Fig. 4. EGF ligand release can be quantitatively tuned across a wide dynamic range. (A) Ligand release rate is measured from the slope of EGF accumulation over time. After 16 hours in serum-free media, cells were switched to fresh serum-free media or to media containing an inhibitor and samples were collected at 2-hour time intervals from triplicate wells. EGF concentration was measured using an EGF ELISA. The approximate ligand release rates (molecules of EGF released/cell/minute), verified in independent experiments, are shown next to each linear fit. (B) TCT release into the media over an 8 hour time period is inhibited using increasing concentrations of batimastat. Fitting the conditioned EGF concentration to a dose-response curve reveals a median inhibition concentration of 0.33 µM batimastat. (C) Adding increasing concentrations of batimastat down-modulates the linear ligand release of TCT cells. Error bars represent one standard deviation from the mean of triplicate samples.