Body fat ‘clogs’ vital cancer-killing cells

Study reveals link between disease and obesity

OBESE people are more likely to get cancer because fat clogs up the immune system, scientists have discovered.

Obesity is the second biggest preventable cause of the disease in Britain, with links to cancers including breast, bowel, ovarian, gullet, pancreatic and kidney.

Now scientists are starting to understand how weight gain gives cancer a helping hand.

A study led by Brigham and Women’s Hospital in Boston, Massachusetts, found too much fat in the body damages the ‘natural killer’ (NK) cells that can destroy tumours.

NK cells are the body’s foot soldiers for fighting cancer but can be ‘clogged up’ by fatty acids which escape from fat tissue.

While they can still latch on to cancer cells, they kill them much more slowly or not at all.

Professor Lydia Lynch, a coauthor of the study and associate professor in immunology at Trinity College Dublin, said: ‘When people are obese, it disrupts the killing machinery in their NK cells so that they are metabolically paralysed. This finding means we could develop drugs to block this reaction from happening, or that people at risk could try to lose weight so that the fatty acids which disrupt NK cells are burned off before they can do harm.’

One in 20 cases of cancer in Britain is thought to be linked to obesity.

Researchers already knew that NK cells struggle to kill cancer tumours in obese people, and that cancer patients with fewer of these cells have a worse prognosis.

But the new research found the immune cells, when taken from obese mice and people, can recognise and attach to tumour cells. They just do not kill them as well, which can allow cancer to spread unimpeded.

Responding to the findings – published in the scientific journal Nature Immunology – Dr Leo Carlin, of the Beatson Institute for Cancer Research in Glasgow, said: ‘Although we know that obesity increases the risk of 13 different types of cancer, we still don’t fully understand the mechanisms underlying the link.

‘This study reveals how fat molecules prevent the immune cells from properly positioning their tumourkilling machinery, and provides new avenues to investigate treatments.’