Fig 1: Identification of NAAG as a crucial tumor-promoting metabolite in BLIS tumors.a Screening criteria of metabolites potentially promoting tumor progression in BLIS tumors. b RFS of patients with different NAAG abundances of BLIS tumors. The P value was calculated by the log rank test. c Confirmation of NAAG by comparison with standard compound. Measured MS/MS spectral fragmentation profiles (top, in red) matched those of chemical standards (bottom, in gray). d Illustration of the NAAG metabolism pathway. e, f mRNA expression of RIMKLA and RIMKLB (e) and their relationship with NAAG abundance in BLIS tumors (f). g Quantification of cell proliferation after knocking down RIMKLB with shRNA and the complement of NAAG. h Right panel: quantification of cells migrating across transwell filters and invading through matrigel-coated transwells after knocking down RIMKLB with shRNA and the complement of NAAG. Left panel: representative images of three replicates. Ten random fields were counted per insert at 20×. i Experimental design. j, k Effect of RIMKLB knockdown and NAAG complement on tumor growth (j) and tumor weight (k) (n = 6 for each group). Statistical comparisons in g–k were conducted using two-tailed Student’s t-test. Data are presented as means ± SEM. Scale bars, 200 µm. ***P < 0.001, **P < 0.01; *P < 0.05; ns, P = 0.05. NAA, N-acetyl-aspartic acid.