Finding better ways to treat and prevent oestrogen receptor positive breast cancer

80% of all breast cancers use hormones called oestrogen and progesterone to survive and grow. Breast cancers that use oestrogen in the body to help them grow are called oestrogen receptor positive or ER-positive. They’re usually slower growing and can be treated with drugs that block the effect of oestrogen. While these drugs can be very effective and have improved survival a lot, not all ER-positive tumours respond to them. So we need to come up with better treatments.

15% of breast cancers are lobular breast cancer. They are more difficult to detect during a mammogram as they look different from other types of breast cancer. Lobular breast cancer can be more difficult to treat than other ER-positive cancers because they behave differently and we have not studied them as much as the more common types of breast cancer.

Cathrin is exploring 2 new ways to treat ER-positive breast cancers. The first is to get rid of a protein that some ER-positive breast cancers use to grow and spread. This protein is called the progesterone receptor. The second is to block another protein, called LOXL1, that’s important in the spread of lobular breast cancer.

Before new treatments can be tested in people with breast cancer, researchers need to show they work in mice.

Previously, Cathrin has developed better ways to study ER-positive breast cancer, including lobular breast cancer, in mice. Now, the team is using this knowledge to understand how ER-positive breast cancers develop. They’ll explore whether these 2 new treatments could change how we treat ER-positive breast cancer in the future. 

Cathrin and her team are focusing on 2 main projects:

1. Finding new therapies to stop treatment resistance
   Cathrin wants to develop new drugs that can block or remove the progesterone receptor. The aim is that these drugs will use the natural recycling system inside the cells to break down the progesterone receptor. 
   
   The team is testing and refining these drugs to see which are most effective at breaking down the protein. They’ll then look at whether these drugs work against ER-positive breast cancer. 
   
   They hope this will lead to more ways to treat ER-positive breast cancer and help prevent drug resistance. Also, ER-positive cancer cells that do not respond to current treatments may benefit from any new drugs.
   
   
   
2. Finding new ways to treat lobular breast cancer
   Previously, Cathrin and her team found that lobular breast cancer cells can make special fibres that act as ‘ropes’ – helping them spread to other organs in the body and grow there. They also found that an existing drug, used to treat another disease, can stop these fibres forming and block the growth and spread of lobular breast cancer cells. 
   
   Researchers are now doing more tests on this drug in the lab. They hope this will lead to clinical trials for lobular breast cancer in the future. And by repurposing a drug that already exists, the team hope that the process can happen quicker. 
   
   This project is part of the Lobular Initiative at our research centre – a collaborative, cross-team project that aims to understand lobular breast cancer more and find better treatments for it.   
   
   

We need better new, more effective treatments for ER-positive breast cancers, especially lobular breast cancer, which can be harder to detect and treat. Cathrin’s research could lead to new ways to treat ER-positive breast cancers and prevent them spreading and becoming incurable.

This research could help many thousands of people. Up to 44,000 breast cancers diagnosed each year in the UK are ER-positive. Many lobular breast cancers are also ER-positive – making up around 15% of all breast cancers.