Animals are frequently used as our surrogates in medical research. Mice, rats, fish, and flies model human diseases and provide guidance to scientists on whether a new drug or vaccine will work in people. Rarely do the animals themselves benefit from any of this experimentation. Rarely, but not never.
(Photo: Poker and his owner, Leslie Rush)
By Anna Shipp
One of the experimental approaches to treating non-Hodgkin’s lymphoma is to use a cancer vaccine.
What is a cancer vaccine?
Cancer vaccines are being developed to provide the immune system with tools to combat cancer-causing viruses, as well as to fight cancer cells themselves once the cancer has been detected.
There are two main types of cancer vaccines:
Treatment vaccines, though still experimental, work to fight already existing cancers by stimulating and reinforcing the body’s immune system; and preventive vaccines, which work to prevent cancer from developing in the first place by attacking cancer-causing diseases and viruses.
Two types of preventive vaccines have been successfully developed and approved by The federal Food and Drug Administration (FDA) for use the United States:
A vaccine against the liver cancer-causing hepatitis B virus, and a vaccine against the cervical cancer-causing human papillomavirus (HPV).
NCI Cancer vaccine factsheet
On April 29, 2010, the FDA approved a vaccine for prostate cancer – it’s the first cancer treatment vaccine to be approved by the FDA.
How does a cancer treatment vaccine work?
Our immune system’s T-cells attack invaders – and the idea with a cancer vaccine is to use T-cells to attack cancerous cells. T-cells “frisk” other cells for signs of disease, including cancers or infections. Once the T-cell recognizes a target, the cell transitions from its search mode into destroy mode.
However, T-cells, found to occur naturally inside tumors, don’t always recognize the subtle molecular differences between cancer cells and normal cells (cancer cells are, after all, mutated versions of our healthy cells), and so don’t “sound the alarm” to initiate the necessary vigorous immune response.
The treatment vaccine functions to help T-cells recognize the minute distinctions between cancerous and non-cancerous cells, effectively stimulating the T-cells to attack accordingly.
This assault by the T-cells is, in turn, intended to slow or completely halt cancer cell growth, hopefully to the point where the tumor actually shrinks, and, ultimately preventing the cancer from returning. This form of therapy is intended to supplement, not replace, other forms of treatment, such as surgery, radiation therapy, or chemotherapy.
What kind of cancer research specifically for humans is being done?
There are many active clinical trials of cancer treatment vaccines, some of which include:
Brain tumors, breast cancer, cervical cancer, melanoma, leukemia, lung cancer, and prostate cancer.
See the National Cancer Institute’s website for a more complete list, as well as links to more information on individual trials.
Canine lymphoma resembles the cancer in humans. Researchers at the University of Pennsylvania are taking advantage of the similarity to research cures for both dogs and people.
What is canine lymphoma?
Lymphoma is a pervasive cancer that grows anywhere in the body where there is lymph tissue, essentially allowing it to jump to every organ in the body. Eventually, the tumor overwhelms an organ to such a degree that the cancer becomes resistant to treatment, and the organ fails.
The prognosis of dogs with lymphoma varies, depending on the clinical stage at diagnosis (there are 5 stages of increasing progression), and the type of tumor. Survival times for most dogs treated with aggressive chemotherapy are in the range of 9 to 12 months. If left untreated, most dogs will only live another two months.
Comparative Oncology Research:
The National Cancer Institute’s Comparative Oncology Program, in the form of the Comparative Oncology Trials Consortium (COTC), allows oncologists (human and veterinary), drug developers, and other scientists to collaborate on their research findings.
While research and testing on animals is common, “the difference here is these are privately owned animals, not laboratory owned. These are people’s pets that developed cancer.”
Currently, there are 19 members of the COTC, with the University of Pennsylvania being one of them.
The members of the COTC are not the limit of comparative oncology research being done every day. A few examples of additional research and resources:
Cancer Vaccine Center, Dana-Farber Cancer Institute at Harvard
Virginia-Maryland Regional College of Veterinary Medicine
Michigan State University is setting up a canine tumor bank, which will serve as a source of research material, allowing for an expanded understanding of the causes of canine cancer.
Poker’s quick pass through an obstacle course in his backyard shows the eleven year old Dalmatian is pretty much back to his old self.
Poker’s owner, Leslie Rush says the dog still wins agility competitions — even after being diagnosed with cancer a year ago.
Rush: But he’s still alive and he’s doing really really well. It’s the amazing thing.
For most dogs, non-Hodgkin’s lymphoma means about a year to live. In Poker’s case, it meant Rush was willing to try chemotherapy.
Rush: It’s a lot of money. It ranged from maybe bottom, maybe $200 per week and if we had tests and scans done it was like $800 per week.
Even after chemotherapy, most dogs relapse with a form of cancer that’s resistant to the treatment within twelve months. Although the timeline is compressed, the cancer closely mimics non-hodgkins lymphoma in humans.
Mason: Many people don’t know this that dogs develop spontaneous tumors that are very similar to tumors in people.
Nicola Mason is a professor at the University of Pennsylvania Veterinary School. Mason is testing two approaches to treat non-Hodgkin’s lymphoma.
Mason: So we believe that when we can find and develop, identify agents that can be used safely in client owned animals and they have a benefit in those dogs then we believe that they’re most likely to have a beneficial effect in humans as well.
One approach she’s taking is a cancer vaccine that would stimulate the animal’s immune system to ward off relapses. Another is a drug that corrects the out of control cell growth in tumors. Leslie Rush volunteered Poker for an experiment on the latter.
Rush: The reason I went for this was like anybody would. They would think, oh my god, this is going to cure my dog. This is why I’m going. I didn’t at that time have any altruistic thoughts like I’m going to cure cancer or any of the plans that Dr. Mason had. I just thought, this could cure my dog. This is the chance I want to take.
Results from both of Mason’s approaches are positive. The trial Poker was in will be expanded to more dogs. The cancer vaccine trial is still being followed for long term results, but several dogs have lived longer than Mason expected.
Levine: The next step is to do a trial in humans.
Bruce Levine is a researcher at the University of Pennsylvania, on the human medical side. Getting new treatments into to dogs first takes less time, less money, and adds more data to an experimental therapy.
Levine: Now is the point where we’re looking for grant funding. It could be biotech investment that licenses the technology so that we further develop that.
Turning animal studies into people studies is no small feat, and the majority of new treatments end of up failing once they are tested in humans. For now, Doctor Mason is focusing on canine patients.
Mason: The fact that it could go on and help people is of course a driving factor, but for me personally as a veternarian, my interests are really with the dogs.
There are currently no medications approved in humans that started out as therapies geared toward helping dogs.