6 Oct, 2020
Genetics and the future of precision medicine
How can our genes reveal personalised treatment options? Genetic counsellor Kira Dineen explains.
What is precision medicine?
'Precision medicine' has become a buzzword in healthcare, but what does it mean? In everyday terms, it is an approach which enables researchers and clinicians to customise a person’s medical care, most notably their treatments. It is the opposite of a one-size-fits-all approach. Instead of providing one treatment for everyone, precision medicine means patients can receive the treatment which is best suited to them as an individual. Genetic data is what makes this possible. Another term for this concept is 'personalised medicine'.
Instead of providing one treatment for everyone, precision medicine means patients can receive the treatment which is best suited to them.
A simple, and one of the oldest, examples of precision medicine is in eye care. An opthamologist does not give the same pair of glasses to all their patients. There is a spectrum of different prescriptions. Some patients need a stronger prescription to correct their vision, while others require a weaker prescription. Taking this a step further, people can even have different prescriptions in different eyes.
Using genetics to target treatment
Now that we understand the concepts behind precision medicine, let’s find out how genetics is used to offer this tailored treatment. Cancer is one of the areas of healthcare where precision medicine has the biggest influence, but it hasn’t always been this way. Years ago people with breast cancer were all treated the same way. Today people receive different treatments based on numerous factors including genetics. Knowing the genetic changes in a cancer can help to target drugs to treat that cancer. One example is the gene HER2, this gene promotes growth in cells, and in cancer it’s out of control (Iqbal 2014). A classic analogy to help understand this concept is to think of a cell as a car with gas and brake pedals, HER2 is a lead foot on the gas which makes this cancer aggressive.
Cancer is one of the areas of healthcare where precision medicine has the biggest influence.
Using precision medicine, we can identify the people who’s breast cancer has this overactive HER2, which ends up being about 1 in 5 people with breast cancer ( American Cancer Society). But how can scientists quickly distinguish which people have overactive HER2? Lucky for us these cells have markers (conveniently called HER2 proteins), that researchers can test for. It’s these same markers that allow a specific drug (Trastuzumab/Herceptin) to target these cells. Continuing our car analogy, these markers on cells are like locks on the car, so it requires a specific key to unlock it. Trastuzumab/Herceptin is the key and once it unlocks the car, it can remove HER2’s lead foot on the gas and then kill the engine/cell. Researchers are able to look at a large group, people with breast cancer, and find a smaller group within it, those with overactive HER2, resulting in doctors being able to more accurately target cancer cells within that group. However, this treatment (Trastuzumab/Herceptin) doesn’t help people who have a fully functioning HER2 gene, because the‘lock’ on those cells won't match with that key. That’s precision medicine.
There are other subgroups of breast cancer that allow for this targeted treatment. Precision medicine has made major progress both in identifying these groups and developing specific treatments for them. Now imagine we were able to assign subgroups to every type of cancer, like in our overactive HER2 example. Then the perfect drug could be given to each subgroup of cancers. This is what the future of precision medicine could look like.
Complexities of precision medicine treatment
However, here’s where it gets more complicated. When someone has cancer, not all of their cancer cells are the same. Some cancer cells may have overactive HER2 while other cells do not. Cancer evolves as it grows. Scientists have been able to draw cancer evolution just like Darwin drew species evolving, an idea which has been explored by scientist and author Kat Arney who was recently interviewed on Sano's The Genetics Podcast. In the graphic below, we see the cancer cells are depicted with various colors representing different genetic changes. Let’s say the orange cells have the overactive HER2, meaning Trastuzumab/Herceptin will only target those orange cells. We are going to need different drugs to target the purple and pink cells. This is why it’s not simple to treat most cancers and why some people with cancer are treated with multiple drugs. The future of precision medicine is to develop drugs that target the purple and pink cells too. To do this researchers need to identify what the targets on these cells are, then develop a drug that is going to go directly to these targets. Someone with the type of cancer illustrated in this graphic may potentially take three drugs, one for each colour of cell, to treat their cancer.
The future of precision medicine
Cancer is just one area of healthcare that is impacted by precision medicine. Other notable areas are heart disease and pharmacogenomics. Pharmacogenomics prescribes drugs based on a person’s genetics, similar to our overactive HER2 example. But what do researchers need in order to identify these targets and develop the drugs? I interviewed Ellen Matoff, CEO of My Gene Counsel, who’s short version of the answer was - more data.
Advancing technologies to read genes (genetic sequencing) and organise medical information via electronic health records has been instrumental in advancing precision medicine. But we also need more institutions to share their data to speed up this research. Precision medicine is an opportunity for people not to be limited to the role of a patient, but be a partner in research and contribute to the cause. With an increase of high-quality genetic data and active patient participation, precision medicine will continue to advance and better treatments will become available.