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Dear Sir,

Tsuge et al. recently reported a variable number of tandem repeats (VNTR) polymorphism in the SMYD3 promoter region to be significantly associated with an increased risk of colorectal cancer, hepatocellular carcinoma and breast cancer (BC), suggesting this variant as susceptibility factor for several cancer types.1, 2 In their Japanese case-control study, they investigated 167 BC patients and 365 healthy control subjects and observed homozygosity for the common three-repeat allele (3/3) to be significantly more frequent in patients when compared to controls (OR = 4.48, 95% CI = 2.71–7.41, p = 7.0 × 10−10). Given these findings, we analyzed the effect of this polymorphism on familial BC risk using 515 BC cases and 698 controls. The case cohort comprised unrelated German, female index cases without BRCA1 and BRCA2 mutations (mean age 45.4 ± 10.2). They were collected during the years 1996–2005 through the Institute of Human Genetics (Heidelberg, Germany), the Department of Gynaecology and Obstetrics (Cologne, Germany) and the Department of Medical Genetics (Munich, Germany). According to the German Consortium for Hereditary Breast and Ovarian Cancer,3 BC cases were classified into 5 categories based on family history: (A1) families with 2 or more BC cases including at least 2 cases with onset below the age of 50 years (38.8%); (A2) families with at least 1 male BC case (0.4%); (B) families with at least 1 breast and 1 ovarian cancer case (25.0%); (C) families with at least 2 BC cases including 1 case diagnosed before the age of 50 years (26.6%); (D) families with at least 2 BC cases diagnosed after the age of 50 years (9.1%). The categories A1 and B were considered as high-risk categories because of the stringent family history inclusion criteria and high BRCA1/2 mutation frequencies in German breast/ovarian cancer families when compared to the remaining categories (category A1: 37%; category B: 53%).3 Among the familial BC cohort, 329 unrelated German women were high-risk cases (mean age 44.1 ± 9.6). All women gave written consent to the molecular analysis of the BRCA1/2 and potential new BC susceptibility genes. Their DNAs were prepared from blood by a conventional phenol–chloroform protocol. Mutations in the open reading frame of BRCA1 and BRCA2 were excluded by applying denaturing high performance liquid chromatography on all exons, followed by direct sequencing of conspicuous exons. The control series consisted of healthy, unrelated German, female blood donors (mean age 47.8 ± 12.4), recruited in 2004 and 2005 by the Institute of Transfusion Medicine and Immunology (Mannheim, Germany) and sharing the ethnic background with the BC patients. According to the German guidelines for blood donation, all blood donors were examined by a standard questionnaire. All blood donors consented to the use of their isolated DNA samples for research studies. The study was approved by the Ethics Committee of the University of Heidelberg (Heidelberg, Germany). Genotyping of the SMYD3 VNTR polymorphism was performed by direct sequencing following standard PCR amplification. Primer sequences were SMYD3_F: 5′-GCC TGT CTT CTG CGC AGT CG-3′ and SMYD3_R: 5′-ACC TTC AGC GGC TCC ATC CTC-3′.

In contrast to the observation of Tsuge et al.,1 we observed an equal distribution of SMYD3 VNTR genotypes among familial BC cases and controls, indicating lack of association (OR = 0.96, 95% CI = 0.74–1.26; p = .78, Table I). Nor did we find an increase of homozygosity for the common 3-repeat allele among high-risk familial BC cases (OR = 0.96, 95% CI = 0.70–1.30, p = .77; Table I). One possible explanation to the contradictory results may be in different study populations, which should be studied further.

Table I. Genotype Frequencies for The SMYD3 Promoter Variant (2, Two-Repeat Allele; 3, Three-Repeat Allele) in Unrelated German BRCA1/2 Mutation-Negative Familial and High-Risk Familial Breast Cancer Patients and Healthy, Unrelated Female Control Subjects
GenotypeControl subjects N (%)Familial BC cases N (%)High-risk familial BC cases N (%)
  1. Genotype-specific odds ratios (OR), 95% confidence intervals (95% CI) and p values were computed by unconditional logistic regression using a tool offered by the Institute of Human Genetics, Technical University Munich, Germany (http://ihg.gsf.de/cgi-bin/hw/hwa1.pl). Hardy-Weinberg equilibrium test was undertaken using Pearson's goodness-of-fit χ2 test with one degree of freedom. Genotype frequencies analyzed were in agreement with Hardy-Weinberg expectations (control subjects: p = 0.94; familial BC cases: p = 0.33; high-risk familial BC cases: p = 0.47).

