What is a receptor? What has it got to do with cancer?
We are developing a lot of new treatments for cancer. These newer treatments tend to be more specific (that means they only affect a small part of the body) and have fewer side effects. The downside is that they are also very expensive.
Many of these new treatments “target” (aim for or work on) things called “receptors” (pronounced ree-sep-tors) but just what is a receptor? What does is do? Is a receptor good or bad?
Well, first things frist, your are full of receptors. You need receptors to live and you have several hundred different types. Mostly receptors have code names, the names are usually 3 or 4 letters long and each letter usually stands for a long and unpronouncable word.
Some Examples of Receptors inside your body…
- FGFR -Fibroblast growth factor receptor
- EGFR -Epidermal growth factor receptor
- IGFR -Insulin like growth factor receptor
- IR -Insulin receptor
- ER -Estorogen (east-roe-gin) receptor
- PR -Progesterone (pro-jest-eh-rone) receptor
Receptors are tiny, really tiny, you can’t see them with your naked eye. You can’t even seen them with most microscopes. What scientists usually do is stain cancer cells with special dyes (often antibodies) and this will show up patches of receptors. A trained pathologist can look at a cancer cell and work out if it has more (or less) receptors than a normal cell.
What difference does it make? Well 10 years ago, not much. Nowadays though we have new drugs and therapies that target (work on) receptors. So for instance, if you have too much of a growth factor you could take a drug to block (stop) that growth factor working. This is the important point, these drugs only work if you have too many of a particualr type of receptor, otherwise you may as well take a sugar pill. These new drugs only work for some people, with some types of cancer.
You hear about these sort of drugs in the news quite a lot. One because when they work, they really work and people can live for years longer than expected. The other reason you hear about them is they are expensive, it can cost tens of thousands of pounds to treat one person for a year and the NHS only has so much money.
I still haven’t answered my first question, what is a receptor? Well a receptor is a protein, that usually sticks out of a cell, it is a bit like a mobile phone mast. It receives signals and passes them on. So if you imagine your nearest hill with a phone mast on is a cell then they sky surrounding your hill is what you’d call the “extracellular space”, this is where the signals are (just like the radiowaves that move through the sky that are picked up by the phone mast). The actual grass on the hill is a bit like the cell membrane (the skin that keeps all the cell contents together). In a cell the receptor extends into the inside of the cell like the mobile phone mast foundations extend deep into the hill. As I’ve said there are lots of different types of receptor, just as there are lots of different types of mast (e.g. a television mast, a radio mast, vodaphone mast, orange mast etc etc). Different masts do different things and have different affects (e.g. you are never going to get a tv picture from a radiowave, just as insulin won’t turn on your FGF receptor.) This means they are “specific”, so a drug that works on the EGF receptor won’t do anything for the FGF receptor)
So to answer my questions
What is a receptor? It is a protein that detects chemical signals in the body.
What does it do? It tells the cells in your body when a particular chemical is there.
So what? This can affect how fast a cancer cell grows. If there is a lot of a chemical telling your cells to grow, then a cancerous tumour will grow faster if it has a lot of those specific receptors.
What can you do about it? Well, for some cancers you can take a drug to block a specific receptor.
How do I know what receptors my cancer has? If you have a type of cancer that can respond to receptor treatment (e.g. breast cancer or prostate cancer). Your doctor will have your cancer tested. This is done by a specalist doctor called a pathologist. If you want to know more you could ask for the details of your “pathology report”.
What receptor blocking drugs are available?
Drug Name Cancer Receptor Name
- Herceptin Some types of breast cancer HER2
- Avastin Some types of colorectal caner VEGF
- Mabthera Some types of B-cell lymphoma CD20
- Tarceva Some types of non small cell lung cancer EGF
Are there other receptor blocking drugs? Yes, there are a lot being developed in laboratories around the world, there are a lot being tested in clinical trials and there are other ones that I haven’t mentioned in this list.
Is a receptor good or bad? It depends, you need receptors in order to live, so from that point of view receptors are good, they allow us to grow, eat, think and reproduce but too many receptors in the wrong place can give us cancer.
Where can I find out more?
Cancer Reserach UK - Information on Biological Therapies - Cancer growth blockers
The CancerBakcup information on Cancer Growth Inhibitors can be found here.
To watch a short (54 second) video of a chemical signal (in purple) binding to a receptor (in blue) have a look at this YouTube video by bluegreenalgae.
If you can’t view YouTube, then you can see a picture of the Estrogen Receptor on the Protein Data Bank “Molecule of the Month” page. There are several pages on Estrogen, the Estrogen Receptor, Tamoxifen and cancer.