Scientists have discovered another way that cancers protect themselves from the immune system, allowing them to grow and spread.
Researchers from QIMR Berghofer have found that a particular chemical produced by tumours turns Natural Killer (NK) immune cells into another type of immune cell that appears to help the cancer to grow.
The findings pave the way for an antibody to be developed to stop the NK cells from being converted, and potentially stop the tumour from spreading.
The findings have been published in the journal Nature Immunology.
Professor Mark Smyth from QIMR Berghofer’s Immunology in Cancer and Infection Laboratory said NK cells had long been known to be the immune system’s first line of defence against cancer and infection.
“Recently, however, it’s been suggested that a very similar type of immune cell, known as a type 1 innate lymphoid cell, or ILC1, is more important in kick-starting an immune response,” Professor Smyth said.
“In this study, we have instead proven that NK cells are the important first line of cells for defending us against cancer. We also found evidence to suggest that ILC1s in fact promote the growth and spread of tumours.”
Professor Smyth and his team conducted a genetic analysis on both cell types and discovered that a chemical produced by tumours – known as TGF-Beta, or TGF-β – converts NK cells into ILC1s.
“Once a tumour starts to grow, it produces more and more of the chemical TGF-β. What then happens is the NK cells, which could have fought the tumour, are converted into cells that either do nothing or could even help the cancer grow,” Professor Smyth said.
“This is yet another escape mechanism tumours have for evading the immune system and winning the battle.
“Once the cancer starts growing, it uses this cell conversion as a way of shutting off the immune response and stopping the immune system from getting back on top of it.”
Professor Smyth said he and his team hoped to develop an antibody to block tumours from turning NK cells into the pro-tumour ILC1s.
“By developing a very specific antibody, we believe we can stop this conversion from occurring,” he said.
“This would mean larger numbers of NK cells at the site of the tumour, which we hope would control the cancer and stop it from spreading to other parts of the body.”
The study involved collaborators from the Walter and Eliza Hall Institute, France, Germany and Japan. The work was funded by the National Health and Medical Research Council, the Cancer Research Institute, Cancer Council Queensland, and the National Breast Cancer Foundation.