As a species, dogs are particularly susceptible to cancer. Approximately one in four dogs will be diagnosed with cancer at some point in their lives. Fifty percent of dogs over ten years of age will develop cancer. Some breeds are more susceptible to cancer than others (1). As medical science advances, pet owners have more treatment options than ever when vets make a cancer diagnosis. However, cancer treatment can be costly, and advanced therapies are not widely available outside of large cities.
A simple way to describe cancer is to call it a disease where cells misbehave. Damage or changes to the genetic programming of a cell can cause it to function and multiply in a different and uncontrolled manner. Even though various cancers are categorized and named according to their location and their expected behaviour, each cancer occurrence is unique, and the course of the disease is notoriously unpredictable. This is why a single treatment or cure for cancer has been so elusive.
Because no one treatment is effective against all cancers, some researchers have shifted their focus to prevention. They are investigating ways to harness the immune system's power to eliminate cancer cells before they have a chance to multiply and establish themselves in the body.
Vaccines and the Immune System
The immune system is an animal's biological security guard. Its job is to recognize and eliminate intruders like bacteria and viruses. Bacteria and viruses contain proteins that are different from the ones in the animal's cells. It is these foreign proteins that alert the immune system to an intruder.
Unfortunately, the first time the immune system encounters a new intruder, it can be slow to recognize and respond to the threat. The better acquainted the immune system is with a threat, the faster and stronger it can react. Vaccines work by familiarizing the immune system with the foreign proteins of a specific intruder. This way, when the intruder appears in real life, the immune system will recognize it faster and respond in a targeted manner to eliminate the threat.
Just like bacteria and viruses, cancer cells are intruders, and they contain foreign proteins. Recent research has focused on identifying proteins present in cancer cells but absent in normal, healthy cells (2). If a common protein can be identified in many different types of cancer, it can be used to develop a vaccine that can prevent multiple cancers. The vaccine will present this cancer-specific protein to the immune system for familiarization. Then, whenever a new cancer cell appears in the body, the protein will act as a flag to alert the immune system of its presence. The hope is that the immune system will quickly destroy the abnormal cell before developing into a tumour.
A few suitable cancer-specific proteins have been identified, and preliminary vaccine investigations in mice have demonstrated promising results (2,3). A 5-year vaccine trial in dogs is currently underway in the United States to see if this technology works in a real-life setting (4,5). If the vaccine is proven safe and effective at reducing cancer occurrence, pet owners may one day have the power to protect their canine companions from one of the leading causes of illness and death in dogs.
Dobson JM. Breed-predispositions to cancer in pedigree dogs. ISRN Vet Sci. 2013;2013:941275.
Lopes, A., Vandermeulen, G., & Préat, V. (2019). Cancer DNA vaccines: current preclinical and clinical developments and future perspectives. Journal of experimental & clinical cancer research : CR, 38(1), 146. https://doi.org/10.1186/s13046-019-1154-7
Thalmensi, J., Pliquet, E., Liard, C., et al. (2019). A DNA telomerase vaccine for canine cancer immunotherapy. Oncotarget, 10(36), 3361–3372. https://doi.org/10.18632/oncotarget.26927
McReynolds, T. (2019, July). Worlds largest canine cancer study would lead to a cancer vaccine for humans. AAHA Newstat. Retrieved from https://www.aaha.org/publications/newstat/articles/2019-07/worlds-largest-canine-cancer-study-could-lead-to-a-cancer-vaccine-for-humans/