Common Dog Tumor May Be Treated Better With New Genetic Discovery

The recent discovery of genetic similarities and differences in the most common type of soft tissue sarcoma in dogs may lead to more precise diagnoses and treatments in the future.

The team of researchers and veterinarians at Washington State University examined the genetic makeup of the three most common subtypes of the tumor using next-generation sequencing techniques and computation approaches. They discovered several therapeutic targets that could be the basis for new treatments.

The study's detailed findings have been published in the journal PLoS One.

Eric Shelden, an associate professor in WSU's School of Molecular Biosciences and the study's corresponding author, says, "The different subtypes of soft tissue sarcomas can look so similar that even trained pathologists have trouble distinguishing one from another. Yet it turns out they are not all the same—they are a very diverse group of cancers."

It is estimated that 95,000 dogs in America are diagnosed with cancer every year. In fact, 20-30% of these cancer dogs die. Sarcomas have several subtypes, but they all have similar characteristics, making diagnosis difficult. The problematic diagnosis, followed by similar treatment, is frequently ineffective.

A veterinary oncologist at WSU and co-author of the study, Rance Sellon, believes the study's findings indicate that a "one-size-fits-all" treatment approach may no longer be appropriate for patients. Instead, clinicians may need to collaborate with veterinary pathologists more closely to identify tumor subtypes for more accurate diagnosis, investigation, and identification of more effective treatment options.

He says, "From a clinical standpoint, the findings of this study hint that perhaps our view of this tumor type should change, and we should be looking to make better distinctions among the various subtypes, ultimately with the goal of better defining treatment and prognosis."

The potential causes of soft tissue sarcomas have been previously examined, and the genetic markers were used to identify soft tissue sarcoma subtypes. The WSU study, on the other hand, was the first to examine gene expression patterns in soft tissue sarcomas of dogs using RNA-sequence analysis of tumor samples. This analysis lets the tumors differentiate, understand the biology that drives their behavior, and identify drug therapy candidates.

Shelden said, "We looked at thousands of genes and their expression patterns at once, and then we tried to unravel computationally whether there are differences between the different tumor types, and there are," continued, "While it will probably take some years before the effect of this study is actually felt in a clinical setting, the hope is that this will make people realize that you shouldn't just treat these tumors similarly because they are in fact biologically different."

Shelden believes that additional research is needed to validate the findings and identify drugs better suited to treating the various tumors.

Sellon estimates that WSU's Veterinary Teaching Hospital sees one or two soft tissue sarcoma patients weekly. He noted that tumors could be challenging to treat and that prognosis varies depending on factors like tumor size and grade. Surgical removal of the tumor is typically followed by radiation therapy.

Sellon said, "A surgical cure can be difficult, or impossible, depending on tumor size and location as these tumors are notorious for locally invasive behavior that can make it difficult for acquisition of 'clean' surgical margins—margins with an adequate amount of normal tissue surrounding the edges of the tumor," continued, "Radiation therapy can be effective to treat residual disease, but for some dogs, recurrence can still be seen after surgery and radiation therapy."

Besides Sheldon and Sellon, co-authors include PhD scientist Lydia Lam and senior fellow Mark Wildung at the WSU School of Molecular Biosciences; oncologists Tien Tien and Janean Fidel from the WSU Division of Veterinary and Clinical Sciences; and Professor Laura White of the Washington Animal Disease Diagnostic Laboratory.

The Marge Crowley Canine Cancer Research Foundation and the Dorothy Shea Brink Memorial Foundation provided funding for the study.