Molecular signals associated with intraperitoneal chemotherapy resistance in gastric cancer with peritoneal metastasis through PIPS GC trial integrated translational research.

Purpose Recent studies have investigated intraperitoneal paclitaxel (IP PTX) combined with systemic chemotherapy for the treatment of gastric cancer peritoneal metastases (GCPM). This clinical trial integrated translational study was conducted to identify biomarkers that can predict patient responses to IP PTX plus systemic systemic S-1 plus oxaliplatin (SOX) chemotherapy. Materials and methods Patients from the PIPS-GC phase Ib/II clinical trial, enrolled at the Korea University Guro Hospital, were included in analyses. Whole exome and transcriptome sequencing were performed on formalin-fixed, paraffin-embedded gastric tumor, normal gastric, and peritoneal tumor tissues. A metastatic tumor-specific gene set was analyzed using The Cancer Genome Atlas (TCGA) gastric cancer data and publicly available single-cell RNA sequencing (scRNA-seq) datasets. Spatial transcriptomic analysis of primary and peritoneal tumors from a non-responder was performed to validate candidate biomarkers. Results Nine patients with gastric cancer were enrolled; six in the response group and three in the non-response group. Candidate genes for predicting IP PTX plus systemic SOX chemotherapy response were identified and compared with TCGA-GC and scRNA-seq datasets. Spatial transcriptomics revealed higher expression of thrombospondin type 1 domain-containing protein 4 (THSD4) in peritoneal tumors, which was associated with chemotherapy resistance via midkine and epithelial-mesenchymal transition pathways. Conclusion This PIPS-GC clinical trial identified THSD4 as a potential biomarker for predicting IP PTX plus systemic SOX response in gastric cancer peritoneal metastasis. Further research is required to elucidate the mechanism of action by which THSD4 affects GCPM and validate its clinical utility as a predictive biomarker for IP PTX response.