Chromatin run-on sequencing analysis finds that ECM remodeling plays an important role in canine hemangiosarcoma pathogenesis

Abstract

Background Canine visceral hemangiosarcoma (HSA) is a highly aggressive cancer of endothelial origin that closely resembles human visceral angiosarcoma, both clinically and histopathologically. Currently there is an unmet need for new diagnostics and therapies for both forms of this disease. The goal of this study was to utilize ChRO-seq and immunohistochemistry (IHC) to identify gene and protein expression signatures that may be important drivers of HSA progression. Methods Chromatin run-on sequencing (ChRO-seq) was performed on tissue isolated from 17 HSA samples and 4 normal splenic samples. Computational analysis was then used to identify differentially expressed genes and these factors were subjected to gene ontology analysis. Next, RT-PCR was performed on a subset of candidate genes to validate the ChRO-seq data. We then performed Masson’s trichrome, H&E, and IHC staining on these tissues to investigate the morphological features of HSA tumor tissue as well as the expression patterns of several proteins identified in our ChRO-seq analysis. Results ChRO-seq analysis revealed over a thousand differentially expressed genes in HSA tissue compared with normal splenic tissue (FDR <0.005). Interestingly the majority of genes overexpressed in HSA tumor tissue were associated with extracellular matrix (ECM) remodeling. This observation correlated well with our histological analysis, which found that HSA tumors contain a rich and complex collagen network. Additionally, we characterized the protein expression patterns of two highly overexpressed molecules identified in ChRO-seq analysis, podoplanin (PDPN) and laminin alpha 4 (LAMA4). We found that the expression of these two ECM-associated factors appeared to be largely limited to transformed endothelial cells within the HSA lesions. Conclusion Outcomes from this study suggest that ECM remodeling has an important role in HSA progression. Additionally, our study identified two potential novel biomarkers of HSA, PDPN and LAMA4. Interestingly, given that function-blocking anti-PDPN have shown anti-tumor effects in mouse models of canine melanoma, our studies raise the possibility that these types of therapeutic strategies could potentially be developed for treating canine HSA.