METTL3 and breast cancer: HBXIP increases the expression of METTL3 through restraining the expression of tumor suppressor let-7g, and METTL3 in turn upregulates HBXIP via m6A modification, thus forming a positive feedback regulatory loop of HBXIP/let-7g/METTL3/HBXIP, and ultimately causing the malignant growth of BC cells (72).