Wortmannin inhibits carcinogen‐stimulated phosphorylation of ethanolamine and choline

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Abstract
We have previously reported that in C3H/10T1/2 fibroblasts the environmental carcinogen 7,12‐dimethyl‐benz[a]anthracene (DMBA) stimulated phosphorylation of ethanolamine (Etn). Here we show that in these fibroblasts DMBA also stimulates phosphorylation of choline (Cho). Wortmannin (50–200 nM), an established inhibitor of phosphatidylinositol‐3‐kinase (PI3K), significantly inhibited DMBA‐induced phosphorylation of both Etn and Cho. Wortmannin also inhibited the effect of insulin, a major activator of PI3K, on DNA synthesis. However, insulin had no effect on the phosphorylation of Etn and Cho. These data suggest that a carcinogen‐induced kinase phosphorylates both Etn and Cho, and that the inhibitory effect of wortmannin on Etn/Cho kinase activity may be unrelated to its inhibitory effect on PI3K activity.