Targeted Photodynamic Virotherapy Armed with a Genetically Encoded Photosensitizer

Photodynamic therapy (PDT) is a minimally invasive antitumor therapy that eradicates tumor cells through a photosensitizer-mediated cytotoxic effect upon light irradiation. However, systemic administration of photosensitizer often makes it difficult to avoid a photosensitive adverse effect. The red fluorescent protein KillerRed generates reactive oxygen species (ROS) upon green light irradiation. Here, we show the therapeutic potential of a novel tumor-specific replicating photodynamic viral agent (TelomeKiller) constructed using the human telomerase reverse transcriptase (hTERT) promoter. We investigated the light-induced antitumor effect of TelomeKiller in several types of human cancer cell lines. Relative cell viability was investigated using an XTT assay. The in vivo antitumor effect was assessed using subcutaneous xenografted tumor and lymph node metastasis models. KillerRed accumulation resulted in ROS generation and apoptosis in light-irradiated cancer cells. Intratumoral injection of TelomeKiller efficiently delivered the KillerRed protein throughout the tumors and exhibited a long-lasting antitumor effect with repeated administration and light irradiation in mice. Moreover, intratumorally injected TelomeKiller could spread into the regional lymph node area and eliminate micrometastasis with limited-field laser irradiation. Our results suggest that KillerRed has great potential as a novel photosensitizer if delivered with a tumor-specific virus-mediated delivery system. TelomeKiller-based PDT is a promising antitumor strategy to efficiently eradicate tumor cells.

Strategic approach to concurrent aberrant left gastric vein and aberrant left hepatic artery in laparoscopic distal gastrectomy for early gastric cancer: A case report

An aberrant left gastric vein (ALGV) directly entering the lateral segment of the liver is a rare variation in the portal vein system, whereas an aberrant left hepatic artery (ALHA) arising from the left gastric artery is observed relatively frequently. Here we report a case in which both ALGV and ALHA were encountered before laparoscopic distal gastrectomy with curative lymphadenectomy for gastric cancer. We accurately diagnosed these vessel anomalies preoperatively on abdominal contrast-enhanced CT. During surgery, we divided the ALGV at the point of entry to the liver and preserved the ALHA by dividing the branches toward the stomach, in consideration of curability and safety. The postoperative course was uneventful overall, although temporary mild liver dysfunction was observed. This case highlights the importance of preoperative evaluation and preparation in a rare case of concurrent ALGV and ALHA.

[Therapeutic Potential of Targeting Cancer-Associated Fibroblasts in Esophageal Cancer]

Advances in molecular and cellular biochemistry, such as the development of targeted cancer therapy, have dramatically improved the prognosis of cancer patients. Emerging data have suggested that bevacizumab treatment may act by controlling the cancer microenvironment. Many reports have examined the interaction of cancer cells with the tumor microenvironment, and cancer-associated fibroblasts (CAFs) are thought to play a central role in this process. We speculated that the cancer microenvironment and in particular, CAFs, strongly influence the development of esophageal cancer. We have analyzed the signaling pathways of molecular targets. However, inhibition of a single signaling pathway is insufficient to treat cancer effectively. Photoimmunotherapy is a molecular-targeted specific cancer therapy using near-infrared radiation, which was introduced by Mitsunaga et al. in 2011. We are using its specific method of killing cells to target CAFs. We will report the results of its effect on cancer cells in the future.

Precise navigation surgery of tumours in the lung in mouse models enabled by in situ fluorescence labelling with a killer-reporter adenovirus

Background

Current methods of image-guided surgery of tumours of the lung mostly rely on CT. A sensitive procedure of selective tumour fluorescence labelling would allow simple and high-resolution visualisation of the tumour for precise surgical navigation.

Methods

Human lung cancer cell lines H460 and A549 were genetically transformed to express red fluorescent protein (RFP). Tumours were grown subcutaneously for each cell line and harvested and minced for surgical orthotopic implantation on the left lung of nude mice. Tumour growth was measured by fluorescence imaging. After the tumours reached 5 mm in diameter, they were injected under fluorescence guidance with the telomerase-dependent green fluorescent protein (GFP)-containing adenovirus, OBP-401. Viral labelling of the lung tumours with GFP precisely colocalised with tumour RFP expression. Three days after administration of OBP-401, fluorescence-guided surgery (FGS) was performed.

Results

FGS of tumours in the lung was enabled by labelling with a telomerase-dependent adenovirus containing the GFP gene. Tumours in the lung were selectively and brightly labelled. FGS enabled complete lung tumour resection with no residual fluorescent tumour.

Conclusions

FGS of tumours in the lung is feasible and more effective than bright-light surgery.

Abstract 4243: Iron control is a novel therapeutic target of cancer stem cells

Background: Iron overload is known to cause cancer in animal models. Several studies have shown that iron deprivation treatment has a strong anti-cancer effect. However, it is unclear whether iron deprivation treatment suppresses cancer stem cells or not. A cancer stem cell model, miPS-LLCcm, was recently epigenetically established from murine induced pluripotent stem cells (miPS cells) in Okayama University. In this model, the green fluorescent protein (GFP) and the puromycin resistant gene were inserted into the 59-bp untranslated region of the Nanog gene of miPS cells. By this procedure, undifferentiated cancer progenitor cells are recognized as GFP positive cells. We then examined the iron dependency of these cancer stem cells both in in vitro and in vivo studies and we used this model to examine the possibility of cancer stem cells by iron deprivation.

Materials and Methods: In in vitro studies, the miPS-LLCcm cells were used as cancer stem cells and colon26 and 4T1 cells were used as differentiated murine cancer cells. Puromycin was used to purify the cancer stem cells before seeding of the miPS-LLCcm cells. The dependency on iron for cell proliferation was examined following transferrin addition. Transferrin (Holo) was used to simulate an iron rich condition. Iron free medium and the iron chelators, Deferasirox and Deferoxamine, plus 1% fetal bovine serum (FBS) were used to simulate iron depletion conditions. Cell proliferation assays and flow cytometric analyses were performed 48 hours after adjustment of the iron concentration level. In in vivo studies, an iron depleted diet was used to simulate iron depleted conditions. Nude mice were divided into normal diet and iron depleted diet groups. The mice were fed with these diets for three weeks and then a suspension of miPS-LLCcm cells was injected into the backs of the nude mice. Tumor size was measured and the tumors were immunohistologically examined.

Results: In the in vitro studies, transferrin strongly promoted the proliferation of cancer stem cells under iron depletion conditions compared to no transferrin(p<0.001). However, transferrin did not promote the proliferation of the differentiated 4T1 and colon26 cancer cells. The number of GFP-expressing cancer stem cells decreased as the iron concentration was decreased. In the vivo studies, iron depletion significantly suppressed the tumor growth of the cancer stem cells (p<0.05). Immunohistological analysis indicated that Nanog expression was also decreased in the tumors of the iron depletion diet group.

Conclusions: Iron is a key element for the proliferation and differentiation of cancer stem cells. Iron controlling therapy including iron chelators is a novel therapeutic target of cancer stem cells.

Citation Format: Takayuki Ninomiya, Toshiaki Ohara, Hajime Kashima, Ryoichi Katsube, Kazuhiro Noma, Yasuko Tomono, Akifumi Mizutani, Tomonari Kasai, Masaharu Seno, Shinji Kuroda, Hiroyuki Kishimoto, Hiroshi Tazawa, Yasuhiro Shirakawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. Iron control is a novel therapeutic target of cancer stem cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4243. doi:10.1158/1538-7445.AM2015-4243

Abstract 3535: A novel tumor-specific oncolytic biological therapy against invasive pancreatic cancer

Pancreatic cancer is one of the worst prognosis disease all over the world and has an overall 5-year survival rate of less than 5%. At the time of diagnosis, more than 80% of patients are not eligible for curative surgical resection due to extensive local tumor invasion and early systemic metastasis. Moreover, even after curative surgery, pancreatic cancers still show poor prognosis due to local recurrence and systemic metastasis. Gemcitabine is the standard chemotherapeutic agent to treat advanced pancreatic cancers, but median overall survival ranged from 5.0 to 7.2 months, suggesting that standard chemotherapy is less effective to most of pancreatic cancer patients. Therefore, the development of novel therapeutic strategy is needed for the treatment of pancreatic cancers. We developed a novel oncolytic adenovirus, OBP-702, in which a human telomerase reverse transcriptase gene promoter drives viral E1 gene for virus replication, and armed with the wild-type tumor suppressor p53 gene. Precise antitumor effects of OBP-702 have been evaluated in human pancreatic cancer cells. We used four pancreatic cancer cell lines with different invasion ability, including non-invasive type (MIA PaCa-2, Panc-1) and invasive type (BxPC-3, Capan-1). The antitumor effect of OBP-702 for each cell line was assessed using XTT assay. OBP-702 induced profound anti-tumor effect in all human pancreatic cancer cells, whereas OBP-301 lacking the p53 tumor suppressor gene showed differential effects among the cell types. OBP-301 induced moderate anti-tumor effect in MIA Paca-2, BxPC-3 and Capan-1 cells and strong anti-tumor effect in Panc-1 cells in a dose-dependent manner, suggesting the broad spectrum of OBP-702's efficacy. The molecular mechanism of anti-tumor effect was assessed by Western blot analysis. OBP-301 induced autophagy-related cell death, whereas OBP-702 induced autophagy- and apoptosis-related cell deaths. These results suggest that an oncolytic adenovirus, OBP-702, is a promising antitumor agent to induce profound cell death in invasive human pancreatic cancer cells. The clinical trial of intratumoral administration of OBP-702 in patients with invasive pancreatic cancer is warranted.

