F-Box And WD Repeat Domain Containing Protein 7 (FBXW7) , also known as FBW7, AGO, or SEL-10, is a crucial component of the Skp1-Cullin1-F-box (SCF) ubiquitin ligase complex, which plays a pivotal role in regulating protein turnover through ubiquitination and subsequent proteasomal degradation. As an F-box protein, FBXW7 functions as the substrate recognition subunit of the SCF complex, specifically targeting a diverse array of oncogenic proteins for degradation, thereby exerting significant tumor-suppressive effects. To test the effect of FBXW7 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 FBXW7. 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 FBXW7 for 72h. The result was shown in Figure 1. It was obvious that FBXW7 significantly increased cell viability of A549 cells. The ED50 of recombinant human FBXW7 is 1.525 μg/ml.