IL1α(Interleukin-1 alpha) is a member of the interleukin 1 cytokine family. This cytokine is produced by monocytes and macrophages as a proprotein, which is proteolytically processed and released in response to cell injury, and thus induces cell apoptosis. It is reported that exposure of MCF-7 cells to certain concentration of IL1α results in inhibition of cell growth. Thus, an cell proliferation assay of MCF-7 was conducted with the addition of IL1α. MCF-7 cells were seeded overnight at a density of 4,000 cells/well, and then treated with or without various concentrations of IL1α for 72h, then cells were observed by inverted microscope and cell viability 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 measure the absorbance at 450 nm using a microplate reader after incubating the plate for 1-4 hours in at 37 °C. Inhibition of MCF-7 cell proliferation after incubation with IL1α for 72h 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 IL1α for 72h. The mean OD value of MCF-7 assessed by CCK-8 was shown in Figure 2. It was obvious that IL1α significantly decreased cell viability of MCF-7 cells and the EC50 was 4.69 ug/ml.