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Bone and soft-tissue sarcomas are rare malignancies with histological diversity and tumor heterogeneity, leading to the lack of a common molecular target. Telomerase is a key enzyme for keeping the telomere length and human telomerase reverse transcriptase (hTERT) expression is often activated in most human cancers, including bone and soft-tissue sarcomas. For targeting of telomerase-positive tumor cells, we developed OBP-301, a telomerase-specific replication-competent oncolytic adenovirus, in which the hTERT promoter regulates adenoviral E1 gene for tumor-specific viral replication. In this study, we present the diagnostic potential of green fluorescent protein (GFP)-expressing oncolytic adenovirus OBP-401 for assessing virotherapy sensitivity using bone and soft-tissue sarcomas. OBP-401-mediated GFP expression was significantly associated with the therapeutic efficacy of OBP-401 in human bone and soft-tissue sarcomas. In the tumor specimens from 68 patients, malignant and intermediate tumors demonstrated significantly higher expression levels of coxsackie and adenovirus receptor (CAR) and hTERT than benign tumors. OBP-401-mediated GFP expression was significantly increased in malignant and intermediate tumors with high expression levels of CAR and hTERT between 24 and 48 h after infection. Our results suggest that the OBP-401-based GFP expression system is a useful tool for predicting the therapeutic efficacy of oncolytic virotherapy on bone and soft-tissue sarcomas. [ABSTRACT FROM AUTHOR]

Stomach cancer carcinomatosis peritonitis (SCCP) is a recalcitrant disease. The goal of the present study was to establish an in vitro-in vivo-like imageable model of SCCP to develop cell-cycle-based therapeutics of SCCP. We established 3-D Gelfoam® histoculture and tumor-sphere models of SCCP. FUCCI-expressing MKN-45 stomach cancer cells were transferred to express the fluorescence ubiquinized cell-cycle indicator (FUCCI). FUCCI-expressing MKN-45 cells formed spheres on agarose or on Gelfoam® grew into tumor-like structures with G0/G1 cancer cells in the center and S/G2 cancer cells located in the surface as indicated by FUCCI imaging when the cells fluoresced red or green, respectively. We treated FUCCI-expressing cancer cells forming SCCP tumors in Gelfoam® histoculture with OBP-301, cisplatinum (CDDP), or paclitaxel. CDDP or paclitaxel killed only cycling cancer cells and were ineffective against G1/G2 MKN-45 cells in tumors growing on Gelfoam®. In contrast, the telomerase-dependent adenovirus OBP-301 decoyed the MKN-45 cells in tumors on Gelfoam® to cycle from G0/G1 phase to S/G2 phase and reduced their viability. CDDP- or paclitaxel-treated MKN-45 tumors remained quiescent and did not change in size. In contrast, OB-301 reduced the size of the MKN-45 tumors on Gelfoam®. We examined the cell cycle-related proteins using Western blotting. CDDP increased the expression of p53 and p21 indicating cell cycle arrest. In contrast, OBP-301 decreased the expression of p53 and p21 Furthermore, OBP-301 increased the expression of E2F and pAkt as further indication of cell cycle decoy. This 3-D Gelfoam® histoculture and FUCCI imaging are powerful tools to discover effective therapy of SCCP such as OBP-301. [ABSTRACT FROM AUTHOR]

