Breast Cancer Stem cells: NCAB 2/07/06

Implications for Prevention and Therapy

Recent decrease in UK and USAbreast cancer mortality at ages 5069 years

Peto et al. Lancet 355:1822, 2000

Year

Ann

ual D

eath

Rat

e pe

r 10

0,00

0 W

omen

UK

USA

0

15

30

45

60

75

90

105

19501960

19701980

19902000

Breast Cancer Development

Normal Pre-neoplastic Neoplastic Metastatic

GeneticsRisk

AssessmentPrevention Detection Therapy

Local Systemic

CANCER STEM CELL HYPOTHESIS

• Cancers Arise From Tissue Stem Or Progenitor Cells

• Cancers Are “Driven” By Cells With Stem Cell Properties

Characteristics of Stem Cells

• Self Renewal

• Multi-Lineage Differentiation

Development of the Mammary Glandand Mammary Tumors

Common characteristics of normal stem cells and tumor stem cells

Normal stem cell functionality

Ability to self- renew

Anchorage independent survival

and ability to migrate

Long lived/immortalActive antiapoptotic

pathways

Telomerase activity

Resistance to damaging agents

Ability to differentiate

Carcinogenesis

High proliferation potential, tightly controlled

Organogenesis

Adult tissue maintenance and repair

Regeneration of an organ/tissue upon transplantation

Generation of all types of differentiated cells in a tissue

Organogenesis

Uncontrolled proliferation

Tumorigenicity

Tumor heterogeneity

Aberrant organogenesis

More exposed to damaging agents, higher risk of accumulating mutations, corbalanced by

Active DNA repair mechanisms

Higher risk of accumulating mutations

Often defects in DNA repair mechanisms, resulting in mutator phenotype and radio resistance

Genomic instability

Increased transporter actvity and toxic agent exclusion

Metastasis

Chemoresistance

Homing

Common characteristics of normal stem cells and tumor stem cells

Normal stem cell functionality

Ability to self- renewAbility to self- renew

Anchorage independent survival

and ability to migrate

Anchorage independent survival

and ability to migrate

Long lived/immortalActive antiapoptotic

pathways

Telomerase activity

Long lived/immortalActive antiapoptotic

pathways

Telomerase activity

Resistance to damaging agents

Resistance to damaging agents

Ability to differentiate

Ability to differentiate

Carcinogenesis

High proliferation potential, tightly controlled

Organogenesis

Adult tissue maintenance and repair

Regeneration of an organ/tissue upon transplantation

High proliferation potential, tightly controlled

Organogenesis

Adult tissue maintenance and repair

Regeneration of an organ/tissue upon transplantation

Generation of all types of differentiated cells in a tissue

Organogenesis

Uncontrolled proliferation

Tumorigenicity

Uncontrolled proliferation

Tumorigenicity

Tumor heterogeneity

Aberrant organogenesis

Tumor heterogeneity

Aberrant organogenesis

More exposed to damaging agents, higher risk of accumulating mutations, corbalanced by

Active DNA repair mechanisms

Higher risk of accumulating mutations

Often defects in DNA repair mechanisms, resulting in mutator phenotype and radio resistance

Genomic instability

Higher risk of accumulating mutations

Often defects in DNA repair mechanisms, resulting in mutator phenotype and radio resistance

Genomic instability

Increased transporter actvity and toxic agent exclusion

Metastasis

Chemoresistance

Homing

Pathways Involved in Stem CellSelf Renewal and Cancer

• Notch

• Hedgehog

• Bmi-1

• Wnt

Hedgehog Target Gli-2 Promotes Ductal Hyperplasia

CANCER STEM CELL HYPOTHESIS

• Cancers Arise From Tissue Stem Or Progenitor Cells

• Cancers Are “Driven” By Cells With Stem Cell Properties

Models of Tumor Heterogenity

Stochastic model Cancer stem cell model

CSC

CSC

CSC

CSC

Cancer cells are heterogeneous, but most cells can proliferate extensively and form new tumors.

Cancer cells are heterogeneous, and only rare cancer stem cells have the ability to proliferate extensively and form new tumors.

The Isolation of Human Cancer Stem Cells

dissociate

stain withantibodies

Flow-cytometry

CSC

CSC

CSC

Tumorigenicity of Cancer Cell Subsets

Cells / injection 5x105 105 5x104 2x104 104 5x103 103 200

Unsorted (T1) 4/4 4/4 6/6 - 2/6 - 0/6 -B38+CD44+CD24+ - - - 0/5 0/5 0/5 0/5 -B38+CD44+CD24- - - - 5/5 5/5 5/5 5/5 -ESA+CD44+CD24- - - - - - - 8/8 4/4

Unsorted (T2) 4/4 4/4 4/4 - 1/6 - 0/6 -B38+CD44+CD24+ - - - 0/5 0/5 0/5 0/5 -B38+CD44+CD24- - - - 5/5 5/5 5/5 5/5 -

Tumor 1 was derived from a metastatic pleural effusion and Tumor 2 was derived from a primary breast tumor.

