METTL3 and breast cancer: Reduced expression of METTL3, METTL14, WTAP and FTO but not ALKBH5 was associated with poor metastasis relapse (MR)-free survival in all BC patients by Kaplan-Meier analysis, meta-analysis (Additional file 1: Figure S1) and univariate Cox analysis (Additional file 1: Table S2-S6) based on the bc-GenExMiner v4.0 database (Fig. 5).