Spontaneous Tumors in Other Animals
For some animals that can be used to study cancer biology, purposefully generating models using the techniques of molecular biology are not widely performed. Nevertheless, investigations into the causes, outcomes, and treatments of the naturally-occurring spontaneous cancers in these animals yield important insights into human cancers, and may benefit the health of these important companion animals or agriculturally important species. In many aspects, these animals have environmental exposures that are more analogous to those of humans, outside of the controlled laboratory setting. Here we explore some aspects of using these animals to expand our knowledge when a cancer has appeared. Information gleaned from these species can benefit humans, and treatments developed in humans may in turn benefit these important animals as well. Rapid advances in genomics will also benefit cancer research in these species, and comparative oncology will generate new knowledge and drive research directions.
As companion animals, dogs share many aspects of the human lifestyle and environment, and studying the cancer incidence and progression in dogs may provide clues for human health. When they develop cancers, their tumors can bear much clinical similarity to human tumors, and their appearance with an intact immune system’s behavior replicates the human situation as well. They have similar responses to many therapies. A formal project has been organized to utilize these opportunities: The Comparative Oncology Trials Consortium (COTC). This project will provide infrastructure and support for this work, and this framework will likely to yield extensive new knowledge. Other projects associated with the dog genome project also offer many avenues of exploration.
The feline situation bears many similarities to that of the canine. They have a similar lifestyle to their human companions, and the development of cancers that can be informative for human health as well. Cats have provided insights into a variety of cancers, one of which involves oncogenic viruses. Feline leukemia virus (FeLV) is a widespread and well studied example. Tumor virology is an area of crucial study, and features of FeLV infection can help broaden our knowledge of viral oncogenesis. Studies of cancer treatments in cats offer insights into the biology of therapeutic responses and survival. Puzzling incidences of feline vaccine sarcoma occurrence spur investigations, and inform therapeutic interventions. The similarity of the injection-site-associated sarcomas to cases of human wound area sarcomas, and the investigations of the biological mechanisms in cats may translate to a better understanding the human cancer developments.
Cancer in horses may provide insight into human cancers in a number of ways. Tumors that are rare in humans but also found in horses can offer ways to understand the biology, such as the case of hepatoblastoma. Ovarian tumors are well studied in horses, as they are more common in horses than in other species. Melanoma is characteristic of some horse breeds, and provides opportunity for assessing biology and treatment protocols. Studying biological principles in horses and other companion animals teach us about the human conditions that can lead to disease states. As with other species, viral infection can generate tumors, and investigations into the mechanisms will provide insights for treatments in horses and other species as well.
An important agricultural species around the world, goats are studied for certain characteristic cancer incidences. As noted for other species, goats are susceptible to oncogenic viruses and the resulting adenocarcinoma can help us understand cancer mechanisms. Melanoma occurs in goats at high rates, and has been proposed as a model for gaining increased understanding of the relationship of sun exposure to skin cancer in humans. Progress in genome projects for the goat will spur additional research on this species.