大澤 英之

BACKGROUND: Neoadjuvant therapy has been increasingly adopted for resectable pancreatic ductal adenocarcinoma (PDAC) in Japan following the Prep-02/JSAP-05 trial. However, real-world evidence regarding effectiveness and underlying pathological mechanisms remains limited. This retrospective study evaluated neoadjuvant chemotherapy with gemcitabine plus S-1 (NAC-GS) impacts on resectable PDAC patient oncological and pathological outcomes. METHODS: Consecutive resectable PDAC patients treated with NAC-GS (n = 60) or upfront surgery (UFS) (n = 101) between 2013 and 2023 were retrospectively analyzed (total diagnosed during the study period, n = 186). An intention-to-treat principle assessed overall survival (OS) and recurrence-free survival (RFS). Propensity score matching using six baseline variables (1:1) minimized selection bias. RESULTS: Fifty-four patients were included in each group. The NAC-GS group demonstrated significantly longer OS than the UFS group (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.25-0.90; P = 0.023). Among resected cases, NAC-GS was associated with improved OS (HR, 0.42; 95% CI, 0.20-0.90; P = 0.026). Pathologically, the NAC-GS group showed significantly lower lymph node stage and less lymphatic invasion. Pathological complete response was observed in 4.0% of NAC-GS patients. DISCUSSION: Neoadjuvant chemotherapy with GS was associated with prolonged survival in resectable PDAC, potentially through lymphatic spread suppression. Pathological complete response was rare but may represent a clinically meaningful benefit of neoadjuvant treatment in selected patients.

BACKGROUND AND PURPOSE: The peritoneal cavity constitutes a unique immune microenvironment that critically influences the pathobiology of peritoneal metastasis (PM). This study aimed to clarify the mechanisms by which local immune alterations affect the efficacy of intraperitoneal (IP) chemotherapy for PM from gastric cancer (GC). METHOD: Peritoneal lavage or ascitic fluid was obtained from 42 patients with GC and PM treated with IP paclitaxel (PTX) in combination with systemic oxaliplatin and oral S-1. Serial samples from 31 patients were analyzed after 1-3 cycles of chemotherapy. Immune cell subsets were evaluated using multicolor flow cytometry with monoclonal antibodies, and the functional properties of peritoneal eosinophils were assessed using gene expression profiling and cytotoxicity assays. RESULTS: IP chemotherapy was associated with decreased CD4(+) T cells and increased CD11b(+) myeloid cells. Notably, many patients, particularly those with negative cytology (CY0), exhibited striking recruitment of CD66b(+) CD16(-) CD193(+) Siglec-F(+) eosinophils into the peritoneal cavity. Eosinophil expansion was correlated with improved clinical outcomes. Post-treatment eosinophils displayed an activated, partially degranulated phenotype with elevated CD11b and CD63 expression and distinct messenger RNA signatures compared with circulating eosinophils. Peritoneal eosinophils demonstrated the ability to induce apoptosis in GC cells. CONCLUSION: IP PTX promotes the recruitment and activation of eosinophils with potent antitumor activity in the peritoneal cavity. Early post-treatment abdominal eosinophilia is a robust prognostic biomarker and may represent a promising therapeutic target to enhance the efficacy of IP chemotherapy in patients with PM from GC.

