Placental alkaline phosphatase, insulin, and adenine nucleotides or adenosine synergistically promote long-term survival of serum-starved mouse embryo and human fetus fibroblasts

Earlier we showed that in serum-starved fibroblasts placental alkaline phos phatase (PALP) can exert growth factor-like effects. Here we report that in mouse embryo (NIH 3T3) and human fetus (HTB-157) fibroblasts, PALP (200 nM ) alone provided full protection against serum starvation-induced cell deat h for 5 days. After 12 days, substantial effects of PALP on cell survival r equired the copresence of insulin (500 nM) and ATP or adenosine (100 muM). In serum-starved NIH 3T3 cells, PALP induced activating phosphorylation of p42/p44 mitogen-activated protein (MAP) kinases; insulin, but not ATP, had small additional effects. PALP also stimulated the expression of various cy clins; ATP both prolonged and enhanced PALP-induced expression of cyclins A and E. Finally, ATP/adenosine enhanced activation of Akt kinase by insulin . The results suggest that PALP may be a regulator of growth and remodeling of fetal tissues during the second and third trimester of pregnancy when i t is expressed. (C) 2000 Elsevier Science Inc. All rights reserved.