These cells were also created using mouse cells, starting with mouse skin cells, and the comparison between what you get from a mouse cell that's transformed this way and an embryonic stem cell, they look to be very similar.

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McCoy mouse cell lines express a polytropic MLV (9) and the RAW cell line was initially transformed by Abelson MLV.

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Dr Lorenz Studer, head of the Stem Cell and Tumor Biology Laboratory at the centre, and the lead researcher on the study, told BBC News Online that the study was "proof of principle" that cloned embryonic stem cells could be reliably transformed into a variety of useful cell types.

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