PATIENTS battling ovarian cancer and a highly aggressive form of breast cancer could be cured in future after scientists in the US discovered a new way to destroy the tumours.

Researchers at Stanford University's School of Medicine made the breakthrough after identifying a new protein, called CD24, which covers the surface of cancer cells, cloaking them from immune system attack.

However, when the team blocked this protein's signals they found that macrophages - the white blood cells which mop up potentially harmful organisms - started "gorging on cancer cells like they were at an all-you-can-eat buffet".

Dr Amira Barkal, lead author on the study, published in Nature, said: "When we imaged the macrophages after treating the cancers with CD24 blockade, we could see that some of them were just stuffed with cancer cells."

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The findings hold "particular promise" in relation to ovarian cancer and triple-negative breast cancer because they showed the strongest response to having CD24 turned off.

Dr Barkal added: "By treating cancers with antibodies that block CD24, we can remove this 'shield of armour' and allow macrophages to effectively, and efficiently, clear the cancer.

"Additional research needs to be done to determine which patients are most likely to benefit from CD24 blocking therapies, and whether CD24 expression may be used to predict which patients are most likely to respond to existing anti-cancer immunotherapies which are already being given to patients.

"Ovarian cancer and breast cancer are two of the most deadly diseases affecting women, and both are very aggressive cancers that are notoriously difficult to treat in the clinic.

"We are excited about the potential of these findings to provide a new strategy to treat and maybe even cure ovarian cancer and breast cancers."

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Around 4700 women are diagnosed with breast cancer in Scotland every year. Of these, 10-20 per cent of cases will be the triple-negative form, which does not respond to treatments such as hormone therapy.

It is aggressive, more likely to spread before being detected, and to recur.

Triple-negative breast cancer is also more common in younger women and in carriers of the BRCA gene mutation.

Ovarian cancer is diagnosed in around 600 women a year in Scotland, but claims 400 lives.

It is often picked up late as there is no effective screening tool and symptoms can be similar to conditions such as irritable bowel syndrome.

An effective new treatment with the potential to increase survival rates would be hugely important for both diseases.

The Stanford study collected ovarian and breast cancer cell samples from female patients over the age of 30 who were being operated on at the Stanford University Medical Centre.

Using a technique which would cause cancer cells high in CD24 to give off a fluorescent glow, the scientists observed that "robust expression of the CD24 protein in breast cancer cells and ovarian cancer cells".

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Once the protein's protective cells was turned off, the cancer cells were mixed in the laboratory with human donor macrophages which "engulfed" them.

They concluded that the high levels of CD24 on ovarian and triple-negative breast cancer cells mean it is the "dominant immune checkpoint" for these cancers and therefore offers "a promising target for cancer immunotherapy".

When the researchers tested their findings using mice grafted with breast or ovarian cancer tumours which they then deprived of CD24, thus enabling the rodents' immune systems to attack, they found that this "was sufficient to substantially reduce tumour growth over several weeks".

It also resulted in a "significant survival advantage" compared to mice not treated in this way.

Rebecca Rennison, Director of Public Affairs and Services at Target Ovarian Cancer, said: “We have seen fantastic results in immunotherapy in other cancers but it has not yet proven effective for ovarian cancer.

"Today’s announcement shows great promise in this area and if borne out by further research, this would represent a major breakthrough."

Kotryna Temcinaite, research communications manager at Breast Cancer Care and Breast Cancer Now, said: "This exciting research could potentially lead to a new treatment option for triple negative breast cancer, which can be difficult to treat.

"It is encouraging to see results which point towards the possibility of much needed targeted treatments for this type of breast cancer. 

“This research also helps to explain why certain existing immunotherapies may not currently be effective at treating some cancers.

"However, the study was carried out in mice and further research is needed to understand the full effect this new immunotherapy could have, and who may benefit most from it."

Researchers at Stanford University have previously shown that another type of protein, CD47, is used by cancer cells to hide from an immune system attack.

Antibodies that block CD47 are in already being tested in clinical trials.

However, not all cancer types respond to having CD47 blocked, leading scientists to search for other proteins - and ultimately to the discovery of CD24.

Senior author Irving Weissman, professor of pathology at the Stanford Institute for Stem Cell Biology and Regenerative Medicine, said: "Finding that not all patients responded to anti-CD47 antibodies helped fuel our research at Stanford to test whether non-responder cells and patients might have alternative 'don't eat me' signals."