Establishment of three-dimensional canine osteosarcoma cell lines showing vasculogenic mimicry and evaluation of biological properties after treatment with 17-AAG.

Vasculogenic mimicry (VM) is an alternative type of blood perfusion characterized by formation of non-endothelial cell-lined microcirculatory channels and is responsible for aggressive tumour biology and increased tumour-related mortality. VM-correlated genes are associated with vascular endothelial grown factor receptor 1 (VEGFR1), and hypoxia-related (hypoxia inducible factor 1 α-HIF1α) signalling pathways, whose molecules are client proteins of Hsp90 (heat shock protein 90) and are potential therapeutic targets. This pilot study was aimed to investigate vasculogenic mimicry in a three-dimensional (3D) cell culture system of two aggressive canine osteosarcoma (OSA) cell lines (D22 and D17), and to evaluate the response of these cells to 17-AAG (17-N-allylamino-17-demethoxygeldanamycin) treatment in relation to tubular-like structure formation in vitro. Only D17 cell line formed hollow matrix channels in long-term 3D cultures and assumed endothelial morphology, with cells expressing both Hsp90 and VEGFR1, but lacking expression of endothelial marker CD31. 17-AAG treatment inhibited migration of D17 OSA cells, also decreasing VM markers in vitro and inducing a reduction of HIF1α transcript and protein in this cell line. Taken together, these preliminary data indicate that the biological effects of 17-AAG on D17 3D culture and on HIF1α regulation can provide interesting information to translate these findings from the basic research to clinical approach for the treatment of canine OSA as a model in comparative oncology.