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Radiotherapy is essential to the treatment of nasopharyngeal carcinoma (NPC) and acquired or innate resistance to this therapeutic modality is a major clinical problem. However, the underlying molecular mechanisms in the radiation resistance in NPC are not fully understood. Here, we reanalyzed the microarray data from public databases and identified the protein tyrosine phosphatase receptor type D (PTPRD) as a candidate gene. We found that PTPRD was downregulated in clinical NPC tissues and NPC cell lines with its promoter hypermethylated. Functional assays revealed that PTPRD overexpression sensitized NPC to radiation in vitro and in vivo. Importantly, miR-454-3p directly targets PTPRD to inhibit its expression and biological effect. Interestingly, mechanistic analyses indicate that PTPRD directly dephosphorylates STAT3 to enhance Autophagy-Related 5 (ATG5) transcription, resulting in triggering radiation-induced autophagy. The immunohistochemical staining of 107 NPC revealed that low PTPRD and high p-STAT3 levels predicted poor clinical outcome. Overall, we showed that PTPRD promotes radiosensitivity by triggering radiation-induced autophagy via the dephosphorylation of STAT3, thus providing a potentially useful predictive biomarker for NPC radiosensitivity and drug target for NPC radiosensitization.

Purpose Nasopharyngeal carcinoma (NPC) is among the most common malignancies derived from the epithelium of the nasopharynx. To date, the regulatory networks involved in NPC have not been fully identified. Previous studies revealed multiple loss-of-function mutations in NPC and specifically in cylindromatosis lysine 63 deubiquitinase (CYLD); however, the exact role of CYLD in NPC progression and its potential mechanism remains unclear. Methods We performed immunohistochemical (IHC) staining and real-time quantitative polymerase chain reaction (qPCR) to measure CYLD expression in NPC tissues, and Western blot was conducted to determine CYLD levels in NPC cell lines. Cell proliferation was detected by CCK8 assay and colony formation analysis, and apoptosis was determined by Annexin V/propidium iodide staining. Potential targets of CYLD were verified by co-immunoprecipitation and mass spectrometry. Xenograft assay was conducted to confirm the role of CYLD in vivo. Results We found that CYLD levels were significantly decreased in both NPC tissues and cell lines, and that CYLD overexpression inhibited NPC cell proliferation and promoted apoptosis. Additionally, we revealed that CYLD bound and upregulated N-Myc downstream regulated 1 (NDRG1), and that silencing NDRG1 abolished the tumor-suppressor effect of CYLD on NPC cells. Furthermore, CYLD suppressed tumor growth in xenograft mice models. Conclusion These results suggest CYLD as a tumor suppressor, potential biomarker for diagnosing NPC, and therapeutic target.

Aberrant cancer metabolism contributes to cell proliferation and tumor progression. However, the contribution of enhanced glycolysis, observed during cancer metabolism, to the pathogenesis and progression of nasopharyngeal carcinoma (NPC) remains unclear. CYLD, an NF-κB inhibitor, is frequently deficient in NPC. Here, we investigated the role of CYLD in the metabolic reprogramming of NPC and found that restoration of CYLD expression suppressed glycolysis in NPC cells. Mechanistic dissection showed that CYLD stabilized p53 and facilitated its nuclear translocation, thereby enhancing p53 activity by removing K63-linked and K48-linked ubiquitin chains of p53, which can bind to the PFKFB3 promoter and inhibit its transcription. Additionally, CYLD interacted with FZR1 to promote APC/C-FZR1 E3 ligase activity, which further ubiquitinated and degraded PFKFB3 via the 26S proteasomal system. Furthermore, clinical tissue array analysis indicated that low expression of CYLD was correlated with high expression of PFKFB3 and poor prognosis among patients with NPC. In conclusion, CYLD suppressed PFKFB3 expression via two factors, namely, p53 and FZR1, to inhibit glycolysis and delay tumor growth and progression in NPC. CYLD is a biomarker indicating poor prognosis of patients with NPC.

Radiotherapy plays an important role in the treatment of nasopharyngeal carcinoma (NPC), however, 20% of patients with NPC exhibit unusual radioresistance. Patients with radioresistance are at risk of recurrence, so it is imperative to explore the mechanism of resistance to radiotherapy. In the past, studies on the mechanism of radioresistance have been restricted to DNA damage and related cell cycle remodeling or apoptosis. So far, no studies have explored the relationship between radioresistance and metastasis. Through the analysis of clinical samples, we observed that the metastasis rate of recurrent NPC was much higher than that of primary patients. In vitro and in vivo experiments showed that NPC cells with acquired radioresistance exhibited a stronger ability for invasion and metastasis. Mechanistically, we found that the Epstein-Barr virus (EBV)-encoded miRNA BART8-3p was increased in patients with NPC, and its expression was positively correlated with adverse prognostic factors, such as radioresistance. Besides this, miR-BART8-3p promoted the epithelial-mesenchymal transition, invasion, and metastasis of radioresistant NPC cells by targeting and inhibiting their PAG1 host gene. These findings suggested a novel role for EBV-miR-BART8-3p in promoting NPC radioresistance-associated metastasis and highlighted its potential value as a prognostic indicator or therapeutic target.

