MRS Observed Effects of Phorbol Myristate Acetate on Lipid Metabolism in DU145 Prostate Tumor Cells

Introduction Tumors have been shown to have a disregulation in choline lipid metabolism. It has been demonstrated that upregulations in choline kinase, the enzyme responsible for the phosphorylation of choline to phosphocholine (PC), may explain the abnormally high levels of PC in a panel of tumors, ranging from breast to prostate tumor cell lines [1, 2]. However, upon drug treatment, tumor cells often exhibit a switch in the [GPC]/[PC] ratio compared to controls [3]. It remains unclear if this is caused by choline uptake, phosphorylation, or the actions of phospholipases. Additionally, often ignored are the peripheral enzymes that contribute to choline lipid metabolite formation, such as protein kinase C (PKC). PKC has been shown to mediate the apoptotic effect of phorbol esters (e.g., PMA) [4] and inhibit proliferation via phosphorylation of EGFR at threonine 654 [5] in prostate cancer cells. Phorbol myristate acetate (PMA) is a known activator of PKC and mimetic analogue of diacylglycerol, the cleavage product of PLC. PMA has also been shown to cause a redistribution of PLC to the plasma membrane in fibroblasts [6]. In this work, we have investigated the effect of PKC activation by PMA on lipid metabolism in DU145 prostate tumor cells. Perfused DU145 cells were treated with PMA and analyzed with P MRS to measure levels of PC. Cultured DU145 cells were also treated with PMA, as well as the phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor D609, and extracts were measured by high-resolution H MRS to examine levels of choline, PC, and GPC. The data shows that PMA affects lipid metabolism and has antiproliferative effects on DU145 prostate tumor cells.