globeandmail.com: Stem cells core of more cancers
Grumble, grumble. I can’t access Sunday’s two Nature advance articles, on the role played by stem cells in tumor growth. (Nature and its ilk are way too expensive for our small local college to carry, which made teaching upper-level biology there . . . interesting). This mainstream media summary is pretty good, though.
No one disputes the similarities between cancer cells and stem cells. The broad question is how this similarity arises. Do differentiated tumor cells, through mutation, acquire stem-cell-like properties, or do endogenous adult stem cells become cancerous? If the latter (and the hypothesis does make a lot of sense), stem cells could be hidden ringleaders promoting tumor growth, which could change the methods used to treat cancer substantially.
Although stem cells are mostly known for their “good” potential to repair and replace cells lost to trauma or chronic disease, researchers have always been concerned about the risk of stem cells growing uncontrollably. In some cases, experimental stem cell transplants have resulted in tumors. However, I don’t think most people realized stem cells gone bad could be the root of familiar cancers like colon cancer. When stem cells are good, they are very, very good; but they may be naughtier than we knew.
Note that seven years ago you could not have said “Although stem cells are mostly known for their “good†potential to repair and replace cells lost to trauma or chronic disease”. This was a major step. The next one which should follow, was to show that the cells that cause tumors to grow are these same stem cells that also repopulate/repair organs. Why does this new revelation assume that the stem cells causing cancer are bad ones? Stems cells are doing what they are supposed to do, should they discriminate in providing new cells for only normal tissue not tumors? The question though is, how does the tumor cell start? The answer should be, it’s a stem cell repairing a damaged cell that has gone bad in the repair stage. It then recruits new stem cells for growth.
By the way, it is mainly not true that stem cells can replace cells lost to chronic disease. It is true if the repair occurs before it is chronic.
lsl
Interesting questions! Because I haven’t been able to read the Nature articles, I can’t speak to exact details. Still, I don’t think this is a “revelation” in how we think about cancer (although it’s probably going to be spun that way in the media). It’s just that until recently, we have not had the molecular markers to clearly identify potential stem cells within a tumor mass. Now we have those tools. The tumor stem cells in these new studies display CD133, a marker found in both normal stem cells and in various cancers (previous studies found CD133 in both neural stem cells and brain tumors). Even if it displays CD133, a normal stem cell is constrained by its niche, dividing at a regulated rate to produce progeny which give rise to normally differentiated cells. This behavior does not produce tumors. So there really is some key difference between a “bad” tumor-producing stem cell, and the normal type of stem cell responsible for maintaining renewal tissues. What are the differences? How do the tumor stem cells arise? Do they require niches, as normal stem cells do? We don’t know.
As for chronic diseases, diabetes and Parkinson disease are both chronic conditions that are hot targets for stem cell therapies. In both cases, the plan is to replace the key cells lost to the disease process, not to repair them. Although the stem cells could certainly be said to “repair” a deficient organ, they would do so by replacement.
can somebody please tell me what do stem cells do? i am doing the essay on it and i don’t know, what they do. plesae tell me, thanks
Jennie, try these links for the basics on stem cells:
http://dels.nas.edu/bls/stemcells/booklet.shtml
http://stemcells.nih.gov/info/faqs.asp