A vaccine to prevent breast cancer? Not just yet

The protoype 'cancer vaccine' is a long way from human trials

Last week it was viruses, this week it’s vaccines. So, are we really on the verge of a ‘revolutionary vaccine’ that could ‘end breast cancer’ – as some of the media have stated?

No. Not yet, anyway.

The headlines in question originated from a paper in Nature Medicine, in which US-based researchers described a series of experiments they’d carried out with specially bred mice.

No studies in people have yet been carried out, and there are reasons to believe the approach the researchers took would be difficult to make work in women.

What did they do?

The US team focused on a protein that seems to be found only in rapidly dividing breast cells, called alpha-lactalbumin. The scientists figured that this protein, which is often found in high levels in breast cancer cells, could be a good way to ‘target’ treatments to breast cancer.

One way to do this, they speculated, was to use alpha-lactalbumin as a vaccine to ‘prime’ the immune system to attack breast cancer cells, in the same way that doctors use fragments of viruses and bacteria to protect us against diseases like measles and tuberculosis.

To begin to test whether their theory was correct, they did what all researchers do when they’ve stumbled across a new, exciting idea: they test it in a model system.  In this case, the team used mice that were genetically predisposed to developing breast cancer – such tests help decide if an idea’s worth pursuing.

In their paper (which is excellently explained in detail on NHS Choices ‘Behind the Headlines’ site), the researchers reported that vaccinating a handful of these cancer-prone mice with alpha-lactalbumin did indeed reduce the rate at which they subsequently developed breast cancers – suggesting that their idea was potentially a good one.

They also showed, in another group of mice, that the vaccine prevented human breast cancer cells from growing.

More research needed

As we frequently find ourselves pointing out on this blog, this is just the beginning of the story, rather than its end.

Neither of the ‘model systems’ above is a woman with breast cancer. The effects of ‘switching on’ a woman’s immune system to target a protein found in her own breast tissue are completely unknown and unguessable.

And, crucially, the vaccine did seem to cause problems in mice that were producing milk – so using this approach could be problematic in pregnant or breastfeeding women, should it ever be trialled in humans. So there is a vast amount of research to be done to take this early work forwards, and no guarantee of success.

Indeed, no vaccine against cancer has successfully been developed so far. The well-known ‘cervical cancer vaccine’ isn’t actually a cancer vaccine in this sense – it protects against a virus, HPV, that can lead to cancer in certain women. These researchers are very much in uncharted territory.

So we have a set of headlines promising progress that hasn’t happened yet, in a different species to our own – although to be fair, most of the actual articles mentioned that the work was done in mice.

Nevertheless anyone with an eye on the media recently could be forgiven for thinking that cancer had already been ‘cured’ when, as we explain all-too-frequently, it’s usually very early days, and much more work needs to be done.

And, as Martin pointed out yesterday, these headlines can – and do – cause alarm, worry and, perhaps worst of all, false hope, amongst people who read them.

Henry

Reference:

Jaini, R., Kesaraju, P., Johnson, J., Altuntas, C., Jane-wit, D., & Tuohy, V. (2010). An autoimmune-mediated strategy for prophylactic breast cancer vaccination Nature Medicine DOI: 10.1038/nm.2161