotting. The cytotoxicity of LK-A in combination with cisplatin to NPC cells was determined by MTT assay. Colony formation assay was used to verify whether LK-A could sensitize NPC cells to radiation and reverse the radiotherapy resistance. In the present study, we found that LK-A reduced the number and size of spheroid formation and decreased the SP cell percentage of the S18 cell line at a low concentration. Furthermore, LK-A treatment downregulated the expression of c-myc and fibronectin in NPC cell lines. Moreover, LK-A could significantly enhance the chemotherapeutic and radiotherapeutic sensitivity of NPC cell lines and reverse acquired radiotherapy resistance of Sune2-IR. Our data revealed that LK-A could suppress the stemness of NPC cells and may enhance the efficacy of radiotherapy and chemotherapy.

Metronomic chemotherapy and nanocarrier platforms

The therapeutic concept of administering chemotherapeutic agents continuously at lower doses, relative to the maximum tolerated dose (MTD) without drug-free breaks over extended periods -known as "metronomic chemotherapy"- is a promising approach for anti-angiogenic cancer therapy. In comparison with MTD chemotherapy regimens, metronomic chemotherapy has demonstrated reduced toxicity. However, as a monotherapy, metronomic chemotherapy has failed to provide convincing results in clinical trials. Therapeutic approaches including combining the anti-angiogenic "metronomic" therapy with conventional radio-/chemo-therapy and/or targeted delivery of chemotherapeutic agents to tumor tissues via their encapsulation with nanocarrier-based platforms have proven to potentiate the overall therapeutic outcomes. In this review, therefore, we focused on the mutual contribution made by nanoscale drug delivery platforms to the therapeutic efficacy of metronomic-based chemotherapy. In addition, the influence that the dosing schedule has on the overall therapeutic efficacy of metronomic chemotherapy is discussed.

Salvage Intensity-Modulated Radiation Therapy (IMRT) for Locally Recurrent Nasopharyngeal Cancer after Definitive IMRT: A Novel Scenario of the Modern Era

Locally recurrent nasopharyngeal carcinoma (rNPC) after definitive IMRT occurs in 10% of all cases and represents a distinct clinical entity that has been selectively enriched by radio-resistant cancer cells. Therefore, we report of the outcomes of 77 patients who had repeat salvage-IMRT for rNPC after only a definitive course of IMRT. Various clinical outcomes were measured. Log-rank tests were used to detect differences in the survival outcomes between factor-defined subgroups. Multivariable analysis was performed using the Cox proportional hazard model. The median follow-up time was 25.7 months (range 3.0–75.7 months), measured from the time of recurrence. The median OS time and PFS time of the entire cohort was 37.0 and 20.5 months, respectively. Thirty-four patients (44.2%) died. Approximately 35% of these patients died from disease progression, but 53% were from treatment-induced severe adverse effects (SAEs) without evidence of disease progression. Higher T-classification of the recurrent tumor and the development of SAEs were found to be the only independent and significant adverse prognostic factors on multivariable analysis. These outcomes underscore the particularly virulent characteristics of rNPC after definitive IMRT. Concerning is the impact of re-irradiation toxicity on patient mortality.

Inflammatory CXCL12-CXCR4/CXCR7 axis mediates G-protein signaling pathway to influence the invasion and migration of nasopharyngeal carcinoma cells

