Genetic Variants of DNA Repair genes and Prostate Cancer:

Department of Epidemiology and Biostatistics

George Washington University

July 2003

A Population-Based Case-Control Study in China

Jamie D. Ritchey

Prostate Cancer • The prostate, anatomical location• International patterns• Etiology• Genetic susceptibility, SNPs, and DNA repair• The Shanghai Prostate Cancer Study• Objectives• Methods: genotyping, statistical analysis• Results• Strengths and limitations• Conclusions• Future Research• Questions

The Male urinary and reproductive system

International Patterns

Hsing, Tsao, and Devesa, International Journal of Cancer, 2000.

African American men

Chinese men in China

Etiology: Risk factors for prostate cancer

Known risk factors:• Age• Race• Family history

Probable Risk factors: • Diet, obesity (BMI, WHR,

IR), leptin, physical activity

• Diabetes, IGF-1, insulin• Androgens• Sexual behavior/sexually

transmitted disease, vasectomy

• Smoking• Alcohol• Liver cirrhosis• Low-penetrant Genetic

component?ACS, www.acs.gov 2003 NCI, www.nci.gov 2003

Genetic susceptibility to cancer

High penetrant genes1

• Rare in the population• Almost always cause

cancer in the individual• Examples:HPC1,

HPC2/ELAC2, HPCX, HPC20, PCAP, CAPB, BRCA1 and BRCA2

Low penetrant genes2

• More common in population, may be a larger risk factor

• Do not always cause cancer in the individual

• Different Single nucleotide polymorphisms (SNPs) of the same marker may increase or decrease cancer risk

• Hormone: AR, SRD5A2, ER, etc.

• DNA repair genes: XRCC1, XRCC3, XRCC5, ERCC1, ERCC2, MGMT, hOGG1, POLB

1Stanford, Epidemiologic Reviews, 2001. 2Greenhut, Kerrigan, and Kelly, http://press2.nci.nih.gov/sciencebehind/snps_cancer/snps_cancer/snps_ , 2003.

Single Nucleotide Polymorphisms (SNPs)

Greenhut, Kerrigan, and Kelly, http://press2.nci.nih.gov/sciencebehind/snps_cancer/snps_cancer/snps_ , 2003.

Change in shape Altered Cancer Risk

SNP: Decreased DNA repair

capacity

Genomic instability

Oncogene activationInactivate Tumor suppressors

Loss of heterozygosity

DNA repair

• Base Excision Repair (BER)1,3

• Direct Damage Reversal1

• Nucleotide Excision Repair (NER)1

• Non-homologous end-joining and Homologous recombination repair (NHEJ and HR)1,3

• Mismatch Repair (MMR)1,2

XRCC1_399

MGMT_84 and MGMT_143

ERCC2_751

XRCC3_241 (specifically in HR)

2No markers in study, ex: MSH2, MLH1, MSH6, PMS2,

PMS1, hOGG1

Pathway Marker

1Poirier, 2002 2Chen, 2001 3Goode, 2002

DNA Repair Pathways

• Reversal of alkyl group(-CH2-CH3, and -CH3)

• DNA Replication or Recombination

• Bulky AdductUV-induced Damage

• Reactive Oxygen, Restriction Enzymes, and Normal Cell Process

Non-Bulky Adduct, Oxidative Stress, and Ionizing Radiation

Environmental Factors(Diet)

+SNP of DNA repair genes

= latent effects increasing

prostate cancer risk ?

Greenhut, Kerrigan, and Kelly,http://press2.nci.nih.gov/sciencebehind/snps_cancer/snps_cancer/snps_ , 2003.

Shanghai Prostate Cancer Study

A Population-Based Case control Study(Cases collected from: 1993-1995)

Study components included:

• In-person interview• Medical record abstraction• Anthropometric measurements• Collection of fasting blood

Objectives

• The primary objective: to investigate whether five different DNA repair markers, specifically: XRCC1_399, XRCC3_241, ERCC2_751, MGMT_84 and MGMT_143 play a role in the etiology of prostate cancer.

