The Stanford University School of Medicine researchers say they discovered that blocking the molecules' function spurs the normally resting cells to begin proliferating strangely -- making too much of one kind of cell and not enough of another.

The scientists note many types of human blood cancers involve a similar disruption in the expression of the same family of molecules. And, the scientists said, the blood stem cells' "misguided enthusiasm" also inhibits their ability to successfully repopulate the immune system of a recipient animal after a bone marrow transplant -- a common leukemia treatment.

The study's first author, postdoctoral student Patrick Viatour, said the finding is the first to directly link the retinoblastoma family of proteins to the cellular production of blood and immune cells.

"These studies, and additional experiments from our lab in other tissues and organs, indicate Rb proteins play a critical role in suppressing tumors originating in adult stem cells populations," said Assistant Professor Julien Sage.

The research is reported in the journal Cell Stem Cell.