Cancer and stem cells: what's the connection?

Economist article leaves something to be desired

This week's Economist (Sept 13-18) put on a show about cancer research and stem cells. The front-page byline is: "The connection that could lead to a cure." Great for pulling in readers, but did the article live up to the cover? Yes, because it's explanation of the science made sense, it was duly cautious about "cures", and it had a bit of history.* From the article, however, it is not easy to know what the fuss is about.

Stem cells and cancer research are certainly converging. Scientists are getting keen and holding meetings on the topic, and drug companies have tentatively mined the field. Researchers have got some promising results, though no decisive ones. One class of study involves separating out two different kinds of tumor cells and measuring their effects on animals -- mice seem to be the in thing here. One kind of cell is no more harmful than a needle prick. The other kind leaves the rodents with a fat brown cancer. Experiments like this were done in 1997 on leukemia, in 2003 for breast cancer, and since then for a long hit-list of different cancers. The bad news is that some cancer victims have died within 14 months even when their tumors housed no stem cells (at least as far as scientists could see, which is not very far in these cases).

But 1997 is a long time (and lots of mice) ago. According to the article, scientists have taken two main strides since then. One is a the use of targeted drugs to weaken stem cells against radiation treatment. The other is the discovery that the non-stem-cells in tumors can morph into stem-cells. As the Economist author points out, this is a blow to the view that stem cells are at the root of the problem.

All this is exciting and equivocal, and the author conveys both aspects. But I don't see what stem cell research has to do with it. I want to know: of all the detailed research that has been done about stem cells, which bits of it help us to understand the behavior of stem cells in tumors, and ultimately to get rid of them? What have scientists learnt from growing livers that can be used to dissolve cancers?

Granted, it's useful to know that cancer cells are of two kinds, and that they breed in the way that stem cells do. But does it tell us something about their chemical structure that we didn't know already, or about their susceptibility to particular drugs, or their life cycles or self-dispersing behavior? I couldn't find much of that kind described in the article.

It's true that one strong lead, noted in the article, is to use a drug developed by the biologist Craig Jordan (Rochester, NY State), and which is known to kill normal stem cells. But the article reads as if this drug was developed to target cancer cells, not stem cells -- it's not clear how the knowledge that the cancer cells are stem cells contributed to the discovery. (I would also quite like to know *when* Craig Jordan made this discovery, which you won't find out from reading the piece).

Recall the byline on the Economist cover. I see the cancer research and stem cell research in the article, but I don't see the connection.


* But one thing puzzled me about the history. The story goes that before the stem-cell theory of cancer there was the mutation theory -- that's where normally sterile cells mutate and start making babies, but they don't have much practice and they make really bad babies. According to this theory, in a healthy body only the sex cells reproduce. But how did people explain the healing of wounds, the growth of hair, and all of the other cell-consuming human events, before the stem-cell theory arrived? Was it just that there was a big lag between the idea of stem cells and their application to cancer?