Does anyone else feel a trifle deceived, or a bit manipulated? The enthusiasm over last week’s announcement that two groups of scientists had coaxed plain old adult skin cells into embryonic-like stem cells—no embryo required—was tempered by one little fact: among the four genes the team from Kyoto University used to reprogram adult cells back to embryonic status was one that causes cancer.

That suggests that using the reprogrammed or “induced” stem cells, or their descendants, to treat diseases might cure Parkinson’s, for instance, but at the cost of giving patients cancer. That led me and many others to raise concerns about the real potential of the new kind of stem cell.

Turns out we needn’t have worried so much, and the Kyoto researchers knew it all along.