Activation of phosphatidylcholine-cycle enzymes in human epithelial ovarian cancer cells

Altered phosphatidylcholine (PC) metabolism in epithelial ovarian cancer (EOC) can provide choline-based imaging approaches as powerful tools to improve diagnosis and identify new therapeutic targets. Biochemical, protein and mRNA expression analyses demonstrated that the increase in the major choline-containing metabolite phosphocholine (PCho) in EOC compared with normal and non-tumoral immortalized counterparts (EONT) mainly rely upon: 1) ChoK activation, consistent with higher protein content and increased ChoKalpha mRNA expression levels; 2) PC-plc activation, consistent with higher, previously reported, protein expression. More limited and variable sources of PCho could derive, in some EOC cells, from activation of Phospholipase D or GPC-pd. Phospholipase A2 activity and isoforms’ expression levels were lower or unchanged in EOC compared with EONT cells. Increased ChoKalpha mRNA, as well as ChoK and PC-plc protein expression, were also detected in surgical specimens isolated from EOC patients. Overall, we demonstrated that the elevated PCho pool detected in EOC cells primarily resulted from the upregulation/activation of ChoK and PC-plc involved in the biosynthetic and in a degradative pathway of the PC-cycle, respectively. 20 EOC frozen surgical specimens, 8 EOC cell lines and Ovarian Surface Epithelial (OSE) cells (4 different preparations, 3 of them pooled in one sample).