Nobel Prize-winning scientist Shinya Yamanaka, facing reporters in Kyoto, decried "three misconceptions" about the induced pluripotent stem, or iPS, cells that he developed in relation to STAP cells were recently unveiled.
The Kyoto University professor said Monday that one of the misconceptions is that iPS cells have a higher risk of developing cancer than STAP cells.
While iPS has for years been a viable alternative to embryonic stem cells, which carry certain ethical challenges, a team of researchers led by Haruko Obokata, a biologist at the Riken Center for Developmental Biology in Kobe, developed STAP, or stimulus-triggered acquisition of pluripotency, cells in mice.
"What hurt us were a lot of reports that concluded STAP cells are safer than iPS cells," Yamanaka said. "The iPS cells announced in 2006 using mice and the iPS cells created now use totally different techniques. I find it quite regrettable that the reports made comparisons with the old technique."
Yamanaka, who works at the Kyoto University Center for iPS Cell Research and Application, added that the safety of human iPS cells is being confirmed in clinical research.
The other two misconceptions he pointed out were the descriptions that the "production efficiency" for iPS cells is believed to be 0.1 percent, against 30 percent for STAP cells, and that iPS cells are considered more difficult to engineer than STAP cells.
IPS cells are made by reprogramming adult cells through the introduction of four genes into them and have been made from human and pig cells.
But reports say there is concern that iPS cells are more susceptible to cancer when they are implanted in the body because they are made through genetic changes, while STAP cells, which undergo no genetic changes in their making, are believed to pose no such concern.