MDM2 and cancer: Previous studies have shown that SPRR3 promoted the proliferation of breast cancer and colorectal cancer cells via the AKT and mitogen-activated protein kinase (MAPK) pathways [16,17] and that SPRR2B facilitated the growth of gastric cancer via the MDM2-p53/p21 signaling pathway [18], suggesting that SPRR family genes may be involved in cancer growth signaling.