Doctors at the National Institutes of Health are proposing a cancer research experiment that would for the first time involve putting genetically altered cells into humans, according to a published report.

The Washington Post reported Wednesday that the proposal would call for doctors to remove human cells from the body, genetically alter them by inserting a "marker" gene into a type of cancer-fighting cell and return the altered cells to the body.

The newspaper said the procedure is designed to track cancer-fighting cells and not as a treatment for cancer. Scientists hope the experiment could open the door for gene therapy as a possible route to finding cures for such illnesses as cystic fibrosis, muscular dystrophy and sickle cell anemia.