Although mammosphere formation has served as an in vitro stem cell criteria, not every breast cancer cell line posses such ability [32], [33].
In the literature they are commonly termed "mesenchymal stem cells" but also here reliable markers for the sub-fraction that meets the specific stem cell criteria are yet elusive and therefore they should rather be named "mesenchymal stromal cells" [4].
Club cells are also able to self-renew and give rise to ciliated cells and therefore meet the stem cell criteria as well.
However, Beier's studies revealed that four of 15 cell lines derived from primary glioblastomas grew adherently in vitro and were driven by CD133- tumor cells that fulfilled stem cell criteria.
However, the elucidation of the molecular complexity of PL products and the identification of both the essential growth factors that determine the fate of a specific stem cell and the criteria to establish dosing require further investigation.
As reported above, enrichment of a clonally proliferative and multipotent stem cell based on the criteria of size and pigmentation suggests that transdifferentiation is an unlikely mechanism to describe these results.
Hans Clevers A minimal definition of an adult stem cell involves only two criteria: 1) an adult stem cell persists for the lifetime of the animal ('longevity'); and 2) an adult stem cell can make all cell types of the tissue to which it belongs ('multipotency'multipotency
The rate of spheroid formation, a criterion for stem cell properties, was higher in the LY6A+ population compared to the other surface epithelial cells.
These cells fulfill the in vitro and in vivo criteria for stem cell activity including the ability to reconstitute a heterogeneous population, sphere- and colony-forming activity, and the ability to form tumors in immune deficient mice.
These stringent criteria for stem cell definition (Ref. 18) are met by haematopoietic stem cells (HSC), which reconstitute bone marrow when clonally derived HSC are transplanted into lethally irradiated mice (Ref. 19).
The quality of derived ESCs was assessed on the basis of three criteria: expression of stem cell markers, chimeric contribution and germline transmission.
