Signaling pathways regulating the differentiation program of epidermal cells overlap widely
with those activated during apoptosis. How differentiating cells remain protected from
premature death, however, is still poorly defined. We show here that the phosphoinositide 3-
kinase (PI3K)/Akt pathway is activated at early stages of mouse keratinocyte differentiation
both in culture and in the intact epidermis in vivo. Expression of active Akt in keratinocytes
promotes growth arrest and differentiation, whereas pharmacological blockade of PI3K …