BackgroundThe peritoneum is one of the most frequent metastatic sites in pancreatic cancer patients, and peritoneal dissemination makes this disease refractory due to aggressive progression and chemoresistance. Although the role of the tumor microenvironment in cancer development is recognized, the correlation between the peritoneal environment and refractoriness of peritoneal dissemination remains unclear. The intraperitoneal tumor-microenvironment and its potential role in the progression of peritoneal dissemination and chemo-refractoriness, focusing especially on macrophages, were investigated.Materials and methodsPeritoneal washes were obtained from pancreatic cancer patients, and cellular components were subjected to immunofluorescence assays. The effects of macrophages induced from monocytic THP-1 cells on pancreatic cancer cells were examined in co-culture conditions. The in vivo effects of macrophages on tumor growth and chemo-sensitivity were investigated by subcutaneously or intraperitoneally co-injecting cancer cells with macrophages into mice.ResultsCD204-positive macrophages were present along with cancer cells in the peritoneal washes. In in vitro co-culture, tumor-associated macrophages affected pancreatic cancer cells, induced the epithelial-to-mesenchymal transition (EMT), and made them more resistant to chemotherapeutic agents. M2 macrophages promoted growth of both subcutaneous tumors and peritoneal dissemination in mice. Furthermore, co-inoculation of M2 macrophages conferred chemoresistance in the peritoneal dissemination mouse model, which significantly shortened their survival.ConclusionIntraperitoneal tumor-associated macrophages potentially play an important role in promotion of peritoneal dissemination and chemoresistance of pancreatic cancer via EMT induction.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0981-2) contains supplementary material, which is available to authorized users.

Epithelial-mesenchymal transition (EMT) is a biological process by which epithelial cells acquire mesenchymal characteristics. In malignant tumors, EMT is crucial for acquisition of a mesenchymal phenotype with invasive and metastatic properties, leading to tumor progression. An inflammatory microenvironment is thought to be responsible for the development and progression of colorectal cancer (CRC); however, the precise role of inflammatory microenvironments in EMT-related CRC progression remains unclear. Here, we show the spatiotemporal visualization of CRC cells undergoing EMT using a fluorescence-guided EMT imaging system in which the mesenchymal vimentin promoter drives red fluorescent protein (RFP) expression. An inflammatory microenvironment including TNF-α, IL-1β, and cytokine-secreting inflammatory macrophages induced RFP expression in association with the EMT phenotype in CRC cells. In vivo experiments further demonstrated the distribution of RFP-positive CRC cells in rectal and metastatic tumors. Our data suggest that the EMT imaging system described here is a powerful tool for monitoring EMT in inflammatory microenvironment–CRC networks.

Pancreatic ductal adenocarcinoma (PDAC) cells have an exceptional ability to invade nerves through pronounced crosstalk between nerves and cancer cells; however, the mechanism of PDAC cell invasion remains to be elucidated. Here, we demonstrate the therapeutic potential of telomerase-specific oncolytic adenoviruses, OBP-301 and tumor suppressor p53-armed OBP-702, against human PDAC cells. Highly invasive PDAC cells exhibited higher levels of phosphorylated extracellular signal-regulated kinases 1 and 2 (ERK1/2) expression independent of KRAS expression; ERK1/2 inhibitor or small interfering RNA (siRNA) treatment significantly reduced the migration and invasion of PDAC cells, suggesting that the ERK signaling pathway is associated with the invasiveness of PDAC cells. OBP-702 infection suppressed ERK signaling and inhibited PDAC cell migration and invasion more efficiently than OBP-301. OBP-702 also effectively inhibited PDAC cell invasion even when invasiveness was enhanced by administration of motility stimulators, such as nerve and neurosecretory factors. Moreover, noninvasive whole-body imaging analyses showed that OBP-702 significantly suppressed tumor growth in an orthotopic PDAC xenograft model, although both viruses were equally effective against subcutaneous tumors, suggesting that OBP-702 can influence the orthotopic tumor microenvironment. Our data suggest that oncolytic virus-mediated disruption of ERK signaling is a promising antitumor strategy for attenuating the invasiveness of PDAC cells.

