The sunburn cell: regulation of death and survival of the keratinocyte.

Sunburn cells are keratinocytes undergoing apoptosis after they have received a physiological UVB dose that irreversibly and severely damaged their DNA or other chromophores. If these cells would escape programmed cell death, a cancer prone phenotype could arise. On the other hand, if the decision to die is made too prematurely, the proliferative compartment of basal keratinocytes would be inevitably lost, thereby hampering normal skin homeostasis. Pro- and anti-apoptotic mediators carefully control crucial points of the cell death program by regulating complex signalling cascades originating at the cell membrane, the nucleus and the cytoplasm. The balance between survival and apoptogenic factors determines the final cell fate, and growing evidence suggests that the deregulation of this balance by chronic UVB stress, results in the development of skin malignancy. The present paper reviews recent data on the major pathways regulating UVB-induced sunburn cell formation and implicates the deregulation of these pathways in the development of skin cancer.