Stem Cells and Cancer
Donald Vander Griend, Ph.D.
Assistant Professor
Department of Surgery,
Section of Urology
Today…
• Pluripotency and Stem Cells
• Tumor Initiating Cells (TICs)
• Cancer Stem Cells (CSCs)
• Stem Cell-Derived Cancers
Stem Cell Potency
• Totipotent: can generate the whole organism
including extra-embryonic tissues. Only the
zygote and early blastomere are totipotent.
• Pluripotent: can generate the whole organism but
not the extra-embryonic tissues. ES cells are
pluripotent.
• Multipotent: can give rise to all cell types within
one particular lineage. HSCs are multipotent.
• Unipotent: only form one cell type.
Spermatogonial stem cells are unipotent.
What defines Pluripotency?
• Pluripotency describes a cell’s ability to
give rise to all of the cells of an embryo
and adult.
• Recently, there has been an ongoing
debate about what molecularly defines
“pluripotency” of ES cells
Measuring Pluripotent Potential
1.
In vitro differentiation: differentiation induced in cell
2.
Teratoma formation: induction of tumors demonstrating the
potential to generate differentiated cell lineages. Limitation:
does not test within normal development, but most useful for
human ES cells.
3.
Chimera formation/Germline contribution: contribution of
cells to normal development and generation of germ cells.
Limitation: may not complement all cell types or over
complement host defects.
4.
Tetraploid complementation: injection of test cells into 4n
blastocyst. Because 4n host cells cannot contribute to
somatic lineages, embyro is exclusively composed of test cells.
culture and cells are assayed for the expression of cell-type
specific markers. Limitation: marker expression is no test for
functionality.
Teratomas: Stem Cell-Derived Tumors
•“Monstrous tumor”
•Tumor tissue of embryonic origin that contains
normal derivatives of all three germ layers.
• Reported to contain hair, teeth, bone and
even more complex organs such as eye, torso,
hands, feet, and other limbs. Also may contain
tissues resembling brain, thyroid, liver, and
lung.
•Can be derived from germ cells or embryonal
cells.
Pluripotent ES cells and Chimeras
Chimeric Mouse
Can Somatic Cells be Reprogrammed?
Takahashi and Yamanaka, Cell 2006
• “Induction of Pluripotent Stem Cells from Mouse
Embryonic and Adult Fibroblast Cultures by Defined
Factors.”
• ES-specific promoter (Fbx15) driving a beta-gal/NeoR
fusion gene (bgeo). Expressed combinations of
cDNAs and screened for ES cell colonies.
Teratomas derived from Induced
Pluripotent Stem Cells (iPSCs)
Chimeras derived from iPSCs
(Derived from Adult Tail Tip Fibroblasts)
GFP IHC of Embryonic Tissues
GFP of Chimeras
Okita et al. Nature 2007
Liver Cells from
Adult Mouse
Oct3/4
Sox2
Klf-4
c-Myc
iPS Cells
Control
WT mouse
+
Chimeric Mouse
w/ Germline
incorporation
Generated F1 and F2 progeny
from iPS cells.
Implications for Cancer
• 7-10 day transient expression of these four
factors caused an adult hepatocyte to become
reprogrammed to a pluripotent ES cell.
• Cells can definitely go backwards in their
differentiation, including gene expression and
methylation.
• Such a phenotype does not require a stable
genetic or epigenetic event. Can be a “hit and
run” transformation event.
• “Royal Flush” hypothesis
“Stemness”
• Self-renewal: maintains a stable
population of itself.
• Hierarchy: generates phenotypically
distinct progeny and lineages.
• Durable: Enhanced mechanisms for
survival and repair of damage.
• Environment: Stem cells are highly
regulated by their niche.
• Asymmetric cell division (?)
Stem Cell Division and Generation of
Lineages
The Immortal Strand Hypothesis
Rando TA vs. Lansdorp PM; Cell 129, 2007
Stem Cells and Tissue Turnover
(Epithelial Glandular Tissue)
Epithelial
Cell Type:
Stem
NE
Basal
Intermediate
Luminal/
Secretory
Renewal
Capacity:
Proliferation:
Glandular
Secretions:
Terminal
Differentiation
Differentiation:
An Essential Concept in Stem Cell Biology
Definition:
The overall process of
progenitor cells activating
genetic and epigenetic
mechanisms to define the
specialized characteristics
of mature cells.
Characteristics:



Less or loss of
proliferative ability
Loss of self-renewal
capability
Moving towards tissuespecific biological
function.
The Tumor Initiating Cell
• Who Cares: Identifying the cell of origin for a type
of cancer is a critical step in understanding
carcinogenesis and disease prevention.
• Cancers behave differently depending on the cell of
origin.
• Examples:
– Breast Cancer: ER/PR/HER2 status. Triple-negative “basallike” tumors are the worst. Also have Luminal A vs. Luminal B
vs. HER2+
– Lung Cancer: NSCLC (squamous, adenocarcinoma, large cell
carcinoma) vs. SCLC (neuroendocrine).
The significance of specific tumor suppressor gene
mutations for determining the tumor initiating cell?
• Loss of Rb predisposes to small cell lung
carcinoma whereas p16 loss/silencing
predisposes to non-small cell carcinoma
• Does this reflect differential roles of these
genes in the respective stem cells of the lung,
ie. neuroendocrine versus epithelial?
Identifying the “Tumor Initiating” Cell.
• Tumors are clonally derived from a single aberrant cell, the “tumor
initiating cell”.
• Tissue stem cells are attractive candidate “tumor-initiating” cells
since they share with tumor cells the capacity for self-renewal and
clonal expansion.
• Do tumorigenic mutations need to occur in stem cells in order to
propagate the tumor on a long term basis?
