Advance Seen in Turning Adult Cells Into Stem Cells
Israeli researchers find molecule that blocks the rapid transformation
It's done by activating just a few key genes that override the identity of an adult cell and send it back to an embryonic-like state. But the process has been hampered by inefficiency, and, Hochedlinger said, "we didn't know why that was."
The new findings point the finger at a molecule called Mbd3. Hanna's team found that blocking its action allowed human skin cells to be transformed into iPS cells almost 100 percent of the time.
Right now, Hochedlinger noted, the most efficient way to convert adult cells into pluripotent stem cells is through a viral vector -- through which a virus is used to transport the necessary "reprogramming factors" into the cell.
The limitation is, the virus genetically alters the cell. And in animal research, that has been shown to sometimes cause cancer, according to the U.S. National Institutes of Health.
But this new process, Hochedlinger said, could make it easier for researchers to efficiently generate human iPS cells using virus-free techniques (which already exist).
Hanna stressed that point. "This is a major advance toward making safer iPS cells, without genetic modifications, at high efficiency," he said.
But another stem cell researcher said it remains to be seen whether iPS cells created this way really do have a low rate of "reprogramming errors" -- including activation of genes that could promote cancer.
It's not only viral vectors that introduce those errors into cells. The reprogramming process itself can do it, said Juan Dominguez-Bendala, of the Diabetes Research Institute at the University of Miami Miller School of Medicine.
"When a cell that has a specific function is forced to wipe out its memory and act as a stem cell, it has to activate genes that normally remain silent in adult cells," Dominguez-Bendala explained. Some of those genes, he said, are involved in controlling cell replication -- and cancer is essentially out-of-control cell growth.
"Since there is a very thin line between a stem cell and a cancer cell," Dominguez-Bendala added, "you want the (reprogramming) process to be as clean as possible."
The new method may indeed be "cleaner," he said, but that's just "conjecture" for now.