The word "cancer" is a fairly nonspecific term and includes a variety of diseases stemming from abnormal cell growth. There are many types of cancer and a number of proposed mechanisms or causes for the development of aberrant cell growth. Inflammation, especially chronic inflammation for example, is one possible mechanism or trigger that induces cancerous changes in cells that make up tissues in the body. Back in 2008, an article published in The Lancet Oncology stated that, annually, approximately 2 million human cancer cases were believed to be caused by infectious agents such as bacteria and viruses. A decade later another article published in PLOS Pathogens stated "the importance of infectious agents in cancer causation remains relatively underappreciated by the general public and even the scientific community. In addition, mechanisms contributing to infection-related cancers and development of potential prevention and treatment approaches are arguably understudied."
The suggestion that an infection could be a root cause of cancer proposes that early diagnosis and treatment of the infection might prevent or resolve the cancerous state. Similarly, a vaccine to prevent that infection could prevent the associated cancer type from developing. These are not theoretical statements. There are several well-documented associations between infectious agents and their association with specific cancers. One of the better known relationships between infection and cancer causation is that of H. pylori (a gastrointestinal pathogen) and its link to the development of gastric MALT lymphoma. In many cases, treatment with an antibiotic can be curative for gastric MALT lymphoma. In other instances, due to a variety of mechanisms, H. pylori infected patients can go on to develop a more serious form of cancer (gastric adenocarcinoma).
We recently spent some time with Edward Breitschwerdt, DVM, DACVIM - a veterinary internal medicine specialist and researcher at North Carolina State University - who is focused on studying vector borne diseases, with a particular interest in Bartonella spp. He spoke with us about what he and his research group have learned about the role of Bartonella spp. in the development of hemangiosarcoma in dogs.
In his presentation "Cancer Attributable to Infection - What we know about the genus Bartonella and its role in the development of hemangiosarcoma in dogs", Dr. Breitschwerdt details the background of his work in researching this particular genus of bacteria and his team's more recent work investigating its possible role in causing hemangiosarcoma in dogs. Hemangiosarcoma is a very aggressive type of cancer with a poor short-term and long-term prognosis. The work that he and his research group are doing in this area is exciting and their determinations may be transformative to the way we approach caring for dogs with this type of cancer in the future. As Dr. Breitschwerdt stated, "We might be able to keep veterinary surgeons from cutting these dogs with a ruptured spleen and belly full of blood in the middle of the night. On a comparative medical basis, Mary-Dell Chilton, Ph.D., was named a 2013 World Food Prize Laureate along with two other distinguished scientists for showing that [the bacteria] Agrobacterium tumefaciens is able to insert its DNA into the plant genome, thereby inducing plant cells to proliferate and turn into tumors. On an evolutionary and phylogenetic basis, Agrobacterium and Brucella are the two closest relatives to the genus Bartonella. I think Bartonella likely inserts DNA into the mammalian genome, similar to Agrobacterium inserting its DNA into plant cells. We just have to be smart enough to figure out how to prove this in the somewhat more complicated mammalian system. We are conducting research now looking at what pathways Bartonella turns on or off that could potentially result in transcription errors and, ultimately, the development of cancer."
He went on to say "I've been trying to convince pharmaceutical companies, many of which I've lectured for and consulted with for over 30 years, that Bartonella is an important, zoonotic, emerging pathogen that induces chronic infection (inflammation) and a spectrum of diseases in pets and people. It is my opinion that we really need a vaccine to protect cats, dogs, and their owners. I think rabies represents a somewhat good analogy. Obviously, rabies is really bad if it infects the unvaccinated dog, but it presents an even worse scenario if that dog then infects or exposes numerous veterinary hospital staff, animal control officers or the pet owner’s family." With respect to what the future holds Dr. Breitschwerdt said "I think, one, we have an opportunity to document the first bacteria in medicine and in veterinary medicine that actually causes a tumor in the dog. And, two, I think we have an opportunity to develop a vaccine, like they did for papilloma virus (to prevent cervical cancer) that will decrease the prevalence of this tumor (hemangiosarcoma). And, so, it's honestly the reason that I keep getting up in the morning and the reason that I'm very happy to come to work. I am so grateful, particularly to the AKC Canine Health Foundation and the Cohen Foundation, because those two foundations have essentially allowed us to do things that we would not have been able to do otherwise. Their financial support of our research has put us in a position where we're literally the leading laboratory in the world trying to define the medical importance of the genus Bartonella, both for veterinary and human medicine. I've been really, really fortunate to be able to surround myself with extremely dedicated, intelligent and hard-working people. And as you know, I can't give them enough credit for what we've been able to accomplish to date. It takes a team in science and medicine to put together epidemiological data, genetic data, biochemical data and, most importantly, clinical data that ultimately defines and solves a problem. If we end up with enough research publications and enough data, then we may be able to come to the conclusion that Bartonella is a cause of hemangiosarcoma in dogs, like Helicobacter pylori is a cause of MALT lymphoma in humans. As you are well aware, in human medicine it probably took thousands of publications to get to the point that anybody was even starting to believe that cancer causation is associated with specific infections. And so, it's going to take considerable work and that is going to take a while. However, if you ask me what I believe, I believe that Bartonella clearly is a cause of hemangiosarcomas. And I believe that if we can create a vaccine, which is also work that's, in part, being supported by the AKC Canine Health Foundation in our laboratory, we may be able to potentially prevent a devastating cancer in man’s best friend."
View his presentation "Cancer Attributable to Infection - What we know about the genus Bartonella and its role in the development of hemangiosarcoma in dogs" On Demand (running time: 37 mins).
