Transferrin (TF) is one of members of anion-binding superfamily of proteins. It is synthesized as a 698 amino acid (aa) precursor, which is mainly in the liver and is present in high concentrations in the bloodstream.TF plays a fundamental role in iron metabolism, protecting tissues from the potentially harmful effects of free iron, which can generate reactive oxygen species and cause oxidative damage. To test the effect of TF on cell proliferation, HepG2 cells were seeded into triplicate wells of 96-well plates and allowed to attach, replaced with various concentrations of recombinant dog TF. After incubated for 72h, cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10 μl of CCK-8 solution was added to each well of the plate, then the absorbance at 450 nm was measured using a microplate reader after incubating the plate for 1-4 hours at 37 ℃. Cell viability was assessed by CCK-8 assay after incubation with recombinant dog TF for 72h. The result was shown in Figure 1. It was obvious that TF significantly increased cell viability of HepG2 cells. The ED50 of recombinant dog TF is 0.292 μg/ml.