Population-based, case-control study of HER2 genetic polymorphism and breast cancer risk

Transmembrane helix-helix interactions involved in ErbB receptor signaling

Among the many transmembrane receptor classes, the receptor tyrosine kinases represent an important superfamily, involved in many cellular processes like embryogenesis, development and cell division. Deregulation and dysfunctions of these receptors can lead to various forms of cancer and other diseases. Mostly, only fragmented knowledge exists about functioning of the entire receptors, and many studies have been performed on isolated receptor domains. In this review we focus on the function of the ErbB family of receptor tyrosine kinases with a special emphasis on the role of the transmembrane domain and on the mechanisms underlying regulated and deregulated signaling. Many general aspects of ErbB receptor structure and function have been analyzed and described. All human ErbBs appear to form homo- and heterodimers within cellular membranes and the single transmembrane domain of the receptors is involved in dimerization. Additionally, only defined structures of the transmembrane helix dimer allows signaling of ErbB receptors.

Polymorphisms in the BRCA1 and ABCB1 genes modulate menopausal hormone therapy associated breast cancer risk in postmenopausal women

Menopausal hormone therapy (HT) is associated with an increased breast cancer risk among postmenopausal women. In this study, we investigated genetic effect modification of HT associated breast cancer risk in 3,149 postmenopausal breast cancer patients and 5,489 controls from the two German population-based case-control studies MARIE and GENICA. Twenty-eight polymorphisms of 14 candidate genes including two drug and hormone transporter genes (ABCB1/MDR1 and SHBG), four genes involved in cell cycle regulation (BRCA1, P21/CDKN1A, STK15/AURKA and TP53), six cytokine genes (IGFBP3, IL6, TGFB1, TNF, LTA and IGF1), and two cytokine receptor genes (EGFR and ERBB2) were genotyped using validated methods. Conditional logistic regression was used to assess multiplicative statistical interaction between polymorphisms and duration of estrogen-progestagen therapy and estrogen monotherapy use with regard to breast cancer risk assuming log-additive and co-dominant modes of inheritance. Women homozygous for the major ABCB1_rs2214102_G allele were found to be at a significantly increased breast cancer risk associated with combined estrogen-progestagen therapy [odds ratio (OR) = 1.17, 95% confidence interval (CI) = 1.12-1.23, P (interaction) = 0.022]. Additionally, risk associated with estrogen monotherapy was modified by BRCA1_rs799917. We observed a trend with increasing minor T alleles leading to the highest risk in homozygous carriers of the minor allele [OR (95% CI) = 1.17 (0.98-1.39), 1.06 (0.98-1.14), and 1.02 (0.94-1.11) for homozygous minor, heterozygous, and homozygous major allele carriers, respectively; P (interaction) = 0.032]. Our results suggest that genetic variants in ABCB1 and BRCA1 may modify the effect of HT on postmenopausal breast cancer risk.

The effects of obesity and HER-2 polymorphisms as risk factors for endometrial cancer in Korean women

OBJECTIVE

To evaluate the relationship between single nucleotide polymorphisms (SNPs) in the HER-2 gene, body mass index (BMI) and the risk of endometrial cancer.

DESIGN

Case-control study.

SETTING

Medical centres in Korea.

SAMPLE

DNA samples and medical histories were obtained from 125 endometrial cancer cases and 302 controls.

METHODS

The genotypes evaluated in HER-2 at positions -423, -655, -776, -857, -1170, -1177, -1253 of the coding region and two SNPs located in an intron by SNP-IT assay using SNPstream Ultra-high throughput system.

MAIN OUTCOME MEASURES

Odd ratio for endometrial cancer associated with HER-2 polymorphisms and BMI.

RESULTS

Cases had a significantly higher BMI than controls and the obese subjects had a 2.65-fold increased risk for endometrial cancer. However, HER-2 polymorphism was not associated significantly with the risk of endometrial cancer. Subjects with BMI > or = 25 kg/m2 who carried rs1801200 AA, rs1801200 GA/GG, rs1810132 CT/CC, rs2517951 CT/TT and rs1058808 CG/GG genotype had significantly increased risk of endometrial cancer than subjects with a normal BMI (P for linear trend <0.05). However, the risk in the subjects with the variant allele for HER-2 genotypes did not differ significantly compared to those with homozygous wild-type allele within specific BMI subgroups.

CONCLUSIONS

Endometrial cancer risk increased significantly in proportion to BMI. However, HER-2 polymorphism did not affect significantly on the risk of endometrial cancer.

