Blocking cancer cells’ metabolism may make treatments more effective, less toxic.
Scientists at Washington University School of Medicine in St. Louis have exploited a common weak point in cancer cell metabolism, forcing tumor cells to reveal the backup fuel supply routes they rely on when this weak point is compromised. Mapping these secondary routes, the researchers also identified drugs that block them. They now are planning a small clinical trial in cancer patients to evaluate this treatment strategy.

The research was published Jan. 24 in the journal Cell Reports.

Studying human cancer cells and mice implanted with patients’ tumor samples, the researchers demonstrate that a double hit – knocking out the weak point and one of the tumor cells’ backup routes – shows promise against many hard–to–treat cancers. Though present in multiple cancer types, the weak point is particularly common in sarcomas — rare cancers of fat, muscle, bone, cartilage and connective tissues. Doctors treat sarcomas primarily with traditional surgery, radiation and chemotherapy, but such treatments often are not effective.

“We have determined that this metabolic defect is present in 90 percent of sarcomas,” said senior author Brian A. Van Tine, MD, PhD, an associate professor of medicine. “Healthy cells don’t have this weakness. We have been trying to create a therapy that takes advantage of the metabolic defect because, in theory, it should target only the tumor. Basically, the defect allows us to force the tumor cells to starve.”

The researchers’ strategy relies on the fact that the vast majority of sarcomas have lost the ability to manufacture their own arginine, a protein building block that cells need to make more of themselves. Lacking this ability, the cells must harvest arginine from the surrounding environment. The supply of arginine in the blood is abundant, and cancer cells have no trouble scavenging it. But remove this environmental supply of arginine and the cells have a problem.

“When we use a drug to deplete arginine in the blood, the cancer cells panic because they’ve lost their fuel supply,” Van Tine said. “So they rewire themselves to try to survive. In this study, we used that rewiring to identify drugs that block the secondary routes.”

Unlike most cancer therapies, depleting arginine in the blood does not affect healthy cells.

Based on this study and related research, Van Tine and his colleagues at Siteman Cancer Center at Barnes–Jewish Hospital and Washington University School of Medicine are planning a clinical trial of the arginine–depleting drug in patients with sarcomas.