Clinical impact of high-quality testing for peritoneal lavage cytology in pancreatic cancer.

In pancreatic ductal adenocarcinoma (PDAC) patients, the importance of peritoneal lavage cytology, which indicates unresectability, remains controversial. This study sought to determine whether positive peritoneal lavage cytology (CY+) precludes pancreatectomy. Furthermore, we propose a novel liquid biopsy using peritoneal lavage fluid to detect viable peritoneal tumor cells (v-PTCs) with TelomeScan F35, a telomerase-specific replication-selective adenovirus engineered to express green fluorescent protein. Resectable cytologically or histologically proven PDAC patients (n = 53) were enrolled. CY was conducted immediately following laparotomy. The resulting fluid was examined by conventional cytology (conv-CY; Papanicolaou staining and MOC-31 immunostaining) and by the novel technique (Telo-CY; using TelomeScan F35). Of them, 5 and 12 were conv-CY+ and Telo-CY+, respectively. All underwent pancreatectomy. The two double-CY+ (conv-CY+ and Telo-CY+) patients showed early peritoneal recurrence (P-rec) postoperatively, despite adjuvant chemotherapy. None of the three conv-CY+ Telo-CY- patients exhibited P-rec. Six of the 10 Telo-CY+ conv-CY- patients (60%) relapsed with P-rec. Of the remaining 38 double-CY- [conv-CY-, Telo-CY-, conv-CY± (Class III)] patients, 3 (8.3%) exhibited P-rec. Although conv-CY+ status predicted poor prognosis and a higher risk of P-rec, Telo-CY was more sensitive for detecting v-PTC. Staging laparoscopy and performing conv-CY and Telo-CY are needed to confirm the indication for pancreatectomy.

Functional remodeling of intraperitoneal macrophages by oncolytic adenovirus restores anti-tumor immunity for peritoneal metastasis of gastric cancer.

Intraperitoneal tumor-associated macrophages (TAMs) are involved in evading anti-tumor immunity and promoting the peritoneal metastasis (PM) of gastric cancer (GC). Oncolytic viruses are known to induce the activation of host anti-tumor immunity in addition to tumor lysis. This study investigated whether a wild-type p53-loading telomerase-specific oncolytic adenovirus (OBP-702) could elicit the remodeling of intraperitoneal macrophages and enhance the efficacy of immune therapy. Increased numbers of CD163 TAMs and few CD8+ lymphocytes were immunohistochemically observed in clinical samples with PM, which suggested that TAMs were associated with the suppression of anti-tumor immunity. OBP-702 induced immunogenic cell death and upregulated PD-L1 expression in human and murine GC cell lines. Intraperitoneal administration of OBP-702 increased recruitment of CD8+ lymphocytes into the PM via the functional remodeling of intraperitoneal macrophages from TAM toward a pro-inflammatory phenotype, resulting in significantly suppressed tumor growth for the in vivo model. Furthermore, the combination of intraperitoneal OBP-702 with anti-programmed cell death-1 antibody enhanced anti-tumor immunity and prolonged the survival of mice bearing PM. Intraperitoneal immunotherapy using OBP-702 restores anti-tumor immunity via the remodeling of intraperitoneal macrophages in addition to direct tumor lysis and cooperates with immune checkpoint inhibitors to suppress PM in GC.

p53-Armed Oncolytic Virotherapy Improves Radiosensitivity in Soft-Tissue Sarcoma by Suppressing BCL-xL Expression.

Soft-tissue sarcoma (STS) is a heterogeneous group of rare tumors originating predominantly from the embryonic mesoderm. Despite the development of combined modalities including radiotherapy, STSs are often refractory to antitumor modalities, and novel strategies that improve the prognosis of STS patients are needed. We previously demonstrated the therapeutic potential of two telomerase-specific replication-competent oncolytic adenoviruses, OBP-301 and tumor suppressor p53-armed OBP-702, in human STS cells. Here, we demonstrate in vitro and in vivo antitumor effects of OBP-702 in combination with ionizing radiation against human STS cells (HT1080, NMS-2, SYO-1). OBP-702 synergistically promoted the antitumor effect of ionizing radiation in the STS cells by suppressing the expression of B-cell lymphoma-X large (BCL-xL) and enhancing ionizing radiation-induced apoptosis. The in vivo experiments demonstrated that this combination therapy significantly suppressed STS tumors' growth. Our results suggest that OBP-702 is a promising antitumor reagent for promoting the radiosensitivity of STS tumors.

