Annexin A1 (ANXA1), also known as lipocortin I, belongs to the annexin family of Ca2 -dependent phospholipid-binding proteins that have a molecular weight of approximately 35,000 to 40,000 and are preferentially located on the cytosolic face of the plasma membrane. Annexin A1 protein has an apparent relative molecular mass of 40kDa with phospholipase A2 inhibitory activity. To test the effect of ANXA1 on cell apoptosis, A549 cells were seeded into 96-well plates at a density of 3,000 cells/well with 1% serum standard DMEM including various concentrations of recombinant rat ANXA1. 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 2h at 37oC. Proliferation of A549 cells after incubation with ANXA1 for 48h observed by inverted microscope was shown in Figure 1. Cell viability was assessed by CCK-8 assay after incubation with recombinant rat ANXA1 for 48h. The result was shown in Figure 2. It was obvious that ANXA1 significantly inhibit cell viability of A549 cells. The ED50 is 1.75µg/mL.

Figure 2. Inhibition of A549 cells proliferation after stimulated with ANXA1.