Introduction: Peritoneal metastasis (PM) is the most common site of recurrence following curative resection for advanced gastric cancer (GC). Along with disease progression, it can lead to complications such as intestinal obstruction, hydronephrosis, obstructive jaundice, and ascites, significantly impairing the patient’s quality of life. Therefore, peritoneal metastasis is considered a critical target for treatment. In general, these patients are treated with systemic chemotherapy; however, the therapeutic effect is often limited due to the anticancer agents’ poor penetration into the peritoneal cavity. We aim to identify factors associated with the best overall survival (OS) in GC patients with peritoneal metastasis. Methods: Patients with advanced GC who were diagnosed as having macroscopic PM or positive peritoneal cytology by staging laparoscopy were enrolled. We introduced intraperitoneal Paclitaxel (IP-PTX) combined with S-1 plus oxaliplatin (SOX). Gastrectomy with lymph node dissection was performed as conversion surgery when the PM showed an excellent response. Results: Ninety-six patients received IP-PTX + SOX, with a median of 16 courses. The 1- and 5-year OS rates were 70.2% and 24.5%, respectively, with a mean survival time (MST) of 20.0 months. No chemotherapy-related mortality was observed. Conversion surgery was performed in 44 patients (45.8%), with a 1-year OS rate of 100%. Conclusions: Combination chemotherapy using the IP-PTX + SOX regimen is highly effective and is recommended as induction chemotherapy for patients with PM from GC. Conversion gastrectomy should be considered following an excellent response, particularly in patients with peritoneal cancer index (PCI) scores below 20.

BACKGROUND: Patients with advanced gastric cancer (GC) with peritoneal involvement have a dismal prognosis. Recent clinical trials have shown that anti-Claudin18.2 (CLDN18.2) antibody (zolbetuximab) enhances survival in patients with GC expressing high levels of CLDN18.2. However, the effectiveness of the zolbetuximab in patients with peritoneal metastases (PMs) remains unclear. In this study, we aimed to evaluate the expression of CLDN18.2 in disseminated lesions to assess the clinical utility of zolbetuximab in the treatment of GC with PM. METHODS: In 42 patients diagnosed with stage IV GC with PM, biopsy samples from the primary tumors and peritoneal metastatic nodules were collected and immunostained using the specific antibody (43-14A, Ventana). The expression of CLDN18.2 was comparatively evaluated based on staining intensity and the proportion of positive cells. RESULTS: Positive immunoreactivity of CLDN18.2 was observed in 37 (88%) of the primary tumors. Specifically, CLDN18.2 positivity was identified in 26 (62%) or 12 (29%) patients based on moderate to strong membrane staining in at least 40% or 75% of tumor cells, respectively. In comparison, the staining intensity in tumor cells was consistently reduced in PM across all patients. CLDN18.2 expression was absent in PM of 29 (69%) patients, while 3 (7.1%) cases were determined to be CLDN18.2-positive based on a cutoff value of 40% for high staining. This trend was particularly pronounced in cases with undifferentiated type and human epidermal growth factor receptor 2 (HER-2) negative primary tumors. CONCLUSIONS: Although CLDN18.2 expression in PM mirrored that in primary lesions, the levels were generally reduced. When zolbetuximab is used for GC patients with peritoneal involvement, it is preferable to assess the expression of CLDN18.2 in the disseminated lesions.

INTRODUCTION: Neoadjuvant gemcitabine plus S-1 (GS) therapy for resectable pancreatic cancer has been shown to prolong overall survival significantly compared with upfront surgery. Herein, we report two opposite cases of patients with resectable pancreatic cancer who underwent distal pancreatectomy after neoadjuvant GS therapy. CASE PRESENTATION: In Case 1, a 49-year-old female with a 12 mm tumor in the pancreatic body (cT1N0M0, cStage IA, union for international cancer control [UICC] 8th edition) underwent two courses of neoadjuvant GS therapy followed by an open distal pancreatectomy. Pathological examination revealed no residual cancer and the patient was diagnosed with a pathological complete response (pCR) without recurrence 31 months after surgery. However, in Case 2, a 74-year-old male with a 12 mm tumor in the pancreatic body (cT1N0M0, cStage IA, UICC 8th edition) also underwent two courses of neoadjuvant GS therapy, and then a laparoscopic distal pancreatectomy was performed. Pathological examination showed invasive pancreatic ductal adenocarcinoma with a 20 mm tumor. The tumor exhibited invasion into the lumen of the splenic vein and retroperitoneal tissue (ypT1N0M0, ypStage IA, UICC 8th edition). Adjuvant chemotherapy with S-1 was started, but 4 months postoperatively, a significant rise in serum CA19-9 levels was observed with multiple hepatic metastases and portal venous tumor thrombus. Gemcitabine plus nab-paclitaxel (GnP) therapy was started, however, the tumor progressed rapidly. The patient died 6 months after surgery. CONCLUSIONS: Neoadjuvant GS therapy is potentially expected to have a significant therapeutic effect as the pCR. Nevertheless, even after surgical resection, some patients still exhibit extremely poor prognosis. Therefore, it is necessary to clarify their clinical characteristics.