Neuroblastoma (NB) is a primary malignant tumor of the peripheral sympathetic nervous system. High-risk NB is characterized by MYCN amplification and human telomerase reverse transcriptase (hTERT) rearrangement, contributing to hTERT activation and a poor outcome. For targeting hTERT-activated tumors, we developed two oncolytic adenoviruses, OBP-301 and tumor suppressor p53-armed OBP-702, in which the hTERT promoter drives expression of the viral E1 gene for tumor-specific virus replication. In this study, we demonstrate the therapeutic potential of the hTERT-driven oncolytic adenoviruses OBP-301 and OBP-702 using four human MYCNamplified NB cell lines (IMR-32, CHP-134, NB-1, LA-N-5) exhibiting high hTERT expression. OBP-301 and OBP-702 exhibited a strong antitumor effect in association with autophagy in NB cells. Virus-mediated activation of E2F1 protein suppressed MYCN expression. OBP-301 and OBP-702 significantly suppressed the growth of subcutaneous CHP-134 tumors. Thus, these hTERT-driven oncolytic adenoviruses are promising antitumor agents for eliminating MYCN-amplified NB cells via E2F1-mediated suppression of MYCN protein.

Background: Epithelial-mesenchymal transition (EMT) is known to be one of the poor prognostic factors. EMT is a biological process, by which epithelial cancer cells lose their epithelial characteristics and gain mesenchymal properties, including invasion, metastasis and drug resistance, resulting in tumor recurrence and poor prognosis. Esophageal cancer is one of the most common cause of cancer-related death worldwide, especially in East Asia. Despite the recent advances in the treatment of esophageal cancer, antitumor therapy to inhibit EMT program remains to be developed. We developed a telomerase-specific replication-selective oncolytic adenovirus (OBP-301; Telomelysin), in which the human telomerase reverse transcriptase promoter drives the expression of E1A and E1B for virus replication. In this study, we explored the biological effect of OBP-301 on EMT in human esophageal cancer cells. Methods: Transforming growth factor-β (TGF-β) was used to induce EMT in human esophageal cancer TE-4 cells. To investigate whether OBP-301 infection affects TGF-β-induced EMT, we performed western blot and real-time PCR analysis for EMT-related markers. We also examined the migration capability using transwell migration assay. In vitro antitumor effect of OBP-301 and chemotherapeutic agents on TGF-β-treated TE-4 cells were assessed by a XTT assay. Results: Administration of TGF-β induced mesenchymal characteristics, including spindle-shaped morphology, increased migration capability, and upregulation of mesenchymal markers N-cadherin and vimentin, in TE-4 cells. When TGF-β-treated TE-4 cells were infected with OBP-301, upregulation of N-cadherin and vimentin expression was attenuated. Upregulation of EMT-transcription factors, Snail, Slug, and ZEB1 by TGF-β was reduced by OBP-301 infection. OBP-301 also inhibited TGF-β-induced enhancement of migration capability. Moreover, interestingly, EMT-induced TE-4 cells acquired chemoresistance, whereas they were sensitive to OBP-301-mediated lytic effect. Conclusion: Our data suggest that telomerase-specific oncolytic virotherapy is a promising antitumor strategy to inhibit TGF-β-induced EMT and warrants clinical trials in human esophageal cancer. Currently, we are conducting a phase I/II clinical study of OBP-301 in combination with radiotherapy for esophageal cancer. Citation Format: Tomoya Masuda, Hiroshi Tazawa, Takeshi Ieda, Yuuri Hashimoto, Shunsuke Tanabe, Kazuhiro Noma, Yasuo Urata, Shunsuke Kagawa, Yasuhiro Shirakawa, Toshiyoshi Fujiwara. Transforming growth factor-b-induced epithelial-mesenchymal transition is attenuated by telomerase-specific oncolytic virotherapy in human esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2033.