title: Genetic and bioinformatic analyses of the expression and function of PI3K regulatory subunit PIK3R3 in an Asian patient gastric cancer library.
abstract: BACKGROUND
  While there is strong evidence for phosphatidylinositol 3-kinase (PI3K) involvement in cancer development, there is limited information about the role of PI3K regulatory subunits. PIK3R3, the gene that encodes the PI3K regulatory subunit p55γ, is over-expressed in glioblastoma and ovarian cancers, but its expression in gastric cancer (GC) is not known. We thus used genetic and bioinformatic approaches to examine PIK3R3 expression and function in GC, the second leading cause of cancer mortality world-wide and highly prevalent among Asians.
  
  
  METHODS
  Primary GC and matched non-neoplastic mucosa tissue specimens from a unique Asian patient gastric cancer library were comprehensively profiled with platforms that measured genome-wide mRNA expression, DNA copy number variation, and DNA methylation status. Function of PIK3R3 was predicted by IPA pathway analysis of co-regulated genes with PIK3R3, and further investigated by siRNA knockdown studies. Cell proliferation was estimated by crystal violet dye elution and BrdU incorporation assay. Cell cycle distribution was analysed by FACS.
  
  
  RESULTS
  PIK3R3 was significantly up-regulated in GC specimens (n = 126, p < 0.05), and 9.5 to 15% tumors showed more than 2 fold increase compare to the paired mucosa tissues. IPA pathway analysis showed that PIK3R3 promoted cellular growth and proliferation. Knockdown of PIK3R3 decreased the growth of GC cells, induced G0/G1 cell cycle arrest, decreased retinoblastoma protein (Rb) phosphorylation, cyclin D1, and PCNA expression.
  
  
  CONCLUSIONS
  Using a combination of genetic, bioinformatic, and molecular biological approaches, we showed that PIK3R3 was up-regulated in GC and promoted cell cycle progression and proliferation; and thus may be a potential new therapeutic target for GC.
authors.affiliation: Laboratory of Hormonal Regulation, Cardiovascular and Metabolic Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhou
authors.forename: Geng Bo
authors.initials: GB
authors.lastname: Chen
authors.forename: Yew Chung
authors.initials: YC
authors.lastname: Tang
authors.forename: Rohit Anthony
authors.initials: RA
authors.lastname: Sinha
authors.forename: Yonghui
authors.initials: Y
authors.lastname: Wu
authors.forename: Chui Sun
authors.initials: CS
authors.lastname: Yap
authors.forename: Guihua
authors.initials: G
authors.lastname: Wang
authors.forename: Junbo
authors.initials: J
authors.lastname: Hu
authors.forename: Xianmin
authors.initials: X
authors.lastname: Xia
authors.forename: Patrick
authors.initials: P
authors.lastname: Tan
authors.forename: Liang Kee
authors.initials: LK
authors.lastname: Goh
authors.forename: Paul Michael
authors.initials: PM
authors.lastname: Yen
mesh_terms: D044466:Asian People / Q000235:genetics*; D049109:Cell Proliferation; D019295:Computational Biology / Q000379:methods*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D059585:G1 Phase Cell Cycle Checkpoints / Q000235:genetics; D005753:Gastric Mucosa / Q000378:metabolism / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D021122:Protein Subunits / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D016192:Resting Phase, Cell Cycle / Q000235:genetics; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013274:Stomach Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology
chemical_list: D019938:Cyclin D1; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016160:Retinoblastoma Protein; C530104:CCND1 protein, human; C523442:PIK3R3 protein, human