Total protein of cells in each group was extracted, respectively. Protein concentration was determined with the bicinchoninic acid protein assay kit (PICPI23223, Thermo, Nanjing, Jiangsu, China). The protein was separated by 10% or 12% polyacrylamide gel (JRDUN Biotechnology Co., Ltd) and electrophoresis and then was put onto a polyvinylidene fluoride membrane after supplementing 5% nonfat dry milk or bovine serum albumin (BSA) into the proteins for blocking for 1 hour at room temperature. After addition with primary antibodies, the sealing fluid was incubated at 4°C overnight. The primary antibodies against P38α (#9218, 1:1000), P53 (#9282, 1:1000), P21 (#2947, 1:1000), and GAPDH (#5174, 1:2000) were bought from Cell Signaling Technology (Danvers, MA, USA). The primary antibody against SMP30 (Ab233007, 1:400) was purchased from Abcam Plc (Cambridge, UK). Then, the membrane was incubated together with horseradish-labeled secondary antibody (Beyotime), including goat anti-rabbit IgG (A0208, 1:1000), donkey anti-goat IgG (A0181, 1:1000), and goat anti-mouse IgG (A0216, 1:1000), at 37°C for 1 hour. Chemiluminescence detection was performed and the protein image was captured by Tanon-5200 (Shanghai Tianneng Technology Co., Ltd, Shanghai, China).