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Immunotherapy “breakthrough” makes big news

by Kat Arney | Analysis

20 June 2008

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Doctors looking at an x-rayIt’s been hard to miss the recent media coverage of the result of a clinical trial by researchers in America, reporting that a man with advanced melanoma (a form of skin cancer) has been successfully treated using his own immune cells.

The story’s been spread by headlines such as “Man beats skin cancer after being treated with five billion clones of his own immune cells
Clone cell cancer ‘cure’ hailed” and “Cancer ‘cured‘ by cell clones” . Cancer Research UK’s team of spokespeople have also been busy doing radio and TV interviews, explaining the science behind the story.

But what have the researchers actually done – and is it really a “breakthrough” and a “cure” for melanoma?

The first thing to point out is the use of the word “result” (singular) in the first paragraph of this post. We’re talking about one man on an early-stage clinical trial that involved a number of other patients who weren’t so lucky. So it’s a bit early to get excited about a “cure” for people with advanced melanoma– a condition that is currently extremely difficult to treat.

But this is a very exciting piece of research, for a couple of reasons. Firstly, many researchers – including several labs funded by Cancer Research UK – are working on immunotherapy, developing treatments that can harness the power of the immune system to fight cancer. At the very least, this positive result is a sign that we’re all heading in the right direction.

Secondly, the work is exciting from a scientific point of view. We’ll look in more detail at what the scientists actually did – but first we need to do a little bit of immunology.

Our immune system is made up of many different types of white blood cells, but this story focuses on a particular sub-group of white cells called ‘T’ cells. There are two main types of these – killer T cells, also known as CD8+ cells (so-called because they carry a protein called CD8 on their surface), and helper T cells, known as CD4+ cells. When you have an infection, the helper T cells literally ‘help’ the killers to recognise infected cells, pointing them in the right direction and producing special molecules to aid the killer cells as they destroy their targets.

Many scientists working on cancer immunotherapy have been looking at ways to purify killer T cells from the body, ‘train’ them to recognise cancer cells and multiply them in the lab, before transplanting them back into a patient (see our recent post about it here). This approach has had some success, because it’s relatively easy to isolate and grow killer cells.

The down side of this approach is that killer T cells don’t live for very long in the body, so any immune response to a tumour is likely to be short-lived. However, helper T cells last much longer (for several months), and they can orchestrate a much bigger immune response. But, until now, scientists have been unable to purify them and grow them in the lab in sufficient numbers to use as a treatment.

Step forward Dr Cassian Yee and his team, at the Fred Hutchinson Cancer Research Centre in the US. They have used a new technique to isolate and grow helper T cells in the lab. In fact, they were able to grow up to 5 billion T helper cells to transplant.

What makes this more interesting is the fact that the helper T cells had been ‘trained’ to tell killer T cells to home in on a specific molecule found on the patient’s melanoma cells. The researchers achieved this by isolating another type of immune cell, called dendritic cells, from the patient, and treating them with the melanoma molecule (as described in this earlier blog post). These dendritic cells then ‘train’ the helper T cells to co-ordinate an immune response and marshal killer T cells to destroy cancer cells carrying that molecule.

But although only half to three-quarters of the patient’s cancer cells carried the ‘trigger’ molecule, all of them were destroyed by the immune system. This tell us that the helper cells may be provoking a much wider immune response – an intriguing finding indeed.

And, fortunately for this one patient, his helper T cells provoked a large enough immune response to completely eradicate his tumours. He has now been free from cancer for 2 years.

It’s too early to shout about a “cure” for advanced melanoma,.But this research is definitely a step along the way to a new breed of cancer treatments, and we welcome it.

In the words of Peter Johnson, Cancer Research UK’s chief clinician, “This is another interesting demonstration of the huge power of the immune system to fight some types of cancer. Although the technique is complex and difficult to use for all but a few patients, the principle that someone’s own immune cells can be expanded and made to work in this way is very encouraging for the work that Cancer Research UK and others are carrying out.”

If you’d like to find out more about some of the immunotherapy work that Cancer Research UK is funding, check out these scientists from our Research Highlights pages: Dr Facundo Batista, Professor Tim Illidge, and Professor Christian Ottensmeier.