Genomics 101: How can genomics help us understand cancer?

In this series, ‘Genomics 101’, we go back to basics and explore some of the most important topics in genomics. In this blog, we explain why genomics is vital to help us understand cancer. 

First things first, what is genomics? 

In short, genomics is the study of the human genome. That is, studying the complete, end-to-end sequence of DNA present in each person. 

You might sometimes hear the genome referred to as an instruction manual, because it provides all the information we need to survive, function, and grow, as well as making each of us unique!  

If you want to read about the genome in more detail, check out our previous explainer blog: What is the genome? 

So then, what is cancer? 

With millions of new cancer cases diagnosed each year, the word cancer is something all of us will have all encountered at some point in time.  

But what exactly does it mean? 

Well, our bodies are made up millions of building blocks called cells. Each of these cells contain a full copy of our genome, and this tells the cell when to grow and divide.  

For example, if we get a cut or a wound, our skin cells will divide more rapidly to heal the wound and replace damaged tissue.  

However, it is also important that our cells know when to stop dividing.  

When the instructions to stop dividing go wrong, cells can start diving uncontrollably, and in some cases can spread around our body and damage other tissues.  

This is what we call cancer – the uncontrolled growth of cells. 

How can changes in the genome lead to cancer? 

Instructions that control how our cells grow and stop growing are sometimes called ‘cancer genes,’.  

The cells in our body read these cancer genes, almost like reading a recipe book, to know how much they should be dividing and when they should stop. 

If one of these cancer genes has a mistake in it, then the body may not be able to read it properly, potentially leading to uncontrolled cell growth.

Are there medical tests to tell us about someone's cancer? 

Yes, there a several different tests that can tell us about the genetic changes causing a person’s cancer.  

Most often, the person will have a biopsy, which is when a portion of both their cancer tissue and their normal tissue is removed, and the DNA from cells in each of these tissues is compared.

This helps us to spot any spelling mistakes in the DNA that might be causing uncontrolled growth.  

For example, we may look for patterns of damage in the genome, like where a cell has lost its ability to repair DNA.  

This information can then help us to understand lots of vital details, such as whether these genetic changes are likely to run in the family, and which medications might work best to treat the patient.  

What happens if the changes are likely to be hereditary? 

If a person has a genetic change that is thought to be inherited, they will likely be advised by healthcare professionals to speak to those who might also be affected. For example, children, siblings, and parents. 

For people who have inherited genetic changes that increase their cancer risk, there are things we can do to help manage and reduce it. 

For example, Lynch syndrome is an inherited genetic condition that increases a person’s risk of several types of cancers, such bowl and womb cancer.  

Those diagnosed with Lynch syndrome can take a daily low dose aspirin, and this reduces their chance of developing bowl cancer by about a half.  

In other cases, a person might have extra screening. This helps to catch any cancers that do occur earlier, when they're more likely to be effectively treated.  

A person might also be offered risk reducing surgery, for example if someone had a higher chance of developing ovarian cancer, after the age of 50, their healthcare professional could offer removal of the tubes and ovaries as their chance of cancer starts to increase. 

How is genomics helping advance our approaches to cancer? 

Genomics is advancing both our understanding of how cancer develops, as well as helping us find new treatments. 

There are many drugs already in use that specifically target the genetic changes found to be causing a patient’s cancer.  

This idea of ‘personalised medicine,’ so treating someone based on their specific genetic changes, is already key area of genomic research. Scientists are using genomic data every day to see how we can make treatments as effective as possible. 

In addition to this, we are also increasingly using genetic testing to identify more at-risk people in the population. This means that if someone does have a higher chance of developing cancer, we can help ensure they get the best prevention and screening programmes available.