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

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE19352 | GEO | 2009/12/08

SECONDARY ACCESSION(S): PRJNA120383

REPOSITORIES: GEO

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Project description:Detection of the abnormal phosphatidylcholine (PtdCho) metabolism in EOC by analysis of magnetic resonance profile (MRS), showed a significant increase of PCho content in EOC cells as compared with non tumoral counterparts associated with activation of choline kinase (ChoK), the enzyme responsible for PCho production following choline phosphorylation in the PtdCho biosynthetic pathway (Kennedy’s pathway). The α-isoform of ChoK has an essential role in growth control and signal transduction and it has been implicated in the carcinogenic process. Aim of the study is the evaluation of the biological relevance of ChoK expression and activity to define its possible role as a non-invasively detectable EOC biomarker and druggable target. We specifically silenced ChoKα expression by transient RNA interference in two different EOC cell lines and evaluated the biological effects related to metabolic profiles, cell proliferation, cell cycle regulation and alteration of global gene expression to possibly identify new pathways implicated in altered choline metabolism. Following ChoKα silencing we observed a 70% reduction of mRNA and protein expression with a similar reduction in PCho accumulation as assessed by HMRS analysis. The ChoKα silencing was accompanied by 20% inhibition of cell growth and similar percentage of cells blocked in the G1-phase of cell cycle. No alteration in cell morphology and modulation of the main survival signaling pathways (PI3K and MAPK-related signaling) were observed. By gene expression analysis we found 476 differentially expressed genes (p< 0.01; FDR 25%) in silenced cells. By transcriptome analysis of CHKA silenced cells as compared to controls, among the most relevant co-repressed genes we found CyclinA, related to regulation of cell cycle progression, and cytokines genes (IL-6 and IL-8) related to inflammation and EOC aggressiveness. Acyl-CoA synthetase medium-chain family member 3 (ACSM3), phosphatidic acid phosphatase type 2 (PPAP2A) and Osteoprotegerin were among the most up-regulated genes. All co-modulated genes have been validated by RTqPCR also in independent biological replicates. Ingenuity System Pathways Analysis (IPA) identified a network of molecules most significantly affected by CHKA silencing whose main functions is related to cell morphology cellular assembly and organization, cellular function and maintenance. Also, the cellular functions predicted to be mostly affected by silencing were cellular movement and cell death that are expected to be respectively decreased and increased in silenced cells. a total of 12 samples were analyzed: Two EOC cell line SKOV3 and INTOV11 were transiently silenced with unrelated or CHKA-specific siRNA pool. Three independent experiment were run for each cell line.

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

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