Citation Format: Takeshi Koujima, Hiroshi Tazawa, Naoto Hori, Shuta Tamura, Shinji Kuroda, Hiroyuki Kishimoto, Masahiko Nishizaki, Yasuo Urata, Shunsuke Kagawa, Toshiyoshi Fujiwara. A novel tumor-specific oncolytic biological therapy against invasive pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3535. doi:10.1158/1538-7445.AM2015-3535

Abstract 5338: Preclinical study of telomerase-specific p53 tumor suppressor gene overexpression in human scirrhous gastric cancer cells with different p53 status

Background: Despite multimodal therapy for scirrhous gastric cancer, many patients show refractory to conventional therapy and rapid progression, leading to poor prognosis. Therefore, the development of novel therapeutic strategy is required to improve the clinical outcome in patients with scirrhous gastric cancers. As novel therapeutic strategies, Ad-p53, a replication-defective adenovirus expressing a tumor suppressor p53 gene, is currently under clinical evaluation for various types of cancers. We recently developed a novel p53-expressing telomerase-specific replication-competent oncolytic adenovirus OBP-702, which induces the p53 gene expression in a telomerase-dependent manner. In this study, we investigated the antitumor effects of Ad-p53 and OBP-702 in human scirrhous gastric cancer cells with different p53 status.

Methods: We used 3 human scirrhous gastric cancer cell lines with different p53 status, NUGC4 (p53 wild-type), GCIY (p53 mutant-type), and KATOIII (p53 null). The antitumor effects of Ad-p53 and OBP-702 were evaluated using XTT assay. The 50% inhibiting dose (ID50) value of Ad-p53 and OBP-702 for each cell was calculated using cell viability data obtained 3 days after virus infection. We evaluated the virus-mediated cell death in the sphere-forming cells by LIVE/DEAD assay. The apoptosis- and autophagy-related cell death was assessed by western blot analysis for cleaved poly (ADP-ribose) polymerase (PARP) and p62.

Results: Ad-p53 suppressed the cell viability in p53-inactivated scirrhous gastric cancer cells (KATO III, GCIY), whereas p53-intact NUGC4 cells were resistant to Ad-p53. OBP-702 efficiently suppressed the cell viability in all scirrhous gastric cancer cells with different p53 function. The ID50 value of OBP-702 was lower than that of Ad-p53 in all cell lines. LIVE/DEAD assay showed that OBP-702 induced cell death more efficiently than Ad-p53 in the sphere-forming cells. OBP-702 induced more profound p53 expression and apoptotic cell death than Ad-p53. Moreover, only OBP-702 induced not only apoptosis but also autophagy.

Conclusions: These results suggest that p53-expressing tumor-specific oncolytic adenovirus OBP-702 is a promising antitumor agent to induce profound cell death in scirrhous gastric cancers with different p53 status. Now, in vivo experiments are under way to investigate the antitumor effect of OBP-702 in the peritoneal dissemination of scirrhous gastric cancer cells.

Citation Format: Naoto Hori, Hiroshi Tazawa, Masahiko Nishizaki, Satoru Kikuchi, Shuya Yano, Michihiro Ishida, Megumi Watanabe, Yasuo Urata, Shunsuke Kagawa, Toshiyoshi Fujiwara. Preclinical study of telomerase-specific p53 tumor suppressor gene overexpression in human scirrhous gastric cancer cells with different p53 status. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5338. doi:10.1158/1538-7445.AM2015-5338

Abstract 401: A novel photoimmunotherapy targeting cancer-associated fibroblasts (CAFs) overcomes therapeutic resistance in human esophageal cancer

Cancer associated fibroblasts (CAFs) are thought to play an essential role in cancer invasion, migration, metastasis and resistance to anticancer drugs. CAFs were originally defined as fibroblasts expressing α-SMA in cancer tissue; however, fibroblast activation protein (FAP) has been recently identified as a more functional and specific surface protein of CAFs. The photoimmunotherapy (PIT) is a new molecular targeted therapy, which is based on a near-infrared (NIR) photosensitizer IR700, conjugated to monoclonal antibody (mAb) targeting particular molecules. PIT induces the selective destruction of targeted cells. The aim of this study is to analyze the influence of CAFs on human esophageal cancer and to develop a novel therapeutic strategy to eliminate CAFs by using FAP-targeting PIT. We produced the IR700-FAP antibody for this study. Human esophageal cancer cell lines (TE-4 and OE-19) and FEF3 human fibroblasts were used in this study. TE-4 and OE-19 cells stimulated with conditioned medium (CM) of CAFs exhibited malignant phenotypes confirmed by invasion assay, migration assay, and colony formation assay. Tumor cells were significantly more malignant when directly co-cultured with CAFs. We further examined whether tumor cells stimulated by CM (CAFs) could acquire the resistance to chemotherapy or radiotherapy. Cell viability assay showed that tumor cells stimulated with CAFs was more resistant to conventional chemotherapy or radiation than unstimulated tumor cells. Western blot analysis demonstrated that E-cadherin expression was decreased and that of vimentin was increased in CAF-stimulated tumor cells, indicating the epithelial mesenchymal transition (EMT) induction. Moreover, OE-19 cells stimulated with CAFs contained more CD133-positive cancer stem-like cells. In vivo experiments demonstrated that subcutaneous TE4 tumors were more refractory to chemotherapy in the presence of co-inoculated CAFs as observed in vitro. Finally, we investigated whether elimination of CAFs by FAP-targeting PIT could affect the resistance to chemotherapy in vitro and in vivo. In vivo PIT following intratumoral anti-FAP mAb-conjugated IR700 suppressed the growth of subcutaneous tumors co-inoculated with CAFs. These results demonstrated that human tumor cells became more malignant and resistant in the presence of CAFs, which could be reversed by using CAF-specific PIT. Targeting fibroblast itself is a unique strategy and can be clinically promising as combination targeting cancer cells and their fundamental microenvironment.

Citation Format: Ryoichi Katsube, Kazuhiro Noma, Shinichiro Watanabe, Shinichi Urano, Takayuki Ninomiya, Toshiaki Ohara, Hiroshi Tazawa, Shunsuke Kagawa, Hisataka Kobayashi, Toshiyoshi Fujiwara. A novel photoimmunotherapy targeting cancer-associated fibroblasts (CAFs) overcomes therapeutic resistance in human esophageal cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 401. doi:10.1158/1538-7445.AM2015-401

Abstract 2368: Differentiated gastric cancer cells have a potential to induce cancer-associated fibroblasts

Gastric cancer is one of the most common causes of cancer death. Stromal fibroblasts in the tumor microenvironment have recently been implicated in tumor growth, invasion and metastasis. Cancer-associated fibroblasts (CAFs) have been suggested to be responsible for progression of undifferentiated scirrhous gastric cancers with vast fibrous stroma. However, the relationship between differentiated gastric cancer cells and CAFs in tumor progression remains unclear. In this study, we investigated whether differentiated and/or undifferentiated human gastric cancer cells induce CAFs. We used two differentiated human gastric cancer cells (MKN-7, MKN-74) and two undifferentiated human scirrhous gastric cancer cells (KATO-III, NUGC-4). Two types of human normal fibroblasts (WI-38, FEF-3) were used for induction of CAFs. The conditioned media (CM) from all cancer cells were obtained 48 hours after serum starvation. The morphological change and expression of CAF-specific markers (α-smooth muscle actin (α-SMA), fibroblast activation protein-α (FAP)) were analyzed by microscopy and Western blot analysis, respectively, in fibroblasts treated with CM for 120 hours. Moreover, the effect of CM from CAFs in the migration ability of cancer cells was evaluated using in vitro Migration assay. The CM from differentiated MKN-7 and MKN-74 cells induced the morphological change like CAFs in normal human fibroblasts, whereas CM from undifferentiated KATO-III and NUGU-4 cells did not induce. In fact, morphologically changed fibroblasts like CAFs showed increased α-SMA expression, whereas FAP expression was not increased. The CM from morphologically changed fibroblasts, but not normal fibroblasts, significantly enhanced the migration ability of MKN-7 cells. These results suggest that differentiated gastric cancer cells have a potential to induce CAFs in the invasion process of gastric cancers. CAF-targeting therapy may be a promising antitumor strategy in differentiated gastric cancers as well as undifferentiated scirrhous gastric cancers with vast fibrous stroma.

