Over the past few years, immunotherapies – treatments which harness the power of the immune system to fight cancer – have been making headlines around the world. But the biggest challenges for immunotherapy have been identifying which molecules on the cancer cells are the best targets, as well as how to get past cancer’s defences.
For now, the immunotherapy treatments available to patients are powerful but blunt weapons, which in some cases can result in a number of potentially serious side effects. What is urgently needed are treatments that can guide immune cells to specifically attack a tumour, while leaving healthy cells alone. And it may have just been discovered. Cancer Research UK scientists have published a new study that has potentially uncovered the intelligence needed to precisely guide these new weapons.
Scientists have tried many different approaches to turn the immune system against cancer, such as cutting the brakes on immune cells, flagging certain cells for destruction, or genetically engineering a patient’s immune cells to directly target cancer cells.
But most of these depend on the immune system being able to recognise cancer cells as the true threat that they are. To do this, specialised immune cells – called T-cells – have to spot the danger signals, or "flags" on the surface of cancer cells.
Once the immune system recognises a cancer specific "flag" it should destroy all cancer cells that carry it. But this doesn’t always happen. So developing better immunotherapies relies on figuring out which “flags” make the best targets for the immune system to attack. And we now have a way of doing that.
13 ways to help prevent cancer
13 ways to help prevent cancer
Stopping smoking. This notoriously difficult habit to break sees tar build-up in the lungs and DNA alteration and causes 15,558 cancer deaths a year
Avoiding the sun, and the melanoma that comes with overexposure to harmful UV rays, could help conscientious shade-lovers dodge being one of the 7,220 people who die from it
A diet that is low in red meat can help to prevent bowel cancer, according to the research - with 30 grams a day recommended for men, and 25 a day recommended for women
Foods high in fibre, meanwhile, can further make for healthier bowels. Processed foods in developed countries appear to be causing higher rates of colon cancer than diets in continents such as Africa, which have high bean and pulse intakes
Two servings of fruit and three servings of vegetables a day were given as the magic number for good diet in the research. Overall, diet causes only slightly fewer cancer deaths than sun exposure in Australia, at 7,000 a year
Obesity and being overweight, linked to poor diet and lack of exercise, causes 3,917 deaths by cancer a year on its own
2007 Getty Images
Dying of a cancer caused by infection also comes in highly, linked to 3,421 cancer deaths a year. Infections such as human papilloma virus - which can cause cervical cancer in women - and hepatitis - can be prevented by vaccinations and having regular check-ups
Cutting back on drinks could reduce the risk of cancers caused by alcohol - such as liver cancer, bowel cancer, breast cancer and mouth cancer - that are leading to 3,208 deaths a year
2014 Getty Images
Sitting around and not getting the heart pumping - less than one hour's exercise a day - is directly leading to about 1,800 people having lower immune functions and higher hormone levels, among other factors, that cause cancers
2011 Getty Images
Hormone replacement therapy, which is used to relieve symptoms of the menopause in women, caused 539 deaths from (mainly breast) cancer in Australia last year. It did, however, prevent 52 cases of colorectal cancers
2003 Getty Images
Insufficient breastfeeding, bizarrely, makes the top 10. Breastfeeding for 12 months could prevent 235 cancer cases a year, said the research
Oral contraceptives, like the Pill, caused about 105 breast cancers and 52 cervical cancers - but it also prevented about 1,440 ovarian and uterine (womb) cases of cancer last year
2006 Getty Images
Taking aspirin also prevented 232 cases in the Queensland research of colorectal and oesophagal cancers - but as it can also cause strokes, is not yet recommended as a formal treatment against the risk of cancer
Tumours change as they grow, building up more and more changes in their genetic code. And it turns out that this overwhelming genetic complexity, which can make cancers so resistant to certain treatments, may actually make them visible to the immune system.
Today’s discovery builds on the idea that some early DNA faults in a tumour’s evolutionary history can persist all the way through its development. And the researchers have shown that some of these early events are being presented as “flags” on the surface of all tumour cells, where they provide an ideal target for the immune system to attack.
Crucially, they have turned this discovery into a computer prediction method to spot the flags that are shared across all tumour cells, based on genetic tumour data.
Using this method they were able to "fish out" immune cells from two lung tumour samples that recognised and latched on to the shared flags.
The hope is that this method could be developed into a way of fishing out the best immune T-cells that target every cell in a tumour. If these immune cells could be isolated and multiplied in the lab, they may offer a potent treatment alongside current therapies that release the “brakes” on the immune system.
Or, the “flags” themselves may even be enough to awaken the immune system, which is why many believe this could be a step towards personalised vaccines to target an individual patient’s tumour.
For the first time, this study shows that there are “good” and “bad” targets for immunotherapy treatments. And it gives us a way of predicting what the good targets will be.
It’s early days, but teams are now working to turn this idea into something that could be applied to many more cancers, finding unique targets on all cancer cells and not just the healthy ones.
And, most importantly, this may provide the tools necessary to give immunotherapy the precision guidance that will make a difference for patients in the future.
Professor Peter Johnson is chief clinician at Cancer Research UK