BACKGROUND: Globally, prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing, and there is an urgent need to develop innovative therapies that promote liver regeneration following hepatectomy for this disease. Surgical excision is a key therapeutic approach with curative potential for liver tumors. However, hepatic steatosis can lead to delayed liver regeneration and higher post-operative complication risk. Mesenchymal stem cells-conditioned medium (MSC-CM) is considered a rich source of paracrine factors that can repair tissues and restore function of damaged organs. Meanwhile, hydrogels have been widely recognized to load MSC secretome and achieve sustained release. This study aimed to evaluate the therapeutic effect of hydrogel-encapsulated MSC-CM on liver regeneration following partial hepatectomy (PHx) in a rodent model of diet-induced hepatic steatosis. METHODS: Male Lewis rats were fed with a methionine and choline-deficient diet. After 3 weeks of feeding, PHx was performed and rats were randomly allocated into two groups that received hydrogel-encapsulated MSC-CM or vehicle via the intra-mesenteric space of the superior mesenteric vein (SMV). RESULTS: The regeneration of the remnant liver at 30 and 168 h after PHx was significantly accelerated, and the expressions of proliferating cell nuclear antigen were significantly enhanced in the MSC-CM group. MSC-CM treatment significantly increased hepatic ATP and β-hydroxybutyrate content at 168 h after PHx, indicating that MSC-CM fosters regeneration not only in volume but also in functionality. The number of each TUNEL- and cleaved caspase-3 positive nuclei in hepatocytes at 9 h after PHx were significantly decreased in the MSC-CM group, suggesting that MSC-CM suppressed apoptosis. MSC-CM increased serum immunoregulatory cytokine interleukin-10 and interleukin-13 at 30 h after PHx. Additionally, mitotic figures and cyclin D1 expression decreased and hepatocyte size increased in the MSC-CM group, implying that this mode of regeneration was mainly through cell hypertrophy rather than cell division. CONCLUSIONS: MSC-CM represents a novel therapeutic approach for patients with MASLD requiring PHx.

This study explores a novel therapeutic approach for peritoneal metastasis (PM) using AAV-mediated delivery of tumor suppressor microRNA-29b (miR-29b) to peritoneal mesothelial cells (PMC). AAV serotypes 2 and DJ demonstrate high transduction efficiency for human and murine PMC, respectively. In vitro analysis indicates that AAV vectors encoding miR-29b precursor successfully elevate miR-29b expression in PMC and their secreted small extracellular vesicle (sEV), thereby inhibiting mesothelial mesenchymal transition and reducing subsequent attachment of tumor cells. A single intraperitoneal (IP) administration of AAV-DJ-miR-29b demonstrates robust and sustained transgene expression, suppressing peritoneal fibrosis and inhibiting the development of PM from gastric and pancreatic cancers. Additionally, AAV-DJ-miR-29b enhances the efficacy of IP chemotherapy using paclitaxel, restraining the growth of established PM. While conventional gene therapy for cancer encounters challenges targeting tumor cells directly but delivering miRNA to the tumor stroma offers a straightforward and efficient means of altering the microenvironment, leading to substantial inhibition of tumor growth. AAV-mediated miR-29b delivery to peritoneum via IP route presents a simple, minimally invasive, and promising therapeutic strategy for refractory PM.