2/211 (1.6)6 (1.2)4 (1.2)
2/3155 (22.2)120 (23.3)77 (23.4)
3/3532 (76.2)389 (75.5)248 (75.4)
Σ698515329
[3/3] vs. [2/3 + 2/2]   
χ2 0.080.09
OR (95% CI) 0.96 (0.74–1.26)0.96 (0.70–1.30)
P value 0.780.77

The strengths of the present study include a sound sample size and a homogeneous study cohort of a single ethnic group, comprising women selected for familial BC. Only BRCA1 and BRCA2 mutation-negative familial BC cases were considered to avoid the effects caused by these high-penetrance susceptibility genes. The power of an association study based on cases with a family history of the disease is at least twice higher when compared to a study using unselected cases,4, 5 emphasizing the significance of our study. Analyses of cases with an extended family history, such as cases associated with the high-risk categories A1 and B, involve a further substantial improvement of power.5 In recent case-control studies, an increase of genotype effects has been observed when exclusively examining high-risk cases.6, 7, 8, 9

Given the power of our study, the hypothesis proclaiming the SMYD3 VNTR polymorphism as a risk factor for human cancers might be worth reconsidering.

Yours sincerely,

References

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  • 1
    Tsuge M, Hamamoto R, Silva FP, Ohnishi Y, Chayama K, Kamatani N, Furukawa Y, Nakamura Y. A variable number of tandem repeats polymorphism in an E2F-1 binding element in the 5′ flanking region of SMYD3 is a risk factor for human cancers. Nat Genet 2005; 37: 11047.
  • 2
    Hamamoto R, Furukawa Y, Morita M, Iimura Y, Silva FP, Li M, Yagyu R, Nakamura Y. SMYD3 encodes a histone methyltransferase involved in the proliferation of cancer cells. Nat Cell Biol 2004; 6: 73140.
  • 3
    Meindl A. German consortium for hereditary breast and ovarian cancer. Comprehensive analysis of 989 patients with breast or ovarian cancer provides BRCA1 and BRCA2 mutation profiles and frequencies for the German population. Int J Cancer 2002; 97: 47280.
  • 4
    Houlston RS, Peto J. The future of association studies of common cancers. Hum Genet 2003; 112: 4345.
  • 5
    Antoniou AC, Easton DF. Polygenic inheritance of breast cancer: implications for design of association studies. Genet Epidemiol 2003; 25: 190202.
  • 6
    Wirtenberger M, Tchatchou S, Hemminki K, Klaes R, Schmutzler RK, Bermejo JL, Chen B, Wappenschmidt B, Meindl A, Bartram CR, Burwinkel B. Association of genetic variants in the Rho guanine nucleotide exchange factor AKAP13 with familial breast cancer. Carcinogenesis 2005; Oct 18 [Epub ahead of print].
  • 7
    Frank B, Klaes R, Burwinkel B. Familial cancer and ARLTS1. N Engl J Med 2005; 353: 3134.
  • 8
    Frank B, Hemminki K, Meindl A, Wappenschmidt B, Klaes R, Schmutzler RK, Untch M, Bugert P, Bartram CR, Burwinkel B. Association of the ARLTS1 Cys148Arg variant with familial breast cancer risk. Int J Cancer, in press.
  • 9
    Frank B, Hemminki K, Wappenschmidt B, Meindl A, Klaes R, Schmutzler RK, Bugert P, Untch M, Bartram CR, Burwinkel B. Association of the CASP10 V410I variant with reduced breast cancer risk and interaction with the CASP8 D302H variant. Carcinogenesis 2005; Oct 26 [Epub ahead of print].

Bernd Frank, Kari Hemminki, Barbara Wappenschmidt, Rüdiger Klaes, Alfons Meindl, Rita K. Schmutzler, Peter Bugert, Michael Untch, Claus R. Bartram, Barbara Burwinkel.