S100 calcium-binding protein 9 (S100A9) also known as calgranulin B, is a member of the S100 family of secreted calcium binding proteins containing 2 EF-hand calcium-binding motifs.S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. Besides, it has been reported that S100A9 can inhibit Hela cells proliferation. To test the effect of S100A9 on cell apoptosis, Hela cells were seeded into 96-well plates at a density of 4,000 cells/well with 1% serum standard DMEM including various concentrations of recombinant human S100A9. After incubated for 48h, 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 the absorbance at 450nm was measured using a microplate reader after incubating the plate for 1h at 37℃. Proliferation of Hela cells after incubation with S100A9 for 48h observed by inverted microscope was shown in Figure 1. Cell viability was assessed by CCK-8 (Cell Counting Kit-8 ) assay after incubation with recombinant human S100A9 for 48h. The result was shown in Figure 2. It was obvious that S100A9 significantly inhibit cell viability of Hela cells. The ED50 is 4.8μg/mL.

Figure 2. Inhibition of Hela cells proliferation after stimulated with S100A9.