Citation Format: Yuncheng Li, Hiroshi Tazawa, Nishizaki Masahiko, Yuuri Hashimoto, Naoto Hori, Ryoichi Katsube, Shinji Kuroda, Kazuhiro Noma, Shunsuke Kagawa, Toshiyoshi Fujiwara. Differentiated gastric cancer cells have a potential to induce cancer-associated fibroblasts. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2368. doi:10.1158/1538-7445.AM2015-2368

Abstract 5520: HER2-targeted gold nanoparticles produce potent antitumor effects on human gastric cancer cells

Background: Antibody-targeted therapy for malignant tumors has been increasingly developed and applied to clinical practice in recent years. Trastuzumab (Tmab) is a humanized monoclonal antibody that binds to the human epidermal growth receptor 2 (HER2) and interferes with its signal transduction leading to tumor progression, and is currently used for patients with breast cancer and gastric cancer. In inoperable recurrent or metastatic gastric cancers, HER2 is reportedly overexpressed in approximately 20% of cases, and Tmab contributes to prolongation of survival for these patients at some level. However, there still remain some issues to be overcome such as limited application of Tmab (only 20%) and limited treatment options for these advanced gastric cancers. Recent progress in nanotechnology is remarkable and various nanomaterials have been developed for medical applications. Gold nanoparticles (AuNPs) have been tested as therapeutic and contrast agents in the medical field, which are stable in vivo and easy to conjugate antibodies, proteins or peptides to the surface. Moreover, reportedly AuNPs show antitumor effect by induction to autophagy and apoptosis. These characteristics make AuNPs more attractive as molecular targeted agents. In this study, we created HER2-targeted AuNPs by conjugating Tmab on the surface of AuNPs, and examined antitumor effects on HER2-positive or negative gastric cancer cells in vitro.

Methods: HER2-positive human gastric cancer cell lines (MKN7, NBI-N87), HER2-negative human gastric cancer cell lines (MKN45, MKN74) and normal human lung fibroblast (NHLF) were used in this study. The antitumor effects of Tmab-conjugated AuNPs (Tmab-AuNPs), PEGylated AuNPs (PEG-AuNPs), Tmab only (antibody amount is presumably equivalent to antibody attached on the surface of Tmab-AuNPs), mixture of PEG-AuNPs and Tmab (PEG-AuNPs + Tmab), and PBS were evaluated by XTT assay. Cellular uptake of AuNPs was observed on dark field microscopy and electron microscopy. HER2 expression was examined by western blotting and flow cytometry.

Results: Dark field microscopy and electron microscopy showed that Tmab-AuNPs were taken up into cells more effectively on MKN7 and NBI-N87 cells (HER2-positive) than PEG-AuNPs and PEG-AuNPs + Tmab. XTT assay showed that Tmab-AuNPs exhibited a stronger antitumor effect on MKN7 and NBI-N87 cells (HER2-positive) than the other control treatments, but not such a strong effect on MKN45 and MKN74 cells (HER2-negative) and NHLF. The antitumor effect of Tmab-AuNPs on NBI-N87 cells was achieved by more than twice as much as Tmab, which means that Tmab-AuNPs enables to reduce the amount of Tmab to less than half.

Conclusions: Tmab-AuNPs proved potent and HER2-dependent antitumor effects on human gastric cancer cells in vitro. Tmab-AuNPs could have the potential to provide more effective and less toxic treatment option for HER2-positive gastric cancer patients.

Citation Format: Tetsushi Kubota, Shinji Kuroda, Katsuyuki Aoyama, Hiroshi Tazawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. HER2-targeted gold nanoparticles produce potent antitumor effects on human gastric cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5520. doi:10.1158/1538-7445.AM2015-5520

Abstract 3531: Companion diagnostics-based telomerase-specific oncolytic virotherapy: preclinical evaluation in human colorectal cancer cell lines differentially affected in the RAS/RAF/MEK signaling pathway

Colorectal cancers harboring KRAS or BRAF mutations often show resistance to anti-cancer drugs, and are poor prognostic disease that causes metastasis and recurrence compared to those with wild type KRAS and BRAF. KRAS/BRAF-wild type colorectal cancers are sensitive to both cetuximab and panitumumab that are epidermal growth factor receptor (EGFR)-targeting agents. However, KRAS/BRAF-mutant colorectal cancers are resistant to EGFR-targeting agents because of constitutive activation of the EGFR-downstream RAS/RAF/MEK signaling pathway. Therefore, the development of novel therapeutic strategy is required to improve the clinical outcome in patients with KRAS/BRAF-mutant colorectal cancers. We developed two types of telomerase-specific replication-competent oncolytic adenoviruses, OBP-301 and OBP-702 armed with the wild-type p53 tumor suppressor gene. In this study, we established the companion diagnostics-based selection algorithm for our oncolytic viruses. We compared the antitumor effects of OBP-301 and OBP-702 in human colorectal cancer cells with wild type KRAS/BRAF (SW48, Colo320DM), mutated KRAS (DLD-1, SW620) and mutated BRAF (RKO, HT29). We evaluated the antitumor effect of OBP-301 and OBP-702 in human colorectal cancer cells using XTT assay. Oncolytic adenovirus-mediated induction of apoptosis- and autophagy-related cell death was analyzed by Western blot analysis. KRAS-mutant colorectal cancer cells were sensitive to both OBP-301 and OBP-702 as well as KRAS/BRAF-wild type cells. In contrast, BRAF-mutant colorectal cancer cells were sensitive to OBP-702 rather than OBP-301. Western blot analysis showed that OBP-301 induced autophagy, whereas OBP-702 induced both autophagy and apoptosis. Taken together, our data suggest that oncolytic viruses should be used according to the genetic background of the RAS/RAF/MEK signaling pathway, especially in patients with colorectal cancer.

Citation Format: Shuta Tamura, Hiroshi Tazawa, Naoto Hori, Takeshi Koujima, Satoru Kikuchi, Shinji Kuroda, Hiroyuki Kishimoto, Takeshi Nagasaka, Masahiko Nishizaki, Yasuo Urata, Shunsuke Kagawa, Toshiyoshi Fujiwara. Companion diagnostics-based telomerase-specific oncolytic virotherapy: preclinical evaluation in human colorectal cancer cell lines differentially affected in the RAS/RAF/MEK signaling pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3531. doi:10.1158/1538-7445.AM2015-3531

Abstract CT123: Phase I/II trial of endoscopic intratumoral administration of OBP-301, a novel telomerase-specific oncolytic virus, with radiation in elderly esophageal cancer patients

Background: Telomerase activation is considered to be a critical step in carcinogenesis and its activity is closely correlated with human telomerase reverse transcriptase (hTERT) expression. We constructed an adenovirus 5 vector OBP-301 (Telomelysin), in which the hTERT promoter drives expression of E1A and E1B genes. OBP-301 causes selective replication and lysis of a variety of human cancer cells, and also inhibits the repair of radiation-induced DNA double-strand breaks, leading to radiosensitization. A phase I study has confirmed the safety and biological activity of intratumoral administration of OBP-301 alone in patients with advanced solid tumors in the United States. To further determine the feasibility, efficacy, and pharmacokinetics of OBP-301 in combination with radiotherapy, a phase I/II study was designed in elderly patients with esophageal cancer.

Methods: Patients with histologically confirmed esophageal cancer who were not eligible for standard treatments such as surgery and chemotherapy were enrolled into this study (UMIN000010158). Study treatment consisted of intratumoral needle injections of OBP-301 on days 1, 18, and 32 of treatment. Radiation therapy was administered concurrently over 6 weeks, beginning on day 4, to a total of 60 Gy. Virus administration was performed by intratumoral injection of the primary or metastatic tumor through a flexible endoscope. OBP-301 doses will be escalated initially in cohorts of two for the first 9 patients (1 × 10e10 and 1 × 10e11 virus particles [vp]). Six subsequent patients will receive the highest dose (1 × 10e12 vp). Virus shedding will be monitored in the saliva, sputum, urine, and plasma by a quantitative DNA-PCR assay.

Results: Six patients were enrolled and treated in the cohort with 1 × 10e10 vp of OBP-301. The patients comprised 4 males and 2 females, with median age of 83.5 years (range, 68 to 92 years). Only two patients had prior platinum-based chemotherapy. By November 2014, 3 patients completed treatment. All patients developed a transient, self-limited lymphopenia. A 92-year-old female showed a grade 4 lymphopenia classified as being possibly related to the treatment, although it recovered by the interruption of radiation. No other virus-related toxicities were noted. Objective responses were complete response (CR) in 2 patients and partial response (PR) with tumor regression, resulting in reopening of the esophagus, in 1 patient. Pathological analysis in biopsy specimens obtained from completely responded patients demonstrated no viable malignant cells for 3 to 5 months after the treatment completion.

Conclusions: Multiple courses of endoscopic OBP-301 injection in combination with locoregional radiotherapy were feasible and well tolerated in elderly patients with esophageal cancer, and appeared to provide clinical benefit.