ABSTRACT In a previous study, we developed fluorescence-guided surgery (FGS) for osteosarcoma using an orthotopic model with 143B human osteosarcoma cells expressing red fluorescent protein (RFP) implanted into the intramedullary cavity of the tibia in nude mice. The FGS-treated mice had a significantly higher disease-free survival (DFS) rate than the bright-light surgery (BLS). However, although FGS significantly reduced the recurrence of the primary tumor, it did not reduce lung metastasis. In the present study, we utilized the OBP-401 telomerase-dependent killer-reporter adenovirus, carrying green fluorescent protein (GFP), to label human osteosarcoma in situ in orthotopic mouse models. OBP-401-illuminated human osteosarcoma cell lines, 143B and MNNG/HOS cells in vitro and in vivo. OBP-401 tumor illumination enabled effective FGS of the 143B-derived orthotopic mouse model of human osteosarcoma model as well as FGS eradication of residual cancer cells after BLS. OBP-401-assisted FGS significantly inhibited local recurrence and lung metastasis after surgery, thereby prolonging DFS and overall survival (OS), achieving a very important improvement of therapeutic outcomes over our previously reported FGS study. These therapeutic benefits of FGS were demonstrated using a clinically-viable methodology of direct labeling of human osteosarcoma in situ with the OBP-401 killer-reporter adenovirus in contrast with previous reports, which used genetically engineered labeled cells or antibody-based fluorescent labels for FGS. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:836-844, 2016. [ABSTRACT FROM AUTHOR]

Fluorescence-guided surgery (FGS) of cancer is an area of intense development. In the present report, we demonstrate that the telomerase-dependent green fluorescent protein (GFP)-containing adenovirus OBP-401 could label colon-cancer liver metastasis in situ in an orthotopic mouse model enabling successful FGS. OBP-401-GFP-labeled liver metastasis resulted in complete resection with FGS, in contrast, conventional bright-light surgery (BLS) did not result in complete resection of the metastasis. OBP-401-FGS reduced the recurrence rate and prolonged over-all survival compared with BLS. In conclusion, adenovirus OBP-401 is a powerful tool to label liver metastasis in situ with GFP which enables its complete resection, not possible with conventional BLS. [ABSTRACT FROM AUTHOR]

Trastuzumab, a humanized antibody targeting HER2, exhibits remarkable therapeutic efficacy against HER2-positive breast and gastric cancers; however, acquired resistance presents a formidable obstacle to long-term tumor responses in the majority of patients. Here, we show the mechanism of resistance to trastuzumab in HER2-positive human cancer cells and explore the molecular sensitization by exogenous expression of HER2-extracellular domain (ECD) in HER2-negative or trastuzumab-resistant human cancer cells. We found that long-term exposure to trastuzumab induced resistance in HER2-positive cancer cells; HER2 expression was downregulated, and antibody-dependent cellular cytotoxicity (ADCC) activity was impaired. We next examined the hypothesis that trastuzumab-resistant cells could be re-sensitized by the transfer of non-functional HER2-ECD. Exogenous HER2-ECD expression induced by the stable transfection of a plasmid vector or infection with a replication-deficient adenovirus vector had no apparent effect on the signaling pathway, but strongly enhanced ADCC activity in low HER2-expressing or trastuzumab-resistant human cancer cells. Our data indicate that restoration of HER2-ECD expression sensitizes HER2-negative or HER2-downregulated human cancer cells to trastuzumab-mediated ADCC, an outcome that has important implications for the treatment of human cancers. [ABSTRACT FROM AUTHOR]

Hypoxia is a microenvironmental factor that contributes to the invasion, progression and metastasis of tumor cells. Hypoxic tumor cells often show more resistance to conventional chemoradiotherapy than normoxic tumor cells, suggesting the requirement of novel antitumor therapies to efficiently eliminate the hypoxic tumor cells. We previously generated a tumorspecific replication-competent oncolytic adenovirus (OBP-301: Telomelysin), in which the human telomerase reverse transcriptase (hTERT) promoter drives viral E1 expression. Since the promoter activity of the hTERT gene has been shown to be upregulated by hypoxia, we hypothesized that, under hypoxic conditions, the antitumor effect of OBP-301 with the hTERT promoter would be more efficient than that of the wild-type adenovirus 5 (Ad5). In this study, we investigated the antitumor effects of OBP-301 and Ad5 against human cancer cells under a normoxic (20% oxygen) or a hypoxic (1% oxygen) condition. Hypoxic condition induced nuclear accumulation of the hypoxia-inducible factor-1a and upregulation of hTERT promoter activity in human cancer cells. The cytopathic activity of OBP-301 was significantly higher than that of Ad5 under hypoxic condition. Consistent with their cytopathic activity, the replication of OBP-301 was significantly higher than that of Ad5 under the hypoxic condition. OBP-301-mediated E1A was expressed within hypoxic areas of human xenograft tumors in mice. These results suggest that the cytopathic activity of OBP-301 against hypoxic tumor cells is mediated through hypoxia-mediated activation of the hTERT promoter. Regulation of oncolytic adenoviruses by the hTERT promoter is a promising antitumor strategy, not only for induction of tumor-specific oncolysis, but also for efficient elimination of hypoxic tumor cells. [ABSTRACT FROM AUTHOR]

