The embryonic stem cell lines faithfully reproduced the nuclear DNA of the person who contributed the skin cell. The expectation is that when cells or tissues made from these stem cells are transplanted into that person, they will slip past his or her immune system unnoticed. The stem cells showed "no gross chromosomal abnormalities," the authors wrote, and appeared every bit as capable of differentiating into a variety of cell types as embryonic stem cells made the old-fashioned way, from excess embryos obtained from fertility clinics. "This is extremely important," Dr. Irving Weissman, a stem cell researcher at Stanford University, said of the new results. Stem cell researcher Dr. Robert Lanza echoed that praise, calling the OHSU team's work "a major scientific achievement." Lanza, the chief scientific officer of Advanced Cell Technology Inc., said it remained to be seen whether embryonic stem cells generated this way were more useful for studying and treating diseases than stem cells created by reprogramming adult cells to an embryonic state. The method for creating such induced pluripotent stem cells, or iPS cells, was recognized with a Nobel Prize last year. But there are lingering questions about whether iPS cells are safe for patients. Scientists use a cancer-causing virus to reprogram the cells, raising concerns that they could cause tumors in patients. And in 2011, when scientists at UC San Diego created iPS cells and reintroduced them into donor mice, the animals' immune systems rejected them. "Some experts are now saying that somatic cell nuclear transfer may be the only way to truly reprogram cells," Lanza said. melissa. [email protected] Copyright © 2013, Los Angeles Times HOUSE_OVERSIGHT_027027