Citation Format: Shunsuke Tanabe, Hiroshi Tazawa, Shunsuke Kagawa, Kazuhiro Noma, Kiyoto Takehara, Takeshi Koujima, Hajime Kashima, Takuya Kato, Shinji Kuroda, Satoru Kikuchi, Yasuhiro Shirakawa, Toshiyoshi Fujiwara. Phase I/II trial of endoscopic intratumoral administration of OBP-301, a novel telomerase-specific oncolytic virus, with radiation in elderly esophageal cancer patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT123. doi:10.1158/1538-7445.AM2015-CT123

Abstract 3412: Virus-guided fluorescence imaging of intraperitoneal free gastric cancer cells: a preliminary clinical study as a potential clinical biomarker

Objectives: In patients with gastric cancer, peritoneal dissemination is the most common metastasis. To predict future peritoneal recurrences, peritoneal lavage cytology is performed during operation. But even cytology-negative patients sometimes develop peritoneal recurrences. Thus an additional method to detect intraperitoneal free gastric cancer cells is necessary. We have developed a genetically engineered adenovirus, TelomeScan, which replicates and expresses GFP only in telomerase-activated cancer cells. Here we detected intraperitoneal free gastric cancer cells using TelomeScan, and investigated the correlation between the number of GFP-positive cells and patient prognosis.

Methods: Peritoneal wash was obtained from 69 gastric cancer patients during operation. The cells in the wash were infected with TelomeScan for 24 hours. Finally, GFP-positive cells were counted under a fluorescence microscope. In some GFP-positive cases immunofluorescence assay was added. Clinicopathological data were obtained from medical records. Then we examined different cut-off values (the number of GFP-positive cells which indicates TelomeScan-positive) and estimated survival curves using the Kaplan-Meier method, and compared using the Wilcoxon test.

Results: For a cut-off value of 10, 25 of the 69 cases were TelomeScan-positive (10 or more GFP-positive cells). And these 25 cases showed the most significant worse prognosis when compared to the 44 TelomeScan-negative cases (p = 0.0040). In addition, 17 of the 69 cases were conventional cytology-positive. Of these 17 cases, 9 were TelomeScan-positive, and these 9 cases showed significantly worse prognosis than the 8 TelomeScan-negative conventional cytology-positive cases (p = 0.0017, MST 195 days). Under fluorescence microscope we observed that GFP-positive cells sometimes formed cell clusters with GFP-negative cells. Immunofluorescence assay showed that these GFP-negative cells expressed CD45, which means these cells were leukocytes.

Conclusion: We have successfully detected cancer cells in peritoneal wash using TelomeScan. The presence of GFP-positive cells in peritoneal wash was associated with worse prognosis. TelomeScan-positive patients, especially in conventional cytology-positive cases, showed remarkably worse prognosis than TelomeScan-negative conventional cytology-positive patients. Our data suggest that TelomeScan-guided cytological detection may have clinical implications as a prognostic biomarker in gastric cancer.

Citation Format: Megumi Watanabe, Shunsuke Kagawa, Kazuya Kuwata, Michihiro Ishida, Yuuri Hashimoto, Naoto Hori, Satoru Kikuchi, Shinji Kuroda, Hiroyuki Kishimoto, Masahiko Nishizaki, Hiroshi Tazawa, Yasuo Urata, Toshiyoshi Fujiwara. Virus-guided fluorescence imaging of intraperitoneal free gastric cancer cells: a preliminary clinical study as a potential clinical biomarker. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3412. doi:10.1158/1538-7445.AM2015-3412

Genetic and epigenetic alterations of netrin-1 receptors in gastric cancer with chromosomal instability

Background

The gene expressions of netrin-1 dependence receptors, DCC and UNC5C, are frequently downregulated in many cancers. We hypothesized that downregulation of DCC and UNC5C has an important growth regulatory function in gastric tumorigenesis.

Results

In the present study, a series of genetic and epigenetic analyses for DCC and UNC5C were performed in a Japanese cohort of 98 sporadic gastric cancers and corresponding normal gastric mucosa specimens. Loss of heterozygosity (LOH) analyses and microsatellite instability (MSI) analysis was applied to determine chromosomal instability (CIN) and MSI phenotypes, respectively. More than 5 % methylation in the DCC and UNC5C promoters were found in 45 % (44/98) and 32 % (31/98) gastric cancers, respectively, and in 9 % (9/105) and 5 % (5/105) normal gastric mucosa, respectively. Overall, 70 % (58 of 83 informative cases) and 51 % (40 of 79 informative cases) of gastric cancers harbored either LOH or aberrant methylation in the DCC and UNC5C genes, respectively. In total, 77 % (51 of 66 informative cases) of gastric cancers showed cumulative defects in these two dependence receptors and were significantly associated with chromosomal instability. Both DCC and UNC5C were inactivated in 97 % of CIN-positive gastric cancers and in 55 % of CIN-negative gastric cancers.

Conclusions

Defect in netrin receptors is a common feature in gastric cancers. DCC alterations are apparent in the early stages, and UNC5C alterations escalate with the progression of the disease, suggesting that the cumulative alterations of netrin-1 receptors was a late event in gastric cancer progression and emphasizing the importance of this growth regulatory pathway in gastric carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0096-y) contains supplementary material, which is available to authorized users.

Color-coding cancer and stromal cells with genetic reporters in a patient-derived orthotopic xenograft (PDOX) model of pancreatic cancer enhances fluorescence-guided surgery

Precise fluorescence-guided surgery (FGS) for pancreatic cancer has the potential to greatly improve the outcome in this recalcitrant disease. To achieve this goal, we have used genetic reporters to color code cancer and stroma cells in a patient-derived orthotopic xenograft (PDOX) model. The telomerase-dependent green fluorescent protein (GFP)-containing adenovirus OBP-401 was used to label the cancer cells of a pancreatic cancer PDOX. The PDOX was previously grown in a red fluorescent protein (RFP) transgenic mouse that stably labeled the PDOX stroma cells bright red. The color-coded PDOX model enabled FGS to completely resect the pancreatic tumors including stroma. Dual-colored FGS significantly prevented local recurrence, which bright-light surgery or single-color FGS could not. FGS, with color-coded cancer and stroma cells has important potential for improving the outcome of recalcitrant-cancer surgery.

Prone-Position Thoracoscopic Ligation of the Thoracic Duct for Chyle Leak Following Radical Neck Dissection in a Patient with a Right Aortic Arch

A chyle leak can occur as a complication after neck or chest surgery. Such a leak prolongs the hospital stay and is sometimes life-threatening. The treatment options are conservative management, interventional radiologic embolization, and surgery. Thoracoscopic ligation of the thoracic duct has emerged as a promising and definitive treatment. The case of a 65-year-old Japanese male patient with a rare congenital right aortic arch (typeⅢB1 of Edward's classification) and a severe chyle leak that occurred after a total pharyngolaryngo-esophagectomy (TPLE) is described. The chyle leak was successfully managed by thoracoscopic ligation of the thoracic duct via a left-side approach with the patient in the prone position.

Targeting tumors with a killer-reporter adenovirus for curative fluorescence-guided surgery of soft-tissue sarcoma

Fluorescence-guided surgery (FGS) of cancer is an area of intense interest. However, FGS of cancer has not yet been shown to be curative due to residual microscopic disease. Human fibrosarcoma HT1080 expressing red fluorescent protein (RFP) was implanted orthotopically in the quadriceps femoris muscle of nude mice. The tumor-bearing mice were injected with high and low-dose telomerase-dependent, green fluorescent protein (GFP)-containing adenovirus OBP-401, which labeled the tumor with GFP. Fluorescence-guided surgery (FGS) or bright light surgery (BLS) was then performed. OBP-401 could label soft-tissue sarcoma (STS) with GFP in situ, concordant with RFP. OBP-401-based FGS resulted in superior resection of STS in the orthotopic model of soft-tissue sarcoma, compared to BLS. High-dose administration of OBP-401 enabled FGS without residual sarcoma cells or local or metastatic recurrence, due to its dual effect of cancer-cell labeling with GFP and killing. High-dose OBP-401 based-FGS improved disease free survival (p = 0.00049) as well as preserved muscle function compared with BLS. High-dose OBP-401-based FGS could cure STS, a presently incurable disease. Since the parent virus of OBP-401, OBP-301, has been previously proven safe in a Phase I clinical trial, it is expected the OBP-401-FGS technology described in the present report should be translatable to the clinic in the near future.

Fluorescence virus-guided capturing system of human colorectal circulating tumour cells for non-invasive companion diagnostics

BACKGROUND

Molecular-based companion diagnostic tests are being used with increasing frequency to predict their clinical response to various drugs, particularly for molecularly targeted drugs. However, invasive procedures are typically required to obtain tissues for this analysis. Circulating tumour cells (CTCs) are novel biomarkers that can be used for the prediction of disease progression and are also important surrogate sources of cancer cells. Because current CTC detection strategies mainly depend on epithelial cell-surface markers, the presence of heterogeneous populations of CTCs with epithelial and/or mesenchymal characteristics may pose obstacles to the detection of CTCs.