Long-term activation of anti-tumor immunity in pancreatic cancer by a p53-expressing telomerase-specific oncolytic adenovirus.

BACKGROUND: Pancreatic cancer is an aggressive, immunologically "cold" tumor. Oncolytic virotherapy is a promising treatment to overcome this problem. We developed a telomerase-specific oncolytic adenovirus armed with p53 gene (OBP-702). METHODS: We investigated the efficacy of OBP-702 for pancreatic cancer, focusing on its long-term effects via long-lived memory CD8 + T cells including tissue-resident memory T cells (TRMs) and effector memory T cells (TEMs) differentiated from effector memory precursor cells (TEMps). RESULTS: First, in vitro, OBP-702 significantly induced adenosine triphosphate (ATP), which is important for memory T cell establishment. Next, in vivo, OBP-702 local treatment to murine pancreatic PAN02 tumors increased TEMps via ATP induction from tumors and IL-15Rα induction from macrophages, leading to TRM and TEM induction. Activation of these memory T cells by OBP-702 was also maintained in combination with gemcitabine+nab-paclitaxel (GN) in a PAN02 bilateral tumor model, and GN + OBP-702 showed significant anti-tumor effects and increased TRMs in OBP-702-uninjected tumors. Finally, in a neoadjuvant model, in which PAN02 cells were re-inoculated after resection of treated-PAN02 tumors, GN + OBP-702 provided long-term anti-tumor effects even after tumor resection. CONCLUSION: OBP-702 can be a long-term immunostimulant with sustained anti-tumor effects on immunologically cold pancreatic cancer.

Fluorescence-guided assessment of bone and soft-tissue sarcomas for predicting the efficacy of telomerase-specific oncolytic adenovirus.

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.

Intraperitoneal Administration of p53-armed Oncolytic Adenovirus Inhibits Peritoneal Metastasis of Diffuse-type Gastric Cancer Cells.

BACKGROUND/AIM: Diffuse-type gastric cancer (GC) frequently exhibits peritoneal metastasis, leading to poor prognosis. However, efforts to develop antitumor strategies for preventing the peritoneal metastasis of GC have been unsuccessful. As diffuse-type GC cells often carry a genetic alteration in the tumor suppressor p53 gene, p53 restoration may be a potent strategy for preventing peritoneal metastasis of GC. In this study, we investigated the therapeutic potential of p53-expressing adenoviral vectors against peritoneal metastasis of diffuse-type GC cells. MATERIALS AND METHODS: Three diffuse-type human GC cell types with different p53 statuses (p53-wild type NUGC-4, p53-mutant type GCIY, and p53-null type KATOIII) were used to evaluate the therapeutic potential of p53 activation induced by the p53-expressing, replication-deficient adenovirus Ad-p53 and oncolytic adenovirus OBP-702. Viability, apoptosis, and autophagy of virus-treated GC cells were analyzed under normal and sphere-forming culture conditions using the XTT assay and western blot analysis. The in vivo antitumor effects of OBP-702 and Ad-p53 were assessed using xenograft tumor models involving peritoneal metastasis of NUGC-4 and GCIY cells. RESULTS: Under normal and sphere-forming culture conditions, OBP-702 induced a significantly greater antitumor effect in GC cells compared with Ad-p53 by strongly inducing p53-mediated apoptosis and autophagy and receptor tyrosine kinase suppression. In vivo experiments demonstrated that intraperitoneal administration of OBP-702 significantly suppressed the peritoneal metastasis of NUGC-4 and GCIY cells compared with Ad-p53, leading to prolonged survival of mice. CONCLUSION: Intraperitoneal administration of OBP-702 inhibits the peritoneal metastasis of GC cells by inducing p53-mediated cytopathic activity.

[Therapeutic Effect of Oncolytic Adenovirus on Pancreatic Cancer Stroma].

