A study led by Ludwig Stanford’s Sanjiv “Sam” Gambhir has for the first time demonstrated a method to visualize and monitor the behavior of immune cells used to treat cancer patients. The new technique allows researchers to see where engineered immune cells used for immunotherapy go in the body as they hunt down tumors. It also reveals whether these immune cells, called T cells, have found a tumor, how many have arrived and whether they’re alive. These capabilities will be useful to clinicians trying to learn if a treatment is working as well as to researchers exploring why immunotherapy doesn’t always work. A paper describing the technique was published online Jan. 18 in Science Translational Medicine.
“This is the first demonstration in humans of actually noninvasively imaging the immune system in action with reporter gene technology,” said Gambhir, who is a Virginia and D.K. Ludwig Professor in Cancer Research and professor and chair of radiology at the Stanford University School of Medicine. “It’s never been done before in a living human.”
The method was evaluated in patients with a type of deadly brain cancer called glioblastoma, but it could be used to track immune cells targeting any kind of tumor, Gambhir said.
Currently, the only way to find out if the T cells used in cell-based immunotherapies are attacking tumors is to wait to see if the tumors shrink, but that can take months. Even if clinicians are sure treatment has failed, they often don’t know why. Did the T cells not reach the tumor? Or did the T cells get to the tumor but fail in their attack?
Gambhir estimates that his lab has produced 50 papers over the last 15 years in the quest to make the T cell imaging technology work, first in animals and now, finally, in humans. To develop the technique, the researchers first engineered T cells to better recognize the patient’s cancer cells. Later, they added a “reporter gene” to the T cells. This gene makes a protein that can be detected with a positron emission tomography scan.
One thing the new technique cannot do is tell researchers whether the T cells are actually attached to tumor cells. But that’s coming. “Right now, the reporter gene is always on,” Gambhir said. “But we could change the reporter gene so it only comes on after it latches onto the tumor cell and kills it.” The approach, he said, works in mice, but isn’t yet ready for human trials.
The full article from which this summary is adapted can be found here.