Lack of replication for the association between HER2 I655V polymorphism and breast cancer risk: a systematic review and meta-analysis

BACKGROUND

Multiple epidemiological studies have investigated rs1136201, a non-synonymous polymorphism of the human epidermal growth factor receptor-2 gene (HER2) resulting in the substitution of valine for isoleucine at codon 655 (Ile655Val) of the HER2 protein, as a risk factor for breast cancer.

METHODS

We searched multiple databases to identify genetic association studies investigating the effect of rs1136201 on breast cancer risk. For each study we calculated unadjusted odds ratios (ORs) with their variance under additive, dominant, recessive and allele-frequency genetic models. Summary ORs with their corresponding confidence interval (CI) were calculated using random effects models.

RESULTS

Based on the 33 case-control studies reporting data for the additive genetic model (20,461 cases/23,832 controls) we did not find evidence of an association between rs1136201 and breast cancer, OR=1.05 (95% CI, 0.99-1.11), with significant between-study heterogeneity (p(Q)<0.001; I(2)=49%). Smaller studies produced more extreme results compared to larger studies (p=0.001). Studies in which genotyping was not blind to case-control status (p=0.01), studies not reporting the use of genotyping quality control (p=0.01), and studies using RFLP-based methods (p=0.01) produced significant associations. Meta-regression results confirmed that there was a significant interaction between lack of quality control (p=0.04) and lack of blinding (p=0.04) and the genetic effect of rs1136201 on breast cancer risk.

CONCLUSIONS

It is unlikely that HER2 rs1136201 is a risk factor for breast cancer. Laboratory artifacts, lack of genotyping quality control or blinding and publication bias appear to have influenced the results published to date and need to be addressed in the design of future studies.

A Haplotype Analysis of HER-2 Gene Polymorphisms: Association with Breast Cancer Risk, HER-2 Protein Expression in the Tumor, and Disease Recurrence in Korea

PURPOSE

A single-nucleotide polymorphism (SNP) in codon 655 of HER-2 has been extensively studied with inconclusive results. The purpose of this study was to investigate the association between common variants of HER-2 and breast cancer risk, HER-2 expression, and survival using a haplotype-based stepwise approach.

EXPERIMENTAL DESIGN

Twenty-nine SNPs listed in the National Center for Biotechnology Information database were screened to identify novel polymorphisms of HER-2 gene in 90 healthy Korean women. Six of 29 SNPs were polymorphic and had greater than 10% of minor allele frequencies. Using these six SNPs, linkage disequilibrium and haplotype patterns were characterized. We tested association between the haplotypes and breast cancer in a large case-control study (n=1,039 cases and 995 controls). Six-hundred two breast cancer patients with follow-up at least 24 months were analyzed for outcome in relation to haplotype. Expression of HER-2 protein was determined by immunohistochemistry in 1,094 cases of invasive breast cancer.

RESULTS

All six SNPs showed a strong linkage disequilibrium pattern and were considered to belong to one haplotype block. Two haplotype-tagging SNPs (I655V and P1170A) for three common haplotypes (>5%) were genotyped in cases and controls. The haplotypes and individual SNPs were not associated with breast cancer risk. In patients with at least one copy of haplotype I (the most common haplotype), HER-2 expression was 1.5 times higher (P = 0.009) and the prognosis was worse (P = 0.032) compared with patients without having that haplotype.

CONCLUSIONS

Our results suggest that the currently identified genetic polymorphisms of HER-2 are not associated with an increased risk of breast cancer in Korean women, whereas one haplotype does affect protein expression of the tumor and disease outcome.

A case-control study of the HER2 Ile655Val polymorphism in relation to risk of invasive breast cancer

Background

Overexpression of the HER2 proto-oncogene in human cancer cells has been associated with a poor prognosis, and survival improves with therapy targeting the HER2 gene. Animal studies and protein modeling suggest that the Ile655Val polymorphism located in the transmembrane domain of the HER2 protein might influence breast cancer development by altering the efficiency of homodimerization.

