Wendell Lim stared at the video playing on his computer screen in amazement. In the inky dark, a yellow blob pulsed: a brain tumor lit up with fluorescent tags. From the edges of the frame, T cells glowing blue crept toward it. When they reached the blob, a switch seemed to flip, and the blue cells turned green.
Lim is a biophysical chemist at the University of California, San Francisco. But what he really does is hack cells. For the last five years, his lab had been working on a new version of CAR-T therapy, re-engineering human immune cells to attack a particularly deadly form of brain cancer. Now those souped up cells had been pumped into a mouse with a human tumor growing in its brain. Lim was watching his armies of fluorescent cellbots lay surgical siege to the Frankencancer on a video feed captured from inside the animal’s skull with a pair of lasers.