Download MSR1 variants and the risks of prostate cancer

Carcinogenesis vol.28 no.12 pp.2530–2536, 2007
doi:10.1093/carcin/bgm196
Advance Access publication September 3, 2007
MSR1 variants and the risks of prostate cancer and benign prostatic hyperplasia:
a population-based study in China
Ann W.Hsing1,, Lori C.Sakoda2, Jinbo Chen3, Anand
P.Chokkalingam4, Isabel Sesterhenn5, Yu-Tang Gao6,
Jianfeng Xu7 and S.Lilly Zheng7
1
Division of Cancer Epidemiology and Genetics, National Cancer Institute,
National Institutes of Health, Bethesda, MD 20892, USA, 2University of
Washington, Seattle, WA 98195, USA, 3University of Pennsylvania,
Philadelphia, PA 19114, USA, 4University of California, Berkeley, CA 94707
USA, 5Armed Forces Institute of Pathology Washington DC 20306, 6Shanghai
Cancer Institute, Shanghai 200032, China and 7Center for Human Genomics,
Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
To whom correspondence should be addressed. Tel: þ1 301 496 1691;
Fax: þ1 301 402 0916;
Email: [email protected]
Data from epidemiologic and twin studies suggest an important
role of genetic susceptibility in prostate cancer. Variants of the
macrophage scavenger receptor 1 (MSR1) gene have been linked
to both hereditary and sporadic prostate cancer, although the
evidence is inconclusive. Most studies have been conducted on
Caucasians. The role of MSR1 in prostate cancer development
among Asians, for whom rates of prostate cancer are low but
rising rapidly, is unclear. To evaluate further the relationship
between MSR1 variants and prostate cancer risk, we sequenced
all the 11 MSR1 exons, exon–intron junctions, promoter regions,
as well as 5# and 3# untranslated regions (UTRs) in 86 individuals
from Shanghai, China. We identified a total of 21 sequence variants, including three novel variants that have not been reported
previously. To balance genotyping cost and the capacity to capture
sufficient genetic variation, we genotyped four haplotype-tagging
variants (P275A, INDEL7, P346P and 3# UTR 70006), which capture 85% of the genetic variation in MSR1 in this population.
These four variants, plus two other variants (PRO3 and INDEL1)
that have been linked to prostate cancer risk in the previous studies, were typed for all study subjects, which included 130 prostate
cancer cases, 130 patients with benign prostatic hyperplasia and
150 controls randomly selected from the population. Three of the
six variants were associated with prostate cancer. Men with
a P346P (a novel variant) G allele (AG 1 GG) had a significantly
reduced risk of total prostate cancer [odds ratio 5 0.47, 95%
confidence interval (CI) 0.23–0.96], whereas those with a P275A
G allele had a 37% reduced risk of prostate cancer (95% CI 0.39–
1.02), with more pronounced reduction in risk seen for localized
cancer cases (odds ratio 5 0.25, 95% CI 0.12–0.52; P 5 0.001). In
addition, men with the INDEL7 variant had a 67% reduced risk
of localized cancer (95% CI 0.16–0.68). Based on the four tagging
variants, we inferred four major haplotypes that accounted for
>90% of the haplotype variation in this population. The haplotype
frequencies were significantly different between localized prostate
cancer cases and controls, with a global P value of 0.004, and the
haplotype containing the minor alleles of the P275A and INDEL7
variants was associated with a significantly reduced risk of localized prostate cancer (odds ratio 5 0.28, 95% CI 0.13–0.59), relative to the most common haplotype. These results, although
modest and confined mainly to localized prostate cancer, suggest
that MSR1 polymorphisms may play a role in prostate cancer
etiology in Chinese men. The role of MSR1 warrants further investigation in larger studies and other populations.
Abbreviations: BPH, benign prostatic hyperplasia; CI, confidence interval;
LD, linkage disequilibrium; MSR1, macrophage scavenger receptor 1; PCR,
polymerase chain reaction; SNP, single-nucleotide polymorphism; UTR, untranslated region; WHR, waist-to-hip ratio.
Published by Oxford University Press 2007.
Introduction
Data from epidemiologic, family and twin studies suggest an important role of genetic susceptibility in prostate cancer (1–3). It is estimated that 42% of the risk of prostate cancer may be due to genetic
influences (1), including individual and combined effects of rare,
highly penetrant genes and more common polymorphisms with mild
effects on androgen biosynthesis/metabolism, DNA repair and
chronic inflammation pathways (3,4).
Emerging epidemiologic evidence suggests that chronic inflammation in the prostate increases the risk of prostate cancer (5–7). For
example, a recent meta-analysis of 11 studies on prostatitis and prostate cancer reported a relative risk of 1.6 for all studies combined (8).