METHODS

We developed a new approach to capture live CTCs among millions of peripheral blood leukocytes using a green fluorescent protein (GFP)-expressing attenuated adenovirus, in which the telomerase promoter regulates viral replication (OBP-401, TelomeScan).

RESULTS

Our biological capturing system can image epithelial and mesenchymal tumour cells with telomerase activities as GFP-positive cells. After sorting, direct sequencing or mutation-specific PCR can precisely detect different mutations in KRAS, BRAF and KIT genes in epithelial, mesenchymal or epithelial-mesenchymal transition-induced CTCs, and in clinical blood samples from patients with colorectal cancer.

CONCLUSIONS

This fluorescence virus-guided viable CTC capturing method provides a non-invasive alternative to tissue biopsy or surgical resection of primary tumours for companion diagnostics.

Feasibility of oral administration of S-1 as adjuvant chemotherapy in gastric cancer: 4-week S-1 administration followed by 2-week rest vs. 2-week administration followed by 1-week rest

In 2006, the Adjuvant Chemotherapy Trial of S-1 for Gastric Cancer (ACTS-GC) demonstrated that S-1 is an effective adjuvant therapy for gastric cancer. Following that study, S-1 has been used as the standard adjuvant therapy for gastric cancer in Japan. However, the 1-year completion rate was only 65.8% in the ACTS-GC study and feasibility remains a critical issue. We conducted a study to evaluate the feasibility of 2 weekly administration regimens of S-1 as adjuvant chemotherapy in gastric cancer. The criteria for eligibility included histologically proven stage II (excluding T1), IIIA or IIIB gastric cancer with D2 lymph-node dissection. The patients were randomly assigned to either arm A (S-1 administration for 4 weeks followed by 2 weeks of rest) or arm B (S-1 administration for 2 weeks followed by 1 week of rest). In each arm, treatment was continued for 12 months unless recurrence or severe adverse events were observed. The primary endpoint was feasibility (protocol treatment completion rate). The secondary endpoints were safety, relapse-free survival and overall survival. A total of 47 patients were assigned to arms A or B between May, 2008 and February, 2010. During the first interim analysis, the protocol treatment completion rates in arms A and B were 83 and 100%, respectively at 6 months and 49 and 89%, respectively, at 12 months (P=0.0046). Therefore, S-1 administration for 2 weeks followed by 1 week rest was more feasible as adjuvant chemotherapy in gastric cancer. Grade 3 adverse events in arm A included fatigue (8.0%), anorexia (8.0%), nausea (4.0%), vomiting (4.0%) and hand-foot syndrome (4.0%), whereas none were observed in arm B. There were no reported grade 4 adverse events in either arm. In conclusion, the 2-week S-1 administration followed by 1-week rest regimen appears to be a more feasible oral administration regimen for S-1 as adjuvant chemotherapy in gastric cancer.

Clinical Significance of MLH1 Methylation and CpG Island Methylator Phenotype as Prognostic Markers in Patients with Gastric Cancer

BACKGROUND

To improve the outcome of patients suffering from gastric cancer, a better understanding of underlying genetic and epigenetic events in this malignancy is required. Although CpG island methylator phenotype (CIMP) and microsatellite instability (MSI) have been shown to play pivotal roles in gastric cancer pathogenesis, the clinical significance of these events on survival outcomes in patients with gastric cancer remains unknown.

METHODS

This study included a patient cohort with pathologically confirmed gastric cancer who had surgical resections. A cohort of 68 gastric cancers was analyzed. CIMP and MSI statuses were determined by analyzing promoter CpG island methylation status of 28 genes/loci, and genomic instability at 10 microsatellite markers, respectively. A Cox's proportional hazards model was performed for multivariate analysis including age, stage, tumor differentiation, KRAS mutation status, and combined CIMP/MLH1 methylation status in relation to overall survival (OS).

RESULTS

By multivariate analysis, longer OS was significantly correlated with lower pathologic stage (P = 0.0088), better tumor differentiation (P = 0.0267) and CIMP-high and MLH1 3' methylated status (P = 0.0312). Stratification of CIMP status with regards to MLH1 methylation status further enabled prediction of gastric cancer prognosis.

CONCLUSIONS

CIMP and/or MLH1 methylation status may have a potential to be prognostic biomarkers for patients with gastric cancer.

Molecular diagnosis and therapy for occult peritoneal metastasis in gastric cancer patients

To apply an individualized oncological approach to gastric cancer patients, the accurate diagnosis of disease entities is required. Peritoneal metastasis is the most frequent mode of metastasis in gastric cancer, and the tumor-node-metastasis classification includes cytological detection of intraperitoneal cancer cells as part of the staging process, denoting metastatic disease. The accuracy of cytological diagnosis leaves room for improvement; therefore, highly sensitive molecular diagnostics, such as an enzyme immunoassay, reverse transcription polymerase chain reaction, and virus-guided imaging, have been developed to detect minute cancer cells in the peritoneal cavity. Molecular targeting therapy has also been spun off from basic research in the past decade. Although conventional cytology is still the mainstay, novel approaches could serve as practical complementary diagnostics to cytology in near future.

[Pathological complete response in a case of advanced gastric cancer after neoadjuvant chemotherapy]

A 6 2-year-old man with advanced gastric cancer was referred to our hospital. A gastroscopy revealed a type 3 tumor invading the esophagus in the lesser curvature of the stomach cardia. We diagnosed the tumor as cStageIIIB(T4bN1M0) gastric cancer. For the best chance of a pathological complete response, we selected neoadjuvant chemotherapy (NAC) with S-1+CDDP (SP therapy). A total gastrectomy with lymph node dissection was performed after 2 courses of SP therapy. Pathological evaluation of the resected stomach and lymph nodes indicated an absence of cancerous cells, confirming a pathological complete response (pCR). The patient has been followed up for 4 months without evidence of recurrence.

[Two cases of Stage IV Gastric cancer responding to chemotherapy and leading to pathological complete response]

Case 1: A 76-year-old man presented with advanced gastric cancer in the esophagogastric junction with para-aortic lymph node metastasis (HER2 positive cT4N1M1 [LYM], cStage IV). After 3 courses of chemotherapy consisting of S-1+docetaxel +trastuzumab were completed, we performed surgery. No cancer cells were revealed during histopathological examination, indicating pathological complete response (pCR). At present, 12 months after treatment, the patient is well, with no signs of recurrence. Case 2: A 74-year-old man presented with advanced gastric cancer with peritoneal metastasis (cT4b[Panc] N1M1[P], cStage IV). After 2 courses of chemotherapy consisting of S-1+CDDP were completed, we performed surgery. Histopathological examination revealed no cancer cells, indicating pCR. At present, 13 months after treatment, the patient is incident-free, with no signs of recurrence.

Abstract 4726: Virus-guided fluorescence imaging of intraperitoneal free gastric cancer cells as a potential clinical biomarker

Peritoneal dissemination is a common pattern of metastasis in patients with gastric cancer, and associated with worse prognosis. Peritoneal lavage cytology during the operation is an important factor in predicting future development of peritoneal metastasis and determining the treatment strategy, but its sensitivity and specificity are unsatisfactory. TelomeScan is an adenovirus engineered to replicate and express GFP only in telomerase-activating tumor cells, so that we can easily detect viable cancer cells even among numerous normal cells. We hypothesized that TelomeScan might be applicable to detecting free cancer cells in peritoneal wash. Methods: Peritoneal washes were obtained from 42 gastric cancer patients during operation. The number of GFP-positive cells was determined for each sample and compared with cytology results and clinicopathological data Results: Clinical stage was ranged from IA to IV, and thirteen cases were diagnosed as class IV or class V by peritoneal lavage cytology. More than 10 GFP-positive cells were detected in 12 out of 42 cases, and these cases showed a worse prognosis when compared to the other 30 cases. Conclusion: We were able to detect gastric cancer cells as GFP-positive cells in peritoneal wash using TelomeScan. Furthermore, the presence of GFP-positive cells in peritoneal wash was associated with worse prognosis. These results suggest that number of cancer cells detected by TelomeScan in the peritoneal wash may have important clinical implication as prognostic and therapeutic biomarkers in gastric cancer.

