METTL4 and neoplasm: The results showed that indeed only hypoxic tumor cells (FADU, BFTC909, KTCC28M) staining with Pimonidazole (a representative sorting was shown in Additional file 1: Fig. S2p) has increased METTL4 expression and increased 6mA levels (Fig. 2f, g; Additional file 1: Fig. S2q).