Escaping the immune system

Immune cells recognise danger through a group of molecules found on the surface of all cells in the body. This helps them inspect potential problems closely and decide whether to attack.

But when a cancer reaches the ‘escape phase’ it can change. The molecules that would otherwise reveal the cancer to the immune system are lost, and killer T cells move past, unaware of the danger the cancer cell could cause.

“That’s a sure-fire way of escaping detection,” says Elliott, adding that it’s one of many escape methods cancer cells use.

“Cancer cells also develop ways to inactivate immune cells by producing molecules that make them stop working.” They also change their local environment, so it becomes a hostile place for immune cells to work.

“Once the tumours have changed their environment, any circulating killer T cells that arrive in this space are rendered inactive,” says Elliott.

Upskilling immune cells

Research has shown that changes to immune cells don’t need to be permanent. The theory is that if there’s a way to reverse these tricks, or stop immune cells falling for them, their cancer-fighting ability could be restored.

This has formed the basis of a growing range of cancer treatments called immunotherapies. And for some cancers, these drugs offer the chance of a cure that would’ve been impossible a decade ago.

They can work by releasing the brakes on immune cells so they can get cancer cells back in line. And a group of these drugs, called checkpoint inhibitors, are now being routinely used to treat a range of cancers, including some melanomas, lung and kidney cancers.