Kei Hiraoka

High expression of tumor-associated antigen RCAS1 in pancreatic ductal adenocarcinoma is an unfavorable prognostic marker.

RCAS1 (receptor‐binding cancer antigen expressed on SiSo cells) is a recently identified human tumor‐associated antigen expressed on various cancer cells. It is thought that tumor cells evade immune surveillance by expression of RCAS1, which induces apoptotic cell death in receptor‐positive immune cells. The purpose of our study was to investigate the relation between RCAS1 expression and the clinicopathological variables and clinical outcome in patients with pancreatic adenocarcinoma. Immunohistochemical analysis for RCAS1 was performed on paraffin‐embedded specimens of 80 patients (mean age, 62 years) who underwent surgical resection for pancreatic adenocarcinoma. Of the 80 specimens, 77 (96%) were positive for RCAS1. No significant correlation was found between RCAS1 expression and age, gender, depth of invasion, tumor diameter, surgical margin, lymphatic invasion, venous invasion or histopathological grading. Borderline correlations between RCAS1 expression were noted for lymph node metastasis and stage (p = 0.0608 and 0.0934, respectively). RCAS1 expression was very frequently observed and the survival of patients with high RCAS1 expression was significantly shorter than that of those with low expression (p = 0.0012). Multivariate analysis using the Cox regression model indicated that high RCAS1 expression was an independent prognostic factor (risk ratio, 3.090; p = 0.0090). These results suggested that RCAS1 might be a significant tumor marker for pancreatic adenocarcinoma and an unfavorable predictor for prognosis of patients who have undergone surgical resection.

The prognostic significance of RCAS1 expression in squamous cell carcinoma of the oesophagus.

Overexpression of RCAS1 (receptor-binding cancer antigen expressed on SiSo cells) protects cancer cells from immune attack and might be related to poor prognosis in several cancers. We investigated the immunoreactivity of RCAS1 and its correlation with clinicopathological features in 95 patients who underwent surgical resection for oesophageal squamous cell carcinoma. Thirty-two of the 95 (33.7%) cases were strongly positive for RCAS1. RCAS1 showed significant correlations with age and stage grouping. Expression of RCAS1 was associated with shorter postoperative survival. Multivariate analysis indicated that RCAS1 positivity was an independent negative prognostic factor. Our study establishes RCAS1 as a novel prognostic marker for surgically resected oesophageal squamous cell carcinoma.

Portal Venous Dilatation and Stenting for Bleeding Jejunal Varices: Report of Two Cases

Abstract We present two patients who underwent a portal stent placement for bleeding jejunal varices of the afferent loop caused by extrahepatic portal venous stenosis. Case 1 involved a 66-year-old woman who developed bleeding jejunal varices due to extrahepatic portal venous stenosis 1 year after a pancreaticoduodenectomy with intraoperative radiation therapy. Percutaneous transhepatic balloon dilatation and stent placement were performed. Since undergoing the procedure, no bleeding has occurred. Case 2 concerned a 44-year-old woman who had a rupture and bleeding of jejunal varices 16 years after a choledocojejunostomy. Stenosis was observed from the right and left branches of the portal vein to its intrahepatic branches. Both balloon dilatation and stent placement were attempted. However, the stent could not be fully inserted into the intrahepatic portal vein. Portal stent placement is less invasive and radical, and therefore should be attempted for the treatment of extrahepatic portal venous stenosis. However, there are limits to its application if the stenosis extends to the intrahepatic branches of the portal vein.

Solitary fibrous tumors of the pleura: clinicopathological and immunohistochemical examination

The purpose of this work was to study clinical and biological characteristics of solitary fibrous tumor (SFT) of the pleura. We reviewed the clinicopathological and immunohistochemical features of 12 patients who underwent surgical resection for SFT. Ten cases were histologically defined as benign; two were found to be malignant. CD34 negativity and strong expression of p53 could be observed in a patient with fatal outcome. Ki-67 expression was increased in malignant cases, as compared with benign. We also found that Bcl-2 expression inversely correlated with a tumor diameter. As the development of malignant SFT might be associated with these molecular statuses, immunohistochemical staining should be performed in all cases to identify the biological characteristics of the tumor.

