Wnt Signaling in Stem Cells and Cancer

Abstract

__Abstract__
\n
\nMammalian development starts from a fertilized egg that initially generates few
\npluripotent cells which eventually give rise to the embryo proper. Different ‘flavors’ of
\npluripotency have been captured in vitro which led to the establishment of different
\npluripotent cell lines. Mouse embryonic stem cells (mESCs) are derived from the preimplantation
\nembryo and have three defining properties: self-renewal, pluripotency, and
\ncontribution to chimera formation. By applying specific culture conditions or ectopic
\nexpression of the pluripotency factors, similar pluripotent cells can be derived from germ
\ncells or differentiated cells referred to as embryonic germ (EG) and induced pluripotent
\ncells (iPSCs), respectively. When established from post-implantation embryo, the cultured
\ncells are termed epi stem cells (EpiSCs). EpiSCs have limited potential for chimerism
\nand germ line transmission and require different culture conditions when compared to
\nESCs. Hence, mouse ESCs and EpiSCs represent two different phases of pluripotency
\nusually referred to as the naïve and primed states. By employing genetic manipulation
\nor specific culture conditions, the different pluripotent cells can be interconverted which
\nleads to several intermediate states. Unlike their murine counterparts, human ESCs
\nclosely resemble the rodent primed EpiSCs and respond to similar signaling pathways.
\nTumorigenic transformation of primordial germ cells (PGC) and gonocytes can also give
\nrise to pluripotent cells known as embryonal carcinoma cells (hECs), thought to represent
\nthe malignant counterpart of hESCs. Among different signaling pathways, Wnt signaling
\nplays a central role in self-renewal and differentiation of pluripotent cells.