title: ras-Induced up-regulation of CTP:phosphocholine cytidylyltransferase α contributes to malignant transformation of intestinal epithelial cells.
abstract: Cancer cells have enhanced lipogenic capacity characterized by increased synthesis of fatty acids and complex lipids, including phosphatidylcholine (PC). As the rate-limiting enzyme in the CDP-choline pathway for PC synthesis, CTP:phosphocholine cytidylyltransferase α (CCTα) is implicated in the provision of membranes and bioactive lipids necessary of cell proliferation. In this study, we assessed the role of CCTα in malignant intestinal epithelial cells transformed with activated H-ras (IEC-ras). Three IEC-ras clones had significant up-regulation CCTα expression, but PC synthesis and in vitro activity of CCTα were similar to control IEC. RNA interference of CCTα in adherent IEC-ras did not affect PC synthesis, confirming that the enzyme was relatively inactive. However, CCTα silencing in ras-transformed IEC reduced anchorage-independent growth, a criterion for malignant transformation, as well as tumorigenicity in mice. Relative to their adherent counterparts, detached IEC-ras had increased PC synthesis that was attenuated by inducible CCTα silencing. Detachment of IEC-ras was accompanied by increased CCTα phosphorylation and cytosolic enzyme activity. We conclude that the expanded pool of CCTα in IEC-ras is activated by detachment. This provides the increased PC biosynthetic capacity that contributes to malignant transformation of intestinal epithelial cells when detached from the extracellular matrix.
authors.affiliation: Atlantic Research Centre, Department of Pediatrics and Biochemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Arsenault
authors.forename: Byong H
authors.initials: BH
authors.lastname: Yoo
authors.forename: Kirill V
authors.initials: KV
authors.lastname: Rosen
authors.forename: Neale D
authors.initials: ND
authors.lastname: Ridgway
mesh_terms: D000818:Animals; D023102:Anoikis; D002448:Cell Adhesion; D002469:Cell Separation; D002471:Cell Transformation, Neoplastic; D019916:Choline-Phosphate Cytidylyltransferase / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology*; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D007422:Intestines / Q000166:cytology*; D008856:Microscopy, Fluorescence / Q000379:methods; D009685:Nuclear Envelope / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D051381:Rats; D015854:Up-Regulation; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D010713:Phosphatidylcholines; D019916:Choline-Phosphate Cytidylyltransferase; D018631:ras Proteins