Megumi Watanabe

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.

Salicylic acid-dependent immunity contributes to resistance against Rhizoctonia solani, a necrotrophic fungal agent of sheath blight, in rice and Brachypodium distachyon

Summary Rhizoctonia solani is a soil‐borne fungus causing sheath blight. In consistent with its necrotrophic life style, no rice cultivars fully resistant to R. solani are known, and agrochemical plant defense activators used for rice blast, which upregulate a phytohormonal salicylic acid (SA)‐dependent pathway, are ineffective towards this pathogen. As a result of the unavailability of genetics, the infection process of R. solani remains unclear. We used the model monocotyledonous plants Brachypodium distachyon and rice, and evaluated the effects of phytohormone‐induced resistance to R. solani by pharmacological, genetic and microscopic approaches to understand fungal pathogenicity. Pretreatment with SA, but not with plant defense activators used in agriculture, can unexpectedly induce sheath blight resistance in plants. SA treatment inhibits the advancement of R. solani to the point in the infection process in which fungal biomass shows remarkable expansion and specific infection machinery is developed. The involvement of SA in R. solani resistance is demonstrated by SA‐deficient NahG transgenic rice and the sheath blight‐resistant B. distachyon accessions, Bd3‐1 and Gaz‐4, which activate SA‐dependent signaling on inoculation. Our findings suggest a hemi‐biotrophic nature of R. solani, which can be targeted by SA‐dependent plant immunity. Furthermore, B. distachyon provides a genetic resource that can confer disease resistance against R. solani to plants.

Integrated fluorescent cytology with nano-biologics in peritoneally disseminated gastric cancer

Gastric cancer patients positive for peritoneal cytology are at increased risk of tumor recurrence, but although a certain proportion of cytology‐positive patients relapse rapidly with aggressive progression, others survive longer with conventional chemotherapies. This heterogeneity makes it difficult to stratify patients for more intensive therapy and poses a substantial challenge for the implementation of precision medicine. We developed a new approach to identify biologically malignant subpopulations in cytology‐positive gastric cancer patients, using a green fluorescent protein (GFP)‐expressing attenuated adenovirus in which the telomerase promoter regulates viral replication (TelomeScan, OBP‐401). The fluorescence emitted from TelomeScan‐positive cells was successfully quantified using a multi‐mode microplate reader. We then analyzed clinical peritoneal washes obtained from 68 gastric cancer patients and found that patients positive for TelomeScan had a significantly worse prognosis. In 21 cytology‐positive patients, the median survival time of those who were TelomeScan positive (235 days) was significantly shorter than that for those who were TelomeScan negative (671 days; P = 0.0062). This fluorescent virus‐guided cytology detects biologically malignant cancer cells from the peritoneal washes of gastric cancer patients and may thus be useful for both therapy stratification and precision medicine approaches based on genetic profiling of disseminated cells.

Training system for laparoscopy-assisted distal gastrectomy

PurposeLaparoscopy-assisted distal gastrectomy (LADG) is likely to become a standard procedure for gastric cancer, which highlights the importance of establishing a training system in which even inexperienced surgeons can perform this procedure safely. This study assesses our training system for LADG based on short-term surgical outcomes.MethodsWe evaluated retrospectively the short-term outcomes of 100 consecutive LADGs with curative D1/D1+ lymph node dissection. Our training system was assessed based on the learning curve of trainees, and factors related to achieving good-quality operations were analyzed statistically.ResultsOverall, postoperative complications developed in 10 patients (10%), and included one case of anastomotic leakage (1%) and one case of pancreatic fistula (1%). The learning curve of the trainees plateaued after 10 operator cases in terms of operation time. The importance of the trainer’s position was also confirmed by the result that the operation time was significantly longer when trainees with ≤10 operator cases performed LADG with a trainer as scopist vs. a trainer as the first assistant. Univariate and multivariate analyses revealed that >10 operator cases were the most important factor for achieving good-quality operations.ConclusionThese results show that our current LADG procedure and training system are appropriate and effective.

Abstract 4156: Functional analysis of tumor-associated macrophage utilizing virus-guided fluorescent imaging of pancreatic cancer cells in the peritoneal cavity

Objectives: Postoperative recurrence occurs in approximately 80% of pancreatic cancer, and the peritoneum is the second most frequent metastatic site next to the liver. Recent evidence suggests that cancer microenvironment plays key roles in metastasis. To investigate mechanism of intraperitoneal metastasis in pancreatic cancer, we tried to detect cancer cell in the peritoneal wash from pancreatic cancer patients and analyze intraperitoneal cancer microenvironment. A genetically engineered adenovirus, TelomeScan, which replicates and expresses GFP only in telomerase-active cancer cells, was employed to detect cancer cells, and it enabled us to distinguish cancer cell from co-existence cells in the abdominal cavity. We explored the role of tumor-associated macrophages (TAMs) by using this virus-guided fluorescent imaging system. Methods: Peritoneal wash was obtained from 20 pancreatic cancer patients during operation. The cells in the wash were infected with TelomeScan for 24 hours. Samples from cases with TelomeScan-expressing GFP-positive cells were further subjected to immunofluorescence assay for analysis of microenvironment. The antibodies against CD45, CD14, and CD204 were used in immunostaining as markers of leukocytes, monocytes and TAMs, respectively. To investigate the effect of TAMs on pancreatic cancer, Panc1 and BxPC-3 cell lines were co-cultured with PMA (phorbol 12-myristate 13-acetate)-treated monocytes and analyzed their changes. Results: The three out of 20 cases were positive in cytology, and GFP positive cells were detected after TelomeScan infection in those cases. In the wash, pancreatic cancer cells existed together with many leukocytes including macrophages. Further analysis demonstrated that those macrophages were TAMs. After Panc1 or BxPC-3 cells were co-cultured with TAMs, E-cadherin was decreased in Panc1, α-SMA and Vimentin was increased in BxPC-3. These results suggested that Epithelial to Mesenchymal Transition (EMT) was induced in pancreatic cancer cells by TAMs. Conclusion: Pancreatic cancer cells and TAMs were detected in the peritoneal wash using TelomeScan and immunostaining. The results suggested that EMT induced by TAMs may promote intraperitoneal metastasis of pancreatic cancer. Citation Format: Kazuya Kuwada, Shunsuke Kagawa, Megumi Watanabe, Shuichi Sakamoto, Satoru Kikuchi, Shinji Kuroda, Ryuichi Yoshida, Hiroshi Tazawa, Tetuya Kagawa, Toshiyoshi Fujiwara. Functional analysis of tumor-associated macrophage utilizing virus-guided fluorescent imaging of pancreatic cancer cells in the peritoneal cavity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4156.

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

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA 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

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

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA 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