Constitutive phosphorylation of the mTORC2/Akt/4E-BP1 pathway in newly derived canine hemangiosarcoma cell lines

Constitutive phosphorylation of the mTORC2/Akt/4E-BP1 pathway in newly derived canine hemangiosarcoma cell lines

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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, kicker pro comp 10 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 jerome brown jersey 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.