Pancreatic ductal adenocarcinoma(PDAC)is lethal malignancy with abundant stroma. Cancer-associated fibroblasts (CAFs) exist in the PDAC stroma and contribute to progression of malignant transformation, treatment resistance, and recurrence. However, effective treatment to control PDAC stroma has not been established. We have developed tumor suppressor gene p53-armed oncolytic adenovirus(OBP-702), and have clarified therapeutic effects on PDAC cells. In this study, we investigate the therapeutic effect of OBP-702 on PDAC CAF.

p53-armed oncolytic adenovirus induces autophagy and apoptosis in KRAS and BRAF-mutant colorectal cancer cells.

Colorectal cancer (CRC) cells harboring KRAS or BRAF mutations show a more-malignant phenotype than cells with wild-type KRAS and BRAF. KRAS/BRAF-wild-type CRCs are sensitive to epidermal growth factor receptor (EGFR)-targeting agents, whereas KRAS/BRAF-mutant CRCs are resistant due to constitutive activation of the EGFR-downstream KRAS/BRAF signaling pathway. Novel therapeutic strategies to treat KRAS/BRAF mutant CRC cells are thus needed. We recently demonstrated that the telomerase-specific replication-competent oncolytic adenoviruses OBP-301 and p53-armed OBP-702 exhibit therapeutic potential against KRAS-mutant human pancreatic cancer cells. In this study, we evaluated the therapeutic potential of OBP-301 and OBP-702 against human CRC cells with differing KRAS/BRAF status. Human CRC cells with wild-type KRAS/BRAF (SW48, Colo320DM, CACO-2), mutant KRAS (DLD-1, SW620, HCT116), and mutant BRAF (RKO, HT29, COLO205) were used in this study. The antitumor effect of OBP-301 and OBP-702 against CRC cells was analyzed using the XTT assay. Virus-mediated modulation of apoptosis, autophagy, and the EGFR-MEK-ERK and AKT-mTOR signaling pathways was analyzed by Western blotting. Wild-type and KRAS-mutant CRC cells were sensitive to OBP-301 and OBP-702, whereas BRAF-mutant CRC cells were sensitive to OBP-702 but resistant to OBP-301. Western blot analysis demonstrated that OBP-301 induced autophagy and that OBP-702 induced autophagy and apoptosis in human CRC cells. In BRAF-mutant CRC cells, OBP-301 and OBP-702 suppressed the expression of EGFR, MEK, ERK, and AKT proteins, whereas mTOR expression was suppressed only by OBP-702. Our results suggest that p53-armed oncolytic virotherapy is a viable therapeutic option for treating KRAS/BRAF-mutant CRC cells via induction of autophagy and apoptosis.

Safety and dose escalation of the targeted oncolytic adenovirus OBP-301 for refractory advanced liver cancer: Phase I clinical trial.

OBP-301 is an oncolytic adenovirus modified to replicate within cancer cells and lyse them. This open-label, non-comparative, phase I dose-escalation trial aimed to assess its safety and optimal dosage in 20 patients with advanced hepatocellular carcinoma. Good tolerance was shown with a maximum tolerated dose of 6 × 1012 viral particles. The most common treatment-emergent adverse events were influenza-like illness, pyrexia, fatigue, decreased platelet count, abdominal distension, and anemia. Cohorts 4 and 5 had approximately 50% higher levels of CD8+ T cells in the peripheral blood after injection. The best target response occurred in 14 patients, 4 of whom had progressive disease. Multiple intratumoral injections of OBP-301 were well tolerated in patients with advanced hepatocellular carcinoma. The stable disease rate for the injected tumors was greater than the overall response rate, even with no obvious tumor response. OBP-301 might have a greater impact on local response as histological examination revealed that the presence of OBP-301 was consistent with the necrotic area at the injection site. Increased infiltration of CD8+ T cells and <1% PD-L1 expression were observed in tumors after injection. Improved antitumor efficacy might be achieved in future studies via viral injection with volume adjustment and in combination with other immuno-therapeutics.

