STAT3 and breast cancer: These include circSEPT9, promoting LIF/Stat3 signaling [46]; hsa_circ_0000199, promoting PI3K/Akt/mTOR signaling [48]; circNR3C2, promoting HRD1 expression (HMG-CoA reductase degradation protein 1) and resulting in increased proliferation, EMT, migration and invasion [49]; and circ_0001667, promoting NCOA3 expression (nuclear receptor coactivator 3) and resistance to Adriamycin in breast cancer cells through competition for miR-4458 [4,50].