Fig. 1. The m⁶A methyltransferase METTL3 is up-regulated in human cancer and essential for the malignant properties, which requires the intact enzymatic activity.

(A to D) Levels of N⁶-methyladenosine (m⁶A) in rRNA-depleted RNAs (A and C) or expression of METTL3 by RT-qPCR (B and D) in either the indicated human cell lines (A and B) or 12 pairs of prostate tumors (PCa) and normal adjacent tissues (Normal) (C and D). (E and F) Representative IHC staining images of METTL3 protein (E) and quantification of IHC scores (F). Scale bar, 50 μm. N, numbers of cases. (G) Immunoblotting in LNCaP cells that were infected with either control shRNA (shCtrl) or METTL3-specific shRNA (shM3#1) and then overexpressed control vector (vector), wild-type METTL3 (M3-WT^R), or catalytically dead mutant (M3-CD^R), which are HA-tagged and resistant to shM3#1. (H to L) Levels of m⁶A in rRNA-depleted RNAs (H), cell growth (I), colony formation assay (J), in vitro transwell migration (K), and invasion (L) assay in the METTL3 rescue system of LNCaP cells that is described in (G). Scale bars, 100 μm (K and L). (M) Tumor growth of prostate cancer xenografts by inoculating the METTL3 rescue system established in 22Rv1 cells. Data are presented as the mean tumor volume in mm³ ± SEM. *P < 0.05; **P < 0.01; NS, not significant. P values in (C) and (D) were calculated by two-tailed paired t test and in (F) by Wilcoxon signed-rank test.