ΔNp63 targets cytoglobin to inhibit oxidative stress-induced apoptosis in keratinocytes and lung cancer

During physiological aerobic metabolism, the epidermis undergoes significant oxidative stress as a result of the production of reactive oxygen species (ROS). To maintain a balanced oxidative state, cells have developed protective antioxidant systems, and preliminary studies suggest that the transcriptional factor p63 is involved in cellular oxidative defence. Supporting this hypothesis, the Delta Np63a isoform of p63 is expressed at high levels in the proliferative basal layer of the epidermis. Here we identify the CYGB gene as a novel transcriptional target of Delta Np63 that is involved in maintaining epidermal oxidative defence. The CYGB gene encodes cytoglobin, a member of the globin protein family, which facilitates the diffusion of oxygen through tissues and acts as a scavenger for nitric oxide or other ROS. By performing promoter activity assays and chromatin immunoprecipitation, reverse transcriptase quantitative PCR and western blotting analyses, we confirm the direct regulation of CYGB by Delta Np63a. We also demonstrate that CYGB has a protective role in proliferating keratinocytes grown under normal conditions, as well as in cells treated with exogenous hydrogen peroxide. These results indicate that Delta Np63, through its target CYGB has an important role in the cellular antioxidant system and protects keratinocytes from oxidative stress-induced apoptosis. The Delta Np63-CYGB axis is also present in lung and breast cancer cell lines, indicating that CYGB-mediated ROS-scavenging activity may also have a role in epithelial tumours. In human lung cancer data sets, the p63-CYGB interaction significantly predicts reduction of patient survival.