Induced pluripotent stem cells, or iPS cells, are a keystone of regenerative medicine. Outside the body, they can be coaxed to become many different types of cells and tissues that can help repair damage due to trauma or disease. Now, a study in mice from the Stanford University School of Medicine suggests another use for iPS cells: training the immune system to attack or even prevent tumors.

The results suggest it may one day be possible to vaccinate an individual with his or her own iPS cells to protect against the development of many types of cancer.

The iPS cells work as an anti-cancer vaccine because, like many cancer cells, they resemble developmentally immature progenitor cells, which are free from the growth restrictions built into mature cells that make up the body’s tissues. Injecting iPS cells that genetically match the recipient, but that are unable to replicate, can safely expose the immune system to a variety of cancer-specific targets, the researchers found.

“We’ve learned that iPS cells are very similar on their surface to tumor cells,” said Joseph Wu, MD, PhD, director of Stanford’s Cardiovascular Institute and professor of cardiovascular medicine and of radiology. “When we immunized an animal with genetically matching iPS cells, the immune system could be primed to reject the development of tumors in the future. Pending replication in humans, our findings indicate these cells may one day serve as a true patient-specific cancer vaccine.”

Wu is the senior author of the study, which was published online Feb. 15 in Cell Stem Cell. Former postdoctoral scholar Nigel Kooreman, MD, is the lead author.

“These cells, as a component of our proposed vaccine, have strong immunogenic properties that provoke a systemwide, cancer-specific immune response,” said Kooreman, who is now a surgery resident in the Netherlands. “We believe this approach has exciting clinical potential.”

Similarities between cancer, iPS cells

To make iPS cells, researchers collect cell samples from an easily accessible source like skin or blood. The cells are then treated with a panel of genes that make them rewind their developmental clock to become pluripotent, allowing them to become nearly any tissue in the body. One key test of pluripotency is the ability of the cells to form a tumor called a teratoma, which is composed of many different cell types, after the cells are injected into animals. (IPS cells used in regenerative-medicine therapies are grown in the presence of other proteins to encourage them to specialize, or differentiate, into specific cell populations before being used clinically.)