Cancer Stem Cells

Nearly 150 years ago it was suggested that cancer might arise from embryonic stem cells. This was mainly due to some common behavioral characteristics between developing tissue in an embryo and the way that cancer develops. Recent research has renewed an interest in that abandoned theory. While not all researchers agree, there's a growing body of evidence that not all cancer cells can give rise to new tumors. Furthermore that it's only a small percentage of tumor cells that can do so, only 1 in a 100 according to Michael Clarke, MD of U of Michigan, in his recent PNAS article.

This opens up the possibility of specifically targeting these few but dangerous stem cells that give rise to new tumors. To do that you need to separate cell populations from the tumor and characterize them. This is done with specific antibodies and flow cytometry to separate the phenotypically heterogenous cancer cells in a tumor into different populations using their cell surface protein markers. This takes a good deal of time but it's not very complicated--unfortunately the same can't be said of how the cancer cells operate. Some of the surface markers, CD34 & CD38 for example, will go up in some types of cancer but down in others. Or vice versa. Another group has published that an increase in CD-44 and lowered or absent CD-24 characterizes these stem cells. When you get to the actual cellular pathways that the proteins activate, the Notch Signal Transduction Pathway for example, the pathway will increase some cancers yet paradoxically decrease others. It makes it very difficult for researchers and physicians to treat patients.

Anyway, that's a little bit of info about cancer stem cells...

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