Shigeyuki Murono

Epstein-Barr Virus Latent Membrane Protein 1 Induces Synthesis of Hypoxia-Inducible Factor 1α

ABSTRACT Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic helix-loop-helix transcription factor composed of HIF-1α and HIF-1β that is the central regulator of responses to hypoxia. The specific binding of HIF-1 to the hypoxia-responsive element (HRE) induces the transcription of genes that respond to hypoxic conditions, including vascular endothelial growth factor (VEGF). Here we report that expression of HIF-1α is increased in diverse Epstein-Barr virus (EBV)-infected type II and III cell lines, which express EBV latent membrane protein 1 (LMP1), the principal EBV oncoprotein, as well as other latency proteins, but not in the parental EBV-negative cell lines. We show first that transfection of an LMP1 expression plasmid into Ad-AH cells, an EBV-negative nasopharyngeal epithelial cell line, induces synthesis of HIF-1α protein without increasing its stability or mRNA level. The mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059 markedly reduces induction of HIF-1α by LMP1. Catalase, an H2O2 scavenger, strongly suppresses LMP1-induced production of H2O2, which results in a decrease in the expression of HIF-1α induced by LMP1. Inhibition of the NF-κB, c-jun N-terminal kinase, p38 MAPK, and phosphatidylinositol 3-kinase pathways did not affect HIF-1α expression. Moreover, LMP1 induces HIF-1 DNA binding activity and upregulates HRE and VEGF promoter transcriptional activity. Finally, LMP1 increases the appearance of VEGF protein in extracellular fluids; induction of VEGF is suppressed by PD98059 or catalase. These results suggest that LMP1 increases HIF-1 activity through induction of HIF-1α protein expression, which is controlled by p42/p44 MAPK activity and H2O2. The ability of EBV, and specifically its major oncoprotein, LMP1, to induce HIF-1α along with other invasiveness and angiogenic factors reported previously discloses additional oncogenic properties of this tumor virus.

Epstein-Barr Virus Latent Membrane Protein 1 Induces Cancer Stem/Progenitor-Like Cells in Nasopharyngeal Epithelial Cell Lines

ABSTRACT Recent studies suggest the existence of cancer stem cells (CSC) and cancer progenitor cells (CPC), although strict definitions of neither CSC nor CPC have been developed. We have produced evidence that the principal oncoprotein of Epstein-Barr virus (EBV), latent membrane protein 1 (LMP1), which is associated with human malignancies, especially nasopharyngeal carcinoma (NPC), promotes tumor cell invasion and metastasis, as well as the epithelial-mesenchymal transition (EMT). However, whether LMP1 is involved in the development of CSC/CPC is still unclear. This study investigates whether the expression of EBV-LMP1 is related to the development of CSC/CPC. Analysis of cancer stem cell markers reveals that LMP1 induces the CD44high CD24low CSC/CPC-like phenotype as well as self-renewal abilities in LMP1-expressing epithelial cell lines. In addition, we show here that LMP1 induction in epithelial cells causes high tumorigenicity and rapid cellular proliferation. Furthermore, we found that LMP1 expression increased the expression of several CPC markers as well as producing increased levels of EMT markers. Our findings indicate that LMP1 can induce a CPC-like rather than a CSC-like phenotype in epithelial cells and suggest that LMP1-induced phenotypic changes contribute to the development of NPC.

Pathogenic role of Epstein–Barr virus latent membrane protein-1 in the development of nasopharyngeal carcinoma

Undifferentiated nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus-associated malignant tumor. A consistent elevation in EBV antibody titers is a well-established risk factor for the development of NPC. The pathophysiological relationship and molecular mechanisms of EBV-mediated carcinogenesis have not been fully elucidated. While NPC tumors are known to express three EBV-encoded proteins, EBNA1, LMP1, and LMP2, they also express a large number of virus-encoded small RNAs (EBERs) and microRNAs (miRNAs). Among them, LMP1 may be a central player in the development of NPC. LMP1, an EBV-encoded primary oncogene, functions as a viral mimic of the TNFR family member, CD40, and engages in a number of signaling pathways that induce morphological and phenotypic alterations in epithelial cells. LMP1 upregulates EMT, and contributes to the highly metastatic features of NPC. Moreover, LMP1-associated EMT is accompanied by the expression of cancer stem cell (CSC)/cancer progenitor cell (CPC) markers (CD44high/CD24low) and the acquisition of stem cell/progenitor cell-like properties. BART miRNAs, encoded from the BamHI-A region of the viral genome, are the most abundant transcripts. They modulate apoptosis and host innate immune defense mechanisms. Some BART1 miRNAs are considered to negatively regulate LMP1 protein expression. LMP1 is secreted via exosomes, is incorporated into EBV-uninfected cells by endocytosis, and affects the environment surrounding the tumor. Here we reviewed the contribution of EBV gene products to NPC pathogenesis in relation with LMP1.

