Jolivet and Chabner [157] measured the dissociation half lives of MTX (Glu1), MTX-Glu2, MTX-Glu3, MTX-Glu4 and MTX-Glu5 in the binding to dihydrofolate reductase (DHFR) in ZR-75-B human breast cancer cells, and reported that their half lives were 12, 39, 102, 108 and 120 min, respectively. Here, DHFR is linked to breast carcinoma.