Transforming growth factor alpha (TGF-α), a ligand for the epidermal growth factor receptor, which activates a signaling pathway for cell proliferation, differentiation and development. To test the effect of TGF-α on cell proliferation of 3T3 fibroblasts, 3T3 cells were seeded into triplicate wells of 96-well plates at a density of 2, 000 cells/well and allowed to attach overnight, then the medium was replaced with serum-free standard DMEM prior to the addition of various concentrations of TGF-α. After incubated for 72h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10µL of CCK-8 solution was added to each well of the plate, then measure the absorbance at 450nm using a microplate reader after incubating the plate for 1-4 hours at 37°C.

The dose-effect curve of TGF-α was shown in Figure 2. It was obvious that TGF-α significantly promoted cell proliferation of 3T3 cells. The ED50 for this effect is typically 0.6198 to 8.210ng/mL.