Anti-LY6A Monoclonal antibody, clone E8 [Alexa Fluor® 700]

The existence of prostate stem cells ( PSCs) was first postulated from the observation that normal prostate regeneration can occur after repeated cycles of androgen deprivation and replacement in rodents(1). Given the critical role of PSCs in maintaining prostate tissue integrity and their potential involvement in prostate tumorigenesis(2), it is important to define specific markers for normal PSCs. Several cell- surface markers have been reported to identify candidate PSCs, including stem cell antigen-1 ( Sca-1, also known as Ly6a), CD133 (Prom1) and CD44 ( refs 3-10). However, many non- PSCs in the mouse prostate also express these markers and thus identification of a more defined PSC population remains elusive. Here we identify CD117 ( c- kit, stem cell factor receptor) as a new marker of a rare adult mouse PSC population, and demonstrate that a single stem cell defined by the phenotype Lin(-) Sca-1(+)CD133(+)CD44(+)CD117(+) can generate a prostate after transplantation in vivo. CD117 expression is predominantly localized to the region of the mouse prostate proximal to the urethra and is upregulated after castration- induced prostate involution - two characteristics consistent with that of a PSC marker. CD117(+) PSCs can generate functional, secretion- producing prostates when transplanted in vivo. Moreover, CD117(+) PSCs have long- term self-renewal capacity, as evidenced by serial isolation and transplantation in vivo. Our data establish that single cells in the adult mouse prostate with multipotent, self- renewal capacity are defined by a Lin(-)Sca-1(+) CD133(+) CD44(+) CD117(+) phenotype.

Background: Stem cell antigen-1 (Sca-1 or Ly6A) is a glycosyl phostidylinositol (GPI)-anchored cell surface protein associated with both stem and progenitor activity, as well as tumor initiating-potential. However, at present the functional role for Sca-1 is poorly defined. Methodology/Principal Findings: To investigate the role of Sca-1 in mammary tumorigenesis, we used a mammary cell line derived from a MMTV-Wnt1 mouse mammary tumor that expresses high levels of endogenous Sca-1. Using shRNA knockdown, we demonstrate that Sca-1 expression controls cell proliferation during early tumor progression in mice. Functional limiting dilution transplantations into recipient mice demonstrate that repression of Sca-1 increases the population of tumor propagating cells. In scratch monolayer assays, Sca-1 enhances cell migration. In addition, knockdown of Sca-1 was shown to affect cell adhesion to a number of different extracellular matrix components. Microarray analysis indicates that repression of Sca-1 leads to changes in expression of genes involved in proliferation, cell migration, immune response and cell organization. Conclusions/Significance: Sca-1 exerts marked effects on cellular activity and tumorgenicity both in vitro and in vivo. A better understanding of Sca-1 function may provide insight into the broader role of GPI-anchored cell surface proteins in cancer.