Purpose: A telomerase-specific oncolytic adenovirus, Telomelysin, can selectively kill cancer cells, and be attenuated in normal cells. We herein describe the oncolytic effect of Telomelysin on human osteosarcoma both in vitro and in vivo. Methods: The anti-tumor effects of Telomelysin were evaluated on human osteosarcoma cell lines in vitro and in a mouse xenograft model of human osteosarcoma in vivo. The replication efficiencies of Telomelysin in human osteosarcoma cell lines and normal cell lines and in osteosarcoma xenografts were determined by the expression levels of E1 mRNA and E1A protein using real-time quantitative PCR, Western blot analysis and immunohistochemistry. The in vitro telomerase-specific replication and the viral infection rate were also confirmed by TelomeScan (Telomelysin-GFP), using fluorescent microscopy and flow cytometry, respectively. The cell viabilities were examined by XTT assay, and the tumor volumes were measured every 2 days. The induction of apoptosis was assessed by Western blot analysis, as well as by TUNEL assay. Results: TelomeScan and Telomelysin were efficiently replicated in human osteosarcoma cell lines and led to a dose- and time-dependent expression of GFP, E1 mRNA and E1A protein. Telomelysin infection induced marked cytolysis and apoptosis in osteosarcoma cell lines in vitro. Neither cytotoxicity nor apoptosis were induced in normal human cell lines. In the human osteosarcoma cell xenograft model, intratumoral injection of Telomelysin resulted in increased viral replication, significant tumor growth suppression and distinct apoptotic cell death. Conclusions: This study indicated that virotherapy with Telomelysin may provide a promising strategy for the treatment of human osteosarcoma. [ABSTRACT FROM AUTHOR]

Cancer surgery requires the complete and precise identification of malignant tissue margins including the smallest disseminated lesions. Internal green fluorescent protein (GFP) fluorescence can intensely illuminate even single cells but requires GFP sequence transcription within the cell. Introducing and selectively activating the GFP gene in malignant tissue in vivo is made possible by the development of OBP-401, a telomerase-dependent, replication-competent adenovirus expressing GFP. This potentially powerful adjunct to surgical navigation was demonstrated in 2 nude mouse models that represent difficult surgical challenges—the resection of widely disseminated cancer. HCT-116, a model of intraperitoneal disseminated human colon cancer, was labeled by virus injection into the peritoneal cavity. A549, a model of pleural dissemination of human lung cancer, was labeled by virus administered into the pleural cavity. Only the malignant tissue fluoresced brightly in both models. In the intraperitoneal model of disseminated cancer, fluorescence-guided surgery enabled resection of all tumor nodules labeled with GFP by OBP-401. The data in this report suggest that adenoviral-GFP labeling tumors in patients can enable fluorescence-guided surgical navigation. [ABSTRACT FROM AUTHOR]