In addition, chronic inflammation induced by bacterial or viral agents
has been implicated as a potential underlying mechanism for the link
between sexually transmitted diseases and prostate cancer (9). A population-based case–control study in the USA reported that men who
have had three or more episodes of gonorrhea had a 3.3-fold risk of
prostate cancer compared with those who had never had gonorrhea
(10). In the same study, men who had a history of syphilis infection
had a significant 2.6-fold prostate cancer risk.
Further supporting the role of chronic inflammation are the reported
associations of prostate cancer with polymorphisms of genes involved
in the inflammation pathway, including the macrophage scavenger
receptor 1 (MSR1) gene (11–22). The MSR1 protein, encoded by
the MSR1 gene, is a transmembrane protein that is expressed mainly
by macrophages. Through binding to a wide range of ligands, including gram-negative and gram-positive bacteria, oxidized low-density
lipoprotein and certain polynucleotides, the MSR1 protein is involved
in an array of hormonal and pathological processes, including inflammation, innate and adaptive immunity, oxidative stress and apoptosis
(21,22). The initial report of MSR1 showed a strong link between
MSR1 mutations and hereditary prostate cancer in men of both
European and African descent (22). However, results from subsequent
studies have been inconclusive. A recent meta-analysis of eight studies on MSR1 suggests that the R293X and D174Y variants are associated with an increased risk of sporadic prostate cancer, particularly
in African Americans (23). Similar studies have not been conducted in
Asian populations, who have, in contrast to African Americans, the
lowest reported rates in the world, although their incidence has been
rising rapidly over the last 10 years (24–27). Reasons for the large
racial differences in prostate cancer risk are unclear but may involve
a complex interplay of genetic factors, including those involved in
inflammation such as the MSR1 gene and lifestyle factors (3).
To evaluate further the relationships between MSR1 and prostate
cancer, we carried out a comprehensive genetic analysis of MSR1 in
a population-based study of prostatic disease in Shanghai, China. We
first sequenced MSR1 in a subset of subjects to identify haplotypetagging variants, and then typed all study subjects for the tagging variants in order to estimate the risk of prostate cancer and
benign prostatic hyperplasia (BPH) associated with common MSR1
polymorphisms.
Materials and methods
Study population
Details of this population-based case–control study have been reported elsewhere (28–31). Briefly, cases were permanent residents of Shanghai who were
newly diagnosed with prostate cancer (ICD-9 185) between 1993 and 1995,
identified through a rapid reporting system in 28 collaborating hospitals in
urban Shanghai. Cases had no history of any cancer. Four cancer cases were
excluded from the study after Chinese and American pathologists jointly
confirmed their diagnosis as BPH. The rapid reporting system captured
2530
MSR1 variants and the risks of prostate cancer and benign prostatic hyperplasia
.95% of the cases diagnosed in urban Shanghai during the study period.
Patients with BPH diagnosed at the same hospitals were randomly selected
for inclusion in the study. BPH cases were matched to the index cancer cases
by age (within 5 years) and hospital. Pathology materials of both cancer and
BPH cases were reviewed by study pathologists in Shanghai and subsequently
confirmed by pathologists at the Armed Forces Institute of Pathology in USA.
Based on records maintained at the Shanghai Resident Registry, male controls
with no history of cancer were selected at random from the 6.5 million permanent Shanghai residents .18 years of age and frequency matched to cancer
cases by age (5-year intervals). This study was approved by the Institutional
Review Boards at the National Cancer Institute and the Shanghai Cancer Institute and written informed consent was obtained from all study subjects.
Interview
Using a structured questionnaire, trained personnel conducted in-person interviews to collect information on demographic characteristics, diet and smoking
history, consumption of alcohol and other beverages, medical history, family
cancer history, physical activity and sexual behavior. Anthropometric measurements were also taken, including waist and hip circumferences, height and
weight. For cases, an interview was conducted within 3 weeks of diagnosis.
Blood collection and DNA extraction
Over 75% of the study subjects provided overnight fasting blood samples.
Blood samples were processed and separated within 2 h of collection at a central laboratory at the Shanghai Cancer Institute. The blood fractions were
stored at 70°C in Shanghai before shipment to USA on dry ice. DNA was
extracted from the buffy coat fractions at the American Type Culture Collection (Manassas, VA). Only subjects with sufficient DNA available were included in the study for genotyping. In total, 130 prostate cancer cases, 130 BPH
cases and 155 population controls were included. Overall, 70% of the cases
in the original study who provided blood samples had sufficient DNA for the
present study. There was no difference in demographic characteristics between
those with and without DNA samples.