Endoscopic nasopharyngectomy for patients with recurrent nasopharyngeal carcinoma at the primary site.

INTRODUCTION Primary nasopharyngeal carcinoma (NPC) is commonly treated by chemoradiotherapy. However, treatment for recurrent or residual tumor in the nasopharynx is still controversial. There are two main modalities for secondor third-line treatments. One is re-irradiation, mainly with an external beam, and, occasionally, brachytherapy with an applicator. Re-irradiation is an established form of salvage treatment. However, high-dose irradiation sometimes causes severe morbidity such as skull-base and brain necrosis, and occasionally results in death. The other modality is surgery. In the view of the drawbacks of high-dose irradiation, various surgical treatments against recurrent and residual NPC have been developed. Most surgeons report better local control and survival data than the reports of re-irradiation studies. Thus, treating recurrent NPC with surgery has become accepted as the standard treatment. Four surgical approaches, the transpalatal, the transmaxillary, the maxillary swing, and the transmandibular, are used, depending on the recurrent T (rT) stage and tumor location. Although these methods are reportedly less invasive than high-dose re-irradiation techniques, there are some side effects, such as oronasal fistula and palatal incompetence. Less invasiveness and a clear view of the operation field enabled endoscopic surgery to become the standard surgical procedure for sinusitis. Moreover, the endoscope is sometimes applied to pituitary surgery. However, because of the complicated structure of the nasal cavity and the narrow space in the nasal cavity, both the endoscope and the instruments reach only a limited area. In this paper, we describe a modification of the endoscopic surgical procedure that remarkably improves these problems.

Tumor‐targeted chemotherapy with the nanopolymer‐based drug NC‐6004 for oral squamous cell carcinoma

Cisplatin (CDDP) has been a key drug for chemotherapy in patients with head and neck squamous cell carcinoma. Nephrotoxicity is one of its adverse reactions that are dose limiting. To increase its antitumor effects and reduce such toxicity problems, polymeric micelles carrying CDDP (NC‐6004) have been developed. The present study was designed to evaluate the efficacy and safety of NC‐6004 for oral squamous cell carcinoma. In vitro antitumor activity was assayed in four oral squamous cell carcinoma cell lines. To investigate the antitumor and nephrotoxic effects of NC‐6004, nude mice bearing OSC‐19 were administered NC‐6004 or CDDP. The in vitro growth‐inhibitory effect of NC‐6004 was significantly less than that of CDDP. However, both NC‐6004 and CDDP showed equivalent antitumor effects in vivo. Mice with CDDP developed renal cell apoptosis; however, those injected with NC‐6004 were almost free of renal cell injury. Moreover, in an orthotopic tongue cancer model using OSC‐19, NC‐6004 reduced the rate of sentinel lymph node metastasis to lower than that with CDDP. In conclusion, considering the potential advantages in terms of noticeable antitumor activity, lymphatic drug delivery and reduced nephrotoxicity, NC‐6004 represents a significant structural improvement in the development of a platinum complex.

MUC1 Induced by Epstein-Barr Virus Latent Membrane Protein 1 Causes Dissociation of the Cell-Matrix Interaction and Cellular Invasiveness via STAT Signaling

ABSTRACT Disruption of cellular adhesion is an essential pathobiologic step leading to tumor dissemination. Mucin 1 (MUC1) is a mucinous glycoprotein expressed at the surfaces of epithelial cells in many tissues and their carcinomas. MUC1 plays crucial roles in tumor invasion and metastasis, especially in opposing cell adhesion. We have shown that virus infection, specifically by the human tumor virus Epstein-Barr virus (EBV) induces a spectrum of cellular invasiveness and metastasis factors. Here we show that expression of MUC1 is increased in diverse latently EBV-infected cell lines that express latent membrane protein 1 (LMP1), the main viral oncoprotein, and that the level of MUC1 was suppressed by expression of a dominant-negative mutant of LMP1. Expression of LMP1 in EBV-negative nasopharyngeal cell lines induces expression of MUC1 through activation of the MUC1 promoter via binding of STAT1 and STAT3. Finally, LMP1 reduces cell adhesion ability, which is restored by inhibition of MUC1 expression with MUC1 small interfering RNA (siRNA). In addition, LMP1 increases cell invasiveness, which is suppressed by MUC1 siRNA. Thus, LMP1 induces MUC1, a factor important in an early step of detachment and release of tumor cells, which along with induction of other invasiveness and angiogenic factors may combine to act in a complex sequential process that culminates in metastasis of EBV-infected tumor cells.

Epstein‐Barr Virus (EBV) Latent Membrane Protein 1 Induces Interleukin‐8 through the Nuclear Factor‐κB Signaling Pathway in EBV‐Infected Nasopharyngeal Carcinoma Cell Line

Background/Objectives: Nasopharyngeal carcinoma (NPC) is a highly invasive and metastatic malignant tumor and is associated with Epstein‐Barr virus (EBV) infection that exhibits type II latency. Angiogenesis is essential for tumor growth, invasion, and metastasis. Our previous studies have indicated that interleukin (IL)‐8 was over‐expressed in many NPC tissues and was found to be significantly correlated with angiogenesis by immunohistochemistry.