Heritable variation of ERBB2 and breast cancer risk

Amplification of the epithelial growth factor receptor gene ERBB2 (HER2, NEU) in breast cancer is associated with a poor clinical prognosis. In mammary gland development, this receptor plays a role in ductal and lobuloalveolar differentiation. We conducted a systematic investigation of the role of genetic variation of the ERBB2 gene in breast cancer risk in a study of 842 histologically confirmed invasive breast cancer cases and 1,108 controls from the Shanghai Breast Cancer Study. We observed that the ERBB2 gene resides within a locus of high linkage disequilibrium, composed of three major ancestral haplotypes in the study population. These haplotypes are marked by simple tandem repeat and single nucleotide polymorphisms, including the missense variants I655V and P1170A. We observed a risk-modifying effect of a highly polymorphic simple tandem repeat within an evolutionarily conserved region, 4.4 kb upstream from the ERBB2 transcription start site. Under a dominant genetic model, the age-adjusted odds ratio was 1.74 (95% confidence interval, 1.27-2.37). Its association with breast cancer, and with breast cancer stratified by histology, by histologic grade, and by stage, remained significant after correction for multiple comparisons. In contrast, we observed no association of ERBB2 single nucleotide polymorphism haplotypes with breast cancer predisposition.

RET finger protein expression in invasive breast carcinoma: relationship between RFP and ErbB2 expression

RET finger protein (RFP), which belongs to the large B-box RING finger protein family, has been reported to be expressed in breast carcinoma cell lines. We conducted this study to evaluate the expression level of RFP in breast carcinomas. Tissue microarrays were constructed from 133 cases of invasive breast carcinoma. Sections obtained from tissue arrays and whole sections from 10 non-neoplastic breast tissues were stained for ER, PR, ErbB2, and RFP using immunohistochemistry, and ErbB2 gene status was evaluated by FISH. The correlation between various immunohistochemical markers was determined. We found nuclear RFP expression in 41.4% of invasive carcinomas and in none of the non-neoplastic breast tissues. We also stained whole sections of 29 cases of invasive breast carcinoma, which included the TMA study, and 10 cases of ductal carcinoma in situ (DCIS) by RFP. We observed that four (40%) of the DCIS cases were positive with RFP. In statistical analysis, there was a significant, positive association between RFP and ErbB2 status at the protein level (p=0.002) and the gene level (p=0.049). There was no statistically significant association between the expression of RFP and tumor size, LN status, ER, PR, and grade (p>0.05). However, we found a significant association between age and RFP expression. RFP expression was stronger in patients 50 years or older (p=0.048). In our study, the expression of RFP correlated strongly with ErbB2 status. Our study is the first in the literature to show expression of RFP in patients with breast carcinoma. However, the possible role of RFP in breast carcinogenesis needs to be investigated in more detailed clinical and experimental studies.

The genetic polymorphisms of HER-2 and the risk of lung cancer in a Korean population

Background

Human Epidermal Growth Factor Receptor 2 (HER-2; also known as erbB-2 or neu), a proto-oncogene of the receptor tyrosine kinase superfamily, has been associated with carcinogenesis and prognosis of human cancers, acting as a binding partner of other epidermal growth factor receptor (EGFR) family in the activation of EGFR signaling. Amplification of the HER-2 gene has been reported in lung cancer, where it has been associated with poor prognosis. In this study, we investigated whether the four polymorphisms (-3444C>T, -1985 G>T, I655A A>G and P1170A C>G) of the HER-2 gene are associated with the risk of lung cancer in Korean populations.

Methods

The frequencies of 4 polymorphisms of the HER-2 gene were examined by the polymerase chain reaction-restriction fragment length polymorphism or the single-nucleotide polymorphism-identification technology assay in the 407 lung cancer patients and 407 healthy controls.

Results

The frequencies of the 4 polymorphisms were not significantly different between patient and control groups in overall subjects. However, in the subgroup analysis, the 3 single nucleotide polymorphisms (-3444C>T, -1985G>T and P1170A C>G) showed statistically significant differences in the subgroups of females, non-smokers, and non-drinkers (p < 0.05). Additionally, we found the association between the risk of lung cancer and the polymorphisms of HER-2 gene in non-smoker subgroups with adenocarcinoma (p < 0.05).

Conclusion

Our results suggest that the polymorphisms of the HER-2 gene are associated with an increased susceptibility to lung cancer in females, non-smokers and non-drinkers subgroups in the Korean population.

