Vaccine drives growth of T cells engineered to attack cancer cells, according to experiments in mice.

People with several types of blood cancer have reaped enormous benefits — including long-term remission — from treatment with CAR-T cells, immune cells modified to fight malignant invaders. But technical hurdles have limited these cells’ effectiveness against colon cancer and other solid tumours.

Seeking to expand the cells’ versatility, Ugur Sahin at Johannes Gutenberg University Mainz in Germany and his colleagues identified a protein, claudin-6, that is found on many types of solid-tumour cells. The researchers made CAR-T cells by adding claudin sensors to infection-fighting T cells; this improved their ability to destroy claudin-bearing cancer cells.

The scientists tested the souped-up T cells on mice implanted with samples of lung, colon or ovarian tumour. Some mice also received a dose of claudin-coding RNA, called an RNA vaccine, that stimulates production of the protein.

In mice that received both T cells and the vaccine, claudin-targeting T cells multiplied, and tumours withered. But in mice that did not receive the vaccine, the tumours grew.

Many types of CAR T-cell might work more effectively if they are supplemented with RNA vaccines against cancer biomarkers, the authors say.