Deciphering metastatic route-specific signals and their microenvironment interactions in peritoneal metastasis of gastric cancer

Gastric cancer (GC) constitutes a significant cause of cancer-related mortality worldwide, with metastatic patterns including hematogenous, peritoneal, and ovarian routes. Although GC gene expression patterns have been extensively researched, the metastasis-specific gene expression landscape remains largely unexplored. This study undertook a whole transcriptome sequencing analysis of 66 paired primary and metastatic (hematogenous, peritoneal, or ovarian) GC tumors from 14 patients, leading to the identification of 122 unique metastasis-specific epithelial-mesenchymal transition (msEMT) genes. These genes demonstrated varying expression patterns depending on the metastatic route, suggesting route-specific molecular mechanisms in GC metastasis. High expression of msEMT genes in primary tumors was associated with more frequent CDH1 mutations, the genomically stable subtype, and poor prognosis in The Cancer Genome Atlas GC cohort. This association was further corroborated by poor prognosis and high predictive performance for peritoneal or ovarian recurrence in two independent cohorts (GSE66229; n=300, GSE84437; n=433). Single-cell RNA sequencing analysis of primary tumors (GSE167297) and four independent ascites samples from GC patients revealed that msEMT genes were predominantly expressed in diverse fibroblast sub-populations, rather than cancer cells. This study illuminates the route-specific mechanisms and underlines the significance of msEMT genes and cancer-associated fibroblasts in GC metastasis, highlighting potential directions for future research.