title: Constitutive phosphorylation of the mTORC2/Akt/4E-BP1 pathway in newly derived canine hemangiosarcoma cell lines.
abstract: BACKGROUND
  Canine hemangiosarcoma (HSA) is a malignant tumor with poor long-term prognosis due to development of metastasis despite aggressive treatment. The phosphatidyl-inositol-3 kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is involved in its endothelial pathologies; however, it remains unknown how this pathway plays a role in canine HSA. Here, we characterized new canine HSA cell lines derived from nude mice-xenografted canine HSAs and investigated the deregulation of the signaling pathways in these cell lines.
  
  
  RESULTS
  Seven canine HSA cell lines were established from 3 xenograft canine HSAs and showed characteristics of endothelial cells (ECs), that is, uptake of acetylated low-density lipoprotein and expression of canine-specific CD31 mRNA. They showed varied morphologies and mRNA expression levels for VEGF-A, bFGF, HGF, IGF-I, EGF, PDGF-B, and their receptors. Cell proliferation was stimulated by these growth factors and fetal bovine serum (FBS) in 1 cell line and by FBS alone in 3 cell lines. However, cell proliferation was not stimulated by growth factors and FBS in the remaining 3 cell lines. Phosphorylated p44/42 Erk1/2 was increased by FBS stimulation in 4 cell lines. In contrast, phosphorylation of Akt at Ser473, mTOR complex 1 (mTORC1) at Ser2448, and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) at Ser65 was high in serum-starved condition and not altered by FBS stimulation in 6 cell lines, despite increased phosphorylation of these residues in normal canine ECs. This suggested that the mTORC2/Akt/4E-BP1 pathway was constitutively activated in these 6 canine HSA cell lines. After cell inoculation into nude mice, canine HSA tumors were formed from 4 cell lines and showed Akt and 4E-BP1 phosphorylation identical to the parental cell lines.
  
  
  CONCLUSIONS
  Our findings suggest that the present cell lines may be useful tools for investigating the role of the mTORC2/Akt/4E-BP1 pathway in canine HSA formation both in vivo and in vitro.
authors: Laboratory of Veterinary Pathology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
authors: Atsuko
authors: A
authors: Murai
authors: Samah Abou
authors: SA
authors: Asa
authors: Atsushi
authors: A
authors: Kodama
authors: Akihiro
authors: A
authors: Hirata
authors: Tokuma
authors: T
authors: Yanai
authors: Hiroki
authors: H
authors: Sakai
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006394:Hemangiosarcoma / Q000378:metabolism*; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D046912:Multiprotein Complexes; D010750:Phosphoproteins; D012333:RNA, Messenger; D000076225:Mechanistic Target of Rapamycin Complex 2; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases