Lucy Cao

Class of '20

Bio

Hi there! My name is Lucy Cao. I am a sophomore in Laguna Blanca School. I’m interested in a wide range things and excited to explore different fields in STEM. Past topics in STEM I really enjoyed include CRISPR, Starshot project to Alpha Centauri, race cars, and haptic technology. A little while ago, I got interested in how hypnosis works and the what are the therapeutic uses of it, so we invited a local hypnotist for a talk to answer these questions. STEM class has given me the opportunity to satisfy my curiosity and to learn beyond my normal high school curriculum.

Currently, I am doing research on transmissible cancer. It is a rare type of disease that sparked my interest. Scientists have only found three cases of transmissible cancer so far--in dogs, Tasmanian devils, and clams. Transmissible cancers are different from normal cancers due to the fact that the cancer cells transmit physically across hosts, which I found fascinating.

Bio

Hi there! My name is Lucy Cao. I began the STEM Science Research Program as a sophomore in Laguna Blanca School. I’m interested in a wide range things and excited to explore different fields in STEM. Topics in STEM I really enjoy include CRISPR, Starshot project to Alpha Centauri, race cars, and haptic technology. Just not long ago, I got interested in how hypnosis works and its therapeutic uses, so we invited a local hypnotist for a talk to answer these questions. STEM class has given me the opportunity to satisfy my curiosity and to learn beyond my normal high school curriculum.

The Devil's Disease

Transmissible cancers and the Devil Facial Tumor Disease

Causing 8.2 million deaths worldwide in 2012 alone, cancer is among the leading causes of deaths, according to the National Cancer Institute. With its great complexity and rapid evolvement, cancer remains a disease without definite cure, even in today’s society. Although scientists have tried many methods to treat cancer and have gained great progress, treatments including surgery, radiation and chemotherapy are not always effective and don’t always eradicate cancer cells thoroughly. For all its horror, fortunately, cancer doesn’t pass on from human to human--if nothing can stop the spreading of cancer cells, the cancer eventually dies with its host.

Now imagine for a moment, what if cancer cells can transmit across individuals? The horror would surely be magnified. With its already striking capacity for destruction, the consequence is unthinkable.

Luckily, there are no signs of transmissible cancer present in humans yet. In nature, however, scientists have already found three types of transmissible cancer: canine transmissible venereal tumour (CTVT), the Tasmanian devil facial tumour disease (DFTD) and the disseminated neoplasia in soft-shell clams. What distinguishes transmissible cancer from normal cancers is the direct transmission of tumor cells across unrelated hosts. It is interesting to note that in normal cases, although cancer is not transmittable, some infections that increase cancer risk can be passed on from person to person, which makes it seem like cancer is contagious. According to the American Cancer Society, certain viruses, bacteria, and parasites can raise a person’s risk of getting some types of cancer, because of the abnormal growth of cells, inflammation, or the weakened immune system caused by these infections. However, the infections themselves are not the direct cause of cancer, and there is no physical transmission of cancer cells.

The prospect of transmissible cancer is both terrifying and very fascinating. Now we will take a closer look at Tasmanian Devil Facial Tumor Disease, a very interesting case study for transmissible cancer.

Saving the Tasmanian Devil:

Although the goal is to develop a vaccine that can effectively treat the disease, no practical treatment has been developed so far. Also, even if a cure is found, it would be difficult to implement it to the whole population while keeping the devils in the wild. Then comes the question: If there is no cure to the disease, how can we save the Tasmanian Devils?

Save the Tasmanian Devil Program is an organization that strives to understand DFTD and to develop strategies to combat the disease. The first stage of the program is to identify and have a general understanding of the disease. The second stage is to have a captive disease-free population of Tasmanian devils to ensure the species don’t go extinct. The program has determined that it is necessary to have 500 active devil population to ensure the genetic diversity of the animal in 50 years, assuming no disease is present. The captive population is initially isolated and quarantined in Tasmania and then sent to Australia mainland to ensure no contact with the disease. The program is also exploring ways to isolate some of devils such as by fencing off geographically suitable areas. A new phase of the project is to release captive-bred devils back into the wild to re-establish a healthy wild devil population.

Roadkill is the other main cause of Tasmanian devil population decline, second to Devil Facial Tumor Disease. Save the Tasmanian Devil Program also launched a roadkill project that gathers information about Tasmanian devil’s travel patterns in an effort to reduce roadkill, and the information learned can also help with understanding the spread of the disease. In fact, for this project, every driver in Tasmania can help by driving carefully especially in seasons when Tasmanian devils are most active.

Devil Facial Tumor Disease (DFTD):

Devil Facial Tumor Disease is one of the rare contagious cancers. DFTD is transmitted directly from individual to individual by biting. Because Tasmanian devils bite each other’s face a lot, especially during mating seasons, it provides a perfect breeding ground for transmissible cancer. The symptom of the disease is characterized by tumors in devil’s mouth or around its face. The animals generally die within five months of showing symptoms of the disease, and there is currently no cure. Either the tumors become so big that the devils can’t close their mouths and die in starvation, or they die because of the breakdown of body functions. The first case of DFTD was discovered in 1969, and it has spread through most of the devil population. Currently only areas of western and northwestern Tasmania are confirmed to have remained disease-free (Cambridge). It has been estimated that there has been a 80% decline in devil population since the disease was first spotted, therefore now the Tasmanian devils are classified as endangered.

Normal cancers are not contagious, because our own immune systems would reject cancer cells from another individual. However, in this case, Tasmanian devils fail to recognize these cancer cells as foreign. One hypothesis that might explain this exception is that because the Tasmanian devils only live in the restricted habitat of Tasmania, they lack genetic diversity within their species. Therefore, when cancer cells from another devil enters their bodies, their immune systems see these new cells as if they are their own cells. The other explanation that I am more reluctant to believe is that transmissible cancers occur in nature more often than we had previously thought.