Methods

To investigate this genetic polymorphism, incident cases of invasive breast cancer (N = 1,094) and population controls of a similar age (N = 976) were interviewed during 2001 to 2003 regarding their risk factors for breast cancer. By using DNA collected from buccal samples mailed by the participants, the HER2 Ile655Val polymorphism was evaluated with the Applied Biosystems allelic discrimination assay. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated by logistic regression adjusted for numerous breast cancer risk factors. Analysis was restricted to women with self-reported European descent.

Results

Prevalence of the Val/Val genotype was 5.6% in cases and 7.1% in controls. In comparison with the Ile/Ile genotype, the Ile/Val genotype was not significantly associated with breast cancer risk (OR 0.97, 95% CI 0.79 to 1.18), whereas the Val/Val genotype was associated with a reduced risk (OR 0.63, 95% CI 0.42 to 0.92). This inverse association seemed strongest in older women (OR 0.51, 95% CI 0.29 to 0.89 for women aged more than 55 years), women without a family history of breast cancer (OR 0.54, 95% CI 0.35 to 0.84), postmenopausal women with greater body mass index (OR 0.43, 95% CI 0.20 to 0.91 for a body mass index of 25.3 kg/m² or more), and cases diagnosed with non-localized breast cancer (OR 0.49, 95% CI 0.26 to 0.90).

Conclusion

Although results from our population-based case-control study show an inverse association between the HER2 Ile655Val polymorphism and risk of invasive breast cancer, most other studies of this single-nucleotide polymorphism suggest an overall null association. Any further study of this polymorphism should involve sample populations with complete risk factor information and sufficient power to evaluate gene-environment interactions between the HER2 polymorphism and factors such as age and family history of breast cancer.

HER2 codon 655 polymorphism and breast cancer: results from kin-cohort and case?control analyses

Several published epidemiologic studies show increased breast cancer risk for carriers of the Val-allele at codon 655 of the HER2 gene. We conducted additional analyses using data from three studies, including case-control analyses stratified on age and kin-cohort analyses using relatives of cases and controls. The results provide additional evidence that HER2 codon 655 genotype may predispose to early-onset breast cancer.

Her2 V655 genotype and breast cancer progression in Korean women

The amplification and overexpression of Her2 proto-oncogene have been found to be associated with the development and progression of human breast cancer. A polymorphic valine allele at codon 655 of the Her2 gene (Her2(V655)) was suggested by some authors to be a susceptible genetic factor for the development of breast cancer. The Her2 polymorphism at codon 655 was investigated in 304 Korean women including 177 patients with breast cancer. The association between Her2 genotype and Her2 protein overexpression was also examined in breast cancers by immunohistochemistry. Her2(V655) was not associated with a significant breast cancer risk (odds ratio (OR), 1.792; 95% confidence interval (CI), 0.459-6.991). The frequency of homozygous or heterozygous valine allele increased in stage 2 patients (OR, 1.67; 95% CI, 0.67-4.19), and patients in stages 3 and 4 (OR, 3.36; 95% CI, 0.85-13.42) compared to patients in stage 0. However, an association between the presence of the valine allele and the overexpression of Her2 protein could not be demonstrated. These results suggest that Her2 polymorphism at codon 655 is not associated with the development of breast cancer in Korean women. However, there is a possibility that the valine allele at codon 655 might be related to increased risk of breast cancer progression.

Ile to Val polymorphism at codon 655 of HER-2 gene and breast cancer risk in Iranian women

The earlier reports on the association between the Ile to Val polymorphism at codon 655 of HER-2 and susceptibility to breast cancer has not been found to hold true for all ethnic populations. Two hundred and four cases and 138 controls were collected to investigate the association of HER-2 Ile655Val polymorphism with the risk of breast cancer development and progression in Iranian population. This association was not found to be significant in the present study (OR = 1.16, 95% CI: 0.67-2.03). The association between HER-2 genotypes frequency and clinicopathological data was also insignificant, suggesting that the HER-2 polymorphism at codon 655 is unlikely to be a susceptibility locus in Iranian patients with breast cancer.

