Retracted: Circular RNA circFAT1(e2) Promotes Osteosarcoma Progression and Metastasis by Sponging miR-181b and Regulating HK2 Expression...H. Gu, X. Cheng, J. Xu et al., “Circular RNA circFAT1(e2) Promotes Osteosarcoma Progression and Metastasis by Sponging miR-181b and Regulating HK2 Expression,” BioMed Research International, vol. 2020, Article ID 3589871, 7 pages, 2020.