'How immune cells kill tumours decoded'

Researchers have identified a mechanism that could help determine whether a cancer patient will respond to immunotherapy.

Ideally, the immune system identifies tumours as threatening elements and deploys immune cells (T cells) to find and kill them, according to the study published in the journal Cell Reports.

However, tumour cells have evolved to employ a protein called PD-L1 to blind T cells from carrying out their functions and evade immune defences.

PD-L1 protects tumour cells by activating a "molecular brake" known as PD-1 to stop T cells.

In important therapeutic progress, antibodies developed to block PD-L1/PD-1 have been clinically proven to benefit certain cancer patients.

Yet why some patients do not respond to such therapy has remained a mystery.

Now, researchers from the University of California San Diego in the US and the Nanjing Medical School in China have uncovered some clues.

They discovered an unexpected twist in the tumour versus T cell battle. Some tumour cells display not only their PD-L1 weapon, but also the PD-1 "brake."