Tumor sentinels

In one type of cancer immunotherapy, a medical team harvests a patient’s own T cells from blood, genetically engineers them to boost their cancer-fighting properties, then releases them back into the patient’s bloodstream. The technique shows promise, but researchers don’t necessarily know how well, or even whether, it is working until months later.

A new Stanford-led study allows researchers, for the first time, to see where immunotherapy cells go in the human body: whether they have found a tumor, how many cells have arrived at the tumor and whether they are alive.

“This is the first demonstration in humans of actually noninvasively imaging the immune system in action,” says Sanjiv “Sam” Gambhir, MD, PhD, professor and chair of radiology and senior author of the study, which was published in January 2017 in Science Translational Medicine.

In the culmination of a 10-year effort, the researchers engineered the T cells to better recognize the patient’s cancer cells, then added a “reporter gene” that made a protein they could see with a positron emission tomography scan. The protein lit up on the scan, revealing how many T cells had reached the tumor. In one patient, the cells migrated both to a known tumor and an unknown one.

Patients can be repeatedly imaged to track T cell behavior over time, which will allow researchers to better understand and refine immunotherapy.