Persistent Infection of a Canine Histiocytic Sarcoma Cell Line with Attenuated Canine Distemper Virus Expressing Vasostatin or Granulocyte-Macrophage Colony-Stimulating Factor

Abstract

Canine histiocytic sarcoma (HS) represents a neoplasia with poor prognosis. Due to the high metastatic rate of HS, there is urgency to improve treatment options and to prevent tumor metastases. Canine distemper virus (CDV) is a single-stranded negative-sense RNA (ssRNA (-)) virus with potentially oncolytic properties. Moreover, vasostatin and granulocyte-macrophage colony-stimulating factor (GM-CSF) are attractive molecules in cancer therapy research because of their anti-angiogenetic properties and potential modulation of the tumor microenvironment. In the present study, an in vitro characterization of two genetically engineered viruses based on the CDV strain Onderstepoort (CDV-Ond), CDV-Ondneon-vasostatin and CDV-Ondneon-GM-CSF was performed. Canine histiocytic sarcoma cells (DH82 cells) were persistently infected with CDV-Ond, CDV-Ondneon, CDV-Ondneon-vasostatin and CDV-Ondneon-GM-CSF and characterized on a molecular and protein level regarding their vasostatin and GM-CSF production. Interestingly, DH82 cells persistently infected with CDV-Ondneon-vasostatin showed a significantly increased number of vasostatin mRNA transcripts. Similarly, DH82 cells persistently infected with CDV-Ondneon-GM-CSF displayed an increased number of GM-CSF mRNA transcripts mirrored on the protein level as confirmed by immunofluorescence and Western blot. In summary, modified CDV-Ond strains expressed GM-CSF and vasostatin, rendering them promising candidates for the improvement of oncolytic virotherapies, which should be further detailed in future in vivo studies.

Functional Granulocyte–Macrophage Colony-Stimulating Factor (GM-CSF) Delivered by Canine Histiocytic Sarcoma Cells Persistently Infected with Engineered Attenuated Canine Distemper Virus

“…It is a highly effective cytokine and one of the most commonly inserted genes in oncolytic viruses [ 7 ]. GM-CSF has already been inserted into adenovirus, herpes simplex virus, new castle disease virus, vaccinia virus, measles virus (MV), and, more recently, canine distemper virus [ 8 , 9 , 10 , 11 , 12 ]. GM-CSF is the first cancer immunotherapeutic approved by the U.S. Food and Drug Administration (FDA) [ 13 ].…”

“…Canine distemper virus (strain Onderstepoort; CDV-Ond), a morbillivirus closely related to MV, has already demonstrated promising anti-tumor effects against canine histiocytic sarcoma in vitro and in a murine xenotransplantation model [ 10 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. In a murine xenotransplantation model using canine histiocytic sarcoma cells (DH82 cells), persistently CDV-infected transplants exhibited complete spontaneous regression [ 33 ], while acutely infected neoplasms showed only transient growth retardation [ 35 ].…”

“…In acutely infected xenotransplants, the increased infiltration of macrophages was noted, which might represent an anti-tumoral immune response [ 35 ]. To enhance this effect, a CDV-Ond strain was genetically engineered to express canine GM-CSF (CDV-Ond neon-GM-CSF [ 10 , 36 ]). CDV-Ond neon-GM-CSF infects DH82 cells at a high rate, and the infected cells produce GM-CSF [ 10 ].…”

“…To enhance this effect, a CDV-Ond strain was genetically engineered to express canine GM-CSF (CDV-Ond neon-GM-CSF [ 10 , 36 ]). CDV-Ond neon-GM-CSF infects DH82 cells at a high rate, and the infected cells produce GM-CSF [ 10 ].…”

Application of oncolytic virus in tumor therapy

“…and Drug Administration (FDA) approved GM-CSF-encoding T-VEC for treating melanoma in October 2015. In addition to T-VEC, GM-CSF has also been used to modify other classes of OVs, including HSV, vaccinia virus (VV), VSV, measles virus (MV), adeno-associated virus (AdV), and RV [75][76][77][78][79]. …”