Expression of human choline kinase in NIH 3T3 fibroblasts increases the mitogenic potential of insulin and insulin-like growth factor I

In mammalian cells, growth factors, oncogenes, and carcinogens stimulate ph osphocholine (PCho) synthesis by choline kinase (CK), suggesting that PCho may regulate cell growth. To validate the role of PCho in mitogenesis, we d etermined the effects of insulin, insulin-like growth factor I (IGF-I), and other growth factors on DNA synthesis in NIH 3T3 fibroblast sublines highl y expressing human choline kinase (CK) without increasing phosphatidylcholi ne synthesis. In serum-starved CK expressor cells, insulin and IGF-I stimul ated DNA synthesis, p70 S6 kinase (p70 S6K) activity, phosphatidylinositol 3-kinase (P13K) activity, and activating phosphorylation of p42/p44 mitogen -activated protein kinases (MAPK) to greater extents than in the correspond ing vector control cells. Furthermore, the CK inhibitor hemicholinium-3 (HC -3) inhibited insulin- and IGF-I-induced DNA synthesis in the CK overexpres sors, but not in the vector control cells. The results indicate that high c ellular levels of PCho potentiate insulin- and IGF-I-induced DNA synthesis by MAPK- and p70 S6K-regulated mechanisms. (C) 2000 Published by Elsevier S cience Inc. All rights reserved.