A cutting-edge cancer treatment can also cure certain kinds of heart failure in mice, scientists reported. 

The treatment is a type of immunotherapy known as CAR-T, which has proved life-changing for some patients with blood cancers. CAR-T relies on engineered white blood cells — T cells — that seek out and destroy malignant cells in the body.

In the study published in the journal Nature, the technology was used to target scar tissue that stiffens the heart and prevents it from fully relaxing between beats in heart failure patients.

“It is potentially a breakthrough paper,” said Richard Lee, professor of stem cell and regenerative biology at Harvard not involved in the study.

But some medical experts asked whether it would be feasible to use the therapy to treat heart patients, at least in the near future. For cancer, CAR-T therapy costs about $450,000 per patient. When hospital stays are included, the price can soar to $1 million or more.

With 6 million U.S. patients with heart failure, the overall costs would be astronomical.

Some patients getting CAR-T therapy experience severe, even fatal, side effects.

In heart failure, the walls of the ventricles, the two large pumping chambers, stiffen and may become enlarged, preventing the heart from pumping blood efficiently. It may result from a number of conditions, including heart attack and high blood pressure.

While many patients respond to drug therapy, those with a type called heart failure with preserved ejection fraction have few options. Half die within five years, a mortality rate comparable to that of some metastatic cancers.

The idea for the study originated with a postdoctoral student in the lab of Jonathan Epstein, professor of cardiovascular research at the University of Pennsylvania Perelman School of Medicine. The student, Haig Aghajanian, wondered: Why can’t we make a CAR-T therapy to kill scar tissue in the heart?

T cells of the immune system are constantly looking for rogue cells to attach themselves to and kill. T cells sometimes do not recognize cancer cells, but researchers can attach a protein to T cells. When these engineered T cells drift near a cancer cell, they latch onto it and kill it.

As long as most healthy cells do not have the docking site for that T cell protein, the treatment can work.

These are cells that help form all tissues, and they play a large role in wound healing. An ideal treatment shouldn’t eliminate fibrosis everywhere, only scars that hinder normal functioning.

The next step was to look for a naturally occurring protein that is present on human fibrosis cells but not on other cells. The group found one, fibroblast activation protein, or FAP, by looking through a large genetic database.“I am hopeful we can move quickly to humans,” Epstein said.

As for the cost, he thinks it will come down. “First-generation cures are often expensive,” Epstein said. But “success and demand drive innovation.”