• The turnover of cycling progenitors may be too rapid to allow them
to accumulate all the required mutations to develop into a tumor”.
• Stem cells not subject to selection until they expand allowing them
to acquire mutations while “resting”. Mutations in oncogenes/TSGs
may not have severe phenotypic consequences for the nonproliferating stem cell pool but would be tumorigenic in the highly
proliferative daughter cells.
• Are stem cells therefore a reservoir of oncogenic mutations?
• If stem cells are the tumor-initiating cells for most cancers then
this may explain why therapies that target proliferating cells
(tumor cells) fail to eliminate cancer on a long term basis since the
mutant stem cell pool would survive and act as a reservoir of
potential tumor cells.
Limitless self-renewal properties
Quiescent
Limited self-renewal properties
Highly proliferative
TUMOR CELLS
Limitless self-renewal properties
Highly proliferative
Do tumor arise clonally from “immortal” stem cells that acquire proliferative potential,
or from highly proliferative progenitors that acquire self-renewal capacity?
Stem cells acquire proliferative/survival potential and their expanded
progenitor progeny then acquire self-renewal potential.
Cancer Stem Cells: Not A New Concept
• The concept that cancer might arise from a rare population of
cells with stem cell properties was proposed about 150 years ago
(German Papers).
• Over 40 years ago it was postulated that tissue-specific stem
cells may be the cell of origin of cancer (Till et al., 1961).
• In 1971, Pierce et al. showed experimentally that cellular
hierarchy existed in squamous cell carcinomas in vivo. They
found that malignant undifferentiated cells gave rise to benign
well-differentiated cells.
• Potter, in 1978, championed the concept of “oncology is blocked
ontogeny” suggesting that a lack of differentiation plays a
critical role in cancer.
Identifying Cancer Stem Cells
Controversial “Stem” of Caution: the use of immunodeficient mice for
transplantation may not accurately reflect what occurs in human cancers.
- Nude
- SCID
- NOD-SCID
- NOG-SCID
Cancer Stem Cells vs. Clonal Evolution
• Frequency of cancer cells
with tumorigenic potential
Cancer Stem
Cell Model
Rare to
Moderate
• Phenotype of cancer cells
Heterogeneous
• Tumor organization
• Intrinsic differences
between tumorigenic and
non-tumorigenic cells
• Rational approach to therapy
• Compelling clinical evidence
Hierarchical
Stable,
epigenetic
Possible to target
only
tumorigenic
cells
Germ lineage
Stochastic Clonal
Evolution Model
High
Heterogeneous or
Homogeneous
Not hierarchical
Unstable, epigenetic or
genetic
Target most or all
cells
HG B Cell lymphoblastic
leukemia
High Frequency of Cancer Forming
Ability (Stochastic Model)
Kelly et al.; Science 2007
Quintana et al.; Nature 2008
A Cancer Stem Cell Example
O’Brien et al.; Nature 2007
CD133+ populations from patients with colon cancer, injected as xenografts
into NOD-SCID mice
Questions:
1. CD133+ cells more tumorigenic that CD133- cells (initiating cells)?
2. Tumor xenograft from CD133+ cells resemble original tumor (subset)?
3. CD133+ derived tumors contain CD133- populations (lineages)?
4. Do CD133+ cells from tumors able to re-derive more tumors (selfrenewal)?
Clinical Relevance of CSCs
Cancer Stem Cell Hypothesis
Heterogeneous Tumor
Treatment
More effective
gene specific
therapies will
cure.
Relapse
Cancer Stem
Cell Model
*
Relapse
More effective
anti-tumor
therapies will
reduce but
NOT cure.
Pursue
different
target.
Multiple Myeloma CSCs Exhibit Differential
Sensitivity to Drugs
Other Clinical Considerations
• Markers for early detection: detection of
CSC populations vs. differentiated cells.
• Cancer Prevention: in some instances normal
stem cell expansion is the first event in
carcinogenesis (inflammation).
• Clinical Trials: short term vs. long term
outcomes (survival). An agent that kills CSCs
may have no measureable short-term benefit.
Identifying Stem-Like
Populations
Surface Markers
Sphere Formation
ABCG2: ATP-Binding Cassette
Transporter Type G2
• Also called BCRP (Breast Cancer Resistance Protein)
• Originally identified as being over-expressed in a
Multiple Drug Resistant (MDR) breast cancer cell line.
• Implicated in the side population phenotype for stem
cells (SP).
P-Glycoprotein (ABCB1)
Out
BCRP (ABCG2) - Homodimerizes
Out
Figure from A.H. Schinkel, J.W. Jonker / Advanced Drug Delivery Reviews 55 (2003) 3–29
Side Population to Identify
ABCG2/BCRP+ Cells
ALDH: Aldehyde Dehydrogenase
•12 ALDH genes in
humans
•Oxidize a variety of
aliphatic and aromatic
aldehydes.
•General detoxifying
enzymes
•ALDH1 is a cytosolic
enzyme which is
important in retinoic
acid signaling.
Figure from Aldagen Talk; Michelle
Fiordalisi, Ph.D.
ALDEFLUOR: Overview
ALDH1
Substrate
(weakly fluorescent)
DEAB
Product
(strongly fluorescent)
Cells
ALDH1+
ALDH1+
Bright
ALDH1-
Dim
+
ALDH1-
ALDEFLUOR to Detect ALDH1 Activity
CD133
• A.K.A. Prominin,
AC133
• Human - 4p16.2-p12
• Location: Stem and
Progenitor Cells,
photoreceptor cells
• Wider expression in
embryonic tissues
• Preference for plasma
membrane protrusions
(Figure from Corbeil et al. Traffic 2001 2: 82–91)
QUESTIONS?
prostate@uchicago.edu