Survival of Mammary Stem Cells in Suspension Culture: Implications for Stem Cell Biology and Neoplasia

There is increasing evidence that a variety of neoplasms including breast cancer may result from transformation of normal stem and progenitor cells. In the past, isolation and characterization of mammary stem cells has been limited by the lack of suitable culture systems able to maintain these cells in an undifferentiated state in vitro . We have recently described a culture system in which human mammary stem and progenitor cells are able to survive in suspension and produce spherical colonies composed of both stem and progenitor cells. Recent observation that adult stem cells from other tissues may also retain the capacity for growth under anchorage independent conditions suggests a common underlying mechanism. We propose that this mechanism involves the interaction between the canonical Wnt signal pathway and E-cadherin. The Wnt pathway has been implicated in normal stem cell self-renewal in vivo . Furthermore, there is evidence that deregulation of this pathway in the mammary gland and other organs may play a key role in carcinogenesis. Thus, the development of in vitro suspension culture systems not only provides an important new tool for the study of mammary cell biology, but also may have important implications for understanding key molecular pathways in both normal and neoplastic stem cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44964/1/10911_2005_Article_2542.pd

New faces in plant innate immunity: heterotrimeric G proteins

Co-existence of species seems to inevitably result in origin of parasitism and hence development of molecular mechanisms of attack and defense. Certain similarities between plant and animal defense systems point to an ancient inheritance of the innate immunity. Heterotrimeric G proteins are structurally conserved signaling molecules connecting plasma membrane bound receptors to cytoplasmic effectors. They were found in most eukaryotic organisms. Their role in human pathophysiology and animal diseases was well established. In plants these proteins were also recently implicated in innate immunity. However, molecular mechanisms governed by G proteins and providing resistance against plant pathogens seem to be different from those in animal systems and largely remain elusive. In this review we attempted to sketch current ideas of plant defense system and to present a contemporary status of heterotrimeric G proteins in plant innate immunity