Repeatable and objective method for evaluating angiogenesis using real‐time RT‐PCR of endoglin expression in canine tumours

Abstract Anti‐angiogenic therapy is a cancer treatment strategy targeting new blood vessel formation. Microvessel density (MVD) is a histopathological method for evaluating angiogenesis and endoglin is used as an activated endothelial marker in human medicine. The assessment of the treatment effect using MVD is difficult because it is a non‐repeatable method. To develop a repeatable method for evaluating angiogenesis, we investigated correlations among MVD, mRNA transcription levels of endothelial markers and angiogenesis factors, and confirmed the agreement of mRNA transcription levels between tissue samples and small samples obtained by fine needle aspiration (FNA). The various types of spontaneous tumours were collected from 51 dogs. MVD was assessed by immunostaining for von Willebrand factor (vWF). mRNA transcription levels of vWF, endoglin, vascular endothelial growth factor (VEGF) and VEGF receptor‐2 (VEGFR2) were analysed using real‐time reverse transcription polymerase chain reaction (real‐time RT‐PCR). There were significant correlations between MVD and mRNA transcription levels of vWF, endoglin and VEGFR2. VEGFR2 was more strongly correlated with endoglin ( P <.01, Rs = 0.649) than vWF ( P <.01, Rs = 0.512), indicating that angiogenesis can be evaluated more accurately by the measurement of mRNA transcription levels of endoglin. The mRNA transcription levels in tissue and FNA samples were strongly correlated, suggesting that evaluating angiogenesis using FNA samples is possible. In conclusion, we developed a repeatable and objective method for angiogenesis evaluation using mRNA transcription levels of endothelial markers by FNA sampling.