Von Hippel Lindau Tumor Suppressor (vHL) is a key tumor suppressor that plays a critical role in regulating cellular responses to oxygen levels. Encoded by the VHL gene, this protein functions primarily as part of a multi-protein E3 ubiquitin ligase complex, which targets specific proteins for degradation via the ubiquitin-proteasome system. To test the effect of vHL on cell proliferation, 293T cells were seeded into triplicate wells of 96-well plates and allowed to attach, replaced with various concentrations of recombinant human vHL. 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 vHL for 72h. The result was shown in Figure 1. It was obvious that vHL significantly decreased cell viability of 293T cells. The ED50 of recombinant human vHL is 1.607 μg/ml.