Citation Format: Megumi Watanabe, Shunsuke Kagawa, Michihiro Ishida, Naoto Hori, Satoru Kikuchi, Shinji Kuroda, Hiroyuki Kishimoto, Masahiko Nishizaki, Hiroshi Tazawa, Toshiyoshi Fujiwara. Virus-guided fluorescence imaging of intraperitoneal free gastric cancer cells as a potential clinical biomarker. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4726. doi:10.1158/1538-7445.AM2014-4726

Abstract 4025: Combination strategy of endoscopic resection and telomerase-targeting oncolytic virus for eradicating lymph node metastasis of submucosal invasive colorectal cancer

Endoscopic resection is now one of the options as minimally invasive therapy for early colorectal cancer, However, surgical resection has been still standard for submucosal invasive colorectal cancer, because about 10% of that have LN metastasis. To secure endoscopic resection for submucosal invasive colorectal cancer, an alternative, innovational strategy to purge potential LN metastasis is required. We previously reported that a telomerase-dependent oncolytic adenovirus (OBP-301) spreads to the regional LNs, selectively replicates, and eradicates metastatic cancer cells in LNs, when administered into the orthotopically xenotransplanted rectal tumor in mouse model. In this study we evaluated whether OBP-301 could inhibit LN metastasis after the local resection mimicking endoscopic resection in a submucosal invasive rectal tumor mouse model. Human colon cancer HCT-116 cells expressing green fluorescent protein (GFP) were orthotopically implanted into the submucosal layer of the rectum in nude mouse, to develop resultant rectal tumor mimicking submucosal invasive one. LN metastasis was observed in 78.5% of mice as early as 7 days after cancer cell inoculation. The rectal tumor was injected with OBP-301 peritumorally, and then got locally excised mimicking Endoscopic submucosal dissection (ESD) technique. Seven days after tumor resection, the treatment with OBP-301 showed a significant inhibition in LN metastasis, whereas the other control treatment did not. Moreover, LN metastatic recurrence was not detected in OBP-301-treated group even 4 weeks after tumor resection. Similar results were also observed in another model with human colon cancer Colo-205-GFP cells. These results suggest that a novel combination of ESD and OBP-301 might have potential to take place of the conventional surgical approach in treating submucosal invasive colorectal cancer.

Citation Format: Naoto Hori, Satoru Kikuchi, Hiroyuki Kishimoto, Hiroshi Tazawa, Yuuri Hashimoto, Shinji Kuroda, Shunsuke Kagawa, Yasuo Urata, Robert M. Hoffman, Toshiyoshi Fujiwara. Combination strategy of endoscopic resection and telomerase-targeting oncolytic virus for eradicating lymph node metastasis of submucosal invasive colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4025. doi:10.1158/1538-7445.AM2014-4025

Abstract 719: Development of systemically-deliverable telomerase-specific oncolytic adenovirus

Background: Oncolytic virotherapy is an emerging treatment strategy that allows to destroy cancer tissues only but not normal tissues. We previously developed a telomerase-specific oncolytic adenovirus (Telomelysin) whose replication is controlled by the human telomerase reverse tran¬scriptase (hTERT) promoter, and the clinical safety and pharmacokinetics of Telomelysin has been already evaluated in the phase I clinical trial conducted in the US. While oncolytic adenoviruses can produce promising treatment efficacy, their application is basically limited to locoregional administration because of nonspecific trapping in the liver and neutralization by immune response after systemic delivery. Nano-sized materials have been identified as effective and attractive drug carriers in the fields of cancer treatment and diagnosis. Liposome is one of the most popular and widely-used drug carriers. In this study, we investigated the possibility of systemic delivery of telomerase-specific oncolytic adenoviral plasmid DNA via lipid encapsulation as an alternative approach to overcome the shortcomings of oncolytic adenovirotherapy.

Methods: TelomeScan, a modified Telomelysin expressing the green fluorescence protein (GFP), is used in this study. Cytotoxic activity of TelomeScan plasmid DNAs encapsulated by liposomes (Lipo-TelomeScan-pDNA) against various types of human cancer cell lines including HCT 116, a human colorectal carcinoma cell line, and MKN1, a human gastric carcinoma cell line, were evaluated by XTT assay and compared with liposome complexes of GFP plasmid DNA controlled by the cytomegalovirus (CMV) promoter (Lipo-GFP-pDNA) as a control agent.

Results: Freeze-thaw procedure proved that viable oncolytic adenoviruses were successfully produced in H1299, a human lung cancer cell line, after Lipo-TelomeScan-pDNA transfection. Lipo-TelomeScan-pDNA showed cytotoxic activity on various types of cancer cell lines. Lipo-TelomeScan-pDNA killed HCT116 and MKN1 cells in a dose-dependent manner and produced more effective cytotoxic activity than Lipo-GFP-pDNA.

Conclusions: Lipo-TelomeScan-pDNA proved potent cytotoxic effects on cancer cells by producing viable oncolytic adenoviruses. In vivo examination is needed for the next step.

Citation Format: Katsuyuki Aoyama, Shinji Kuroda, Hiroshi Tazawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. Development of systemically-deliverable telomerase-specific oncolytic adenovirus. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 719. doi:10.1158/1538-7445.AM2014-719

Oncolytic adenovirus-induced autophagy: tumor-suppressive effect and molecular basis

Autophagy is a catabolic process that produces energy through lysosomal degradation of intracellular organelles. Autophagy functions as a cytoprotective factor under physiological conditions such as nutrient deprivation, hypoxia, and interruption of growth factors. On the other hand, infection with pathogenic viruses and bacteria also induces autophagy in infected cells. Oncolytic virotherapy with replication-competent viruses is thus a promising strategy to induce tumor-specific cell death. Oncolytic adenoviruses induce autophagy and subsequently contribute to cell death rather than cell survival in tumor cells. We previously developed a telomerase-specific replication-competent oncolytic adenovirus, OBP-301, which induces cell lysis in tumor cells with telomerase activities. OBP-301-mediated cytopathic activity is significantly associated with induction of autophagy biomarkers. In this review, we focus on the tumor-suppressive role and molecular basis of autophagic machinery induced by oncolytic adenoviruses. Addition of tumor-specific promoters and modification of the fiber knob of adenoviruses supports the oncolytic adenovirus-mediated autophagic cell death. Autophagy is cooperatively regulated by the E1-dependent activation pathway, E4-dependent inhibitory pathway, and microRNA-dependent fine-tuning. Thus, future exploration of the functional role and molecular mechanisms underlying oncolytic adenovirus-induced autophagy would provide novel insights and improve the therapeutic potential of oncolytic adenoviruses.

Advances in adenovirus-mediated p53 cancer gene therapy

INTRODUCTION

The tumor suppressor p53 gene regulates diverse cellular processes, such as cell-cycle arrest, senescence, apoptosis and autophagy, and it is frequently inactivated by genetic alterations in ∼ 50% of all types of human cancers. To restore wild-type p53 function in p53-inactivated tumors, adenovirus-mediated p53 gene therapy has been developed as a promising antitumor strategy in preclinical experiments and clinical studies.

AREAS COVERED

This review focuses on the clinical relevance of replication-deficient adenovirus vectors that carry the wild-type p53 gene (Ad-p53; Advexin, Gendicine and SCH-58500) in clinical studies of patients with various cancers and the future perspectives regarding conditionally replicating adenovirus vectors expressing the wild-type p53 gene (CRAd-p53; AdDelta24-p53, SG600-p53, OBP-702) in preclinical experiments. Moreover, the recent advances in our understanding of the molecular basis for the p53-mediated tumor suppression network induced by Ad-p53 and CRAd-p53 vectors and the combination therapies for promoting the therapeutic potential of adenovirus-mediated p53 gene therapy are discussed.

EXPERT OPINION

Exploration of the molecular mechanism underlying the p53-mediated tumor suppression network and the effective strategy for enhancing the p53-mediated cell death signaling pathway would provide novel insights into the improvement of clinical outcome in p53-based cancer gene therapy.

Effects of escitalopram on plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, in Japanese patients

INTRODUCTION

The effects of escitalopram (10 mg/d) coadministration on plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, were studied in 13 Japanese psychiatric patients and compared with those of paroxetine (10 mg/d) coadministration.

METHODS

The patients had received 6-24 mg/d of aripiprazole for at least 2 weeks. Patients were randomly allocated to one of 2 treatment sequences: paroxetine-escitalopram (n=6) or escitalopram-paroxetine (n=7). Each sequence consisted of two 2-week phases. Plasma concentrations of aripiprazole and dehydroaripiprazole were measured using liquid chromatography with mass spectrometric detection.

RESULTS

Plasma concentrations of aripiprazole and the sum of aripiprazole and dehydroaripiprazole during paroxetine coadministration were 1.7-fold (95% confidence intervals [CI], 1.3-2.1, p<0.001) and 1.5-fold (95% CI 1.2-1.9, p<0.01) higher than those values before the coadministration. These values were not influenced by escitalopram coadministration (1.3-fold, 95% CI 1.1-1.5 and 1.3-fold, 95% CI 1.0-1.5). Plasma dehydroaripiprazole concentrations remained constant during the study.

CONCLUSION

The present study suggests that low doses of escitalopram can be safely coadministered with aripiprazole, at least from a pharmacokinetic point of view.

A genetically engineered oncolytic adenovirus decoys and lethally traps quiescent cancer stem-like cells in S/G2/M phases

PURPOSE

Because chemoradiotherapy selectively targets proliferating cancer cells, quiescent cancer stem-like cells are resistant. Mobilization of the cell cycle in quiescent leukemia stem cells sensitizes them to cell death signals. However, it is unclear that mobilization of the cell cycle can eliminate quiescent cancer stem-like cells in solid cancers. Thus, we explored the use of a genetically-engineered telomerase-specific oncolytic adenovirus, OBP-301, to mobilize the cell cycle and kill quiescent cancer stem-like cells.