RCAS1 expression as a prognostic factor after curative surgery for extrahepatic bile duct carcinoma

BackgroundRCAS1 (receptor-binding cancer antigen expressed on SiSo cells) is a cancer cell-surface antigen and has been identified as a prognostic factor in several cancers. It is thought that tumor cells escape from immune attack by expressing RCAS1, which induces apoptosis in receptor-positive immune cells. We investigated the relationship between RCAS1 expression and clinicopathologic features and clinical outcome in patients with extrahepatic bile duct carcinoma (EBDC) who underwent curative resection.MethodsRCAS1 expression was determined by immunohistochemistry in 60 patients with EBDC who underwent curative resection from 1992 to 1999. The patients were divided into two groups on the basis of the extent of RCAS1 expression: a low-expression group (immunoreactivity in <25% of cells) and a high-expression group. Expression was correlated with clinicopathologic features and prognosis.ResultsRCAS1 was expressed in 52 (86.7%) of 60 tumors and at a high frequency in all histopathologic stages. High expression of RCAS1 was detected in 46 (76.7%) of 60 cases. No correlation existed between the pattern of RCAS1 expression and any clinicopathologic feature, although high expression did correlate with poor prognosis. High RCAS1 expression was an independent negative predictor for survival.ConclusionsRCAS1 expression predicts poor outcome in resectable EBDC.

Toca 511 gene transfer and treatment with the prodrug, 5-fluorocytosine, promotes durable antitumor immunity in a mouse glioma model

Abstract Background. Toca 511 (vocimagene amiretrorepvec) is a retroviral replicating vector encoding an optimized yeast cytosine deaminase (CD). Tumor-selective expression of CD converts the prodrug, 5-fluorocytosine (5-FC), into the active chemotherapeutic, 5-fluorouracil (5-FU). This therapeutic approach is being tested in a randomized phase II/III trial in recurrent glioblastoma and anaplastic astrocytoma (NCT0241416). The aim of this study was to identify the immune cell subsets contributing to antitumor immune responses following treatment with 5-FC in Toca 511–expressing gliomas in a syngeneic mouse model. Methods. Flow cytometry was utilized to monitor and characterize the immune cell infiltrate in subcutaneous Tu-2449 gliomas in B6C3F1 mice treated with Toca 511 and 5-FC. Results. Tumor-bearing animals treated with Toca 511 and 5-FC display alterations in immune cell populations within the tumor that result in antitumor immune protection. Attenuated immune subsets were exclusive to immunosuppressive cells of myeloid origin. Depletion of immunosuppressive cells temporally preceded a second event which included expansion of T cells which were polarized away from Th2 and Th17 in the CD4+ T cell compartment with concomitant expansion of interferon gamma–expressing CD8+ T cells. Immune alterations correlated with clearance of Tu-2449 subcutaneous tumors and T cell–dependent protection from future tumor challenge. Conclusions. Treatment with Toca 511 and 5-FC has a concentrated effect at the site of the tumor which causes direct tumor cell death and alterations in immune cell infiltrate, resulting in a tumor microenvironment that is more permissive to establishment of a T cell mediated antitumor immune response.

Inhibition of Eph receptor A4 by 2,5-dimethylpyrrolyl benzoic acid suppresses human pancreatic cancer growing orthotopically in nude mice

Ephrin receptor A4 (EphA4) is overexpressed in human pancreatic adenocarcinoma (PDAC) and activate cell growth. Recent studies have identified small molecules that block EphA4. In this study, we investigated the correlation between EphA4 expression and the prognosis of patients with PDAC. We also examined the cytostatic efficacy of 2,5-dimethylpyrrolyl benzoic acid (compound 1), a small molecule that blocks EphA4, in PDAC cells. Overall survival of patients with EphA4 positivity was significantly shorter than that of patients with EphA4 negativity (P = 0.029). In addition, multivariate analysis revealed that EphA4 expression was an independent prognostic factor in PDAC patients (P = 0.039). Compound 1 showed a cytostatic efficacy in PDAC cells expressing EphA4 in vitro and in vivo. Our study indicated that compound 1 suppressed both EphA4 and Akt phosphorylations, and induced apoptosis in PDAC cells expressing EphA4. In conclusion,compound 1 has a high potential as a therapeutic agent for patients with PDAC.