Currently available methods for detection of tumors in vivo such as computed tomography and magnetic resonance imaging are not specific for tumors. Here we describe a new approach for visualizing tumors whose fluorescence can be detected using telomerase-specific replication-competent adenovirus expressing green fluorescent protein (GFP) (OBP-401). OBP-401 contains the replication cassette, in which the human telomerase reverse transcriptase (hTERT) promoter drives expression of E1 genes, and the GFP gene for monitoring viral replication. When OBP-401 was intratumorally injected into HT29 tumors orthotopically implanted into the rectum in BALB/c nu/nu mice, para-aortic lymph node metastasis could be visualized at laparotomy under a three-chip color cooled charged-coupled device camera. Our results indicate that OBP-401 causes viral spread into the regional lymphatic area and selectively replicates in neoplastic lesions, resulting in GFP expression in metastatic lymph nodes. This technology is adaptable to detect lymph node metastasis in vivo as a preclinical model of surgical navigation. [ABSTRACT FROM AUTHOR]

Presents a study that examined the potential mechanism of apoptosis induced by Adenovirus vector/p16 expression (Adv/p16) infection. Functions of p16 expression; Effects of Adv/p16 on retinoblastoma (Rb); Impact of Rb on apoptosis; Role of caspase-3 in apoptosis.

The tumor suppressor gene p53 is a potent transcriptional regulator of genes which are involved in many cellular activities including cell cycle arrest, apoptosis, and angiogenesis. Recent studies have demonstrated that the activation of the transcriptional factor nuclear factor κB (NF-κB) plays an essential role in preventing apoptotic cell death. In this study, to better understand the mechanism reponsible for the p53-mediated apoptosis, the effect of wild-type p53 (wt-p53) gene transfer on nuclear expression of NF-κB was determined in human colon cancer cell lines. A Western blot analysis of nuclear extracts demonstrated that NF-κB protein levels in the nuclei were suppressed by the transient expression of the wt-p53 in a dose-dependent manner. Transduced wt-p53 expression increased the cytoplasmic expression of IκBα as well as its binding ability to NF-κB, thus markedly reducing the amount of NF-κB that translocated to the nucleus. The decrease in nuclear NF-κB protein correlated with the decreased NF-κB constitutive activity measured by electrophoretic mobility shift assay. Furthermore, parental cells transfected with NF-κB were better protected from cell death induced by the wt-p53 gene transfer. We also found that the wt-p53 gene transfer was synergistic with aspirin (acetylsalicylic acid) in inhibiting NF-κB constitutive activity, resulting in enhanced apoptotic cell death. These results suggest that the inhibition of NF-κB activity is a plausible mechanism for apoptosis induced by the wt-p53 gene transfer in human colon cancer cells and that anti-NF-κB reagent aspirin could make these cells more susceptible to apoptosis. Oncogene (2000) 19, 726–736. [ABSTRACT FROM AUTHOR]

Adenovirus serotype 5 (Ad5) is widely and frequently used as a virus vector in cancer gene therapy and oncolytic virotherapy. Oncolytic virotherapy is a novel antitumor treatment for inducing lytic cell death in tumor cells without affecting normal cells. Based on the Ad5 genome, we have generated three types of telomerase-specific replication-competent oncolytic adenoviruses: OBP-301 (Telomelysin), green fluorescent protein (GFP)-expressing OBP-401 (TelomeScan), and tumor suppressor p53-armed OBP-702. These viruses drive the expression of the adenoviral E1A and E1B genes under the control of the hTERT (human telomerase reverse transcriptase-encoding gene) promoter, providing tumor-specific virus replication. This review focuses on the therapeutic potential of three hTERT promoter-driven oncolytic adenoviruses against bone and soft-tissue sarcoma cells with telomerase activity. OBP-301 induces the antitumor effect in monotherapy or combination therapy with chemotherapeutic drugs via induction of autophagy and apoptosis. OBP-401 enables visualization of sarcoma cells within normal tissues by serving as a tumor-specific labeling reagent for fluorescence-guided surgery via induction of GFP expression. OBP-702 exhibits a profound antitumor effect in OBP-301-resistant sarcoma cells via activation of the p53 signaling pathway. Taken together, telomerase-specific oncolytic adenoviruses are promising antitumor reagents that are expected to provide novel therapeutic options for the treatment of bone and soft-tissue sarcomas. [ABSTRACT FROM AUTHOR]

