?Noggin（NOG）, a secreted glycoprotein, plays a pivotal role in embryonic development and cellular differentiation. It functions as a key antagonist of bone morphogenetic proteins (BMPs), a subgroup of the transforming growth factor-beta (TGF-β) superfamily. By binding directly to BMP ligands, NOG inhibits their interaction with cell surface receptors, thereby modulating critical signaling pathways that govern tissue patterning, and organogenesis. To test the effect of NOG on cell proliferation, U2OS cells were seeded into triplicate wells of 96-well plates and allowed to attach, replaced with various concentrations of recombinant human NOG. 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 NOG for 72h. The result was shown in Figure 1. It was obvious that NOG significantly increased cell viability of U2OS cells. The ED50 of recombinant human NOG is 0.292 μg/ml.