Figure 6.

Effect of stem cell self-renewal and restrictive divisions on the efficiency of mammosphere formation. (a) Asymmetric stem cell self-renewal divisions result in constant mammosphere numbers in serial passages. (b) Proliferation of stem cells or progenitor cells through restrictive divisions results in a decreasing number of spheres in serial passages. (c) Symmetric self-renewal divisions of stem cells result in an increasing number of mammospheres in serial passages.