A phase I clinical trial was conducted to determine the clinical safety of Telomelysin, a human telomerase reverse transcriptase (hTERT) promoter driven modified oncolytic adenovirus, in patients with advanced solid tumors. A single intratumoral injection (IT) of Telomelysin was administered to three cohorts of patients (1 × 1010, 1 × 1011, 1 × 1012 viral particles). Safety, response and pharmacodynamics were evaluated. Sixteen patients with a variety of solid tumors were enrolled. IT of Telomelysin was well tolerated at all dose levels. Common grade 1 and 2 toxicities included injection site reactions (pain, induration) and systemic reactions (fever, chills). hTERT expression was demonstrated at biopsy in 9 of 12 patients. Viral DNA was transiently detected in plasma in 13 of 16 patients. Viral DNA was detectable in four patients in plasma or sputum at day 7 and 14 post-treatment despite below detectable levels at 24 h, suggesting viral replication. One patient had a partial response of the injected malignant lesion. Seven patients fulfilled Response Evaluation Criteria in Solid Tumors (RECIST) definition for stable disease at day 56 after treatment. Telomelysin was well tolerated. Evidence of antitumor activity was suggested. [ABSTRACT FROM AUTHOR]

Background: We previously reported that an attenuated adenovirus (OBP-301, 'Telomelysin'), in which the hTERT promoter element drives expression of E1A and E1B genes linked with an IRES, could replicate in cancer cells, and causes selective lysis of cancer cells. In this study, we further investigated the virus replication and antitumor activity of Telomelysin in various human cancer cell lines, and also established the assay to determine the concentration of Telomelysin in circulating blood. Methods: We designed the specific primer targeted for E1 gene or IRES sequence for real-time quantitative PCR (Q-PCR), and then analyzed its potent of quantity and sensitivity. We also analyzed the correlation between hTERT mRNA expression and viral replication of Telomelysin in human cancer cells. CAR expression was determined by flow cytometry, and cell killing effect of Telomelysin in 13 human cancer cell lines and normal human fibroblasts was examined by XTT assay. Results: By Q-PCR, the minimum detection limit was 100 plaque-forming units (PFU)/ml of Telomelysin in the plasma, using the primer for IRES. A positive correlation tendency was observed between hTERT mRNA expression and viral replication of Telomelysin in human cancer cells. Telomelysin killed all human cancer cell lines dose-dependently, but not normal human fibroblasts. Average of ID50 after three days of infection was 12.1 multiplicity of infection (MOI). Conclusion: Our data suggested that Telomelysin may be useful for treatment of various human cancer cells, and telomerase activity is a marker for Telomelysin replication in cancer cells.Molecular Therapy (2006) 13, S56–S56; doi: 10.1016/j.ymthe.2006.08.164 [ABSTRACT FROM AUTHOR]

Gene therapy was investigated as a promising treatment for cancer. However, low transduction efficiency limits the efficacy of gene therapy in clinics. We previously demonstrated that telomerase- specific replication-competent adenovirus (Telomelysin, OBP-301), in which the human telomerase reverse transcriptase (hTERT) promotor element drives expression of E1A and E1B genes linked with an IRES, induced selective E1 expression and efficient antitumor effect in human cancer cells, but not normal human fibroblasts. In this study, we evaluated the anticancer effect of the combination therapy of E1-deleted replication-deficient adenovirus expressing the wild-type p53 tumor suppressor gene (ADVEXIN, Ad-p53) and OBP-301 in human H1299 non-small cell lung cancer cells and SW620 colon cancer cells by using cell proliferation assay, immunoblotting, and cell-cycle analysis. We found that E1-deficient Ad-p53 could replicate in human cancer cells in the presence of OBP-301 and kill infected cells more efficiently than Ad-p53 alone or OBP-301 alone. Western Blotting Analysis demonstrated that OBP-301 plus Ad-p53 induced high levels of p53 protein expression, leading to cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP). In addition, flowcytometry showed that the sub-G1 population was dramatically increased with OBP-301 and Ad-p53 infection. The in vivo combination effect of intratumoral injection of Ad-p53 and OBP-301 in a human tumor xenograft model will be also reported. Our data demonstrate that OBP-301 in combination with Ad-p53 efficiently enhances antitumor activity, and provide the potential to affect the development of oncolytic virotherapy and gene therapy.Molecular Therapy (2006) 13, S114–S114; doi: 10.1016/j.ymthe.2006.08.353 [ABSTRACT FROM AUTHOR]