Induction of Receptor for Advanced Glycation End Products by EBV Latent Membrane Protein 1 and Its Correlation with Angiogenesis and Cervical Lymph Node Metastasis in Nasopharyngeal Carcinoma

Purpose: The EBV oncoprotein, latent membrane protein 1 (LMP1), contributes to the metastasis of nasopharyngeal carcinoma (NPC) by inducing factors to promote tumor invasion and angiogenesis. The receptor for advanced glycation end products (RAGE) is associated with abnormal angiogenesis in diabetic microangiopathies. Moreover, some papers have suggested the association of RAGE overexpression with tumor metastasis; thus, the associations of RAGE with LMP1 and angiogenesis in NPC were examined. Experimental Design: Forty-two patients with NPC were evaluated for expressions of LMP1, RAGE, and S100 proteins and for microvessel counts by immunohistochemistry. Then, the RAGE induction by LMP1 was examined with Western blotting and luciferase reporter assay. Results: The microvessel counts were significantly higher in patients with high LMP1 expression or high RAGE expression compared with cases with low expressions (P = 0.0049 and P < 0.0001), respectively. Patients with advanced N classification were also significantly increased in these groups (P = 0.0484 and P = 0.0005). The expressions of LMP1 and RAGE proteins were clearly correlated in NPC tissues (P = 0.0093). Transient transfection with LMP1 expression plasmid induced RAGE protein in Ad-AH cells. The expression of LMP1 transactivated the RAGE promoter as shown by luciferase reporter assay. Mutation of the reporter at nuclear factor-κB binding site (−671 to −663) abolished transactivation of the RAGE promoter by LMP1. Conclusion: These results suggest that LMP1-induced RAGE enhances lymph node metastasis through the induction of angiogenesis in NPC. Nuclear factor-κB binding site (−671 to −663) is essential for transactivation of the RAGE promoter by LMP1.

Assessment of antitumor activity and acute peripheral neuropathy of 1,2-diaminocyclohexane platinum (II)-incorporating micelles (NC-4016).

Oxaliplatin, a third-generation platinum compound incorporating oxalate and 1,2-diaminocyclohexane platinum, has been widely used in chemotherapy regimens for the treatment of metastatic colorectal cancer. Because of its wide spectrum of antitumor activity, oxaliplatin has been applied for the treatment of other carcinomas. However, the antitumor activity of single-agent oxaliplatin is insufficient. To increase its antitumor effects, polymeric micellar nanoparticles incorporating 1,2-diaminocyclohexane platinum (NC-4016) have been developed. The present study was designed to evaluate the efficacy of NC-4016 and its association with peripheral neuropathy, which is a primary dose-limiting factor in oxaliplatin therapy. The in vitro antitumor activity of NC-4016 was investigated using human carcinoma cell lines. To investigate the antitumor effects of NC-4016 in vivo, nude mice bearing the human carcinoma cell line KB were administered NC-4016 or oxaliplatin. The in vitro growth-inhibiting effect of NC-4016 was significantly weaker than that of oxaliplatin. However, the antitumor efficacy of NC-4016 was superior to that of oxaliplatin in vivo. Moreover, we compared the severity of peripheral neuropathy induced by oxaliplatin and NC-4016 in a rat model. Oxaliplatin, NC-4016, or 5% glucose (control) were administered by a single tail vein injection. In the oxaliplatin-treated rats, neither mechanical nor heat allodynia was observed during the experimental period, whereas cold hyperalgesia/allodynia was observed from day 1 to 7. Conversely, cold hyperalgesia/allodynia was not observed in the NC-4016-treated rats. The present study demonstrated that the antitumor efficacy of NC-4016 was superior to that of oxaliplatin in a mouse model of human carcinoma cell line KB. In addition, NC-4016-treated rats did not develop acute cold hypersensitivity, which is frequently experienced by patients after oxaliplatin administration.

Expression of seven-in-absentia homologue 1 and hypoxia-inducible factor 1 alpha: Novel prognostic factors of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an EBV-associated cancer. We analysed Siah1 expression as well as LMP1 and HIF1α expression by immuno-histochemical staining in 74 NPC biopsy specimens and found that the expression of Siah1 was significantly correlated with advanced tumour status and stage. Moreover, Siah1-positive and HIF1α-positive cases had significantly worse prognoses. The expression score for LMP1 was remarkably correlated with that of Siah1, whereas there was little correlation between LMP1 expression and the other markers evaluated. This is the first study to evaluate the pattern and clinical significance of Siah1 and HIF1α expression in NPC, and such an evaluation is valuable for identifying those patients at a high risk for a poor prognosis.