Oncolytic virus-mediated reducing of myeloid-derived suppressor cells enhances the efficacy of PD-L1 blockade in gemcitabine-resistant pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is often refractory to treatment with gemcitabine (GEM) and immune checkpoint inhibitors including anti-programmed cell death ligand 1 (PD-L1) antibody. However, the precise relationship between GEM-resistant PDAC and development of an immunosuppressive tumor microenvironment (TME) remains unclear. In this study, we investigated the immunosuppressive TME in parental and GEM-resistant PDAC tumors and assessed the therapeutic potential of combination therapy with the telomerase-specific replication-competent oncolytic adenovirus OBP-702, which induces tumor suppressor p53 protein and PD-L1 blockade against GEM-resistant PDAC tumors. Mouse PDAC cells (PAN02) and human PDAC cells (MIA PaCa-2, BxPC-3) were used to establish GEM-resistant PDAC lines. PD-L1 expression and the immunosuppressive TME were analyzed using parental and GEM-resistant PDAC cells. A cytokine array was used to investigate the underlying mechanism of immunosuppressive TME induction by GEM-resistant PAN02 cells. The GEM-resistant PAN02 tumor model was used to evaluate the antitumor effect of combination therapy with OBP-702 and PD-L1 blockade. GEM-resistant PDAC cells exhibited higher PD-L1 expression and produced higher granulocyte-macrophage colony-stimulating factor (GM-CSF) levels compared with parental cells, inducing an immunosuppressive TME and the accumulation of myeloid-derived suppressor cells (MDSCs). OBP-702 significantly inhibited GEM-resistant PAN02 tumor growth by suppressing GM-CSF-mediated MDSC accumulation. Moreover, combination treatment with OBP-702 significantly enhanced the antitumor efficacy of PD-L1 blockade against GEM-resistant PAN02 tumors. The present results suggest that combination therapy involving OBP-702 and PD-L1 blockade is a promising antitumor strategy for treating GEM-resistant PDAC with GM-CSF-induced immunosuppressive TME formation.

An oncolytic virus as a promising candidate for the treatment of radioresistant oral squamous cell carcinoma.

We evaluated the usefulness of an oncolytic virus (Suratadenoturev; OBP-301) against radioresistant oral squamous cell carcinoma. We confirmed the expression of human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor in cell lines. Also, we examined the potential presence in a patient who has received existing therapy that is amenable to treatment with OBP-301. We evaluated: (1) the antitumor effects of OBP-301 alone and in combination with radiotherapy on radioresistant cell lines, (2) the molecular mechanism underlying the radiosensitizing effect and cell death increased by the combination therapy, and (3) the antitumor effect of the combination therapy in vivo using xenograft models (a radioresistant cell line-derived xenograft in mouse and a patient-derived xenograft). Human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor were expressed in all cell lines. OBP-301 decreased the proliferative activity of these cell lines in a concentration-dependent manner, and significantly enhanced the antitumor effect of irradiation. Phosphorylated STAT3 and its downstream molecules, which correlated with apoptosis and autophagy, showed significant changes in expression after treatment with OBP-301. The combination therapy exerted a significant antitumor effect versus radiotherapy alone in both xenograft models. Combination of OBP-301 with radiotherapy exerts a synergistic effect and may represent a promising treatment for radioresistant oral squamous cell carcinoma.

Oncolytic virus-mediated p53 overexpression promotes immunogenic cell death and efficacy of PD-1 blockade in pancreatic cancer.

Immune checkpoint inhibitors, including anti-programmed cell death 1 (PD-1) antibody, provide improved clinical outcome in certain cancers. However, pancreatic ductal adenocarcinoma (PDAC) is refractory to PD-1 blockade therapy due to poor immune response. Oncolytic virotherapy is a novel approach for inducing immunogenic cell death (ICD). We demonstrated the therapeutic potential of p53-expressing telomerase-specific oncolytic adenovirus OBP-702 to induce ICD and anti-tumor immune responses in human PDAC cells with different p53 status (Capan-2, PK-59, PK-45H, Capan-1, MIA PaCa-2, BxPC-3) and murine PDAC cells (PAN02). OBP-702 significantly enhanced ICD with secretion of extracellular adenosine triphosphate and high-mobility group box protein B1 by inducing p53-mediated apoptosis and autophagy. OBP-702 significantly promoted the tumor infiltration of CD8+ T cells and the anti-tumor efficacy of PD-1 blockade in a subcutaneous PAN02 syngeneic tumor model. Our results suggest that oncolytic adenovirus-mediated p53 overexpression augments ICD and the efficacy of PD-1 blockade therapy against cold PDAC tumors. Further in vivo experiments would be warranted to evaluate the survival benefit of tumor-bearing mice in combination therapy with OBP-702 and PD-1 blockade.