This study explored whether the migration, invasion, and apoptosis of nasopharyngeal carcinoma (NPC) cells were affected by the CXCR4/CXCR7-CXCL12 axis and if this mechanism was related to G-protein signaling pathway. A total of 72 NPC patients admitted in our hospital between April 2013 and February 2015 were incorporated in this study. Immunohistochemistry was performed to compare the expression levels of CXCR4, CXCR7, and CXCL12 between NPC tissues and adjacent normal tissues. Then, the correlation analysis was implemented to assess the association among CXCR4, CXCR7, and CXCL12 expressions. Jellyfish glow protein experiment was carried out after the cultivation of CNE-2Z cell lines in order to observe the intracellular calcium mobilization resulted from G-protein activation contributed by CXCR4/CXCR7-CXCL12 axis. The impact of CXCR4/CXCR7-CXCL12 axis on the migration and invasion of NPC cells was explored using transwell experiments. Finally, the anti-apoptosis effects of CXCR4/CXCR7-CXCL12 axis on NPC cells were investigated by the splicing of poly ADP-ribose polymerase (PARP). Compared to NPC patients with low-grade (stage I-II) tumor node metastasis (TNM) and those without lymph node metastasis, the expression of CXCR4, CXCR7, and CXCL12 were significantly higher in NPC patients with high-grade (stage III-IV) TNM and those with lymph node metastasis (P < 0.05). Moreover, there was significant positive correlation between the expression level of CXCL12 and CXCR7 (r s = 0.484, P < 0.001) as well as the expression level of CXCL12 and CXCR4 (r s = 0.414, P < 0.001). As suggested by cellular experiments using CNE-2Z, the calcium mobilization degree induced by CXCR4-CXCL12 axis in activating G proteins seemed to be slightly more effective than that induced by CXCR4/CXCR7-CXCL12 axis, while the CXCR7-CXCL12 axis could hardly activate calcium mobilization. Furthermore, the transwell experiment showed that CXCR4/CXCR7-CXCL12 axis could exacerbate the migration and invasion of NPC cells (P < 0.05). The transwell experiment also suggested that the CXCR4/CXCR7-CXCL12 axis was associated with the expression of matrix metallo proteinase 9 (MMP9) which is a substance in the downstream of G-protein pathways (P < 0.05). Results from PARP shear zone also indicated that the CXCR4/CXCR7-CXCL12 axis could suppress NPC cell apoptosis (P < 0.05). The expressional levels of CXCR4, CXCR7, and CXCL12 significantly varied with clinical stages and status of lymph node metastasis of NPC patients. This revealed potential indicators which can be used for NPC prognosis. Additionally, the CXCR4/CXCR7-CXCL12 axis may regulate the expression of downstream proteins (e.g., MMP-9) through the activation of G-protein signaling pathways. These conclusions may provide key evidence for NPC aetiology which can be further investigated to develop novel molecular targets for NPC treatments.

Pancreatic cancer stem cells: Advances and perspectives

The evolution of certain types of malignancies including pancreatic carcinoma, as verified in mountains of literature published since the 1970s, is due in great measure to cancer stem cells located within the hierarchically organized tumor structure. However, by now, the results of numerous attempts to relate cancer stem cell theory to malignant biological behavior of cancers have appeared rather discouraging in terms of explaining and overcoming tumor heterogeneity in both in vitro and in vivo conditions. In seeking to describe the cancer stem cells in pancreatic adenocarcinoma, in the current editorial, we rely primarily on the existing evidence to gain a comprehensive perspective toward this area.

Safety and efficacy study of nasopharyngeal cancer stem cell vaccine

In this trial, nasopharyngeal cancer stem cells (CSCs) were separated and cultured to produce a vaccine; its safety and efficacy were prospectively evaluated in low-, medium-, and high-dose groups. Between April and September 2014, we enrolled 90 patients who met the enrolment criteria, and assigned them to three groups (n=30). Throughout the trial, injection site reaction was the most common reaction (81%), and fever was least common (31%); however, there was no difference among the three groups. When the immune responses pre- and post-vaccination were compared, we found that the CSC-specific and -nonspecific response in the medium- and high-dose groups were both significantly enhanced. This study is the first clinical trial of a nasopharyngeal CSC vaccine and preliminarily proves its safety and efficacy.

Molecular screening for Epstein Barr virus (EBV) among Sudanese patients with nasopharyngeal carcinoma (NPC)

Objective

The aim of this study was to screen for the presence of Epstein Barr Virus (EBV) among Sudanese patients with Nasopharyngeal Carcinoma (NPC).

Methods

In this study, 150 tissue samples that were previously diagnosed as having NPC were screened for the presence of EBV using Polymerase Chain Reaction (PCR). PCR was performed to amplify two viral genes; EBV nuclear antigen-4 (EBNA-4) and latent membrane protein-1 (LMP1).

Results

EBV genes were detected in 92/150 (61.3%) tissue samples. Of the 92 infected samples, 58/92 (63%) were found among males and 34/92 (37%) were among females.

Conclusion

EBV is prevalent in the Sudan and responsible of the vast majority of cases of NPC.

Pancreatic cancer stem cells

Studies are emerging in support of the cancer stem cells (CSCs) theory which considers that a tiny subset of cancer cells is exclusively responsible for the initiation and malignant behavior of a cancer. This cell population, also termed CSCs, possesses the capacity both to self-renew, producing progeny that have the identical tumorigenic potential, and to differentiate into the bulk of cancer cells, helping serve the formation of the tumor entities, which, altogether, build the hierarchically organized structure of a cancer. In this review, we try to articulate the complicated signaling pathways regulating the retention of the characteristics of pancreatic CSCs, and in the wake of which, we seek to offer insights into the CSCs-relevant targeted therapeutics which are, in the meantime, confronted with bigger challenges than ever.