Cisplatin-induced WWP1-eccDNA expression contributes to ovarian cancer resistance

Multidrug resistance remains a major obstacle in the treatment of ovarian cancer (OC) patients. Recent research has underscored the critical role of extrachromosomal circular DNA (eccDNA) in tumor initiation and progression. However, there is limited comprehensive understanding of the role eccDNA plays in tumor resistance. This study investigates the involvement of WWP1-eccDNA in the resistance mechanisms of OC. Human OC cells (SKOV3 and cisplatin-resistant SKOV3/DDP) were cultured and high-throughput sequencing was performed, leading to the identification of eccDNA in SKOV3/DDP cells. Female BALB/cA-nu nude mice with SKOV3 and SKOV3/DDP xenografts received cisplatin (5.5 mg/kg), hydroxyurea (50 mg/kg) or saline for 14 days, followed by tumor weight assessment. Digital droplet polymerase chain reaction (ddPCR) and real-time quantitative polymerase chain reaction (qPCR) were used to quantify WWP1-eccDNA, evaluating their sensitivity and accuracy. Linear DNA removal and BsmI digestion were tested to improve eccDNA detection. WWP1-eccDNA was among the top upregulated eccDNA in SKOV3/DDP cells. Both cisplatin and hydroxyurea reduced tumor growth in mice, with cisplatin showing limited efficacy in resistant tumors. The ddPCR outperformed RT-qPCR in sensitivity, and linear DNA removal improved WWP1-eccDNA detection. WWP1-eccDNA levels were significantly elevated in SKOV3/DDP tumors. Treatment with cisplatin further increased its expression, whereas hydroxyurea led to a reduction in WWP1-eccDNA levels. WWP1-eccDNA is critical in OC resistance, with cisplatin treatment increasing WWP1-eccDNA levels, contributing to resistance. The ddPCR proves to be a superior method for eccDNA detection.