大澤 英之

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.