Oxidative Stress in Canine Histiocytic Sarcoma Cells Induced by an Infection with Canine Distemper Virus Led to a Dysregulation of HIF‐1α Downstream Pathway Resulting in a Reduced Expression of VEGF‐B in vitro

Histiocytic sarcomas represent malignant tumors which require new treatment strategies. Canine distemper virus (CDV) is a promising candidate due to its oncolytic features reported in a canine histiocytic sarcoma cell line (DH82 cells). Interestingly, the underlying mechanism might include a dysregulation of angiogenesis. Based on these findings, the aim of the present study was to investigate the impact of a persistent CDV‐infection on oxidative stress mediated changes in the expression of hypoxia‐inducible factor (HIF)‐1α and its angiogenic downstream pathway in DH82 cells in vitro. Microarray data analysis, immunofluorescence for 8‐hydroxyguanosine, superoxide dismutase 2 and catalase, and flow cytometry for oxidative burst displayed an increased oxidative stress in persistently CDV‐infected DH82 cells (DH82Ond pi) compared to controls. The HIF‐1α expression in DH82Ond pi increased, as demonstrated by Western blot, and showed an unexpected, often sub‐membranous distribution, as shown by immunofluorescence and immunoelectron microscopy. Furthermore, microarray data analysis and immunofluorescence confirmed a reduced expression of VEGF‐B in DH82Ond pi compared to controls. In summary, these results suggest a reduced activation of the HIF‐1α angiogenic downstream pathway in DH82Ond pi cells in vitro, most likely due to an excessive, unusually localized, and non‐functional expression of HIF‐1α triggered by a CDV‐induced increased oxidative stress.