Background: Radiotherapy plays an important role in the treatment of nasopharyngeal carcinoma (NPC), however, 20 % of patients with NPC exhibit unusual radioresistance. Patients with radioresistance are at risk of recurrence, so it is imperative to explore the mechanism of resistance to radiotherapy. In the past, studies on the mechanism of radioresistance have been restricted to DNA damage and related cell cycle remodeling or apoptosis. So far, no studies have explored the relationship between radioresistance and metastasis. Methods: We analyzed the metastasis rate of patients with recurrent NPC and that of patients with primary NPC. Constructing an acquired radioresistant NPC cell line and detect their metastatic ability in vivo and in vitro. RNA-deep sequencing was performed to predict the targeted host genes of EBV-miR-BART8-3p. Western blotting, real-time PCR and immunochemistry were conducted to investigate the relationship of clinicopathologic features and EBV-miR-BART8-3p or PAG1. Results:Through the analysis of clinical samples, we observed that the metastasis rate of recurrent NPC was much higher than that of primary patients. In vitro and in vivo experiments showed that NPC cells with acquired radioresistance exhibited a stronger ability for invasion and metastasis. Mechanistically, we found that the Epstein–Barr virus (EBV)-encoded miRNA BART8-3p was increased in patients with NPC and its expression was positively correlated with adverse prognostic factors, such as radioresistance. Besides, miR-BART8-3p promoted the epithelial-mesenchymal transition (EMT), invasion, and metastasis of radioresistant NPC cells by targeting and inhibiting their PAG1 host gene. Conclusion: These results demonstrated a correlation between radioresistance and metastasis in NPC, which depended on the elevated levels of the EBV-encoded miRNA BART8-3p and the inhibition of the PAG1 host gene. These findings suggested a novel role for EBV-miR-BART8-3p and PAG1 in recurrence NPC and highlighted their potential value as prognostic indicators or therapeutic targets.

Purpose Nasopharyngeal carcinoma (NPC) is among the most common malignancies derived from the epithelium of the nasopharynx. To date, the regulatory networks involved in NPC have not been fully identified. Previous studies revealed multiple loss-of-function mutations in NPC and specifically in cylindromatosis lysine 63 deubiquitinase (CYLD); however, the exact role of CYLD in NPC progression and its potential mechanism remains unclear. Methods We performed immunohistochemical (IHC) staining and real-time quantitative polymerase chain reaction (qPCR) to measure CYLD expression in NPC tissues, and Western blot was conducted to determine CYLD levels in NPC cell lines. Cell proliferation was detected by CCK8 assay and colony formation analysis, and apoptosis was determined by Annexin V/propidium iodide staining. Potential targets of CYLD were verified by co-immunoprecipitation and mass spectrometry. Xenograft assay was conducted to confirm the role of CYLD in vivo. Results We found that CYLD levels were significantly decreased in both NPC tissues and cell lines, and that CYLD overexpression inhibited NPC cell proliferation and promoted apoptosis. Additionally, we revealed that CYLD bound and upregulated N-Myc downstream regulated 1 (NDRG1), and that silencing NDRG1 abolished the tumor-suppressor effect of CYLD on NPC cells. Furthermore, CYLD suppressed tumor growth in xenograft mice models. Conclusion These results suggest CYLD as a tumor suppressor, potential biomarker for diagnosing NPC, and therapeutic target.

The epithelial-mesenchymal transition (EMT) is crucial to cancer progression and metastasis. Although multiple cellular miRNAs have been identified to regulate the EMT and metastasis in cancers, the role of viral miRNAs in cancer progression remains largely unknown. Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated malignancy typically characterized by its early metastasis. In the present study, we have discovered the involvement of a viral miRNA, EBV-miR-BART7-3p, in the EMT and metastasis of NPC cells. Initially, we observed that EBV-miR-BART7-3p was highly expressed in NPC and positively correlated with lymph node metastasis and clinical stage of NPC. Subsequently, we demonstrated that EBV-miR-BART7-3p enhanced cell migration/invasion in vitro, cancer metastasis in vivo, and particularly the EMT characterized by loss of epithelial markers and gain of mesenchymal features in NPC cells. Furthermore, mechanistic studies disclosed that EBV-miR-BART7-3p targeted a major human tumor suppressor PTEN, modulating PI3K/Akt/GSK-3β signaling and eventually leading to the high expression and nuclear accumulation of Snail and β-catenin, which favor EMT. Knockdown of PTEN could phenocopy the effect of EBV-miR-BART7-3p, whereas re-expression of PTEN resulted in a phenotypic reversion. Moreover, these findings were supported by an observation of an EBV-positive cell model in which silencing of endogenous EBV-miR-BART7-3p partially attenuated cell migration/invasion and altered EMT protein expression pattern via reverting PI3K/Akt, Snail and β-catenin expression. Thus, this study suggests a novel mechanism by which EBV-miR-BART7-3p modulates the EMT and metastasis of NPC cells, and a clinical implication of EBV-miR-BART7-3p as a potential biomarker or therapeutic target.