[Telomerase-Specific Oncolytic Adenovirus Expressing p53 Gene Stimulating CD8+ Memory T Cells in Pancreatic Cancer].

Pancreatic cancer has poor prognosis despite the various developed multimodal treatment strategies. Currently, neoadjuvant chemotherapy and immunotherapy have attracted substantial attention as effective treatment strategies. However, amplifying immune response with existing treatments is difficult. We developed telomerase-specific oncolytic adenoviruses (OAs), including OBP-301 that is currently tested in a clinical trial of combined anti-PD-1 antibody and p53-armed OBP- 301 variant(OBP-702). OAs have immune-modulation functions and induce CD8+ T cells into tumors by releasing immunogenic cell death markers, such as extracellular adenosine triphosphate. Here, we investigated the effectiveness of OBP- 702 in pancreatic cancer treatments, focusing on the influence on CD8+ memory T cells.

Modulation of p53 expression in cancer-associated fibroblasts prevents peritoneal metastasis of gastric cancer.

Cancer-associated fibroblasts (CAFs) in the tumor microenvironment are associated with the establishment and progression of peritoneal metastasis. This study investigated the efficacy of replicative oncolytic adenovirus-mediated p53 gene therapy (OBP-702) against CAFs and peritoneal metastasis of gastric cancer (GC). Higher CAF expression in the primary tumor was associated with poor prognosis of GC, and higher CAF expression was also observed with peritoneal metastasis in immunohistochemical analysis of clinical samples. And, we found transcriptional alteration of p53 in CAFs relative to normal gastric fibroblasts (NGFs). CAFs increased the secretion of cancer-promoting cytokines, including interleukin-6, and gained resistance to chemotherapy relative to NGFs. OBP-702 showed cytotoxicity to both GC cells and CAFs but not to NGFs. Overexpression of wild-type p53 by OBP-702 infection caused apoptosis and autophagy of CAFs and decreased the secretion of cancer-promoting cytokines by CAFs. Combination therapy using intraperitoneal administration of OBP-702 and paclitaxel synergistically inhibited the tumor growth of peritoneal metastases and decreased CAFs in peritoneal metastases. OBP-702, a replicative oncolytic adenovirus-mediated p53 gene therapy, offers a promising biological therapeutic strategy for peritoneal metastasis, modulating CAFs in addition to achieving tumor lysis.

Overexpression of Adenovirus E1A Reverses Transforming Growth Factor-ß-induced Epithelial-mesenchymal Transition in Human Esophageal Cancer Cells.

The epithelial-mesenchymal transition (EMT), a normal biological process by which epithelial cells acquire a mesenchymal phenotype, is associated with migration, metastasis, and chemoresistance in cancer cells, and with poor prognosis in patients with esophageal cancer. However, therapeutic strategies to inhibit EMT in tumor environments remain elusive. Here, we show the therapeutic potential of telomerase-specific replication- competent oncolytic adenovirus OBP-301 in human esophageal cancer TE4 and TE6 cells with an EMT phenotype. Transforming growth factor-ß (TGF-ß) administration induced the EMT phenotype with spindleshaped morphology, upregulation of mesenchymal markers and EMT transcription factors, migration, and chemoresistance in TE4 and TE6 cells. OBP-301 significantly inhibited the EMT phenotype via E1 accumulation. EMT cancer cells were susceptible to OBP-301 via massive autophagy induction. OBP-301 suppressed tumor growth and lymph node metastasis of TE4 cells co-inoculated with TGF-ß-secreting fibroblasts. Our results suggest that OBP-301 inhibits the TGF-ß-induced EMT phenotype in human esophageal cancer cells. OBP-301-mediated E1A overexpression is a promising antitumor strategy to inhibit EMT-mediated esophageal cancer progression.