CD44+;B38.1+CD24+

CD44+;B38.1+CD24-

Tumor Formation by Human Breast Cancer Cells in Mouse Model

Both Non-Tumorigenic Cancer Cells and Cancer Stem Cellshave a Malignant Appearance, but Only Stem Cells Give

Rise to New Tumors

Cancer stem cellsNon-tumorigenic cellsTumorigenic

Isolatedhumanbreastcancercells

Injectionsites inthe mice

Breast Cancer Stem Cells give rise to Phenotypically Diverse Tumors after Transplantation

Initial tumor CSCs from initial tumor Secondary tumor

Y

X

T1

T2

Hedgehog Activation & Bmi-1 Expression in Cancer Stem Cells

00.00050.001

0.00150.002

0.00250.003

0.00350.004

0.00450.005

PTCH1

Rel

ativ

e m

RN

A ex

pres

sion

(PTC

H1

/ RPL

P0)

Total cellsNon-tumorigenic cellsTumorigenic cells

*

* p < 0.05

00. 0050. 01

0. 0150. 02

0. 0250. 03

0. 0350. 04

0. 0450. 05

Gli1 Gli2

Rel

ativ

e m

RN

A ex

pres

sion

(Glis

/ R

PLP0

)

Total cellsNon-tumorigenic cellsTumorigenic cells

** p < 0.05

00. 020. 040. 060. 080. 1

0. 120. 140. 160. 18

hBmi-1

Rel

ativ

e m

RN

A ex

pres

sion

(hBm

i-1 /

RPL

P0)

Total cellsNon-tumorigenic cellsTumorigenic cells

*

* p < 0.05

Hedgehog signaling pathway

Notch signaling pathway

Bmi-1

Shh, Ihh, Dhh DSL

Cyclopamine GSI

Gli1Gli2

Figure 10

Mammary stem cell self-renewal pathways

Tumorigenic Stem cell

Normal Tumor

Normal Stem cell

Self-renewal Self-renewal

Tumorigenic Stem cellNormal Stem cell

Deregulation

Differentiation Differentiation

Differentiated cells Non-tumorigenic cells

↑PTCH1↑Ihh↑Bmi-1

BMI-1 “Stem-Cell” Signature and Patient Survival

Glinsky et al. JCI 115:1503, 2005

Implications of TSC –Profiling/Diagnosis/Prevention

• Cell of origin may determine molecular profile

• Molecular profiling may miss important TSC genes

• Significance of TSC in metastasis

• Identification of TSC in situ may have diagnostic/prognostic value

• Elimination of mutated stem/progenitor cells important prevention strategy

Normal Development

Stem cell ER-

Self-renewal

Myoepithelial cell

Myoepithelial progenitor

Progenitor cell

?

??

Diff

eren

tiatio

n

ER+ progenitor cell

Paracrine signals

Ductal luminal progenitors

Ductal epithelial cell Alveolar cell

ER+

ER-

Carcinogenesis

Basal

ER-

Cancer stem cell

ER-

ER-

Cancer stem cell

Luminal

B

ER+

ER-

Cancer stem cell

ER-

ER-

Cancer stem cell

ER+

Luminal

A

Cancer stem cell

ER+

Cancer stem cell

ER+

CSC with PARTIAL malignant potential

CSC

TDC

TDC

TDC

TDC

TDC

TDC

No MetastasesCSC=Cancer Stem Cell

TDC=Terminally Differentiated Cell

Cancer Stem Cells: Implications For Metastasis

1o

Tumor CSC with FULL malignant potential

Secondary Oncogenic “Hits” and/or Changes in Microenvironment

Subsequently to other sites

Metastases in months to few years

Dormancy followed by Metastases after many years:

TDC only

NO CSC

The Implications of Human CancerStem Cells (CSCs) for Treatment

Drugs thatkill cancer cellsbut not CSCs

CSCs regenaratetumor

Drugs that killcancer stem cells

Tumor looses itsability to generatenew cells

Tumor degenerates,patient is cured

CSC

CSC

CSC

Tumor regresses

Tumor recurs

Implications of TSCTherapeutics

• Tumor regression inadequate endpoint

– Preclinical models

– Phase II clinical trials

• TSC may be resistant to therapy (apoptosis)

• Effective therapies should target TSC while sparing normal cells

• Genes in TSC self-renewal pathway may provide new therapeutic targets

Evidence for “ Stem Cells”in Human Cancer

• Breast Cancer

• Leukemia

• Multiple Myeloma

• Brain Cancer

• Lung Cancer

• Prostate Cancer

• Melanoma