Sequence analysis and genotyping
Sequencing. To identify novel variants, we sequenced all 11 MSR1 exons,
exon–intron junctions, promoter regions and 5# and 3# untranslated regions
(UTRs) (32) in 86 individuals (66 prostate cancer cases and 20 non-cancer
cases). As shown in Table I, we identified a total of 21 sequence variants
(variants 1–21), including one missense change (variant 11), two synonymous
changes (variants 13 and 15) and six variants in the 3# UTR (variants 16–21).
Of the 21 variants, three (variants 4, 14 and 15) were novel variants that have
not been reported previously. Figure 1 shows the location of and distance
between these variants in the MSR1 gene, and Table I shows the position,
dbSNP ID and minor allele frequency of these variants in the 86 samples.
All polymerase chain reactions (PCRs) were conducted in a volume of 10 ll
containing 30 ng of genomic DNA, each primer at 0.2 lM, each deoxynucleoside triphosphate at 0.2 mM, 1.5 mM MgCl2, 20 mM Tris–HCl, 50 mM KCl and
0.5 U of Taq polymerase (Life Technologies, Gaithersburg, MD). PCR cycling
conditions were as follows: 94°C for 4 min; 30 cycles of 94°C for 30 s, the
specified annealing temperature for 30 s, and 72°C for 30 s and a final extension
of 72°C for 6 min. All PCR products were purified using the QuickStep PCR
purification kit (Edge BioSystems, Gaithersburg, MD) to remove deoxynucleoside triphosphates and excess primers. All reactions were performed using dyeterminator chemistry (BigDye, ABI, Foster City, CA), with 63.5% ethanol for
precipitation. Samples were loaded onto an ABI 3700 DNA Analyzer after
adding 8 ll of formamide. Genetic variants were identified using Sequencher
software version 4.0.5 (Gene Codes Corporation, Ann Arbor, MI).
Haplotype tagging. Of the 21 variants identified, three (variants 3, 13 and 16)
had a minor allele of frequency ,5% and one (variant 12, INDEL7) deviated
from Hardy–Weinberg equilibrium among control subjects (these four variants
were not included in the derivation of haplotype tagging single-nucleotide
polymorphisms (SNPs)). Results of pairwise linkage disequilibrium (LD) analysis showed three regions with strong LD (variants 1–2, 6–8 and 14–21). There
were a total of 24 estimated haplotypes, with six common haplotypes (frequency .5%) that represented 81% of all haplotypes. Haplotype-tagging analysis showed that four variants (variants 11, 12, 15 and 17) captured 85% of the
haplotype diversity in this population. Thus, we typed these four tagging
variants (three SNPs and one insertion/deletion) for all study subjects: variant
11 (P275A, rs3747531, a missense change in exon 6), variant 12 (INDEL7,
rs3036811, a 3 bp insertion/deletion in intron 7), variant 15 (P346P, a synonymous change) and variant 17 (3# UTR 70006, rs12678016). In addition, we
included two variants, variant 3 (PRO3, rs433235, in the promoter region)
and variant 8 (INDEL1, rs11274081, a 15 bp insertion/deletion in intron 1),
that have been reported in previous studies to be associated with prostate cancer
risk.
Genotyping. Genotyping of the four SNPs (PRO3, P275A, P346P and 3# UTR
70006) was performed using the MassARRAY system (SEQUENOM), whereas
genotyping of the two insertion/deletions (INDEL1 and INDEL7) was performed using the 3700 DNA Analyzer (Applied Biosystems, Foster City,
CA). DNA samples were arranged in triplets (cancer case, BPH and control)
and identified by specimen ID only. Laboratory personnel had no information
on case–control status. In addition to quality control samples included in each
batch by the laboratory, blinded quality control samples were included to
monitor the reproducibility of the genotyping assays. The genotyping failure
rate was low (,2%) and concordance of duplicate samples was .99%.
Statistical analysis
Differences in selected characteristics between cancer cases, BPH cases and
controls were tested using the Fisher’s exact test for categorical variables and
the t-test for continuous variables.
Single locus associations. Among control subjects, genotype frequencies of
each MSR1 variant were examined for departure from Hardy–Weinberg equilibrium, using the Pearson v2 test. Differences in genotype frequencies between BPH cases, prostate cancer cases and controls were assessed with the
Fisher’s exact test. Through the use of unconditional logistic regression, ageadjusted odds ratios and 95% confidence intervals (CIs) were derived, comparing BPH patients and cancer patients to control subjects separately, to
evaluate the relationship of each MSR1 polymorphism with risks of BPH
and prostate cancer. The homozygous genotype of the most common allele
was used as the reference category. Tests for linear trend in risk according to
the number of copies of the variant allele (0, 1 or 2) were also conducted to
assess potential dose–response effects (33). Risk estimates were not calculated
for comparisons if the sample size was ,5. When the number of subjects with
homozygous genotype of the variant allele was ,5, instead of the test for trend
analysis, we tested the disease risk associated with the presence or absence of
the minor allele.
