Gene expression in stem cells.

Both embryonic and adult stem cells promise a precious cell source for the treatment of various degenerative diseases due to their capacity for self-renewal and ability to differentiate along multiple cell lineages. A lack of understanding surrounding the basic biology of stem cells, the stemness, continues to challenge successful clinical application of these cells. Gene expression analysis, both genome-wide and targeted at specific gene subsets, has played a key role in improving our understanding of the genetic attributes of stem cells through identification of molecular signatures that characterize normal stem cell function. Such approaches have facilitated the investigation of stemness in a subset of tumor cells, so-called cancer stem cells, and have started to unravel their roles in initiation and progression of tumors. This review summarizes recent advances of gene expression analysis in stem cell research and also discusses critical issues that remain to be elucidated in the search for cancer stem cells markers.