IL24 (interleukin 24) is a cytokine that belongs to IL10 family. This protein can induce apoptosis selectively in various cancer cells, including ECV304. Thus, inhibition of cell proliferation assay of IL24 was conducted using ECV-304 cells. Briefly, ECV-304 cells were seeded into triplicate wells of 96-well plates at a density of 2,000 cells/well and allowed to attach overnight, then the medium was replaced with serum-free standard 1640 prior to the addition of various concentrations of IL24. 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 1-4 hours at 37°C. Inhibition of ECV-304 cells proliferation after incubation with IIL24 for 48h observed by inverted microscope was shown in Figure 1. Cell viability was assessed by CCK-8 (Cell Counting Kit-8 ) assay after incubation with various concentrations of IL24 for 48h. The mean OD value of ECV-304 assessed by CCK-8 was shown in Figure 2. It was obvious that IL24 significantly decreased cell viability of ECV-304 cells.