Secreted Frizzled-Related Protein 2 (SFRP2) is a key member of the SFRP family of extracellular signaling molecules. By inhibiting the Wnt/β-catenin pathway, SFRP2 plays a crucial role in regulating fundamental cellular processes. Its primary functions include the suppression of cellular proliferation and the induction of apoptosis. To test the effect of SFRP2 on cell proliferation, A549 cells were seeded into triplicate wells of 96-well plates and allowed to attach, replaced with various concentrations of recombinant human SFRP2. 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 human SFRP2 for 72h. The result was shown in Figure 1. It was obvious that SFRP2 significantly increased cell viability of A549 cells. The ED50 of recombinant human SFRP2 is 1.655 μg/ml.