EXPERIMENTAL DESIGN

We established CD133(+) cancer stem-like cells from human gastric cancer MKN45 and MKN7 cells. We investigated the efficacy of OBP-301 against quiescent cancer stem-like cells. We visualized the treatment dynamics of OBP-301 killing of quiescent cancer stem-like cells in dormant tumor spheres and xenografts using a fluorescent ubiquitination cell-cycle indicator (FUCCI).

RESULTS

CD133(+) gastric cancer cells had stemness properties. OBP-301 efficiently killed CD133(+) cancer stem-like cells resistant to chemoradiotherapy. OBP-301 induced cell-cycle mobilization from G0-G1 to S/G2/M phases and subsequent cell death in quiescent CD133(+) cancer stem-like cells by mobilizing cell-cycle-related proteins. FUCCI enabled visualization of quiescent CD133(+) cancer stem-like cells and proliferating CD133(-) non-cancer stem-like cells. Three-dimensional visualization of the cell-cycle behavior in tumor spheres showed that CD133(+) cancer stem-like cells maintained stemness by remaining in G0-G1 phase. We showed that OBP-301 mobilized quiescent cancer stem-like cells in tumor spheres and xenografts into S/G2/M phases where they lost viability and cancer stem-like cell properties and became chemosensitive.

CONCLUSION

Oncolytic adenoviral infection is an effective mechanism of cancer cell killing in solid cancer and can be a new therapeutic paradigm to eliminate quiescent cancer stem-like cells.

Abstract 3298: Neotargeting HER2 negative cancer cells with Trastuzumab-based photoimmunotherapy by viral transduction of HER2-extracellular domain

The prognosis of HER2 positive breast cancer has been improved by Trastuzumab which features high specificity and limited side effects. Numerous randomized trials have confirmed the efficacy and safety of Trastuzumab in HER2-overexpressing cancers. However, many patients who initially respond to Trastuzumab ultimately develop disease progression. Strategies to overcome Trastuzumab-refractory cancer are sought, and drug-conjugation is one of candidates. Trastuzumab-IR700 which is Trastuzumab conjugated with a near-infrared (NIR) photosensitizer, phthalocyanine dye, IR700, has recently been developed as a new type of molecular-target photoimmunotherapy(PIT). This PIT can induce target-selective necrotic cell death only at the place which have Trastuzumab's target part and where exposure of NIR light. Disappointingly, HER2-targeting therapy is applicable to only Her2-expressig tumors which consist of approximately 20-25% of primary breast cancers. In previous study, we developed the adenoviral vector to express HER2-extracellular domain (HER2-ECD), Ad/HER-ECD, and confirmed that it efficiently induced HER2 expression for HER2 negative and HER2-downregulated human cancer cells. So, we hypothesized that Ad/HER-ECD expand the range of tumor entities suitable for Trastuzumab-based PIT. By using Ad/HER-ECD and Trastuzumab-IR700 with PIT we revealed that the direct cell membrane destruction are induced at HER2 negative cancer cells, similarly at HER2 positive cancer cells, in vitro. These results suggest that combination of virally-transduction of target antigen and an antibody-based PIT would expand and potentiate target therapy even for target-negative or attenuated cancer cells.

Citation Format: Michihiro Ishida, Shunsuke Kagawa, Kyoko Shimoyama, Shinichiro Watamabe, Kazuhiro Noma, Hiroshi Tazawa, Yuuri Hashimoto, Junji Matsuoka, Hisataka Kobayashi, Toshiyoshi Fujiwara. Neotargeting HER2 negative cancer cells with Trastuzumab-based photoimmunotherapy by viral transduction of HER2-extracellular domain. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3298. doi:10.1158/1538-7445.AM2013-3298

Abstract 1570: Novel strategy for eradicating lymph node metastasis of early-stage colorectal cancers using telomerase-dependent replicating adenoviral agent

One of the biggest challenges in endoscopic therapeutic approach for early colorectal cancer with submucosal invasion is how to treat regional lymph nodes (LNs) possibly metastasized. The rate of LN metastasis in submucosal invasive colorectal cancer are estimated approximately 10%. Since endoscopic treatment can't clean LNs outside the bowel physically, open or laparoscopic surgical treatment is still gold standard for submucosal invasive colorectal cancer. We previously reported that in an orthotopic rectal tumor mouse model, a telomerase-dependent tumor killing adenoviral agent (OBP-301) spreads to the regional LNs, selectively replicates in cancer cells in metastasized LNs, and inhibits LN metastasis, when administered into the primary advanced rectal tumor. In this study we evaluated the effectiveness of novel less invasive treatment against submucosal invasive colorectal cancer, using local tumor resection such as endoscopic submucosal dissection (ESD) and OBP-301. HCT-116-GFP human colon cancer cells were orthotopically implanted into the submucosal layer of nude mouse rectum with resultant submucosal invasive early rectal tumor. LN metastasis was observed in 78.5% of mice as early as 7 days after cancer cell inoculation, and the rectal tumor of mice with LN metastasis got locally excised with prior peritumoral injection of OBP-301 solution, mimicking ESD technique. Seven days after tumor resection, treatment of OBP-301 showed a significant inhibition in LN metastasis status compared to control group. Moreover, LN metastatic recurrence was not detected in OBP-301 treated group even 4 weeks after tumor resection. The combination of ESD and OBP-301 has promising potential to take place of the conventional surgical approach in treating submucosal invasive colorectal cancer.

Citation Format: Satoru Kikuchi, Hiroyuki Kishimoto, Hiroshi Tazawa, Yuuri Hashimoto, Futoshi Uno, Masahiko Nishizaki, Shunsuke Kagawa, Yasuo Urata, Robert M. Hoffman, Toshiyoshi Fujiwara. Novel strategy for eradicating lymph node metastasis of early-stage colorectal cancers using telomerase-dependent replicating adenoviral agent. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1570. doi:10.1158/1538-7445.AM2013-1570

Synergistic interaction of telomerase-specific oncolytic virotherapy and chemotherapeutic agents for human cancer

Replication-selective tumor-specific viruses present a novel approach for treatment of neoplastic disease. These vectors are designed to induce virus-mediated lysis of tumor cells after selective viral propagation within the tumor. Telomerase activation is considered to be a critical step in carcinogenesis through the maintenance of telomeres, and its activity correlates closely with human telomerase reverse transcriptase (hTERT) expression. We constructed an attenuated adenovirus 5 vector, in which the hTERT promoter element drives expression of E1 genes, OBP-301 (Telomelysin). Since only tumor cells that express telomerase activity would activate this promoter, the hTERT proximal promoter allows for preferential expression of viral genes in tumor cells, leading to selective viral replication and oncolytic cell death. OBP-301 alone exhibited substantial antitumor effects both in animal models and in clinical trials; data regarding combination therapy with OBP-301 and chemotherapeutic agents are preliminary but encouraging. This article reviews synergistic interaction of virotherapy and chemotherapy, and illustrates the potential application for the treatment of human cancer.

Chronic hemodynamic compromise and cerebral ischemic events in asymptomatic or remote symptomatic large-artery intracranial occlusive disease

BACKGROUND AND PURPOSE

In asymptomatic or remote symptomatic LAICOD, the risk of ischemic events is low in general, but there may be a subgroup of higher risk patients who require aggressive medical management. The purpose of this study was to determine whether chronic hemodynamic compromise is a predictor of ischemic events in asymptomatic or remote symptomatic LAICOD.

MATERIALS AND METHODS

We prospectively studied 51 asymptomatic, 19 coexistent asymptomatic, and 19 remote (>6 months) symptomatic patients with atherosclerotic intracranial internal carotid artery or middle cerebral artery disease by using (15)O-PET. MP was defined as decreased CBF, increased OEF, and a decreased CBF/CBV ratio. All patients were followed up for 2 years or until occurrence of stroke or TIA or death.

RESULTS

Bypass surgery was performed in 4 patients (2 with MP). Three cerebral ischemic events (1 TIA in an asymptomatic patient, 1 stroke, and 1 TIA in a remote symptomatic patient) occurred in the vascular territory ipsilateral to LAICOD. Kaplan-Meier analysis with censoring at the time of bypass surgery revealed that the incidence of ipsilateral ischemic events in patients with MP (2/5) was significantly higher than that in patients without MP (1/84) (log-rank test; P < .0001). The relative risk conferred by MP was 83.1 (95% confidence interval, 6.8-1017.4; P < .001). The incidence of ipsilateral ischemic events in patients with decreased CBF/CBV (2/9) was also significantly higher than that of patients without it (1/80) (P = .0001).

CONCLUSIONS

Chronic hemodynamic compromise may be a predictor of ischemic events in both asymptomatic and remote symptomatic LAICOD.

