HEREDITARY BREAST CANCER IN DEVELOPING COUNTRIES

Richard G. Pestell, MD, PhD

Kimmel Cancer Center

Jefferson University Hospital

Major Genetic Defects in Breast Cancer

Established Familial Breast Genes (All Tumor Suppressors)

Gene Chromosomal Location

Disease

TP53 (p53)

17p13 (mutated, LOH) Li-Fraumeni syndrome of multiple hereditary cancers

PTEN 10q23 (mutated, LOH) Cowden’s syndrome of multiple hereditary cancers

BRCA-1 17q21 (mutated, LOH) Familial female breast and ovarian cancers

BRCA-2 13q14 (mutated, LOH) Familial female and male breast cancers

Established Breast Cancer Progression Genes

Gene

Chromosomal Location Class Function

C-ERBB2 17q12 Oncogene (amplified) Growth factor receptor subunit

C-MYC 8q24 Oncogene (amplified) Cell-cycle/cell death regulator; protein synthesis

CCND1 (cyclin D1) 11q13 Oncogene (amplified) Cell-cycle G1 regulator

CDKN2 (p16) 9p21 Suppressor gene (methylated, LOH)

Cell-cycle G1 regulator

RB-1 13q14 Suppressor gene (mutated, LOH)

Cell-cycle G1 and G1/S regulator

TP53 (p53) 17p13 Suppressor gene (mutated, LOH)

Cell-cycle/cell death/DNA repair regulator

CDH1 (E-cadherin) 16q22-23 Suppressor gene (methylated, LOH)

Cell-cell adhesion protein

Major Genetic Defects in Breast Cancer

Sex Hormone Regulation of Growth Factor Systems in Breast Cancer

EGF FAMILY

Growth factors: EGF, TGF-, amphiregulin

Receptors: EGFR, c-erbB2

IGF FAMILY

Growth factors: IGF-2

Receptors: IGF-1R, IGF-2R, insulin receptor

Binding proteins: BP-2, BP-3, BP-4, BP-5

TGF- FAMILY

Growth factors: TGF-1, TGF-2, TGF-3

PDGF FAMILY

Growth factors: PDGF-1, PDGF-2

BP, binding protein; EGF (R) , epidermal growth factor (receptor); IGF, insulin-like growth factor; PDGF, platelet-derived growth factor; TGF, transforming growth factor.

Metastatic Cancer

Further phenotypic alterations in cell cycle

Further phenotypic alterations in cell death and response to therapy

Phenotypic changes in growth factor secretion governing angiogenesis and metastatic spread

Mutations in pathways governing invasion CDH1

Defects in mismatch repair of DNA

Predisposing genetic risk

Mutations affecting DNA repair and apoptosis in BRCA-1 BRCA-2

TP53

PTEN

Carcinoma in Situ

Mutations in Growth Factor and Sex Steroid pathways governing the cell cycleC-ERBB2C-MYCCCDN1CDKN2RB-1

Mutations in Cell Death PathwaysTP53

Overall Chromosomal Instability

Hyperplasia

Overstimulation of cell cycle and suppression of apoptosis by Estrogen Progesterone Growth Factors

Immortalization of cells by expression of Telomerase

Genetic Alteration of Mammary Epithelial Cells - Progression of Breast Cancer

BRCA1 Protein Function

• Regulation of cell cycle progression

• DNA repair: “caretaker” function

• Programmed cell death (apoptosis)

• Regulation of gene transcription

BRCA1 Protein: Structural Features

-1863 aa-220 kDa nuclear phosphoprotein-N-terminal RING domain (aa 20-64)

interacts with BARD1ubiquitin ligase activity

-C-terminal TAD (last 95-100 aa)mediates transactivationBRCT repeats

Role in DNA Damage Response

Specialized DNA repair processes-Homology-directed repair-Transcription coupled repair-Mismatch repair-Nucleotide excision repair-Fanconi repair

DNA damage signaling: ATM, ATR, Chk2

DNA damage responsive cell cycle checkpoints: S & G2/M

Regulation of BRCA1 Expression

Increased Expression-cancer chemoprevention – indole-3-carbinol, genistein-mammary epithelial cell differentiation-cell cycle - in late G1, early S-phase

Decreased Expression-30-40% sporadic breast cancers: promoter methylation-ethanol-polycyclic aromatic hydrocarbons – B(a)P, BPDE-persistent organochlorines (PCBs)-p53 activation-Id4 (bHLH transcriptional regulator)

BRCA1 Regulated Transcriptional Pathways

-interacts w/ basal transcription factor (RNA helicase A)-C-terminus: chromatin unfolding activity (COBRA1)-associates w/ Brg1 (SWI/SNF chromatin remodelling)-stimulates Gadd45, p21WAF1, p27Kip1 expression-coactivator for p53-inhibits c-Myc activity and TERT expression-interacts with STAT1–interferon -mediated transcription-regulates nuclear receptor function

BRCA1 transcriptional regulation

BRCA1-interacting proteins

BRCA1-transcription repression

Science, V284, p1354, 1999

BRCA1 represses ER

BRCA1 Domains for ERInhibition

Du-145T47D

220

200

120

100

80

60

40

20

0

Lu

cife

rase

Act

ivit

y(%

of

pcD

NA

3 V

ecto

r C

ontr

ol)

pcD

NA

3

wt

BR

CA

1

5677

-In

sA

Bam

H1

Kp

n 1

Eco

R 1

185d

elA

G

T30

0G

RX

RX

H

5382

InsC

C53

65G

1

1

1

1

1

1

1

1

1

RING NLS Rad51 TAD

1 500 1000 1500 1863

1852

1313

771

302

38

61 Cys/Gly

358 RXRXH

1863

1863

1755

1749Pro/Arg 1863

wt BRCA1

5677-InsA

Bam H1

Kpn 1

EcoR 1

185delAG

T300G

RXRXH

5382InsC

C5365G

LXCXE

ER Binds Cyclin D1

Western IP WB

E2- + - +

A B

ER

ER

HE74

F

1-530

E/F

1-282

DBD LBD

AF-1 AF-2

1-378

ER

HE74

F

1-530

E/F

1-282

1-378

***

Cancer Res, Wang et al 2005

GST-Cyclin D1 Binds to ER

GS

T

GS

T D

1

ER

ER

HE74

F

1-530

E/F

1-282

DBD LBD

AF-1 AF-2

HE19C

***1 595

1 595

179 595

1 554

1 530

1 388

1 282

Cancer Res, Wang et al 2005

Cyclin D1 Overcomes Repression by BRCA1

N C

BRCA1

BRCA1

BRCA1

N CN C

ER ER ER

Co-activator

Co-activator

Co-activator

D1

D1

Hereditary Breast Cancer in Developing Countries

-Relative contribution to breast cancer ?-Common or distinct mutations ?-Role of polymorphisms in onset,progression and therapy(cyclin D1,Bcl2, other) ?-Role in screening- cultural sensitivity vs treatment triage-Economic priorities ?-Global collaboration in molecular epidemiology ?

BRCA1 Inhibits Estrogen-Induced GenesD

ME

M+

10%

FC

S

- + - + E2 (10-6M)- - + + wtBRCA1

pS2

Cathepsin-D

-Actin

DM

EM

+10

%F

CS

- + - + E2 (10-6M)- - + + wtBRCA1

pS2

Cathepsin-D

-Actin

Serum-Free DMEM Serum-Free DMEM