Soft-tissue sarcomas are a common type of tumor found in dogs, which can arise in connective, muscle, or nervous tissues. These soft-tissue cancers typically require surgical removal, but often grow back if some cancer cells remain. Using a therapeutic virus could help to reduce the possibility of the tumor regrowing. However, no such viruses are available to treat dogs, and canine cancer cells can generate specific biomolecules, such as interferons, that inhibit viral replication. One option may be to co-treat the dogs with a drug that inhibits the action of interferons while administering the virus, to maximize the chances of success. Read More
With this aim, Professor Amy MacNeill of Colorado State University and colleagues investigated the potential of using a combination treatment, consisting of a virus called myxoma virus and a drug called oclacitinib that inhibits the action of interferons. They tested the treatment on dogs who had developed soft-tissue sarcomas, with the consent of their owners.
Initially, the researchers tested the interplay between viral infection and interferon levels in cancerous canine cells in a dish. As mentioned, canine cells can sometimes protect themselves from viral infection by releasing interferons that inhibit viral replication. Professor MacNeill’s team found that when interferon levels were increased within the cancer cells, viral replication was significantly reduced, supporting their rationale for a combination treatment.
Following this, the researchers applied a combination treatment to dogs who had undergone surgery to remove soft-tissue sarcomas. They injected a solution containing the myxoma virus directly into the tumor site, after it had been removed. This was followed by a second treatment two weeks later. Some of the dogs also received combination therapy in the form of an additional oclacitinib treatment that started 7 days before the surgery and continued for another 7 days afterwards.
The dogs tolerated the treatments well, and no adverse effects were noted. Tumor regrowth was observed in two out of four dogs treated with the virus alone and three out of four dogs treated with the combination therapy. While the rates of tumor regrowth were reduced compared with previous dogs who had received no treatment following surgery, the researchers did not observe any additional benefit from the inclusion of oclacitinib.
The choice of drug to reduce interferon activity and the dose at which it is administered may have affected the outcome. The researchers are hopeful that larger studies with greater range of drugs and doses may reveal whether combination therapy has additional benefit. The quest for an effective treatment that can prevent the regrowth of soft-tissue sarcomas in our canine companions continues!
