Lysophosphatidic acid (LPA) is a lipid growth factor that induces proliferation of fibroblasts by activating the cAMP response element binding protein (CREB). Here, we further investigated whether LPA induces proliferation of P19 cells, a line of pluripotent embryonic carcinoma cells. 5?-Bromo-2-deoxyuridine incorporation and cell viability assays showed that LPA stimulated proliferation of P19 cells. Immunoblot experiments with P19 cells revealed that the mitogen activated protein kinases, including p-ERK, p38, pAKT, glycogen synthase kinase 3?, and CREB were phosphorylated by treatment with 10 ?M LPA. LPA-indu-ced phosphorylation of CREB was efficiently blocked by U0126 and H89, inhibitors of the MAP kinases ERK1/2 and mitogen- and stress-activated protein kinase 1, respec-tively. Involvement of cyclin D1 in LPA-induced P19 cell proliferation was verified by immunoblot analysis in combination with pharmacological inhibitor treatment. Furthermore, LPA up-regulated CRE-harboring cyclin D1 promoter activity, suggesting that CREB and cyclin D1 play significant roles in LPA-induced proliferation of P19 embryonic carcinoma cells.

Keywords: cAMP response element binding protein (CREB), cyclin D1, lysophosphatidic acid, P19 embryonic carcinoma cell, proliferation