HER2 codon 655 polymorphism and risk of breast cancer in African Americans and whites

BACKGROUND

Several recent epidemiologic studies examined the association between breast cancer risk and an inherited, single-nucleotide polymorphism in the HER2 gene, codon 655 G to A, which leads to an amino acid substitution of Ile to Val. Results of previous studies have been mixed, with most studies showing no association but some suggesting an association in younger women or women with a family history of breast cancer.

METHODS

We conducted an association study of HER2 codon 655 genotype and breast cancer within the Carolina Breast Cancer study, a population-based, case-control study of in situ and invasive breast cancer in African American and white women in North Carolina. A total of 2015 cases and 1808 controls were genotyped.

RESULTS

We observed no overall association between HER2 genotype and breast cancer. However, a modest positive association (OR = 2.3, 95% CI 1.0-5.3) was observed for Val/Val + Ile/Val versus Ile/Ile genotypes in women age 45 or younger with a family history of breast cancer. Val/Val homozygotes were more common among cases with in situ versus invasive disease (P = 0.002). Breast tumors from women with Val/Val genotype were more likely to exhibit HER2 overexpression, but the results were not statistically significant (P = 0.17).

CONCLUSIONS

The HER2 codon 655 polymorphism may be one of many low-penetrant genes that make a minor contribution to breast cancer, particularly in subgroups of women. Additional large studies, as well as data pooling, will be needed to estimate the contribution of such genes to breast cancer risk.

No association between HER-2 gene polymorphism at codon 655 and a risk of bladder cancer

The amplification and overexpression of the human epidermal growth factor receptor 2 gene HER-2 (also known as c-erb-B2 or neu) have been shown to be associated with bladder cancer and its progression. Recent studies indicated an association between the Ile to Val polymorphism at codon 655 of HER-2 and susceptibility to breast cancer. To investigate the correlation between the Ile/Val polymorphism and the susceptibility and progression of bladder cancer, we analyzed the polymorphism in 232 patients with transitional cell carcinoma of the bladder and 408 normal controls. The frequencies of the Ile/Ile, Ile/Val and Val/Val genotype were 75.9%, 21.6% and 2.6%, respectively, in patients with bladder cancer and 75.7%, 23.0% and 1.2%, respectively, in controls. Statistical analyses of the genotype prevalence showed no significant difference between bladder cancer patients and normal controls (p = 0.419). Moreover, no significant differences in the genotype prevalence were observed when the patients were stratified according to the tumor grade, stage and smoking habits. When the Ile/Ile genotype was compared to the Ile/Val and Val/Val genotypes, a significant difference was found only between the patients with tumor stage Ta and those with T1-4 (age, gender and smoking habits-adjusted odds ratio = 2.13, 95% confidence interval = 1.09-4.15, p = 0.027). When the Ile/Ile + Ile/Val genotypes compared to the Val/Val genotype, no significant findings were observed. These results suggested that the HER-2 polymorphism at codon 655 is unlikely to be associated with the onset of bladder cancer. Furthermore, the findings suggest no association between this polymorphism and the disease progression in bladder cancer, although the possibility remains that the Ile/Ile genotype may be related to an increased risk of disease progression.

Distribution of HER2(V655) genotypes in breast cancer cases and controls in the United States

The minor variant frequency of a HER2 polymorphism (HER2(V655)) has been determined for 471 United States women enrolled in a multiracial case-control study. Allelic frequencies varied significantly by race. Genotypic distributions showed no excess breast cancer risk associated with inheritance of HER2(V655) either as carriers (OR=1.2, 95% CI=0.8-1.9), heterozygotes (OR=1.2, 95% CI=0.8-1.9), or homozygotes (OR=1.4, 95% CI=0.4-4.2). Nor was there a significant association when each racial group was considered separately. The current study suggests the HER2(V655) allele is not a breast cancer risk factor for Caucasians, African-Americans, or Latinas.