Dr Katie Snape: How can genomics help us understand cancer?

In this explainer episode, we’ve asked Dr Katie Snape, principal clinician at Genomics England, cancer geneticist, and specialist in inherited cancer, to explain how genomics can help us understand cancer.

You can also find a series of short videos explaining some of the common terms you might encounter about genomics on our YouTube channel.

If you’ve got any questions, or have any other topics you’d like us to explain, let us know on podcast@genomicsengland.co.uk.

You can download the transcript or read it below.

Flo: How can genomics help us understand cancer?  

I'm Florence Cornish, and today I'm joined with Katie Snape, who is Principal Clinician here at Genomics England, lead Consultant for Cancer Genetics at the Southwest Thames Centre for Genomics, and Chair of UK Cancer Genetics Group.

So Katie, it's probably safe to say that everyone listening will have heard the word cancer before. Lots of people may have even been directly affected by it or know someone who has it or who has had it, and I think the term can feel quite scary sometimes and intimidating to understand. So, it might be good if you could explain what we actually mean when we say the word cancer.  

Katie: Thanks, Florence. So, our bodies are made up of millions of building blocks called cells. Each of these cells contains an instruction manual, and our bodies read this to build a human and keep our bodies working and growing over our lifetimes. So, this human instruction manual is our genetic information, and it's called the human genome.

Throughout our lifetime, our cells will continue to divide and grow to make more cells when we need them. And this means that our genetic information has to contain the right instructions, which tell the cells to divide when we need new cells, like making new skin cells, for example as our old skin cells die, but they also need to stop dividing when we have enough new cells and we don't need anymore. And this process of growing but stopping when we don't need anymore cells, keeps our bodies healthy and functioning as they should do.

However, if the instructions for making new cells goes wrong and we don't stop making new cells when we're supposed to, then these cells can grow out of control, and they can start spreading and damaging other parts of our body. And this is basically what cancer is. It's an uncontrolled growth of cells which don't stop when they're supposed to, and they grow and spread and damage other tissues in our body.

Florence: So, you mentioned there that cancer can arise when the instructions in our cells go wrong. Could you talk a little bit more about this? How does it lead to cancer?

Katie: Yeah. So the instructions that control how our cells should grow and then stop growing are usually called cancer genes. So our body reads these instructions a bit like we might read an instruction manual to perform a task.

So if we imagine that one of these important cancer genes that has a spelling mistake, which means the body can't read it properly, then those cells won't follow the right instructions to grow and then stop growing like they should. So if our cells lose the ability to read these important instructions due to this type of spelling mistake, then that's when a cancer can develop. As these spelling mistakes happen in cancer genes, we call them genetic alterations or genetic variants.

Florence: And so, when you're in the clinic seeing somebody who has cancer, what kinds of genomic tests can they have to help us find out a little bit more about it?

Katie: So the genetic alterations that can cause cancer can happen in different cells. So that's why cancer can affect many different parts of the body. If a genetic alteration happens in a breast cell, then a breast cancer might develop. If the alteration happens in a skin cell, then a skin cancer could develop. We can take a sample from the cancer. This is often known as a biopsy, and then we can use this sample to extract the genetic information to read the instructions in the cancer cells, and when we do this, we are looking for spelling mistakes in the important cancer genes, which might of course, those cells to grow out of control.

We can also look for patterns of alterations in the cells, which might tell us the processes that led to those genetic alterations occurring. For example, we can look at patterns of damage in the genetic information caused by cigarette smoke, or sunlight, or problems because the cell has lost its ability to mend and repair its genetic information.

And we can also count the number of different alterations in the cancer cell, which might tell us how different that cancer cell is from our normal cells, and that can be important because we might be able to use medications to get our immune system to attack the cancer cells.

So where we see genetic alterations in a cancer cell, we call them acquired or somatic alterations because we weren't born with them, but they've happened in a cell in our body at a later stage, and they've caused those cells to become uncontrollable and to keep growing.

Sometimes people can be born with a genetic alteration in a cancer gene that significantly increases the chance of them developing cancer in their lifetime. This type of genetic alteration can be inherited, and so these changes can be shared by relatives. If we see more cancer in a family than we would expect by chance, or unusually young cancers or patterns of cancer, or there are other signs that a cancer patient might have an inherited cancer gene causing their cancer, then we can offer a test to check for this as well.

Florence: And so, when we do these tests, what are we looking for specifically? What is it that we're trying to find out about a person's cancer that could help us to treat it as effectively as possible?

Katie: So all of these genetic tests are helping us understand why a cancer has developed and what are the underlying changes that cause the cells to grow out of control. If we understand why the cancer developed, we can choose medications to try and treat the cancer and these specifically target the underlying problems in the cell, and hopefully attack the cancer cells, but not the normal cells in the body.

We call this precision or personalised medicine. Many newer cancer drugs specifically target the changes that have occurred in the cancer cells as part of this process for becoming cancer, and they kill those that carry specific genetic changes which have caused those cells to grow uncontrollably.

Florence: I wanted to ask you now about inherited cancer risk. So by this we mean if a parent has a change in one of their genes that increases their risk of developing cancer, there's a possibility that they can then pass this gene along to their children. Is there anything we can do to manage these inherited risks?

Katie: If a person has an inherited change, increasing cancer risk, we can offer them programs to help reduce that risk. There are different things that we might offer them. So, for example, for some conditions we have preventative medication. There is a condition called Lynch syndrome, which is due to a change in some cancer genes, and people who have Lynch syndrome have a high chance of developing bowel and womb cancers, amongst others.

For people with Lynch syndrome, they can take a daily low dose aspirin, and this reduces their chance of developing a bowel cancer by about a half. Or in other cases, we can offer extra screening and that will allow us to catch any cancers that do occur at an earlier stage when they're more likely to be more effectively treated. So for example, if someone has a high risk of breast cancer, we could offer them extra and more frequent screening of their breast.

Another option is we could offer risk reducing surgery. So, for example, if someone had a higher chance of developing ovarian cancer after the age of 50, we could offer removal of the tubes and ovaries as their chance of cancer starts to increase, and that would significantly reduce their risk of developing cancer in the future. 

Florence: And, working in this space, you and I know that research groups are working all the time to try and better understand cancer and how we might be able to treat it more effectively. Could you tell me about how genomics in particular is helping to advance the detection and treatment of cancer? 

Katie: Genomics is helping develop both our understanding of how and why cancer develops, and as well as that, it's also helping us find new cancer treatments all the time.  

There are already many drugs that are available to cancer patients that specifically target the genetic changes found in their cancer. In addition to that, there are many clinical trials now for cancer patients, which use the information from genomic sequencing to help guide new research into better treatments based on the genetic alterations in the cancer cell. 

We are increasingly using genetic testing to identify more at-risk people with inherited changes in the population as well, so that we can make sure if they have a higher chance of developing cancer in their lifetime, that they get the best prevention and screening programs available. our understanding of genomics is really impacting both our understanding of what causes cancer, how we treat it, and how we can prevent it as well. 

Florence: So, I think we'll finish there. Katie, it's been so great to talk to you and to learn more about why genomics is proving to be so important in helping us to understand cancer.  

If listeners want to hear more, explain episodes like this, you can find them on our website@www.genomicsengland.co.uk or wherever you get your podcasts. Thank you for listening.