Memory cells enhance strategy for fighting blood cancers

WASHINGTON — Stem cells with memory may improve a powerful new type of cancer therapy.

Recently, scientists have engineered cells from a patient’s own immune system to fight blood cancers. The treatment with the engineered immune cells, called CAR-T cell therapy, may work even better if doctors transplant a subset of immune cells known as memory T cells, researchers reported February 14 at the American Association for the Advancement of Science’s annual meeting.

A single engineered memory T cell was enough to replenish the infection-fighting ability of mice lacking T cells, said Dirk Busch, an immunologist at the Technical University of Munich. That finding indicates that very low numbers of the cells in the body could be enough to protect human patients from maladies ranging from infections to cancer.

In preliminary clinical trials, CAR-T cell therapy using the memory T cells eliminated cancer in 27 of 29 patients with acute lymphoblastic leukemia, or ALL, for whom other treatments had failed. Stanley Riddell, an immunotherapy researcher at the Fred Hutchinson Cancer Research Center in Seattle, reported the finding. Memory CAR-T cell therapy also melted away tumors in six of seven patients in whom cancer had spread from the bone marrow to other parts of the body. And 10 of 11 patients who had previously undergone CAR-T cell therapy with a mixed bag of engineered T-cells were in remission after being treated with just the engineered memory cells, Riddell reported.

Only a few hundred to a few thousand of the memory cells were needed to melt a patient’s tumor, Riddell said. The low doses also lessened side effects of the therapy, he said.

CAR-T cells are genetically engineered versions of immune cells called T cells. T cells prowl the body and identify invaders, such as bacteria, viruses, parasites and other foreign cells. For decades, researchers have been trying to boost cancer patients’ immune systems in order to kill cancer cells. Recently, researchers have created CAR-T or “chimeric antigen receptor” T cells that make proteins that allow the cells to track down and kill particular types of cells. Researchers removed T cells from ALL patients and genetically engineered the cells to hunt and destroy cells that make a protein called CD19. Such cells include antibody-producing B cells, which overgrow in patients with ALL and some other types of lymphoma or leukemia.

Gene edited CAR-T cells were recently used to treat a baby with leukemia (SN: 12/12/15, p. 7).

Engineered memory T cells can persist in patients for at least 14 years, Chiara Bonini of the San Raffaele Scientific Institute in Milan, Italy, reported. Such cells may “act as a living drug that can persist and respond in a patient in case the tumor comes back,” she said.