Therapeutic activity of retroviral replicating vector-mediated prodrug activator gene therapy for pancreatic cancer

Toca 511, a retroviral replicating vector (RRV) encoding the yeast cytosine deaminase (yCD) prodrug activator gene, which mediates conversion of the prodrug 5-fluorocytosine (5-FC) to the anticancer drug 5-fluorouracil (5-FU), is currently being evaluated in Phase II/III clinical trials for glioma, and showing highly promising evidence of therapeutic activity. Here we evaluated RRV-mediated prodrug activator gene therapy as a new therapeutic approach for pancreatic ductal adenocarcinoma (PDAC). RRV spread rapidly and conferred significant cytotoxicity with prodrug in a panel of PDAC cells. Efficient intratumoral replication and complete inhibition of tumor growth upon 5-FC administration were observed in both immunodeficient and immunocompetent subcutaneous PDAC models. Biodistribution of RRV was highly restricted in normal tissues, especially in immunocompetent hosts. Tumor growth inhibition by Toca 511 followed by 5-FC was also confirmed in the orthotopic PDAC model. This study provides the first proof-of-concept for application of Toca 511 and Toca FC (extended release 5-FC) to the treatment of human PDAC, and provided support for inclusion of PDAC in a Phase I study evaluating Toca 511 in various systemic malignancies, (NCT02576665), which has recently been initiated.

673. Therapeutic Efficacy of Retroviral Replicating Vector (RRV) -Mediated Prodrug Activator Gene Therapy for Pancreatic Cancer

Pancreatic ductal adenocarcinoma is one of the most lethal cancers, thus new therapeutic strategies for this disease are urgently needed. Retroviral replicating vectors (RRV)-mediated prodrug activator gene therapy with Toca 511 (vocimagene amiretrorepvec), an optimized RRV encoding yeast cytosine deaminase (yCD) which converts the prodrug 5-fluorocytosine (5-FC) to the anticancer drug 5-fluorouracil (5-FU), is showing promising clinical activity in patients with recurrent high grade glioma, and is now being evaluated in a multi-center Phase II/III clinical trial. In the present study, we evaluated the therapeutic efficacy of RRV-mediated prodrug activator gene therapy in preclinical models of pancreatic cancer. We first examined the replication kinetics of RRV expressing the GFP reporter gene (RRV-GFP) in murine (Pan02) and human (MIAPaCa-2, BxPC-3, PANC-1 and SUIT-2) pancreatic cancer cell lines by flow-cytometric analysis and quantitative PCR. In all of these pancreatic cancer lines, RRV-GFP inoculated at MOI=0.05 (~5% initial transduction levels) showed rapid viral replication subsequently resulting in high levels of transduction, with the majority of pancreatic cancer lines reaching >90% GFP-positive cells over time. Next, we tested in vitro cytotoxicity by MTS assay after prodrug treatment of pancreatic cancer cells (Pan02 and MIAPaCa-2) transduced with Toca 511. In RRV-transduced pancreatic cancer cells, significant (~90%) cytotoxicity was induced by exposure to 0.1-1.0 mM 5-FC prodrug for 4 days, compared to untransduced and RRV-GFP transduced controls. We then evaluated in vivo therapeutic efficacy of Toca 511/5-FC prodrug activator gene therapy in Pan02 pancreatic tumor models established subcutaneously in immunocompetent syngeneic C57BL/6 mice. While 5-FC treatment alone showed no obvious inhibition of tumor growth as well as the nontreated control group, the majority (n=7/8) of Toca 511-transduced tumors showed complete regression after 5-FC treatment. Notably, systemic biodistribution studies showed no detectable RRV signals in genomic DNA from normal tissues of treated mice. In orthotopic models using luciferase-marked MIAPaCa-2 tumors established in the pancreas in nude mice, significant inhibition of bioluminescent signals was observed by optical imaging after 5-FC administration in mice with Toca 511-infected tumors, as compared to untreated control tumors. Thus, RRVs are highly efficient vehicles for delivering prodrug activator genes such as yCD to pancreatic cancer cells, thereby achieving significant cell killing upon pro-drug administration. Further preclinical studies are ongoing toward translating this novel therapeutic strategy into clinical trials for patients with pancreatic cancer.