Despite advances in systemic chemotherapy, patients with gastric cancer (GC) and peritoneal metastases (PMs) continue to have poor prognoses. Intraperitoneal (IP) administration of Paclitaxel (PTX) combined with systemic chemotherapy shows promise in treating PMs from GC. However, methods of drug administration need to be optimized to maximize efficacy. In this study, we utilized a mouse model with PMs derived from a human GC cell line, administering PTX either IP or intravenously (IV), and Carboplatin (CBDCA) IV 0, 1, and 4 days after PTX administration. The PMs were resected 30 min later, and concentrations of PTX and CBDCA in resected tumors were measured using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Results indicated that PTX concentrations were higher with IP administration than with IV administration, with significant differences observed on days 0 and 1. CBDCA concentrations 4 days post-IP PTX administration were higher than with simultaneous IV PTX administration. These findings suggest that IP PTX administration enhances CBDCA concentration in peritoneal tumors. Therefore, sequential IV administration of anti-cancer drugs appears more effective than simultaneous administration with IP PTX, a strategy that may improve prognoses for patients with PMs.

Abstract The vagus nerve is the only pathway for transmitting parasympathetic signals between the brain and thoracoabdominal organs, thereby exhibiting anti-inflammatory functions through the cholinergic anti-inflammatory pathway. Despite often being resected during lymph node dissection in upper gastrointestinal cancer surgery, the impact of vagotomy on postoperative outcomes in gastric cancer patients remains unclear. Sub-diaphragmatic vagotomy was performed on C57BL/6 mice. Three weeks later, syngeneic murine gastric cancer cell line YTN16P was injected into the peritoneal cavity, and the number of peritoneal metastases (PM) on the mesentery and omentum compared with control mice. The phenotypes of immune cells in peritoneal lavage and omental milky spots one day after tumor inoculation were analyzed using flow cytometry and immunohistochemistry. Intraperitoneal transfer of 3 × 10⁵ YTN16P significantly increased the number of metastatic nodules on the mesentery in the vagotomy group compared to the control group. The omental metastasis grade was also significantly higher in the vagotomy group. Phenotypic analysis of immune cells in peritoneal lavage did not reveal significant differences after vagotomy. However, vagotomized mice exhibited a notable increase in milky spot area, with a higher presence of cytokeratin(+) tumor cells, F4/80(+) macrophages, and CD3(+) T cells. Vagus nerve signaling appears to regulate the immune response dynamics within milky spots against disseminated tumor cells and inhibits the development of PM. Preserving the vagus nerve may offer advantages in advanced gastric cancer surgery to reduce peritoneal recurrence.

Abstract The spleen is a key source of circulating and tumor-infiltrating immune cells. However, the effect of splenectomy on tumor growth remains unclear. At 3 weeks after splenectomy, we subcutaneously injected LuM1 cells into BALB/c mice and evaluated the growth of primary tumors and lung metastases at 4 weeks after tumor inoculation. In addition, we examined the phenotypes of immune cells in peripheral blood by using flow cytometry and in tumor tissue by using multiplex immunohistochemistry. The growth of primary tumors was reduced in splenectomized mice compared with the sham-operated group. Conversely, splenectomized mice had more lung metastases. Splenectomized mice had fewer CD11b⁺cells, especially monocytic MDSCs (CD11b⁺Gr-1^neg-lowLy6c^high), and NK cells (CD49b⁺CD335⁺). The proportion of NK cells was inversely correlated with the number of lung metastases. In splenectomized mice, the density of CD3⁺ and granzyme B⁺ CD8⁺ T cells was increased, with fewer M2-type macrophages in primary tumors, but NK cells were decreased markedly in lung. Splenectomy concurrently enhances T cell-mediated acquired immunity by reducing the number of monocytic MDSCs and suppresses innate immunity by decreasing the number of NK cells. Splenectomy has opposite effects on primary and metastatic lesions through differential regulation on these two immune systems.