Haplotype associations. Pairwise D’ (34) and r2 (35) values were calculated to
examine the extent of LD between the six MSR1 loci. Using the haplo.stats
package (http://mayoresearch.mayo.edu/mayo/research/schaid_lab/software.
cfm) in R (version 2.2.0, http://www.r-project.org), haplotype frequencies were
estimated for cases and controls applying the expectation-maximization algorithm (36); differences in haplotype frequencies between BPH cases, cancer
cases and controls were assessed by a global score test (37) and age-adjusted
odds ratios and 95% CIs were generated to examine the association of MSR1
haplotypes with risks of BPH and prostate cancer, with the most common
haplotype defined as the referent category.
We also investigated potential combined effects of MSR1 polymorphisms
with other factors, including abdominal obesity [measured by waist-to-hip
ratio (WHR)], body mass index (weight in kilogram divided by height in
square meter) and insulin resistance, all of which have been linked to both
inflammation and/or prostate cancer (28,30,38–40). The significance of the
interaction terms representing the modifying effects of these putative risk
factors with MSR1 markers was assessed using the likelihood ratio test. All
reported P values are two-sided.
Results
Table I shows the position and minor allele frequency of the 21 sequence variants in the 86 samples and of the six haplotype-tagging
variants in control subjects. The genotype distributions for the six loci
among controls were in Hardy–Weinberg equilibrium, with minor
allele frequencies ranging from 10.4 to 45.9%.
Selected characteristics of cases and controls are shown in Table II.
Among cancer cases, most tumors were moderately or poorly differentiated, with about one-third of the cases displaying clinically significant, advanced cancers in remote stages. The mean WHR and
insulin resistance ratios differed significantly between cancer cases
and controls (P , 0.01). Prostate specific antigen (PSA) levels in
cases were high due to infrequent prostate cancer screening in China
during the study period.
Table III shows prostate cancer risk associated with the six MSR1
loci. As shown, only one marker (P346P) was significantly associated
with total prostate cancer, with men having the P346P G allele (AG þ
GG genotypes) at a 53% significantly reduced risk of prostate
cancer (95% CI 0.23–0.96). Two MSR1 markers, including P275A
and INDEL7, were associated with significantly reduced risk of localized prostate cancer. Men with the P275A G allele (CG þ GG) had
a 75% reduction in risk (95% CI 0.12–0.52) and those with INDEL7
2531
A.W.Hsing et al.
2532
Table I. Sequence variants in the MSR1 gene identified in 86 samples, Shanghai
Variant number
Position
Region
Flanking region
Nucleotide change
dbSNP ID
1
2
3
4c
5
6
7
8
9
10
11
12
13
14c
15c
16
17
18
19
20
21
15
15
14
14
14
14
14
14
Promoter
Promoter
Promoter
Exon 1
Exon 1
Intron 1
Intron 1
Intron 1
Intron 2
Intron 4
Exon 6
Intron 7
Exon 8
Intron 9
Exon 10
3# UTR
3# UTR
3# UTR
3# UTR
3# UTR
3# UTR
CGAGCGGA[C/T]CATGAGGT
CGGGTGTG[A/G]TGGCACACG
ATTAAGAAAG[A/G]TTTTCAACGC
GCAGGAAT[G/C]TGTCATTT
AGTGGATA[A/G]ATCAGTGC
GATGAATG[C/A]TTTATTGTA
ATGCTTTAT[T/A]GTATCAGC
TTTATTGTA[INS]TCAGCAATA
TTAAATGTA[A/T]GTGGATGT
CAAGAGGT[A/G]AGAGTTT
AAAGGTCCT[C/G]CTGGACC
TGTCCATTC[INS-TTA]TATTATATT
GGGGAAAA[G/A]GGGAGTG
TTTTTTTTT[A/T]ACTTTACAGC
TTTACAGCTCC[A/G]TTTACGA
TGCATCATATT[T/G]TCATTCAC
TTTAGATTAC[A/G]GGATTAAT
ACACCTTCAT[G/A]CTTACTAT
ACTTATATGC[T/C]GAATTGAA
AAAGGCCAA[G/C]GGTAATAG
ATCTCAATGT[G/A]CAATAACTTG
C/T
A/G
A/G
G/C
A/G
C/A
T/A
15 bp INDEL
A/T
A/G
C/G
3 bp INDEL
G/A
A/T
A/G
T/G
A/G
G/A
T/C
G/C
G/A
rs416748
rs433235
NA
rs13306541
NA
NA
rs11274081
rs414580
rs13306550
rs3747531
rs3036811
rs13306540
NA
NA
rs12677608
rs12678016
rs12675467
rs13306544
rs13306546
rs918
a
22
34
34
59
59
69
70
70
70
70
70
110
026
742
725
637
468
462
458
196
9534
850
504
639
346
360
888
006
032
116
163
392
Allele frequency among 86 subjects (66 cases and 20 non-cases).