• Secondary objectives included: the risk of prostate cancer and the five DNA repair markers by the probable risk factors:

-Waist to hip ratio, WHR -Insulin resistance, IR -Diet

Shanghai Prostate Cancer Study Study Design

268 Prostate cancer cases

Interview

200 cases provided 20 ml fasting blood

330 controls provided 20 ml of fasting blood

191 Cases Genotyped

305 controlsGenotyped

495 Population Controls

243 cases interviewed

472 controls interviewed

Genotyping Blood

Buffy coat

Purified DNA

MALDI-TOF/hME assaysXRCC1_399, XRCC3_241, ERCC2_751, MGMT_84, MGMT_143

191 Cases Genotyped

305 controlsGenotyped

Statistical Analysis

Logistic regression was used to calculate the ORs and the 95% CIs to investigate marker main effects and markers by other potential risk factors

RESULTS

Selected demographic characteristicsCharacteristic Cases (n=162) Controls (n=251)

N

61

50

51

%

15

12

12

N

78

89

84

%

19

22

20

14

124

24

0

9

76

15

0

29

191

30

1

12

76

12

~1

61

50

48

2

38

31

30

1

-

-

-

-

-

-

-

-

Age<69

70-75>76

EducationNone

Elementary-high

College/ above

OtherStage

LocalizedRegionalRemote

Unknown/unstaged

PSA

G e n e t ic M a r k e r s M a in E f f e c t s

1 0 .8 3

2 .1 8

G G A G A A

A d ju s te d fo r a g e

1

1 .95

3 .39

CC CT TT

10 .8 4

2 .2 3

C C C T T T

1

1 .5 5

A A A G G G

N /A

X R C C 1 _ 3 9 9 M G M T _ 8 4

X R C C 3 _ 2 4 1

E R C C 2 _ 7 5 1

M G M T _ 1 4 3

1

0 .8 7

A A A C C C

N /A

Genetic Markers and other Factors: Combined Effects

XRCC1_399

1.89 1.96

3.02

10.53

3.21

GG AG AA

<0.097

>=0.097

2.29 2.02

3.19

10.79

3.85

GG AG AA

<0.892

>=0.892

Waist to Hip Ratio

InsulinResistance

Age-Adjusted

Genetic Markers and other Factors: Combined Effects

MGMT_84

1.05

4.76

11.92

CC CT+TT

<0.892

>=0.892

1.99

6.37

1 0.95

CC CT+TT

<0.097

>=0.097

Waist to hip Ratio

Insulin Resistance

Age-Adjusted

Genetic Markers and other Factors: Combined Effects

XRCC1_399 Total Preserved Food

1.791.48

1 1.08

GG AG+AA

<12.7

>=12.7

Age-adjusted

Genetic Markers and other Factors: Combined Effects

MGMT_84 Total Preserved Food

1.66

2.81

1

2.31

CC CT+TT

<12.7

>=12.7

Genetic Markers and other Factors: Combined Effects

XRCC1_399Allium Vegetable intake

1 1.08

0.530.39

GG AG+AA

>=5.83

<5.83

Genetic Markers and other Factors: Combined Effects

MGMT_84Allium Vegetable intake

1

2.34

0.54 0.63

CC CT+TT

>=5.83

<5.83

Study strengths

• Population-based

• High response rates

• Nearly compete case ascertainment

• Pathology review

• In-person interviews

• High accuracy of Laboratory results

Study limitations

• Small Sample size

• Generalizability

Conclusions• XRCC1_399 AA and the MGMT_84 CT/TT

may increase prostate cancer risk

• DNA repair capacity of both markers may be effected by: abdominal obesity, insulin resistance, preserved food consumption and allium vegetables

• No association was seen with alleles of XRCC3_241, ERCC2_241 and MGMT_143, but these may still increase or decrease cancer risk

Future Research

• Larger Studies

-- Accrue greater number of cases

-- Enroll larger set of controls

• Confirmation in Western populations

• Additional markers investigated in each

pathway

AcknowledgementsNational Cancer Institute

Shanghai Cancer Institute

Shanghai Tumor Hospital

George Washington University

Ann Hsing, Ph.D.

Joseph Fraumeni, Jr., M.D.

Gloria Gridley, M.S.

Yu-Tang Gao, M.D.

Jie Deng, M.D.

Ming-Chang Shen, M.D.

Paul Levine, M.D.