Fig. 7

METTL1 low expression in PCa is associated with increased cytotoxic infiltration and good response to ICB treatment. A Cytokine content in PC3 METTL1 KO compared to WT cell-conditioned media shows upregulation of pro-inflammatory (red) and downregulation of anti-inflammatory (blue) cytokines in METTL1 KO cells. The mean ± SD log₂ fold change is shown (n = 4). The full expression array is shown in supplementary figure S8. B The upper panel shows a schematic overview of the workflow followed to analyse M1- or M2-like endotype polarisation of THP-1-derived Mø macrophages exposed to METTL1 KO and WT cell-conditioned medium (c.m.). The lower panel shows the T-distributed stochastic neighbour embedding (tSNE) analysis of macrophage polarisation (n = 3). C Proliferation of human peripheral blood CD3+ T cells co-cultured with primary Mø macrophages exposed to PC3 WT or METTL1 KO cells’ c.m. (n = three technical, two biological replicates). D Migration of human peripheral blood CD3+ T cells towards primary macrophages exposed to PC3 WT or METTL1 KO cells’ c.m. (n = three technical, two biological replicates). E Correlation between METTL1 expression and the immune cell infiltrates of M1-like macrophages (CD86), M2-like macrophages (CD163), and CD8+ T cells in human PCa samples. Immunostainings are shown in supplementary figure S8. F Prostate tumour volume from Pten-KO/Mettl1 + / + and Pten-KO/Mettl1^flox/flox five-month-old mice reflects reduced tumour burden after conditional Mettl1 deletion. Ventral (V), dorsal (D) and anterior (A) lobes. Mean ± SD, n ≥ 5. G Conditional deletion of Mettl1 resulted in reduced tumour proliferation (Ki67 + cells) and increased immune infiltration of iNOS + (M1-like) macrophages and CD8+ T cells. Staining of tumours from Pten-KO/Mettl1 + / + (+ / +) and Pten-KO/Mettl1^flox/flox (fl/fl) five-month-old mice. Mean ± SD, n ≥ 5, > 10 images per biological replicate. H Fold change of cytokines content in Pten-KO/Mettl1^flox/flox versus Pten-KO/Mettl1 + / + tumours (n = 3). I Significant decrease in tumour volume (fold change: FC) in Pten-KO/Mettl1^flox/flox (fl/fl) mice treated with anti-PD1 + anti-CTLA4 antibodies compared to untreated controls (IgG). Pten-KO/Mettl1 + / + (+ / +) mice tumour volume did not change after anti-PD1 + anti-CTLA4 treatment. Mean ± SD, n ≥ 6. J METTL1 mRNA expression levels in anti-PD1 responders and non-responders in clinical trials of breast cancer, ovarian cancer, colorectal cancer, and glioblastoma (n = 484). The data were retrieved from the ROC plotter. Statistical tests: Pearson’s correlation (r), p-value (pV), and linear regression with 95% confidence (bands) are shown (E). One-tailed Student’s t-test (A, C, D, G), Mann–Whitney test (F, I, J), *p < 0.05, **p < 0.01, ***p < 0.001