The results of CCK-8, colony formation, and EdU assays suggested that under hypoxic conditions, DDB2 silencing reversed the promoting effect of circPFKFB4 overexpression on BC cell proliferation, while DDB2 overexpression abrogated the inhibitory role of circPFKFB4 knockdown in BC cell proliferation (Fig. 8A-E and Fig. S10A-C). The gene discussed is DDB2; the disease is breast cancer.