Autoimmune disease has devastating consequences for healthy tissue. Now, in mice, the same cells that can drive the body to destroy its own tissue have been used to fight cancer.

The cells are a recently discovered type of immune cell called Th17. These cells play a key role in autoimmune disease – in which the immune system mistakenly identifies the body’s own tissues as foreign and attack them.

We already know that some people’s immune systems have a natural ability to fight some types of cancer. But how exactly this works – and why it doesn’t always do so – isn’t known.

Discovered in 2005, Th17 cells are thought to have a part in triggering the inflammation and tissue injury associated with autoimmune diseases. But they also have a helpful role in fighting bacterial infections.


Guilt assumed

In addition, Natalia Martin-Orozco at the MD Anderson Cancer Center in Houston, Texas, and her colleagues noticed Th17 cells infiltrating cancerous tumours. But as inflammation is known to promote the growth of cancer, they assumed that the cells were helping the tumours to grow.

To investigate further, the team engineered mice that were deficient in Th17 cells and then injected them with a strain of melanoma that affects the lungs.

To their surprise, they found that these Th17-deficient mice experienced far more aggressive cancer growth than normal mice – with the cancer completely smothering the lungs within 16 days. “It was the opposite of what we expected,” says Martin-Orozco. “If anything, [the Th17 cells] were promoting an anti-tumour response.”

Next, they incubated Th17 cells with proteins specific to the lung melanoma. This process was designed to enable the cells to recognise such a tumour if they encountered it. The researchers then injected these tumour-specific cells into mice at the same time as injecting melanoma cells.

After 16 days, mice injected with the tumour-specific Th17 cells had barely detectable tumours, compared with mice injected with tumour cells alone. What’s more, injecting the cells into mice with established tumours reduced the tumours’ mass by 75 per cent.

Set the T cells on them

Martin-Orozco believes that Th17 cells recognise tumours and, in response, release chemicals that attract immune cells called dendritic cells to the tumour. These seize tumour proteins and take them to lymph nodes, where the dendritic cells prime killer T cells to recognise and attack the tumour.

The next step is to see if Th17 cells from humans also have an anti-tumour effect. “While there is much work to be done, these findings imply the possibility of taking a patient’s Th17 cells, expanding them in the lab and then reinfusing them as a treatment,” adds Chen Dong, also of MD Anderson, who supervised the work.

Similar approaches using killer T cells are already being investigated as a cancer treatment, with some promising results.

The researchers also plan to explore whether the production of extra Th17 cells could be stimulated through vaccination.

To avoid the risk of injected cells destroying healthy tissue, Th17 cells that are reactive to tumours but not to normal tissues would have to be identified, Dong cautions.

The team also needs to figure out which types of cancer Th17 cells respond to, and at which stage of the disease.

Caetano Reis e Sousa, head of the immunobiology lab at Cancer Research UK’s London Research Institute, sounds says the work is “exciting” but cautions that it is at an early stage.

“The results need to be validated and extended before scientists know if a treatment based on this approach could one day be used to help cancer patients.”

Journal reference: Immunity, DOI: 10.1016/j.immuni.2009.09.014