Dual programmed cell death pathways induced by p53 transactivation overcome resistance to oncolytic adenovirus in human osteosarcoma cells

Tumor suppressor p53 is a multifunctional transcription factor that regulates diverse cell fates, including apoptosis and autophagy in tumor biology. p53 overexpression enhances the antitumor activity of oncolytic adenoviruses; however, the molecular mechanism of this occurrence remains unclear. We previously developed a tumor-specific replication-competent oncolytic adenovirus, OBP-301, that kills human osteosarcoma cells, but some human osteosarcoma cells were OBP-301-resistant. In this study, we investigated the antitumor activity of a p53-expressing oncolytic adenovirus, OBP-702, and the molecular mechanism of the p53-mediated cell death pathway in OBP-301-resistant human osteosarcoma cells. The cytopathic activity of OBP-702 was examined in OBP-301-sensitive (U2OS and HOS) and OBP-301-resistant (SaOS-2 and MNNG/HOS) human osteosarcoma cells. The molecular mechanism in the OBP-702-mediated induction of two cell death pathways, apoptosis and autophagy, was investigated in OBP-301-resistant osteosarcoma cells. The antitumor effect of OBP-702 was further assessed using an orthotopic OBP-301-resistant MNNG/HOS osteosarcoma xenograft tumor model. OBP-702 suppressed the viability of OBP-301-sensitive and -resistant osteosarcoma cells more efficiently than OBP-301 or a replication-deficient p53-expressing adenovirus (Ad-p53). OBP-702 induced more profound apoptosis and autophagy when compared with OBP-301 or Ad-p53. E1A-mediated miR-93/106b upregulation induced p21 suppression, leading to p53-mediated apoptosis and autophagy in OBP-702-infected cells. p53 overexpression enhanced adenovirus-mediated autophagy through activation of damage-regulated autophagy modulator (DRAM). Moreover, OBP-702 suppressed tumor growth in an orthotopic OBP-301-resistant MNNG/HOS xenograft tumor model. These results suggest that OBP-702-mediated p53 transactivation is a promising antitumor strategy to induce dual apoptotic and autophagic cell death pathways via regulation of miRNA and DRAM in human osteosarcoma cells.

A novel synergistic effect of iron depletion on antiangiogenic cancer therapy

Iron is an essential element for both normal and cancer cells in humans. Treatment to reduce iron levels has been shown to suppress tumor growth in vivo. However, iron depletion monotherapy by iron decreased treatment has not been thought to be superior to ordinary chemotherapy and is not part of the standard therapeutic strategy for the treatment of cancer. Iron depletion is also known to reduce serum hemoglobin and oxygen supply to the tissue, which indicates that iron depletion may induce angiogenesis. Therefore, we hypothesized that iron depletion with antiangiogenic therapy can have a novel therapeutic effect in the treatment of cancer. Human nonsmall cell carcinoma cell lines A549 and H1299 were used in our study. An iron-deficient diet and an iron chelator were used to simulate an iron-depleted condition. The antitumor effects of iron depletion and antiangiogenic therapy were determined on A549 xenograft mice. The iron-depleted condition produced by an iron-deficient diet suppressed tumor growth. Tumor tissue from the iron-deficient diet group showed that cancer cell proliferation was suppressed and hypoxia was induced. Microvessel density of this group was increased which suggested that the iron-depleted condition induced angiogenesis. Bevacizumab administration had a synergetic effect on inhibiting the tumor growth on Day 39. An iron-depleted condition inhibited cancer cell proliferation and reciprocally induced angiogenesis. Bevacizumab synergistically enhanced the iron-depleted antitumor effect. Treatment to deplete iron levels combined with anti-angiogenic therapy could induce a novel therapeutic effect in the treatment of cancer.

Mechanism of resistance to trastuzumab and molecular sensitization via ADCC activation by exogenous expression of HER2-extracellular domain in human cancer cells

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.

[Stent placement using a double-balloon endoscope for malignant duodenal obstruction with Roux-en-Y Anastomosis-a case report]

A 79-year-old man who had previously undergone partial resection of the remnant stomach and Roux-en-Y reconstruction was diagnosed as having peritoneal recurrence near the ligament of Treitz. In the course of chemotherapy for recurrent gastric cancer, he complained of colic pain. CT examination revealed a marked dilation of the duodenum suggesting the presence of a distal duodenal stricture resulting from the known recurrent tumor. To palliate this intestinal obstruction, we successfully placed an expandable metal stent(EMS) using a double-balloon enteroscope(DBE), which achieved immediate relief of the obstruction and enabled the resumption of oral intake and chemotherapy. While the endoscopic placement of an EMS is available for malignant gastro-intestinal obstruction, it is considerably more difficult to approach the duodenum with Roux-en-Y anastomosis. A DBE has made it possible to place an EMS deep in the small intestine. In the present case, this minimally invasive procedure avoided the need for surgery and greatly contributed to palliation. Thus, EMS placement using a DBE is a possible palliative treatment for malignant small bowel obstruction.

[A case of transverse myelopathy due to spinal bone metastasis of gastric cancer]

We report a case of gastric cancer that presented as transverse myelopathy due to spinal bone metastasis. A 45-year- old man with advanced gastric cancer underwent distal gastrectomy and lymph node dissection for curative intent. However, pathological examination of the specimen revealed positive cytological findings in the peritoneal lavage fluid in addition to serosal invasion and lymph node metastasis(pT4aN3bCY1, stage IV). Three months after the operation, during the second course of chemotherapy with S-1, he began to complain of back pain, and positron emission tomography-computed tomography revealed spinal bone metastasis. Despite immediate radiotherapy for the bone metastasis, he soon suffered from paraplegia in the lower extremities followed by disturbances of bladder and bowel function. We created a sigmoid colostomy, which enabled self-care for defecation, and resumed radiotherapy and chemotherapy. Bone metastasis of gastric cancer is rare but the prognosis is very poor. Because of a rapidly deteriorating clinical course, early diagnosis and multidisciplinary approaches are important for gastric cancer patients with spinal metastasis.

Overexpressed cyclin D1 protein related to p53 and retinoblastoma proteins in transitional cell carcinoma of the urinary tract

We employed immunohistochemical methods to investigate the overexpression of cyclin D1 protein as well as p53 protein and retinoblastoma protein (pRb) in 57 patients with transitional cell carcinoma (TCC) of the urinary tract, in order to determine their frequency and significance, and also association with the clinicopathological behavior of this tumor. Nuclear immunostaining with cyclin D1 antibody revealed 7 homogeneously stained tumors (12.3%), including 4 heterogeneous pRb expressions, of which only one was also positive for p53. Positive immunostaining with each antibody to p53 or pRb was obtained in 15 (26.3%) and 49 (86%) tumors, respectively. The 49 pRb-positive tumors included 6 homogeneous and 43 heterogeneous nuclear immunostaining patterns. The remaining pRb-negative 8 tumors included 5 cyclin D1-negative tumors. The prevalence of p53 staining was higher in high-grade (P<0.05) and invasive types of tumors (P<0.05) than the other types studied. On the other hand, no significant relationship was found between cyclin D1- or pRb-immunoreactivity and clinicopathological factors. These findings provide evidence for infrequent cyclin D1 protein overexpression in TCC independently associated with p53 protein and/or pRb overexpression.

The hTERT promoter enhances the antitumor activity of an oncolytic adenovirus under a hypoxic microenvironment

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 tumor-specific 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-1α 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.

Genetically engineered oncolytic adenovirus induces autophagic cell death through an E2F1-microRNA-7-epidermal growth factor receptor axis

Autophagy is known to have a cytoprotective role under various cellular stresses; however, it also results in robust cell death as an important safeguard mechanism that protects the organism against invading pathogens and unwanted cancer cells. Autophagy is regulated by cell signalling including microRNA (miRNA), a post-transcriptional regulator of gene expression. Here, we show that genetically engineered telomerase-specific oncolytic adenovirus induced miR-7 expression, which is significantly associated with its cytopathic activity in human cancer cells. Virus-mediated miR-7 upregulation depended on enhanced expression of the E2F1 protein. Ectopic expression of miR-7 suppressed cell viability and induced autophagy by inhibiting epidermal growth factor receptor (EGFR) expression. Our results suggest that oncolytic adenovirus induces autophagic cell death through an E2F1-miR-7-EGFR pathway in human cancer cells, providing a novel insight into the molecular mechanism of an anticancer virotherapy.

Abstract 2442: A precise orthotopic rectal tumor model for evaluating therapeutic response of cancer treatment

We have previously reported a “true” orthotopic rectal model in which tumors start forming in the rectal mucosal tissue from which tumors actually arise. The model was generated by intrarectal transplantation of mouse rectal cancer cells stably expressing fluorescent protein, followed by disrupting the epithelial cell layer of the rectal mucosa by soaking with an acetic acid solution. Early stage tumor was detected on the rectal mucosa from as early as 6 days after transplantation, which then became invasive into the submucosal tissue. The tumor incidence on the rectal mucosa was 100%, and it was proved that this rectal tumor model reflects the natural course of rectal cancer accurately. Spontaneous lymph node metastasis and lung metastasis were observed 4 weeks after transplantation in over 90% of mice. In the present study, we will report whether this model is useful for evaluating therapeutic response of surgical local resection of tumor with combination of anticancer drugs such as a telomerase-specific replicating adenovirus designed for cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2442. doi:1538-7445.AM2012-2442