Scientists turn probiotic bacteria into tiny drug factories for pancreatic cancer

 Cancer immunotherapy has dramatically changed how doctors treat many forms of cancer, yet pancreatic cancer has remained particularly resistant to these advances. A major obstacle is the environment that develops around pancreatic tumors. These tumors often create a "cold" tumor microenvironment that blocks immune cells from launching an effective attack.

Researchers at the University of Chicago have now developed a new approach that could help overcome this problem. In a study published in Science Advances, the team used BifidoSumIL-2, an engineered strain of Bifidobacterium longum, a probiotic bacterium naturally found in the gut, to carry an immune-stimulating treatment directly into tumors.

In animal models, the therapy slowed the growth of pancreatic tumors by selectively activating T cells that fight cancer. Its effects became even stronger when researchers combined it with chemotherapy, radiotherapy or immunotherapy. The findings suggest that BifidoSumIL-2 could eventually provide a new way to improve how pancreatic tumors respond to treatment.

Using Bacteria to Deliver Cancer Therapy

"A big unmet medical need has been pancreatic cancer, and so that was going to be our mountain to climb," said Ralph Weichselbaum, MD, the Daniel K. Ludwig Distinguished Service Professor and Chair of Radiation and Cellular Oncology at the University of Chicago.

BifidoSumIL-2 was created to release a modified version of interleukin-2 (IL-2) once it reaches a tumor. IL-2 is a potent immune signaling molecule that activates T cells involved in attacking cancer. Conventional IL-2 treatment, however, can produce serious side effects and can also stimulate immune cells that actually weaken the antitumor response.

The researchers sought to avoid these problems by using SumIL-2, a modified form of IL-2 engineered to more precisely activate cancer-fighting T cells while reducing stimulation of regulatory T cells. They then placed SumIL-2 inside Bifidobacterium longum so that the therapeutic molecule could be concentrated within tumors instead of throughout the body.

Developing the treatment required scientists from several disciplines to work together, including specialists in microbiology, synthetic biology, oncology, and immunology.

"This was a highly interdisciplinary effort," said Mark Mimee, PhD, Assistant Professor of Microbiology at the University of Chicago. "We had to bring together people who understand bacteria, people who understand tumors, and people who understand the immune system to make something like this possible."

Why Bifidobacterium Can Target Tumors

Bifidobacterium offered the researchers an unusual advantage as a delivery system. The bacterium grows in anaerobic environments, meaning places with very little oxygen. Low oxygen levels are common inside many solid tumors, including pancreatic tumors, while healthy tissues generally contain more oxygen and are therefore less suitable for the bacteria.

Source: ScienceDaily