Frequency of 155 alleles.
c
Novel variants identified in this study.
b
Tag SNP
Common name
PRO3
INDEL1
X
X
P275A
INDEL7
X
P346P
X
3# UTR 70006
Allele frequencya (%)
C
A
G
C
G
A
A
þ
A
G
G
A
T
G
G
G
A
C
C
A
38.6
38.1
8.9
0.6
10.6
7.4
7.5
7.5
36.1
11.4
48.1
55.5
1.2
17.9
8.9
3.0
20.0
20.0
20.0
20.0
20.0
Allele frequencyb (%)
G
13.2
þ
12.3
G
37.0
45.9
G
10.4
G
14.4
MSR1 variants and the risks of prostate cancer and benign prostatic hyperplasia
Fig. 1. Twenty-one sequence variants in the MSR1 gene in the Shanghai population.
Table II. Selected characteristics for cancer cases, BPH, and controls
Selected characteristic
Control
Total, n
Age, mean (SD)
Education, n (%)
None
Elementary
Middle school
High school
Graduate and above
Marital status, n (%)
Married
Living together
Widowed
Divorced
Never married
Smoking, n (%)
Non-smoker
Former smoker
Current smoker
Drinking, n (%)
Non-drinker
Former drinker
Current drinker
Differentiation, n (%)
Cannot be assessed
Well differentiated
Moderately differentiated
Poorly differentiated
Missing data
Clinical stage, n (%)
Unstaged
Localized
Regional
Remote
Total PSA, median
Total calories, mean (SD)
WHR, mean (SD)
Body mass index (kg/m2), mean (SD)
Insulin resistance (HOMA-IR), mean (SD)
155
70.8 (8.1)
130
71.9 (7.6)
21 (13.5)
56 (36.1)
38 (24.5)
23 (14.8)
17 (11.0)
9 (6.9)
47 (36.2)
24 (18.5)
25 (19.2)
25 (19.2)
P 5 0.13
11
44
24
25
26
139 (89.7)
3 (1.9)
11 (7.1)
1 (0.6)
1 (0.6)
117 (90.0)
0 (0.0)
11 (8.5)
2 (1.5)
0 (0.0)
P 5 0.49
128 (98.5)
0 (0.0)
2 (1.5)
0 (0.0)
0 (0.0)
P 5 0.05
52 (33.5)
42 (27.1)
61 (39.4)
54 (41.5)
34 (26.2)
42 (32.3)
P 5 0.34
66 (50.8)
24 (18.5)
40 (30.8)
P 5 0.01
86 (55.5)
10 (6.5)
59 (38.1)
93 (71.5)
15 (11.5)
22 (16.9)
P 5 0.0003
84 (64.6)
15 (11.5)
31 (23.8)
P 5 0.02
Cancer
P 5 0.28
BPH
130
68.6 (6.0)
(8.5)
(33.8)
(18.5)
(19.2)
(20.0)
P 5 0.008
P 5 0.11
24 (18.5)
10 (7.7)
40 (30.8)
53 (40.8)
3 (2.3)
1.5
2330.0 (807.0)
0.89 (0.06)
21.7 (3.1)
1.8 (2.0)
1 (0.8)
47 (36.2)
41 (31.5)
41 (31.5)
84.0
2426.1 (619.5)
0.91 (0.05)
21.5 (2.9)
4.8 (8.1)
P
P
P
P
5
5
5
5
0.26
0.005
0.62
0.0001
6.8
2500.3 (670.0)
0.90 (0.05)
22.4 (3.6)
3.7 (6.5)
P
P
P
P
5
5
5
5
0.05
0.06
0.08
0.002
P value for t-test.
P values of Fisher’s exact test comparing control group to cancer and BPH groups separately.
deletion had a 67% reduction in risk (95% 0.16–0.68). Subjects with
both the P275 G allele and INDEL7 deletion had 78% reduced risk of
localized prostate cancer (95% CI 0.10–0.50) Further adjustment for
education, body mass index and WHR did not materially change the
results. We found no association between MSR1 polymorphisms and
BPH risk.
