CircRNA DONSON contributes to cisplatin resistance in gastric cancer cells by regulating miR-802/BMI1 axis.

Background: Circular RNA downstream neighbor of SON (circDONSON) has been revealed to promote gastric cancer (GC) growth and invasion, while the role and molecular mechanism underlying circDONSON in GC cisplatin (DDP) resistance remain unclear.

Methods: Levels of circDONSON, microRNA (miR)-802, and B lymphoma Mo-MLV insertion region 1 (BMI1) mRNA were detected using quantitative real-time polymerase chain reaction. Cell viability and apoptosis were measured by cell counting kit-8 assay, colony formation assay and flow cytometry, respectively. Protein levels of BMI1, Cyclin D1, p27, Caspase-3 Cleavage and Caspase-9 Cleavage were determined by western blot. The interaction between miR-802 and circDONSON or BMI1 was confirmed by dual-luciferase reporter assay. In vivo experiments were conducted via the murine xenograft model.

Results: CircDONSON was elevated in GC tissues and cell lines, especially in DDP-resistant GC tissues and cells. Knockdown of circDONSON sensitized GC cells to DDP by inhibiting cell viability and promoting cell apoptosis in vitro. Further mechanism-related investigations suggested that circDONSON functioned as "sponge" by competing for miR-802 binding to modulate its target BMI1. Silencing miR-802 reversed the inhibition of DDP-resistance in GC cells induced by circDONSON down-regulation. Besides, miR-802 alleviated DDP resistance in GC cells by targeting BMI1. Functionally, circDONSON knockdown enhanced the cytotoxicity of DDP in GC in vivo.

Conclusion: Our findings demonstrated circDONSON promoted cisplatin resistance in gastric cancer cells by regulating miR-802/BMI1 axis, shedding light on the development of a novel therapeutic strategy to overcome chemoresistance in gastric cancer patients.