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Background: In gastric solid-type poorly differentiated adenocarcinoma (PDA), the role of microsatellite instability and immune escape mechanism remains unclear. The current study aimed to elucidate the clinical significance of mismatch repair (MMR) status, genome profile, C-X-C motif chemokine receptor 2 (CXCR2) expression, and myeloid-derived suppressor cell (MDSC) infiltration in solid-type PDA., Methods: In total, 102 primary solid-type PDA cases were retrieved, and classified into 46 deficient-MMR (dMMR) and 56 proficient-MMR (pMMR) cases based on immunohistochemistry (IHC) and polymerase chain reaction-based molecular testing results. The mRNA expression profiles (NanoString nCounter Assay) of stage-matched dMMR (n = 6) and pMMR (n = 6) cases were examined. The CXCR2 expression and MDSC infiltration (CD11b- and CD33-positive cells) were investigated via IHC in all solid-type PDA cases., Results: mRNA analysis revealed several differentially expressed genes and differences in biological behavior between the dMMR (n = 46) and pMMR (n = 56) groups. In the multivariate analysis, the dMMR status was significantly associated with a longer disease-free survival (hazard ratio = 5.152, p = 0.002) and overall survival (OS) (hazard ratio = 5.050, p = 0.005). CXCR2-high expression was significantly correlated with a shorter OS in the dMMR group (p = 0.018). A high infiltration of CD11b- and CD33-positive cells was significantly correlated with a shorter OS in the pMMR group (p = 0.022, 0.016, respectively)., Conclusions: dMMR status can be a useful prognostic predictor, and CXCR2 and MDSCs can be novel therapeutic targets in patients with solid-type PDA., (© 2024. The Author(s) under exclusive licence to The International Gastric Cancer Association and The Japanese Gastric Cancer Association.)

Aims: Collecting duct carcinoma (CDC) and fumarate hydratase-deficient renal cell carcinoma (FH-deficient RCC) have similar histological morphologies and both show a poor prognosis. Programmed death ligand 1 (PD-L1) inhibitor has been approved for the treatment of RCC. However, tumour-infiltrating neutrophils stimulated by interleukin-8 (IL-8) interfere with PD-L1 inhibitors. Here, we retrospectively analysed PD-L1 and IL-8 expression, and examined its relationship with infiltrating immune cells., Methods: Nine cases of CDC and seven cases of FH-deficient RCC were selected. We defined PD-L1 and IL-8 expression by the Tumour Proportion Score and Combined Positive Score (CPS). We counted the numbers of CD8 + , CXCR2 + , CD11b + , CD66b + and CD33 + immune cells located in the tumour components., Results: A number of CXCR2 + (p=0.0058), CD11b + (p=0.0070) and CD66b + (p=0.0067) immune cells infiltrating into CDC were significantly higher than those infiltrating into FH-deficient RCC. In CDC, PD-L1 expression was correlated with a high density of CD8 + lymphocytes (p=0.0389), but was not in FH-deficient RCC (p=0.6985). IL-8 CPS was significantly higher in CDC than in FH-deficient RCC (p=0.0069). In addition, among the CDC cases, IL-8 CPS showed significant positive correlations with CXCR2 + , CD11b + and CD66b + immune cell densities (p=0.0250, p=0.0104 and p=0.0374, respectively), whereas FH-deficient RCC showed no significant correlations between IL-8 CPS and immune cell densities., Conclusions: Our results suggest the difference of each tumour microenvironment between CDC and FH-deficient RCC, and IL-8 is a potential therapeutic target for treating CDC, but not FH-deficient RCC., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Detecting the toxic effects of chemicals on reproduction and development without using mammalian animal models is crucial in the exploitation of pharmaceuticals for human use. Zebrafish are a promising animal model for investigating pharmacological effects and toxicity during vertebrate development. Several studies have suggested the use of zebrafish embryos for the assessment of malformations or embryo-fetal lethality (MEFL). However, a reproducible protocol as a standard for the zebrafish MEFL test method that fulfills global requests has not been established based on the International Council of Harmonisation (ICH) S5 (R3) guidelines. To establish such a toxicity test method, we developed a new and easy protocol to detect MEFL caused by chemicals, especially those with teratogenic potential, using fertilized zebrafish eggs (embryos) within 5 days of development. Our toxicity test trials using the same protocol in two to four different laboratories corroborated the high inter-laboratory reproducibility. Our test method enabled the detection of 18 out of 22 test compounds that induced rat MEFL. Thus, the prediction rate of our zebrafish test method for MEFL was almost 82% compared with that of rat MEFL. Collectively, our study proposes the establishment of an easy and reproducible protocol for the zebrafish MEFL test method for reproductive and developmental toxicity that meets ICH guideline S5 (R3), which can be further considered in combination with information from other sources for regulatory use.

