Establishment of canine hemangiosarcoma xenograft models expressing endothelial growth factors, their receptors, and angiogenesis-associated homeobox genes

Atsushi Kodama,Hiroki Sakai,Toshiaki Masegi,Tokuma Yanai,Takashi Mori,Mami Murakami,Atsuko Murai,Kouji Maruo,Satoko Matsuura,Tohru Kimura

doi:10.1186/1471-2407-9-363

Abstract

BackgroundHuman hemangiosarcoma (HSA) tends to have a poor prognosis; its tumorigenesis has not been elucidated, as there is a dearth of HSA clinical specimens and no experimental model for HSA. However, the incidence of spontaneous HSA is relatively high in canines; therefore, canine HSA has been useful in the study of human HSA. Recently, the production of angiogenic growth factors and their receptors in human and canine HSA has been reported. Moreover, the growth-factor environment of HSA is very similar to that of pathophysiological angiogenesis, which some homeobox genes regulate in the transcription of angiogenic molecules. In the present study, we established 6 xenograft canine HSA tumors and detected the expression of growth factors, their receptors, and angiogenic homeobox genes.MethodsSix primary canine HSAs were xenografted to nude mice subcutaneously and serially transplanted. Subsequently, the expressions of vascular endothelial growth factor (VEGF)-A, basic fibroblast growth factors (bFGF), flt-1 and flk-1 (receptors of VEGF-A), FGFR-1, and angiogenic homeobox genes HoxA9, HoxB3, HoxB7, HoxD3, Pbx1, and Meis1 were investigated in original and xenograft tumors by histopathology, immunostaining, and reverse transcription polymerase chain reaction (RT-PCR), using canine-specific primer sets.ResultsHistopathologically, xenograft tumors comprised a proliferation of neoplastic cells that were varied in shape, from spindle-shaped and polygonal to ovoid; some vascular-like structures and vascular clefts of channels were observed, similar to those in the original tumors. The expression of endothelial markers (CD31 and vWF) was detected in xenograft tumors by immunohistochemistry and RT-PCR. Moreover, the expression of VEGF-A, bFGF, flt-1, flk-1, FGFR-1, HoxA9, HoxB3, HoxB7, HoxD3, Pbx1, and Meis1 was detected in xenograft tumors. Interestingly, expressions of bFGF tended to be higher in 3 of the xenograft HSA tumors than in the other tumors.ConclusionWe established 6 xenograft canine HSA tumors in nude mice and found that the expressions of angiogenic growth factors and their receptors in xenograft HSAs were similar to those in spontaneous HSA. Furthermore, we detected the expression of angiogenic homeobox genes; therefore, xenograft models may be useful in analyzing malignant growth in HSA.

Highlights

Human hemangiosarcoma (HSA) tends to have a poor prognosis; its tumorigenesis has not been elucidated, as there is a dearth of HSA clinical specimens and no experimental model for HSA
In recent studies into canine and human HSA, expressions of both vascular endothelial growth factor A (VEGF-A) and their receptors, especially flk-1, were evident, and the presence of an autocrine or paracrine mechanism underpinning the growth factors might be associated with the malignant proliferation of canine HSA [9,10]
All the tumors grew to large masses in the subcutis of nude mice, at 36 weeks after the pieces of the original tumors had been inoculated (Figure 1)

Summary

Introduction

Human hemangiosarcoma (HSA) tends to have a poor prognosis; its tumorigenesis has not been elucidated, as there is a dearth of HSA clinical specimens and no experimental model for HSA. The incidence of spontaneous HSA is relatively high in canines; canine HSA has been useful in the study of human HSA. The production of angiogenic growth factors and their receptors in human and canine HSA has been reported. We established 6 xenograft canine HSA tumors and detected the expression of growth factors, their receptors, and angiogenic homeobox genes. In recent studies into canine and human HSA, expressions of both vascular endothelial growth factor A (VEGF-A) and their receptors, especially flk-1, were evident, and the presence of an autocrine or paracrine mechanism underpinning the growth factors might be associated with the malignant proliferation of canine HSA [9,10]. Considering the similarities shared by human and canine HSAs, a canine HSA model may be useful in the study of human HSA

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Discussion

Conclusion