Oncolytic adenoviruses are being developed as novel anticancer therapeutics and currently undergoing clinical trials. We previously demonstrated that telomerase-specific replication-competent adenovirus (Telomelysin: OBP-301), in which the hTERT promoter regulates viral replication, efficiently killed human tumor cells. We further constructed OBP-401 (Telomelysin-GFP) that expresses the green fluorescent protein (GFP) reporter gene under the control of the cytomegalovirus promoter in the E3 region to monitor viral distribution. Here, we examined the feasibility of a single-agent therapy with OBP-401 as well as of combining OBP-401 with chemotherapeutic agents. Infection of OBP-401 alone or followed by the treatment of a chemotherapeutic drug, docetaxel (Taxotere), resulted in a profound in vitro cytotoxicity and GFP expression in various human cancer cell lines originating from different organs (lung, colon, esophagus, stomach, liver, and prostate), although the magnitude of antitumor effect varied among the cell types. Other chemotherapeutic drugs such as vinorelbine (Navelbine) and SN38 (the potent active metabolite of irinotecan) combined with OBP-401 also inhibited the growth of human cancer cells. Quantitative real-time PCR analysis demonstrated that docetaxel did not affect viral replication. For in vivo evaluation, nu/nu mice xenografted with H1299 human lung tumor received intratumoral injection of OBP-401 and intraperitoneal administration of docetaxel. Analysis of growth of implanted tumors showed a significant, therapeutic synergism, although OBP-401 alone and docetaxel alone showed modest inhibition of tumor growth. Thus, OBP-401 in combination with docetaxel efficiently enhances the antitumor efficacy both in vitro and in vivo, the outcome has important implications for tumor- specific oncolytic chemovirotherapies for human cancers.Molecular Therapy (2006) 13, S116–S116; doi: 10.1016/j.ymthe.2006.08.358 [ABSTRACT FROM AUTHOR]

Malignant mesothelioma is an extraordinarily challenging disease to treat; however, locoregional virotherapy may be applicable for this aggressive disease because of the accessibility by intrapleural and/or intratumoral virus delivery. We previously reported that an attenuated adenovirus OBP-301 (Telomelysin), in which the human telomerase reverse transcriptase (hTERT) promoter element drives expression of E1A and E1B genes linked with an internal ribosome entry site, could replicate in and causes selective lysis of human cancer cells. In the present study, we examined the antitumor effect of Telomelysin on human malignant mesothelioma cell lines in vitro and in vivo. The XTT assay demonstrated that Telomelysin could efficiently kill four human mesothelioma cell lines H2052, H2452, H28, and 211H, all of which expressed the coxsackievirus and adenovirus receptor (CAR), in a dose-dependent manner. In vivo antitumor effect was also evaluated in an orthotopic pleural dissemination model. Intrathoracic administration of 2 × 108 plaque forming units (PFU) of Telomelysin markedly reduced the size (1 ± 1.8 mg vs. 190 ± 75 mg, p < 0.01) of H2452 tumors intrathoracically implanted into BALB/c- nu/nu mice compared to mock-treated mice. These results suggest that locoregional administration of Telomelysin into the thoracic cavity may be efficacious in the prevention and treatment of pleural dissemination of human malignant mesothelioma.Molecular Therapy (2006) 13, S118–S118; doi: 10.1016/j.ymthe.2006.08.365 [ABSTRACT FROM AUTHOR]