MDM2 and gastric cancer: Although no study has focused on the biological functions of SPRR1A in any cancer, previous studies have argued that other SPRR family genes, such as SPRR2B in gastric cancer and SPRR3 in breast and colorectal cancers, enhance cancer cell proliferation and were involved in cancer growth signaling, such as the AKT, MAPK and MDM2-p53/p21 signaling pathways in vitro [16–18].