Enhancing factor (EF), a growth factor modulator, is the mouse homologue of human secretory group II phospholipase A2. EF in the presence of EGF (Epidermal growth factor) has been shown to give cells a growth advantage, and is known to play a role in phenotypic transformation of normal cell in vitro. EGF interacts with EF and is known to be involved in stem cell regulation. This suggests that EF may have a role in stem cell regulation. In these K14-EF mice, we would like to delineate the role of EF in epidermal stem cell regulation.