High-fat diets could make an aggressive breast cancer more difficult to treat, new research suggests, highlighting the possible role diet may play in cancer progression.
Triple negative breast cancer most commonly affects women under 40-years-old and accounts for around 15 per cent of breast cancer cases.
It tends to be more aggressive than other breast cancers, with faster growth rate and higher risk of recurrence, meaning chemotherapy is almost always necessary.
There has been a lot of research into whether diet increases breast cancer risk, with experts suggesting last week a vegetarian diet can help protect against the disease.
Now researchers at Princeton University have discovered that a high-fat diet, which over time increases levels of so-called 'bad' cholesterol in the blood, could accelerate tumour growth in breast cancer patients.
'We were hoping to identify dietary conditions that would slow tumour growth,' Professor Celeste Nelson, biochemist and study author explained.
'Instead, we found one dietary condition - a high-fat diet - that sped up tumour growth.'
The research, published in the journal AIP Publishing, found that high-fat conditions altered cell metabolism and increased production of a protein that helps tumours spread.
The team exposed lab-grown tumours to different nutrient environments in an effort to better understand why obesity speeds up cancer progression.
They focused on triple negative breast cancer - the deadliest form of the disease - and tested five different nutrient conditions.
Analysis revealed that under high-fat conditions, tumours grew larger and invaded surrounding tissue more quickly, fueling cancer progression.
But rather than increasing the speed at which cells divide, high-fat conditions were found to increase production of a protein called MMP1.
This protein has been linked to poorer outcome in breast cancer patients because it helps cancer cells move and spread more quickly by breaking down tissue surrounding tumours.
Interestingly, tumours exposed to a high ketone environment - designed to mimic the metabolic state triggered by a high fat, low carbohydrate diet - didn't show the same acceleration in growth or invasion.
The researchers also found that tumours grown in high-fat conditions developed hollow spaces in their centres - not because cells were dying, but because they were moving outward and attacking surrounding tissue.
This, they said, suggests that fat availability has a strong effect on how aggressively certain breast cancers behave.
The researchers hope their results will help inform the link between diet and cancer.
Prof Nelson added: 'We plan to make the same system and define whether tumours respond differently to chemotherapy when grown in conditions mimicking the different dietary conditions.
'This would allow physicians to potentially make recommendations about what a patients should eat if prescribed a specific therapy.'
In the UK, breast cancer cases have risen sharply over the past three decades.
Roughly one in seven women are diagnosed with breast cancer in their lifetime - with around 56,500 new cases a year - making it the most common cancer in the UK.
Around 85 per cent of women diagnosed with breast cancer survive more than five years.
However, triple negative breast cancer is far more challenging.
Typically, it grows and spreads faster than other breast cancer types and has fewer treatment options.
It is also more difficult to treat because it doesn't interact with hormones such as oestrogen -- for which there are targeted therapies.
On average around 77 per cent of women with triple negative breast cancer will survive their cancer for five years or more after they are diagnosed, but depending on the stage this can fall as low as 12 per cent.
This is compared to around 90 per cent of women with other forms of breast cancer who will survive for at least five years.
Despite the importance of fast access to diagnosis and treatment in improving outcomes, figures published yesterday suggest breast cancer cases will surge by almost a third by 2050.
A major international analysis found breast cancer diagnoses are on track to climb from 2.3 million a year to 3.5 million, while annual deaths from the disease are projected to jump 44 percent, to almost 1.4 million.
Researchers say more than a quarter of the healthy years lost to breast cancer globally can now be traced to seven modifiable risk factors: obesity, high blood sugar, smoking, secondhand smoke, heavy alcohol use, low physical activity and high red meat intake.