Phase Ia dose escalation study of OBP-801, a cyclic depsipeptide class I histone deacetylase inhibitor, in patients with advanced solid tumors.

Background Dysregulation of histone deacetylases (HDACs) is common in cancer and is critical to the development and progression of the majority of tumors. This first-in-human Phase Ia study assessed the safety, efficacy, and pharmacokinetics (PK) of OBP-801, a cyclic depsipeptide class I HDAC inhibitor. Methods Adult patients with advanced solid tumors were treated in 3 dose cohorts (1.0 mg/m2, 2.0 mg/m2 or 2.8 mg/m2) of OBP-801 that was administered via intravenous infusion weekly. Initially, an accelerated titration design was used that was followed by a 3 + 3 dose escalation strategy. Primary objective was assessment of safety. Secondary objectives included determination of PK and objective response rate. Results Seventeen patients were enrolled, of which 8 patients were evaluable for efficacy. Drug-related ≥ Grade 3 treatment-emergent adverse events included abdominal pain, anemia, fatigue, gamma glutamyl-transferase increase, hypertriglyceridemia and vomiting. No dose-limiting toxicity was observed in the 1.0 mg/m2 cohort. The PK data showed that OBP-801 and its active metabolite OBP-801-SH exposure increased proportionally and more than proportionally, respectively. No accumulation of either agent was noticed after repeat administration. Best response was stable disease (37.5%), with one patient each in the three cohorts. Conclusion Further investigations of the OBP-801 1.0 mg/m2 dose will be needed to better understand the efficacy of the agent, either alone or in combination. Trial registration: NCT02414516 (ClinicalTrials.gov) registered on April 10, 2015.

Oncolytic virotherapy reverses chemoresistance in osteosarcoma by suppressing MDR1 expression.

BACKGROUND: Osteosarcoma (OS) is a malignant bone tumor primarily affecting children and adolescents. The prognosis of chemotherapy-refractory OS patients is poor. We developed a tumor suppressor p53-expressing oncolytic adenovirus (OBP-702) that exhibits antitumor effects against human OS cells. Here, we demonstrate the chemosensitizing effect of OBP-702 in human OS cells. MATERIALS AND METHODS: The in vitro and in vivo antitumor activities of doxorubicin (DOX) and OBP-702 were assessed using parental and DOX-resistant OS cells (U2OS, MNNG/HOS) and a DOX-resistant MNNG/HOS xenograft tumor model. RESULTS: DOX-resistant OS cells exhibited high multidrug resistant 1 (MDR1) expression, which was suppressed by OBP-702 or MDR1 siRNA, resulting in enhanced DOX-induced apoptosis. Compared to monotherapy, OBP-702 and DOX combination therapy significantly suppressed tumor growth in the DOX-resistant MNNG/HOS xenograft tumor model. CONCLUSION: Our results suggest that MDR1 is an attractive therapeutic target for chemoresistant OS. Tumor-specific virotherapy is thus a promising strategy for reversing chemoresistance in OS patients via suppression of MDR1 expression.

Phase I dose-escalation study of endoscopic intratumoral injection of OBP-301 (Telomelysin) with radiotherapy in oesophageal cancer patients unfit for standard treatments.