The Val allele of HER-2 codon 655 predicts the progression of oral squamous cell carcinoma

HER-2 proto-oncogene is important for oral carcinogenesis. HER-2 codon 655 polymorphism, either isoleucine (Ile: ATC) or valine (Val: GTC), was associated with the risk of breast carcinoma. This study investigated the clinicopathological implications of this polymorphism in oral carcinoma. We found that 79% of oral carcinoma patients had A/A (Ile/Ile) genotype and 21% had A/G (Ile/Val) genotype, with a G (Val) allelic frequency of 0.10. Univariate analysis indicated a significantly higher Val allelic frequency in cases having nodal metastasis or tumor recurrence; and Val allele was associated with poorer recurrence-free survival of patients. Multivariate analysis after adjusting confounding factors by logistic regression analysis indicated that patients carrying Val allele had a 8.79- and 4.25-fold higher risk for nodal metastasis and recurrence, respectively. Using Cox proportional hazard model, the risk of tumor recurrence was 3.35-fold higher in patients carrying Val allele. This is the first report demonstrating that the Val allele of HER-2 codon 655 could be an independent predictor for oral carcinoma progression.

Focus on ERBB2

The ERBB2 (HER2) gene codes for a tyrosine kinase receptor that activates pathways involved in cell division, differentiation and apoptosis. Gene amplification, and as a result protein overexpression, are commonly seen in breast tumors and correlate with poor prognosis. The overexpressed protein is the target of trastuzumab, a monoclonal antibody routinely used in clinical practice. A new tyrosine kinase inhibitor, lapatinib, is already an alternative in women progressing despite treatment with trastuzumab. Using comprehensive tagging approaches, highly-powered association studies concluded that ERBB2 was unlikely to be a breast cancer predisposition gene. ERBB2 pharmacogenomics are of little relevance at present, since we have no knowledge of polymorphisms in the gene that could affect the binding, efficacy or tolerability of trastuzumab or lapatinib. There is minor contribution from hepatic cytochrome CYP2C19 to the metabolism of lapatinib, whereas in vitro studies have shown the drug to be a substrate for the transporter P-glycoprotein. If, and how, the pharmacokinetics of lapatinib would be altered in individuals carrying polymorphisms in CYP2C19 or ABCB1 – the gene that codes for the P-glycoprotein – is yet to be determined.

Effect of deleterious nsSNP on the HER2 receptor based on stability and binding affinity with herceptin: a computational approach

In this study, we identified the most deleterious non-synonymous SNP of ERBB2 (HER2) receptors by its stability and investigated its binding affinity with herceptin. Out of 135 SNPs, 10 are nsSNPs in the coding region, in which one of the nsSNP (SNPid rs4252633) is commonly found to be damaged by I-Mutant 2.0, SIFT and PolyPhen servers. With this effort, we modelled the mutant HER2 protein based on this deleterious nsSNP (rs4252633). The modeled mutant showed less stability than native HER 2 protein, based on both total energy of the mutant and stabilizing residues in the mutant protein. This is due to a deviation between the mutant and the native HER2, having an RMSD of about 2.81 A. Furthermore, we compared the binding efficiency of herceptin with native and mutant HER2 receptors. We found that herceptin has a high binding affinity with mutant HER2 receptor, with a binding energy of -24.40 kcal/mol, as compared to the native type, which has a binding energy of -15.26 kcal/mol due to six-hydrogen bonding and two salt bridges exist between herceptin and the mutant type, whereas the native type establishes four hydrogen bonds and two salt bridges with herceptin. This analysis portrays that mutant type has two additional hydrogen bonds with herceptin compared with the native type. Normal mode analysis also showed that the two amino acids, namely Asp596 and Glu598 of mutant HER2, forming additional hydrogen bonding with herceptin, had a slightly higher flexibility than the native type. Based on our investigations, we propose that SNPid rs4252633 could be the most deleterious nsSNP for HER2 receptor, and that herceptin could be the best drug for mutant compared to the native HER2 target.

In Search of Breast Cancer Culprits: Suspecting the Suspected and the Unsuspected

I would like to welcome breast cancer research community to the first editorial of our newest journal “Breast Cancer: Basic and Clinical Research”. In pursuit of breast cancer culprits, we have come a long way since the early 90's when the first breast cancer susceptibility gene BRCA1 was mapped and cloned. In the past few years, several new loci associated with the various degree of breast cancer risk have been identified using “Candidate Gene Association Study (CGAS) and Genome-Wide Association Study (GWAS)” approaches. This editorial is meant to quickly glance over recent findings of these population-based association studies.

