MMP14 and neoplasm: Interestingly, the 89Zr-DFO-LEM2/15 antibody only caused a very weak signal in an orthotopic U251 tumor model and did not show a significant difference between tumor/blood ratios of the specific labeled antibody and control 89Zr-DFO-IgG1 (0.23±0.04 and 0.30±0.03 versus 0.17± 0.05 and 0.21± 0.10, at 2 and 4 days p.i., respectively) (S3A Fig), despite the considerably higher expression of MT1-MMP on U251 cells as compared with TS543 neurospheres (Fig 1C).