Cisplatin-induced ecDNA enhances tumor malignancy and accelerates chemoresistance acquire in gastric cancer.
BACKGROUND Extrachromosomal DNA (ecDNA), as a dynamic genetic vector, enables tumor cells to exhibit enhanced adaptability under chemotherapeutic stress. However, its functional role in tumor malignancy and the development of drug resistance in gastric cancer (GC) remains unclear. OBJECTIVE This study aims to investigate the relationship between chemotherapy and ecDNA in GC, and explore its potential as a novel therapeutic target. METHODS We first analyzed our clinical data to reveal associations between ecDNA induction by chemotherapy and metastatic progression. Then we investigated the role of ecDNA in mediating chemoresistance and malignant phenotypes in cisplatin-resistant cell models using WGS, SEM, western blot, qPCR, flow cytometry, and immunofluorescence. RESULTS We found that neoadjuvant chemotherapy (NAC) promoted ecDNA formation from linear amplicons, which was associated with increased tumor mutational burden, poorer survival, and higher distant metastasis risk. The generation of ecDNA in GC was more likely to originate from chromosomes 5, 7, 8, 9, and 12. In cisplatin-resistant models, ecDNA emergence promoted various malignant phenotypes, including DNA damage repair, G1 arrest, autophagy, proliferation, migration, and invasion, which were attenuated by ecDNA inhibition. EcDNA inhibitors delayed acquired resistance in wild-type cells and showed combinatorial activity with cisplatin in resistant GC, supporting clinical potential. CONCLUSION Our study revealed that cisplatin could promote ecDNA generation, which enhanced malignant phenotypes, including cell proliferation, motility and drug resistance, and was associated with poorer patient prognosis. Targeting ecDNA with inhibitors could reverse these effects, supporting further preclinical evaluation.