Background and Aims: EUS-guided FNA/biopsy (EUS-FNA/B) is the citerion standard for diagnosing subepithelial lesions (SELs); however, its diagnostic ability for SELs <20 mm is low. We developed a new diagnostic method to differentiate between GI stromal tumor (GIST) and non-GIST by measuring high-frequency impedance (H-impedance) using an EUS-FNB needle., Methods: The H-impedance of gastric epithelial neoplasms from 16 cases were measured with a conventional impedance probe to confirm whether H-impedance is clinically useful for assessing cell density (study 1). The H-impedance values of exposed SELs from 25 cases with use of the conventional probe (study 2) and nonexposed SELs from 20 cases with use of the EUS-FNB needle probe (study 3) were measured to determine the diagnostic ability of H-impedance for differentiating GISTs from non-GISTs., Results: H-impedance significantly positively correlated with cell density (P = .030) (study 1). The H-impedance of GIST (99.5) measured with a conventional probe was significantly higher than with those of the muscular layer (82.4) and leiomyoma (89.2) (P < .01) (study 2). The H-impedance of GIST measured with the EUS-FNB needle was also significantly higher than that of leiomyoma (GIST: 80.2 vs leiomyoma, 71.8; P = .015). The diagnostic yield of the impedance method for differentiating GISTs from non-GISTs had 94.4% accuracy, 88.9% sensitivity, 100% specificity, and 0.95 area under the curve. Diagnostic ability was not affected by lesion size (P = .86) (study 3)., Conclusion: Auxiliary differential diagnosis between gastric GISTs and non-GISTs by the H-impedance measurement during EUS-FNB could be a good option, especially when the lesion is <20 mm., (Copyright © 2023 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.)

Solid-type poorly differentiated adenocarcinoma (solid-type-PDA) of the stomach is a unique histological subtype of "tubular adenocarcinoma", but little is known about its clinicopathological features, molecular pathological characteristics and immunoregulatory tumor microenvironment. Herein, we examined the immunohistochemical expressions of mismatch repair (MMR) proteins (MLH1, PMS2, MSH2, MSH6) in 57 cases of solid-type-PDA and classified them as either MMR-deficient or -proficient (dMMR, N = 23; pMMR, N = 34), and additionally identified 18 dMMR-well-differentiated adenocarcinoma (WDA) and 34 pMMR-WDA as control groups. We analyzed and compared solid-type-PDA with WDA by evaluating the immunoexpressions of key immune pathway proteins (programmed death ligand 1 (PD-L1) and indoleamine 2,3-dioxygenase 1 (IDO1)) and tumor-infiltrating lymphocytes (TILs) (CD8, Foxp3 and PD-1). The results reveled IDO1 was significantly more frequent in dMMR-solid-type-PDA than in dMMR-WDA (P = 0.0046). Moreover, dMMR-solid-type-PDA tended to have higher mean CD8+ and Foxp3+ TILs compared with dMMR-WDA [P = 0.0006 (CD8+) and P = 0.1061 (Foxp3+)], and IDO1-positive tended to be associated with a large number of CD8+, Foxp3+ or PD-1+ TILs in almost all tumor subtypes. PD-L1 was significantly observed in 44 % (15/34) of pMMR-solid-type-PDA compared with 18 % (6/34) of pMMR-WDA (P = 0.0344). Although they are molecularly and morphologically classified as the same chromosomal instability subtype, overall survival (OS) and disease-free-survival (DFS) in pMMR-solid-type-PDA were significantly worse than those in pMMR-WDA [P = 0.0216 (OS) and P = 0.0160 (DFS)]. Our study demonstrates that immunoexpressions of several immunoregulatory proteins and TILs are more prevalent in dMMR-solid-type-PDA, potentially a useful discovery for designing tumor treatments with immune checkpoint inhibitors or combination therapies with a PD-1/PD-L1-inhibitor and IDO1-inhibitor., Competing Interests: Declaration of Competing Interest All authors declare that they have no conflicts of interest to disclose., (Copyright © 2022 Elsevier GmbH. All rights reserved.)