PURPOSE: OBP-301 (Telomelysin) is an attenuated type-5 adenovirus that contains the human telomerase reverse transcriptase promoter to regulate viral replication. OBP-301 sensitises human cancer cells to ionising radiation by inhibiting DNA repair, and radiation enhances coxsackievirus and adenovirus receptor-mediated OBP-301 infection on the contrary. We assessed OBP-301 with radiotherapy in oesophageal cancer patients unfit for standard chemoradiation treatments. METHODS: A phase I dose-escalation study of OBP-301 with radiotherapy was conducted in 13 histologically confirmed oesophageal cancer patients deemed unfit to undergo surgery or chemotherapy. Study treatment consisted of OBP-301 administration by intratumoural needle injection using a flexible endoscope on days 1, 18 and 32. Radiotherapy was administered concurrently over 6 weeks, beginning on day 4, to a total of 60 Gy. RESULTS: Of the 13 patients, 7, 3 and 3 patients were treated with 1010, 1011 and 1012 virus particles, respectively. Study group comprised 10 males and 3 females, with a median age of 82 years (range, 53-91 years). All patients developed a transient, self-limited lymphopenia. Distribution studies revealed transient virus shedding in the plasma. Eight patients had local complete response (CR); all of them exhibited no pathologically viable malignant cells in biopsy specimens, and 3 patients had a partial response. The objective response rate was 91.7%. The clinical CR rate was 83.3% in stage I and 60.0% in stage II/III. Histopathological examination revealed massive infiltration of CD8+ cells and increased PD-L1 expression. CONCLUSION: Multiple courses of endoscopic intratumoural OBP-301 injection with radiotherapy are feasible and provide clinical benefits in patients with oesophageal cancer unfit for standard treatments.

Local oncolytic adenovirotherapy produces an abscopal effect via tumor-derived extracellular vesicles.

Extracellular vesicles (EVs) play important roles in various intercellular communication processes. The abscopal effect is an interesting phenomenon in cancer treatment, in which immune activation is generally considered a main factor. We previously developed a telomerase-specific oncolytic adenovirus, Telomelysin (OBP-301), and occasionally observed therapeutic effects on distal tumors after local treatment in immunodeficient mice. In this study, we hypothesized that EVs may be involved in the abscopal effect of OBP-301. EVs isolated from the supernatant of HCT116 human colon carcinoma cells treated with OBP-301 were confirmed to contain OBP-301, and they showed cytotoxic activity (apoptosis and autophagy) similar to OBP-301. In bilateral subcutaneous HCT116 and CT26 tumor models, intratumoral administration of OBP-301 produced potent antitumor effects on tumors that were not directly treated with OBP-301, involving direct mediation by tumor-derived EVs containing OBP-301. This indicates that immune activation is not the main factor in this abscopal effect. Moreover, tumor-derived EVs exhibited high tumor tropism in orthotopic HCT116 rectal tumors, in which adenovirus E1A and adenovirus type 5 proteins were observed in metastatic liver tumors after localized rectal tumor treatment. In conclusion, local treatment with OBP-301 has the potential to produce abscopal effects via tumor-derived EVs.

Oncolytic virotherapy promotes radiosensitivity in soft tissue sarcoma by suppressing anti-apoptotic MCL1 expression.

Soft tissue sarcoma (STS) is a rare cancer that develops from soft tissues in any part of the body. Despite major advances in the treatment of STS, patients are often refractory to conventional radiotherapy, leading to poor prognosis. Enhancement of sensitivity to radiotherapy would therefore improve the clinical outcome of STS patients. We previously revealed that the tumor-specific, replication-competent oncolytic adenovirus OBP-301 kills human sarcoma cells. In this study, we investigated the radiosensitizing effect of OBP-301 in human STS cells. The in vitro antitumor effect of OBP-301 and ionizing radiation in monotherapy or combination therapy was assessed using highly radiosensitive (RD-ES and SK-ES-1) and moderately radiosensitive (HT1080 and NMS-2) STS cell lines. The expression of markers for apoptosis and DNA damage were evaluated in STS cells after treatment. The therapeutic potential of combination therapy was further analyzed using SK-ES-1 and HT1080 cells in subcutaneous xenograft tumor models. The combination of OBP-301 and ionizing radiation showed a synergistic antitumor effect in all human STS cell lines tested, including those that show different radiosensitivity. OBP-301 was found to enhance irradiation-induced apoptosis and DNA damage via suppression of anti-apoptotic myeloid cell leukemia 1 (MCL1), which was expressed at higher levels in moderately radiosensitive cell lines. The combination of OBP-301 and ionizing radiation showed a more profound antitumor effect compared to monotherapy in SK-ES-1 (highly radiosensitive) and HT1080 (moderately radiosensitive) subcutaneous xenograft tumors. OBP-301 is a promising antitumor reagent to improve the therapeutic potential of radiotherapy by increasing radiation-induced apoptosis in STS.