Expression of stromal genes associated with the angiogenic response are not differentiated between human tumour xenografts with divergent vascular morphologies

Human tumour xenografts have commonly been used to explore the mechanisms of tumour angiogenesis and the interaction of tumour cells with their microenvironment, as well as predict potential utility of anti-angiogenic inhibitors across different tumour types. To investigate how well human tumour xenografts can be used to differentiate the effects of stromal targeting agents we performed a comparative assessment of the murine angiogenic response across a panel of pre-clinical tumour xenografts. By analysing a panel of 22 tumour xenografts with a range of vascular morphologies, micro-vessel densities and levels of fibroblast and inflammatory infiltrate, we have examined the relationship between angiogenic stroma and human tumour models. These models were studied using a combination of immunohistochemistry and species specific mRNA profiling to differentiate the tumour and stromal transcript mRNA profiles. Principal Component Analysis (PCA) and regression analysis was used to investigate the transcriptional relationships between the individual models and the correlation with the stromal architecture. We found the human tumour cell expressed factors to be independent of the murine host responses such as microvessel density, and fibroblast or macrophage cellular infiltrate. Moreover mRNA profiling of the mouse stroma suggested that the host response to the different tumours was relatively uniform despite differences in stromal structures within the tumour. Supporting this, models with different stromal compositions responded similarly to cediranib, a small molecule inhibitor of VEGF signalling. The data indicate that although the angiogenic response to the tumour results in reproducible stromal architectures, these responses are not differentiated at the level of gene expression.