Among control subjects, strong LD was present for four of six
markers (PRO3, INDEL1, P275A and INDEL7), with pairwise D’
values ranging from 0.73 to 1.0. Based on these four tagging variants
(in the order of P275A, INDEL7, P346P and 3# UTR 70006), we
inferred four major haplotypes (Table IV): (i) C-()-A-A,
(ii) G-(þ)-A-A, (iii) C-(þ)-A-A and (iv) C-()-G-G, which accounted for .90% of the all possible haplotype variation (16 altogether) (Table IV). The haplotype frequencies were significantly different
between cancer cases and controls, with a global P value of 0.01 for
advanced cancer and 0.004 for localized cancer. When specific haplotypes were examined, the haplotype G-(þ)-A-A was associated with
a 68% reduced risk of localized cancer (95% CI 0.13–0.59; global
2533
A.W.Hsing et al.
2534
Table III. ORs and 95% CIs for prostate cancer and BPH in relation to six MSR1 variants
Variant (position) and genotypes
Total
PRO3 (14 742)
AA
AG
GG
AG or GG
INDEL1 (14 458)b
þ
þþ
þ or þþ
P275A (22 850)
CC
CG
GG
P trend
CG or GG
INDEL7 (34 504)c
þ
þþ
P trend
þ or þþ
P346P (59 360)
AA
AG
GG
AG or GG
3# UTR (70 006)
AA
AG
GG
AG or GG
Controls
Total prostate cancer
a
a
Advanced prostate cancer
a
95% CI
108
22
0
22
1.00
0.62
—
0.61
Reference
0.34–1.14
—
0.33–1.10
Reference
0.41–1.59
—
0.52–1.87
105
23
0
23
1.00
0.74
—
0.72
Reference
0.41–1.36
—
0.39–1.31
1.00
1.00
1.31
Reference
0.55–1.82
0.56–3.10
1.00
0.86
1.48
Reference
0.50–1.46
0.69–3.17
1.06
0.62–1.88
50
54
21
0.55
75
0.97
0.59–1.61
1.00
1.13
1.56
Reference
0.57–2.23
0.68–3.59
Reference
0.42–1.37
0.88–3.71
1.23
0.64–2.36
33
54
36
0.13
90
1.00
0.76
1.81
0.16–0.68
17
45
18
0.31
36
0.98
0.56–1.72
1.00
0.65
—
0.61
Reference
0.25–1.70
—
0.23–1.57
74
7
0
7
1.00
0.43
—
0.40
Reference
0.18–1.05
—
0.17–0.97
109
20
1
21
1.00
0.86
—
0.84
Reference
0.45–1.65
—
0.45–1.59
1.00
0.57
—
0.55
Reference
0.22–1.46
—
0.23–1.34
56
23
0
23
1.00
1.50
—
1.26
Reference
0.80–2.81
—
0.68–2.32
90
35
3
38
1.00
1.45
—
1.31
Reference
0.81–2.56
—
0.76–2.26
N
155
130
112
38
1
39
96
26
5
31
1.00
0.81
—
0.94
Reference
0.46–1.43
—
0.54–1.62
34
11
1
12
1.00
0.96
—
1.02
Reference
0.44–2.08
—
0.48–2.17
62
14
4
18
1.00
0.67
—
0.84
Reference
0.34–1.34
—
0.44–1.60
115
35
1
36
96
27
5
32
1.00
0.93
—
1.07
Reference
0.52–1.65
—
0.62–1.85
34
11
1
12
1.00
1.06
—
1.12
Reference
0.48–2.31
—
0.52–2.39
61
15
4
19
1.00
0.80
—
0.99
62
48
15
0.16
63
1.00
0.60
0.78
Reference
0.36–1.00
0.35–1.66
1.00
0.24
0.29
Reference
0.11–0.54
0.08–1.07
0.63
0.39–1.02
32
10
3
0.001
13
0.25
0.12–0.52
29
38
12
0.63
50
1.00
0.69
0.89
Reference
0.39–1.21
0.43–1.85
Reference
0.15–0.70
0.12–1.05
0.74
0.43–1.26
21
16
5
0.01
21
1.00
0.33
0.35
101
38
61
23
0.60
84
0.33
120
27
2
29
116
13
0
13
1.00
0.51
—
0.47
Reference
0.25–1.03
—
0.23–0.96
41
6
0
6
112
31
6
37
95
29
1
30
1.00
1.11
—
0.96
Reference
0.62–1.97
—
0.55–1.67
38
6
1
7
90
37
86
25
95% CI
N
OR
95% CI
47
OR, odds ratio.
a
Adjusted for age. P , 0.05; P , 0.01.
b
‘þ’ and ‘’ denote with and without the 15 bp sequence ‘QAATGCTTTATTGTA’, respectively.
c
‘þ’ and ‘’ denote with and without the 3 bp sequence ‘TTA’, respectively.
