title: Regulation of Akt(ser473) phosphorylation by choline kinase in breast carcinoma cells.
abstract: BACKGROUND
  The serine/threonine kinase PKB/Akt plays essential role in various cellular processes including cell growth and proliferation, metabolism and cell survival. The importance of the Akt pathway is highlighted by the mutation of various components of the pathway such as the PTEN and PI3-kinase (P110alpha) in human cancers. In this paper, we employed an RNA interference library targeting all human kinases to screen for kinases involved in the regulation of Akt activation, in particular serine 473 phosphorylation. Here, we transfected the MDA-MB 468 breast cell line with the human kinome siRNA library and measured Akt activation using an antibody specific for phosphoserine 473 of Akt.
  
  
  RESULTS
  The screen revealed that phosphorylation of Akt(ser473) can be regulated by more than 90 kinases. Interestingly, phosphorylation of Akt(ser473), but not thr308, can be severely reduced by inhibition of Choline kinase activity via siRNA or small molecule inhibitors. We show here that the regulation of Akt phosphorylation by Choline kinase is PI3K-independent. In addition, xenograft tumors treated with Choline kinase inhibitors demonstrated a statistically significant decrease in Akt(ser473) phosphorylation. Importantly, the reduction in phosphorylation correlates with regression of these xenograft tumors in the mouse model.
  
  
  CONCLUSIONS
  High Choline kinase expression and activity has previously been implicated in tumor development and metastasis. The mechanism by which Choline kinase is involved in tumor formation is still not fully resolved. From our data, we proposed that Choline kinase plays a key role in regulating Akt(ser473) phosphorylation, thereby promoting cell survival and proliferation.
authors.affiliation: Singapore OncoGenome Project, Institute of Medical Biology, A*STAR, 8A Biomedical Grove, 06-06 Immunos, Singapore. boontin.chua@imb.a-star.edu.sg
authors.forename: Boon Tin
authors.initials: BT
authors.lastname: Chua
authors.forename: David
authors.initials: D
authors.lastname: Gallego-Ortega
authors.forename: Ana
authors.initials: A
authors.lastname: Ramirez de Molina
authors.forename: Axel
authors.initials: A
authors.lastname: Ullrich
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Lacal
authors.forename: Julian
authors.initials: J
authors.lastname: Downward
mesh_terms: D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D002455:Cell Division; D045744:Cell Line, Tumor; D002797:Choline Kinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020868:Gene Silencing; D006801:Humans; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D012694:Serine / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D012694:Serine; D002797:Choline Kinase; D051057:Proto-Oncogene Proteins c-akt