Embryonic stem cells are under study for their therapeutic possibilities, because they potentially transform into nearly any type of human body tissue. A new study from City of Hope researchers shows these cells might actually go awry in certain settings, however, prompting scientists to urge careful and wise use of the cells.
In a recent paper in the journal Stem Cells and Development, Chu-Chih Shih, Ph.D., assistant professor in the Division of Hematology & Hematopoietic Cell Transplantation, found that unlike adult stem cells, embryonic stem cells (dubbed ES cells for short) in some settings can generate malignant tumors.
“This study shows that we need to be cautious,” said Shih. “It doesn’t mean that stem cells can’t be used for therapies, but it means we need to be able to guide ES cells to make the kind of cells necessary for transplant.”
Collaborating with Stephen Forman, M.D., the Francis and Kathleen McNamara Distinguished Chair in Hematology and Hematopoietic Cell Transplantation and clinical director of the Division of Cancer Immunotherapeutics & Tumor Immunology, and Marilyn Slovak, Ph.D., professor of pathology and director of the Section of Cytogenetics, Shih used government-approved human ES cell lines combined with a unique method of grafting human tissues onto a mouse.
That enables scientists to test stem cell therapies on human tissues without putting humans at risk.
In the current study, Shih and colleagues found that when they injected high numbers of ES cells into the tissues, something ominous happened: Rather than merging with the grafted human pancreatic or lung tissues many ES cells formed carcinomas resembling malignant tumors.
While the study does not rule out using embryonic rather than adult stem cells for potential replacement therapies, Shih notes that scientists must develop ways to separate healthy maturing ES cells from potentially tumor-forming cells before any transplant or cell replacement procedure.
Adult stem cells are used to reconstitute a new immune system after bone marrow transplant, Shih explained. The risk of tumors forming from adult stem cells is much lower than with ES cells.
“Adult stem cells have been safely used for bone marrow transplants for the last 30 years,” said Shih.
Peiguo Chu, M.D., also contributed to the study. Grants from the National Institutes of Health, the Ella Fitzgerald Charitable Foundation, the California Community Foundation and the Rosalinde and Arthur Gilbert Foundation funded the research.