BPH
ORa
N
56
72
18
OR
Localized prostate cancer
N
OR
95% CI
82
N
130
MSR1 variants and the risks of prostate cancer and benign prostatic hyperplasia
Table IV. ORs and 95% CIs for prostate cancer and BPH in relation to common MSR1 haplotypes
Haplotype
Controls %
Total prostate cancer
%
Four variantsb
Common haplotypes
C-()-A-A
44.2
G-(þ)-A-A
32.4
C-(þ)-A-A
7.3
C-()-G-G
6.3
Rare haplotypes
9.8
Six variantsd
Common haplotypes
A-()-C-()-A-A 34.3
A-()-G-(þ)-A-A 32.0
A-()-C-(þ)-A-A
6.2
G-(þ)-C-()-A-A
9.4
A-()-C-()-G-G
6.2
Rare haplotypes
11.9
a
OR
Localized prostate cancer
a
OR
Advanced prostate cancer
BPH
95% CI
%
95% CI
%
95% CI
%
OR
OR
95% CI
49.4 1.00
23.2 0.67
12.5 1.33
—
—
14.9 0.82
P 5 0.10c
Reference
0.43–1.05
0.71–2.50
—
0.50–1.35
63.2
1.00
13.7
0.28
12.4
0.94
4.0
0.37
6.7
0.53
P 5 0.004c
Reference
0.13–0.59
0.40–2.20
0.08–1.71
0.20–1.42
41.0
1.00
28.8
1.07
12.7
1.72
—
—
17.5
1.17
c
P 5 0.01
Reference
0.63–1.80
0.83–3.56
—
0.66–2.06
39.2 1.00
29.8 1.11
14.2 1.99
5.7 1.00
11.1 1.39
P 5 0.26c
Reference
0.72–1.71
1.06–3.76
0.43–2.32
0.74–2.62
39.4 1.00
22.7 0.66
11.5 1.41
10.2 1.07
—
—
16.2 0.81
P 5 0.15c
Reference
0.41–1.05
0.69–2.89
0.57–2.02
—
0.49–1.34
53.3
1.00
13.8
0.27
12.4
1.04
9.8
0.81
—
—
10.7
0.39
P 5 0.002c
Reference
0.13–0.58
0.42–2.57
0.32–2.09
—
0.18–0.86
31.1
1.00
28.0
1.09
11.1
1.82
10.2
1.31
—
—
19.6
1.25
c
P 5 0.67
Reference
0.62–1.90
0.78–4.21
0.63–2.72
—
0.69–2.24
29.5 1.00
30.4 1.16
14.5 2.21
8.1 0.90
6.1 1.07
11.4 1.24
P 5 0.29c
Reference
0.73–1.83
1.12–4.35
0.44–1.83
0.47–2.43
0.66–2.38
OR, odds ratios.
a
Adjusted for age.
b
Haplotypes of four tagging variants (in the order of P275A, INDEL7, P346P and 3# UTR 70006).
c
_
Global test, OR and 95% CI adjusted for age (categorically, G65,
66–75 and 75þ).
d
Haplotypes of six variants (in the order of PRO3, INDEL1, P275A, INDEL7, P346P and 3# UTR 70006).
P value 5 0.004), relative to the most frequent haplotype (C-()-A-A).
In contrast, the haplotype C-(þ)-A-A was associated with a 1.9-fold
risk of BPH, although the global test was not statistically significant
(P 5 0.26). Since the two non-tagging variants (PRO3 and INDEL1)
were not associated with prostate cancer risk individually, including
these two in the haplotype analysis did not substantially change the
haplotype frequency distribution and risk estimates. There was also no
interaction between these two variants with haplotypes inferred by the
four tagging variants (data not shown). In addition, there was no interaction among any of the MSR1 variants with body mass index,
WHR or insulin resistance in the study.
Discussion
In this population-based study of Chinese men, we used a haplotypetagging approach based on sequencing data to provide a comprehensive
assessment of the association between MSR1 variation and prostate
cancer risk. We found that the MSR1 P346P variant was associated
with a 53% reduced risk of prostate cancer and the P275A and INDEL7
variants were associated with a reduced risk of localized prostate cancer. Haplotype data further support a link between the P275A and
INDEL7 variants and localized prostate cancer. However, we found
no evidence of a clear link between MSR1 variation and BPH risk.
The P346P variant, associated with total and advanced prostate cancer
risk in the study, is a synonymous polymorphism in exon 10. This novel
variant has not been reported previously and its function is unclear. Of
the 21 variants identified by sequencing in this population, P346P was
not strongly linked to any of the other SNPs. It is unclear whether the
association of this variant is linked to other unmeasured variants.
