CCNE1 and osteosarcoma: For instance, circ-0001721 accelerates the development of osteosarcoma via the miR-372-3p/MAPK7 axis (Gao et al., 2020), and circRNA circAGFG1 accelerates the progression of triple-negative breast cancer via regulating CCNE1, the sponge of miR-195-5p (Yang et al., 2019).