METTL3 and breast cancer: METTL3 is an important methylase for m6A modification, and it shows important performance in lung cancer, breast cancer, ovarian cancer, gastrointestinal cancer, and leukemia by regulating downstream targets BCL-2, MEC6, and PTEN to inhibit apoptosis (Vu et al., 2017; Wei et al., 2019; Wang et al., 2020b; Wang et al., 2020c; Bi et al., 2021).