Metastasis is an important factor contributing to poor prognosis in patients with gastric cancer; yet, the molecular mechanism leading to this cell behavior is still not well understood. In this study, we explored the role of cysteine protease inhibitor SN (Cystatin SN, CST1) in promoting gastric cancer metastasis. We hypothesized that CST1 could regulate gastric cancer progression by regulating GPX4 and ferroptosis. Whole transcriptome sequencing suggested that the expression of CST1 was significantly increased in metastatic cancer, and high CST1 expression was correlated with a worse prognosis. Our data further confirmed that the overexpression of CST1 may significantly promote the migration and invasion of gastric cancer cells in vitro and enhance liver, lung, and peritoneal metastasis of gastric cancer in nude mice. Meanwhile, high expression of CST1 promoted the epithelial-mesenchymal transition (EMT) of gastric cancer cells. Mechanistically, a co-immunoprecipitation experiment combined with mass spectrometry analysis confirmed that CST1 could interact with GPX4, a key protein regulating ferroptosis. CST1 relieves GPX4 ubiquitination modification by recruiting OTUB1, improving GPX4 protein stability and reducing intracellular reactive oxygen species (ROS), thereby inhibiting ferroptosis and, in turn, promoting gastric cancer metastasis. Moreover, clinical data suggested that CST1 is significantly increased in peripheral blood and ascites of gastric cancer patients with metastasis; multivariate Cox regression model analysis showed that CST1 was an independent risk factor for the prognosis of gastric cancer patients. Overall, our results elucidated a critical pathway through which high CST1 expression protects gastric cancer cells from undergoing ferroptosis, thus promoting its progression and metastasis. CST1 may be used as a new oncological marker and potential therapeutic target for gastric cancer metastasis.

The peritoneum is the most common metastatic site of advanced gastric cancer and is associated with extremely poor prognosis. Endothelial-specific molecule 1 (ESM1) was found to be significantly associated with gastric cancer peritoneal metastasis (GCPM); however, the biological functions and molecular mechanisms of ESM1 in regulating GCPM remain unclear. Herein, we demonstrated that ESM1 expression was significantly upregulated in gastric cancer tissues and positively correlated with platelet endothelial cell adhesion molecule-1 (CD31) levels. Moreover, clinical validation, in in vitro and in vivo experiments, confirmed that ESM1 promoted gastric cancer angiogenesis, eventually promoting gastric cancer peritoneal metastasis. Mechanistically, ESM1 promoted tumor angiogenesis by binding to c-Met on the vascular endothelial cell membrane. In addition, our results confirmed that ESM1 upregulated VEGFA, HIF1α, and MMP9 expression and induced angiogenesis by activating the MAPK/ERK pathway. In conclusion, our findings identified the role of ESM1 in gastric cancer angiogenesis and GCPM, thus providing insights into the diagnosis and treatment of advanced gastric cancer.

Gastric cancer (GC) persists as one of the most lethal malignancies globally, primarily due to late‐stage diagnosis, limited therapeutic targeting options, and inherent resistance to conventional therapies. While molecular profiling has advanced our understanding of GC, the development of effective delivery systems capable of precise tumour targeting and enhanced treatment response remains an unmet need. In this work, we explored targeted therapeutic approaches for GC by leveraging patient‐derived organoid models. Firstly, we confirmed claudin‐4 (CLDN4) as an overexpressed target in malignant epithelial cells in GC through comprehensive analysis of multiple single‐cell RNA sequencing datasets. Capitalising on this discovery, we developed an innovative nano‐therapeutic biomaterial, designated NESC (NK‐sEV‐SpoVM‐c‐CPE ^Q317I ), by engineering natural killer cell‐derived small extracellular vesicles (NK‐sEVs) with a CLDN4‐targeting peptide and a membrane‐curvature‐sensing domain. Multimodal imaging further confirmed tumour‐specific accumulation of NESC, underscoring its targeting precision. Proteomic profiling and functional assays revealed that NK‐sEVs possessed intrinsic radiosensitising properties, which were significantly augmented upon conjugation with the targeting peptide. The resulting NESC platform demonstrated robust tumour‐suppressive activity and enhanced radiosensitisation in both GC organoids and organoid‐derived xenograft models. Collectively, by harnessing patient‐derived organoids for functional validation, this study not only establishes a versatile framework for developing targeted sEV‐based therapeutics but also provides a translational foundation for future clinical applications in GC management.

Chemotherapy remains the cornerstone of gastric cancer (GC) treatment, with Oxaliplatin (OXA) being a critical first-line agent. However, chemotherapy resistance, compounded by increased stemness, poses a significant challenge in GC management. In this study, we demonstrate that JMJD3, encoded by KDM6B and catalyzing the demethylation of H3K27me3, is highly expressed in both GC tissues and patient-derived chemotherapy-resistant xenograft (PDX) models and contributes to increased malignancy and chemoresistance. Overexpression of JMJD3 enhanced stemness and chemoresistance in GC cells, while JMJD3 knockdown had opposite effects. Mechanistically, JMJD3 promotes GC cell stemness and chemoresistance by reducing H3K27me3 on the ALOX5 promoter, a histone modification associated with ALOX5 transcriptional activation. Tumorigenesis induced by N-methyl-N-nitrosourea (MNU) was reduced in mice with gastric epithelial cell-specific deletion of Kdm6b . Importantly, ALOX5 upregulation due to the elevated JMJD3 function sensitized GC cells to ferroptosis inducers. These findings suggest that JMJD3 plays a pivotal role in GC chemoresistance by modulating both stemness and ferroptosis sensitivity. Targeting JMJD3 may provide a novel therapeutic strategy for overcoming chemotherapy resistance, with ferroptosis inducers potentially offering a promising adjunctive treatment in GC.