MTOR and osteosarcoma: In osteosarcoma, it has been observed that hsa_circ_0001649, by sponging miR-338-5p, miR-647 and miR-942, inhibits the STAT signaling pathway to decrease cellular proliferation and promote apoptosis (Sun and Zhu, 2020) whereas, in retinoblastoma, hsa_circ_0001649 was observed to exert its actions via the modulation of the AKT/mTOR signaling pathway (Xing et al., 2018) and this suggests that even though dysregulated circRNA may play a role in the pathogenesis of cancer, they may not be useful as biomarkers of prognosis and response to chemotherapy.