BACKGROUND: Adjuvant nivolumab therapy has become the standard therapy for patients with localized advanced esophageal cancer with non-pathological complete response after neoadjuvant chemoradiotherapy followed by curative surgery. However, the necessity of this therapy for patients after neoadjuvant chemotherapy (NAC) with docetaxel, cisplatin, and 5-fluorouracil (DCF) regimen followed by surgery is unclear, and the prognosis of grouping based on the presence or absence of pathological tumor and lymph node findings has not been analyzed. Therefore, our study aimed to address these questions. METHODS: This retrospective cohort study included patients with cT1N1-3M0 and cT2-3N0-3M0 esophageal cancer according to the Japanese Classification of Esophageal Cancer, 11th edition, who received NAC with DCF followed by curative surgery between 2008 and 2020 at Jichi Medical University Hospital. We divided patients with ypT0-3N0-3M0 into four histological groups, namely ypT0N0, ypT+N0, ypT0N+, and ypT+N+, and we evaluated overall survival as the primary outcome and the prognostic relationship of lymph node metastasis as the secondary outcome. RESULTS: A total of 101 patients were included in this study. Kaplan-Meier analysis showed that the curves of the ypT0N0 and ypT+N0 groups were almost identical, while they differed from the other two groups. The hazard ratio of ypN+ was 4.44 (95% confidence interval: 2.03-9.71; P<0.001). CONCLUSIONS: The prognosis of the ypT+N0 group after NAC with DCF followed by surgery was similar to that of pathological complete remission. Grouping patients according to pathological lymph node status is a reasonable predictor of prognosis.

Although miR-29b levels in peritoneal exosomes was markedly reduced in patients with peritoneal metastases(PM), their role has not been fully clarified. Bone marrow derived mesenchymal stem cells(BMSC)were transfected with miR-29b- integrating lentivirus and exosomes isolated from culture supernatants using ultracentrifugation. The effects of the exosomes on human peritoneal mesothelial cells(HPMC)were examined in vitro. The in vivo effect of murine BMSC-derived exosomes was examined with a syngeneic PM model. Culture of HPMC with TGF-β1 decreased expression of E-cadherin and calretinin with increased expression of vimentin, totally restored by adding miR-29b-rich exosomes. The exosomes inhibited proliferation and migration of HPMC, and inhibited adhesion of gastric cancer cells to HPMC. Intraperitoneal(IP)transfer of miR- 29b-rich exosomes every 3 days markedly reduced the number of PM of a murine gastric cancer cell, YTN16P, on the mesentery of C57/BL6 mice. IP administration of miR-29b-containing exosome suppresses the development of PM of gastric cancer.

AIM: The clinical efficacy of chemoradiotherapy (CRT) is largely dependent on host immune status. The aim of this study was to identify possible markers expressed on circulating mononuclear cells to predict tumour response in patients with locally advanced rectal cancer (LARC). METHODS: Peripheral blood samples were obtained from 47 patients diagnosed with LARC before and after CRT. The numbers of lymphocytes and monocyte subsets were analysed using flow cytometry. Based on clinical and pathological findings, patients were classified as high or low responders. RESULTS: Lymphocyte counts were markedly decreased after CRT. Total numbers of lymphocytes (p = 0.030) and CD4(+) T cells (p = 0.041) in post-CRT samples were significantly lower in low responders than in high responders. In contrast, monocyte counts were not reduced and the number of CD14dim (+) CD16(+) nonclassical (patrolling) monocytes were somewhat increased after CRT (p = 0.050). Moreover, the ratios of programmed cell death ligand 1 (PD-L1) (+) cells on patrolling monocytes before and after CRT were significantly higher in low responders than in high responders (p = 0.0046, p = 0.0006). The same trend was observed for classical and intermediate monocytes. The expression of PD-L1 on patrolling monocytes before CRT correlated inversely with the number of T cells and natural killer (NK) cells after CRT. PD-L1(+) ratio in patrolling monocytes was an independent predictor for response to CRT. CONCLUSION: Programmed cell death ligand 1 (PD-L1) expression on patrolling monocytes suppresses cell-mediated immunity in patients receiving CRT which could be related to tumour response, and may be a useful biomarker for decision-making in the management of patients with LARC.