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. Today they are reporting that they were able to convert adult mouse or human skin cells into embryonic-like stem cells without inserting the tumor-causing gene, called c-Myc. As they report this afternoon in the online edition of Nature Biotechnology, eliminating the need for c-Myc is a critical step if these “reprogrammed” cells are ever to be safe to use in patients. No kidding.

This time the Kyoto group has generated embryonic-like cells from adult human skin cells with only three genes, not including c-Myc. To see whether the absence of c-Myc makes the reprogrammed cells less likely to form tumors, the scientists compared mice containing many specialized cells derived from the embryonic-like stem cells with and without c-Myc. None of the 26 mice with cells lacking c-Myc died of tumors; six of the 37 with cells containing c-Myc did. The only drawback is that without c-Myc retrovirus, fewer of the initial adult skin cells could be reprogrammed to become embryonic-like stem cells: in about half the experiments, they could not accomplish the transformation.

The Kyoto group submitted its paper to Nature Biotechnology on Nov. 6, which means they knew their results a full two weeks before a flood of stories went out saying the presence of cancer genes in the reprogrammed cells raised questions about their safety. Apparently, secrecy and getting as big a bang as possible from your scientific paper—not letting the cat out of the bag before the paper is officially published—counts for more these days than honest public discourse.