stem cell isolation - stem cell markers and stem cell sphere (Nov/19/2004 )

hi,everyone, i am a new one in stem cell research. i read a few papers about neural stem cells mammary stem cell, and heart stem cells. all of the authors cultured their candidate stem cells into spheres, such as neurospheres, mammaryspheres in serum-free media. if there's no useful markers, how to isolate stem-like or stem cell from a tissue? your advice will be greatly appreciated.

In most cases (especially adult stem cells) and not like HSC, there is no appropriate stem cell marker available, people use "clonogenic property" of stem cells to isolate them from single cell growing in 3D semiliquid environment. That's the "sphere form" comes from, very much like EB formation of ES cell field.

thanks your advice. if i cultured my tumor cells in serum-free media and they formed spheres and the spheres could be passaged for a long time, does it imply that there may be some stem or stem-like cells?

Most tumor cells when reach confluency will pile up called foci formation. It is one of the hallmark of transformed cells.
You raise an interesting idea that also has been proposed by many cancer biologists - they propose that the origin of cancer is from stem cells (called cancer stem cells) undergo indefinite self-renewal but lacking final differentiation (through certain mutatuion). There are many observations that support this idea. One of those is that many proto-oncogene, tumor suppressor, cell cycle regulators are all found actively expressed in stem cells and that "differentiation therapy" being a promising strategy.

However, one way to verify the tumor cells you isolated are really stem cell originated: differentiate them to see if they can be induced to do so (tumor regression as functional readout).
Remember that two typic characteristics of stem cells: self-renewal and differentiation potential.