Page 41 - Mouse Molecular Genetics

Full Abstracts
Program number is above title. Author in bold is the presenter.
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Medical Center, New York, NY; 3) Departments of Urology and Pathology and Cell Biology, Columbia University Medical
Center, New York, NY; 4) Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY.
A key issue in cancer biology is whether oncogenic transformation of different cell types of origin within an adult tissue gives
rise to distinct tumor subtypes that differ in their prognosis and/or treatment response. In the case of prostate cancer, the identity
of the normal cell type(s) of origin is currently under investigation. Several studies have shown that the prostate basal epithelial
compartment contains stem cells that can be transformed to initiate tumors in tissue reconstitution assays. However, previous
lineage-tracing studies from our laboratory have identified a luminal stem cell population in mouse that can serve as a cell of
origin for prostate cancer in vivo. Here, we have undertaken a comprehensive ex vivo and in vivo analysis using genetic lineage-
marking to examine the properties of the identical basal cell population in multiple assays for stem cell function, and to compare
prostate tumors originating from basal cells and luminal cells at the phenotypic and molecular levels. Specifically, we have
utilized CK5-CreERT2 transgenic mice for inducible lineage-marking of basal cells, followed by analysis of their properties in
prostate sphere and tissue reconstitution assays, as well as in androgen-mediated prostate regeneration and tissue homeostasis.
Our results reveal that normal basal cells display considerable plasticity in different stem cell assays. While a relatively large
subpopulation of basal cells (around 4%) display stem cell properties in sphere formation and tissue reconstitution assays, the
percentage of basal stem cells identified by their ability to generate luminal cells in vivo is much lower (0.05%). Furthermore,
using cell-type-specific deletion of Pten using CK5-CreERT2 or Nkx3.1-CreERT2, we find that both basal and luminal cells can
serve as cells of origin for prostate cancer, giving rise to tumors with similar histological phenotypes that resemble human
prostate adenocarcinoma. However, our cross-species molecular and bioinformatic analysis of basal versus luminal origin tumors
shows that the luminal origin tumors are more aggressive, and identifies a 68-gene molecular signature that has predictive value
for human patient survival. These results reveal the inherent plasticity of basal cells, and support the cell of origin model as a
basis for distinct prostate cancer subtypes.
21
Wnt/beta-catenin, BMP and HGF in cancer stem cells. Walter Birchmeier
1
,
Peter Wend
1,2
,
Ulrike Ziebold
1
,
Jane Holland
1
.
1)
Max-Delbrueck-Center for Molecular Medicine (MDC), 13125 Berlin, Germany; 2) David Geffen School of Medicine,
University of California at Los Angeles, CA 90095, USA.
We show that the combination of activated Wnt/-catenin and blocked Bmp signaling in salivary glands created cancer stem
cells and rapidly growing tumors. Cancer stem cells were promoted into a selfrenewing state, and the activities of -catenin, CBP
and trithorax-related MLL1 were critical to maintain proliferation and heightened H3K4 trimethylation. Blocking -catenin-CBP
with the small molecule inhibitor ICG-001 and by -catenin, CBP or MLL1 siRNA abrogated selfrenewal and forced cancer stem
cells to differentiate into organotypic structures. ICG-001 treatment decreased H3K4me3 at promoters of stem cell signature
genes and resulted in tumor remission following transplantation. Blocking Bmp signaling reduced apoptosis. We also show that
compound gain-of-function mutations of -catenin and HGF using the WAP promotor resulted in the expansion of mammary
gland cancer stem cells that rapidly formed basal-like tumors. In cultured cancer stem cells, Wnt signaling stimulated self-
renewal, while Met signaling suppressed differentiation. We identified a set of genes whose expression is regulated by Wnt and
Met in cancer stem cells, among these CXCL12, the ligand for the chemokine receptor CXCR4. Ablation and inhibition of
CXCR4, which acts in the Met pathway, resulted in a signifcant delay in tumor onset and induced differentiation. Furthermore,
the expression of the Wnt/Met signature could predict for poor survival in patients with Basal subtypes of breast cancer. Our
findings encourage the use of signaling inhibitors for therapy that targets cancer stem cells.
22
Discovery of a novel, developmentally restricted hematopoietic stem cell.
Anna Beaudin, Scott Boyer,
Camilla Forsberg
.
Institute for the Biology of Stem Cells, Department of Biomolecular Engineering, University of California Santa Cruz, Santa
Cruz, CA.
We want to understand the cellular and molecular mechanisms of hematopoietic stem cell (HSC) specification and
differentiation. We recently established a lineage tracing mouse model where differentiation stage-specific expression of Cre
recombinase results in the irreversible switching of a ubiquitous dual-color reporter from Tomato to GFP expression. Using this
model, we have demonstrated that, in adult mice, all lineages differentiate through a Flk2-positive stage; that Flk2+ progenitors
contribute equally to granulocyte/monocyte and megakaryocyte/erythroid lineages in vivo; and that Flk2+ cells do not
dedifferentiate into HSC. In addition, the fact that all functional, adult HSC remain Tomato+ conclusively demonstrates that all
developmental precursors of adult HSC lack Flk2 expression. Surprisingly, we found that GFP+ HSC coexist with Tomato+ HSC
during fetal development. These GFP+ HSC support long-term, multilineage hematopoiesis when transplanted into adult
recipients. Like Tomato+ adult and fetal HSC, the GFP+ HSC retain long-term reconstitution potential in serial transplantation
assays, but display differential lineage bias and give rise to distinct subsets of mature immune cells. Thus, we have identified a
novel, fetal population of HSC that are capable of reconstituting adult recipients, but do not persist in adulthood or give rise to
adult HSC. This finding has important implications for developmental hematopoietic disorders, pediatric leukemias, and
derivation of engraftable HSC from pluripotent precursors.
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A defensive role of Sirt3 against oxidative stress and aging in preimplantation embryos. Yumiko Kawamura
1,2,3
,
Yasunobu
Uchijima
1
,
Koichi Nishiyama
1
,
Yukiko Kurihara
1
,
Kiyoshi Kita
2
,
Hiroki Kurihara
1
. 1)
Dept. of Phys. Chem. and Meta., Grad.