The P275A (a missense change in exon 6) and INDEL7 (4 bp
insertion/deletion of ‘TTA’ in intron 7) variants are more common
and have been reported to be associated with prostate cancer in Caucasians, although the evidence is inconclusive. In our study, both
variants were associated with a significantly reduced risk of localized
prostate cancer risk. The magnitude of the observed associations was
similar to the pooled estimated odds ratios of .1000 Caucasian cases
and controls in a recent meta-analysis (22), although the prevalence of
the minor allele is quite different. For example, the prevalence of the
G allele in the P275A marker was 24% in the meta-analysis of mostly
Caucasian subjects and 58% in our study. The prevalence of the
INDEL 7 ‘þ/ or þ/þ’ was 10.2% in the meta-analysis and 70.9% in
our study. In our study, the risk of prostate cancer associated with
P275A and INDEL7 was more pronounced but did not reach significant interaction, perhaps due to small numbers. It is noteworthy that
the specific haplotype, G-(þ)-A-A, that was associated with a significantly reduced risk contained the minor allele of these two markers,
further suggesting a potential role for these two variants. Given the
nature of the MSR1 protein, the associations between MSR1 P275A
and INDEL7 variants and prostate cancer are biologically plausible.
Although the specific functions of these variants are unclear, preliminary functional data suggest that INDEL7 (the 15 bp insertion/
deletion polymorphism in intron 7) affects transcription of the
MSR1 gene (data not shown). The missense change of P275A could
affect the function of the MSR1 protein because it changes a conserved
residue in the first Gly-X-Y repeat of the collagenous domain of the
protein (23). Thus, it is possible that these variants may be involved in
binding, internalization and processing of a wide range of macromolecules, thereby helping macrophages clean-up cellular debris from
bacterial infection or damaged fats or lipids (23). Recent studies also
suggest that the degree of macrophage infiltration is associated with
prostate cancer prognosis, further strengthening the link between
MSR1 and prostate cancer (19). In addition, inflammation and other
features such as proliferative regeneration of prostate epithelium in
the presence of increased oxidative stress that are associated with
MSR1 expression contribute to the development of prostate cancer.
A recent meta-analysis examining the results of three rare variants
(R293X, S41T and D174Y) and five common variants (PRO3,
INDEL1, IVS5-59, P275A and INDEL7) in eight studies revealed that
most findings are inconsistent and that a mild risk of prostate cancer is
associated with the R293X variant in Caucasian men and with the
D174Y variant found only in African American men (23). Both
R293X and D174Y are rare variants (,2%) and D174Y is found only
in African Americans. In our study of 86 samples, we did not observe
any variation in these two markers. Clearly, there is substantial allelic
variation in the MSR1 gene by race. For example, although the
INVS5-59 marker is considered a common variant in Caucasians,
we did not observe this variant in our study. In addition, the frequency
for the homozygous GG genotype in the PRO3 marker was 14% in
a Caucasian population but only 0.67% in our population (21). In one
study, 12.9% of the Caucasians had the P275A CG genotype, whereas
2535
A.W.Hsing et al.
48% of the Chinese men in our study harbored this genotype. Whether
racial differences in MSR1 variation partly explain the large racial
differences in prostate cancer risk warrants further investigation.
Strengths and limitations of the study should be noted. Selection
and survival biases should be minimal, since .90% of the eligible
cases and controls participated in the study. In addition, demographic
and clinical factors did not differ between interviewed subjects who
did and did not participate in the blood collection. Although not all
study subjects who donated blood had sufficient DNA for genotyping,
both clinical and selected characteristics did not differ between subjects with or without sufficient DNA, further suggesting little selection bias. Misclassification of genotype is also probably minimal as
evidenced by the .99% concordance in duplicate samples. Our assessment of gene–environment interaction was limited by small numbers, such that we may have been unable to detect modest true
interactions. In addition, the population in Shanghai is ethnically
homogeneous, so our results may not be generalizable to other
populations. However, the effect of population stratification (i.e. different genotype frequencies observed may reflect different genetic
background in case subjects and control subjects) is probably to be
minimal.
In summary, this population-based study, conducted in a low-risk
population for prostate cancer, suggests that variants in the MSR1
gene are associated with a lower risk of prostate cancer and provides
some support for the role of inflammation in prostate cancer. Although
we are unable to generalize our results directly to other populations,
similar underlying biological mechanisms may exist for other racial/
ethnic groups. Larger studies in other populations are needed to
confirm our results.
Funding
Intramural Research Program of the National Institute of Health,
National Cancer Institute.
Acknowledgements
We thank J.Cheng of the Shanghai Cancer Institute for specimen collection and
processing; collaborating hospitals and urologists for data collection; pathologists for pathology review; L.Lannom, J.Heinrich and M.Bendel of Westat for
study management and data preparation; G.Yuan of Information Management
Systems and S.Niwa of Westat for data management and analysis and J.Koci of
the Scientific Applications International Corporation for management of the
biologic samples.
Conflict of Interest Statement: None declared.
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Received May 21, 2007; revised July 31, 2007; accepted August 17, 2007