Lysosomal drug sequestration as a mechanism of drug resistance in vascular sarcoma cells marked by high CSF-1R expression

Abstract

BackgroundHuman angiosarcoma and canine hemangiosarcoma are thought to arise from vascular tissue or vascular forming cells based upon their histological appearance. However, recent evidence indicates a hematopoietic or angioblastic cell of origin for these tumors. In support of this idea, we previously identified an endothelial-myeloid progenitor cell population with high expression of endothelial cell markers and the myeloid cell marker, colony stimulating factor 1 receptor (CSF-1R). Here, we further characterized these cells to better understand how their cellular characteristics may impact current therapeutic applications.MethodsWe performed cell enrichment studies from canine hemangiosarcoma and human angiosarcoma cell lines to generate cell populations with high or low CSF-1R expression. We then utilized flow cytometry, side population and cell viability assays, and fluorescence based approaches to elucidate drug resistance mechanisms and to determine the expression of hematopoietic and endothelial progenitor cell markers.ResultsWe demonstrated that cells with high CSF-1R expression enriched from hemangiosarcoma and angiosarcoma cell lines are more drug resistant than cells with little or no CSF-1R expression. We determined that the increased drug resistance may be due to increased ABC transporter expression in hemangiosarcoma and increased drug sequestration within cellular lysosomes in both hemangiosarcoma and angiosarcoma.ConclusionsWe identified drug sequestration within cellular lysosomes as a shared drug resistance mechanism in human and canine vascular sarcomas marked by high CSF-1R expression. Taken together, our results demonstrate that studies in highly prevalent canine hemangiosarcoma may be especially relevant to understanding and addressing drug resistance mechanisms in both the canine and human forms of this disease.

Interactions between CXCR4 and CXCL12 promote cell migration and invasion of canine hemangiosarcoma

“…Overall, our data support the prevailing notion that signalling through CXCR4/CXCL12 mediates tumour cell migration and invasion, potentially creating a favourable environment for metastasis . For HSA in particular, the mechanisms that mediate CXCL12/CXCR4‐dependent migration and invasion can be inferred from a careful review of the literature . Specifically, canine HSAs can be classified according to their angiogenic, inflammatory and adipogenic potential; these phenotypes, which may be peculiar to the HSA cell of origin appear to be conserved in humans .…”

Modulation of fatty acid metabolism and immune suppression are features of in vitro tumour sphere formation in ontogenetically distinct dog cancers

“…Surface marker expression and DyeCycle Violet dye‐efflux assays were performed by flow cytometry as described . The primary antibodies used for surface markers staining were: anti‐CD117‐PE (c‐Kit) and anti‐CD34‐PE (eBioscience, San Diego, California).…”

A double blinded, placebo-controlled pilot study to examine reduction of CD34+/CD117+/CD133+ lymphoma progenitor cells and duration of remission induced by neoadjuvant valspodar in dogs with large B-cell lymphoma

“…To confirm that the clinical grade compound retained potency after compounding, we examined its effect to inhibit DCV efflux using the flow cytometric side population assay. COSB canine hemangiosarcoma cells contain a subpopulation of cells that shows robust dye efflux in this assay 30 ( Figure 2, Dataset 1). The compounded, clinical grade valspodar was as effective as the research grade valspodar in this assay, eliminating >90% of the side population ( i.e.…”

“…Side populations were measured as described 30 . Briefly, DyeCycle Violet (DCV) (Life Technologies, Eugene, OR) was added to a final concentration of 10 μM, and 5 × 10 5 cells were incubated for an additional 60 minutes at 37°C with intermittent mixing.…”