Role of the HER2 [Ile655Val] genetic polymorphism in tumorogenesis and in the risk of trastuzumab-related cardiotoxicity

BACKGROUND

To examine the impact of a frequent her2 gene polymorphism (Ile655Val) on tumor growth and on the pharmacodynamics of treatment by trastuzumab.

PATIENTS AND METHODS

Experimental study: The growth characteristics of cells expressing the Ile or Val isoform were examined in vitro and after injection into nude mice. The effect of trastuzumab was determined in both experimental models. Clinical study: 61 patients with advanced breast cancers and treated by trastuzumab were genotyped for HER2 by PCR-RFLP. The influence of HER2 genotype on the trastuzumab treatment was examined.

RESULTS

Experimental study: HER2-expressing cells acquired the characteristics of tumor cells. The Val isoform-expressing cells showed the highest growth capacity and developed aggressive tumors sensitive to trastuzumab. Clinical study: There was no link between tumor response or survival and HER2 genotype. All cases of treatment-related cardiotoxicity were found in the Ile/Val group and there was no cardiac toxicity in the Val/Val and Ile/Ile patients.

CONCLUSIONS

This study establishes a clear-cut difference between the two HER2 isoforms regarding their tumorogenic potential with an advantage for the Val/HER2 isoform. In breast cancer patients treated with trastuzumab, the presence of a Val allele may constitute a risk factor for cardiac toxicity.

Increased survival in dogs with malignant mammary tumours overexpressing HER-2 protein and detection of a silent single nucleotide polymorphism in the canine HER-2 gene

The aims of this study were to explore the relationship between clinical outcome and HER-2 protein expression in dogs with malignant mammary tumours after surgery and to determine the sequence of the HER-2 gene. Tissues from 91 dogs diagnosed with malignant mammary tumours, six with benign lesions and two normal mammary glands were analysed for the expression of HER-2 by immunohistochemistry (IHC). Exons 14-18 of the HER-2 gene were amplified by reverse transcriptase polymerase chain reaction and sequenced in 19 tumours with IHC scores >2+; larger coding regions of HER-2 were analysed in five tumours. HER-2 protein overexpression was found in 27/91 (29.7%) of canine malignant mammary tumours. Dogs with HER-2-overexpressing malignant mammary tumours tended to have a higher survival rate than those that expressed a normal level of HER-2 within 2 years of surgery. In 3/19 cases, HER-2 sequences had a single nucleotide polymorphism, T(1725)C, with no change in the amino acid identity (Cys). No other sequence aberration of HER-2 was found.

ERBB2 genetic polymorphism and breast cancer risk in Chinese women: a population-based case-control study

A polymorphism at codon 655 (ATC/isoleucine to GTC/valine [Ile655Val], rs1801200) in the transmembrane domain-coding region of human ERBB2 gene has been previously evaluated for its association with breast cancer risk with mixed results. We evaluated this polymorphism in association with breast cancer in a group of women who participated in a large-scale, population-based, case-control study of breast cancer in Shanghai, China, followed by an in vitro analysis of the function of this polymorphism. Genomic DNA from 3,012 patients with breast cancer and 3,004 healthy controls was examined for the Ile655Val polymorphism using a TaqMan genotyping method. Adjusted odds ratios (OR) were derived from multiple logistic regression. In vitro analyses were carried out to examine whether the Ile655Val polymorphism affect ERBB2 expression and the activity of its downstream targets. Approximately 2% of study subjects carry the Val/Val genotype. Compared with women with the Ile/Ile (76%) genotype, women who had the Ile/Val (22%) or Val/Val genotype did not have an elevated risk of breast cancer. Stratified analyses by age and menopausal status revealed no apparent association with this polymorphism in any subgroups of women. In a serious of biochemical analyses, we found that the Ile655Val substitution did not alter ErbB2 and its downstream signaling molecule activity. These study results suggest that Ile655Val polymorphism of the ERBB2 gene do not alter its activity and may not be associated with increased breast cancer risk among Chinese women.

The oncogene HER2: its signaling and transforming functions and its role in human cancer pathogenesis

The year 2007 marks exactly two decades since Human Epidermal Growth Factor Receptor-2 (HER2) was functionally implicated in the pathogenesis of human breast cancer. This finding established the HER2 oncogene hypothesis for the development of some human cancers. The subsequent two decades have brought about an explosion of information about the biology of HER2 and the HER family. An abundance of experimental evidence now solidly supports the HER2 oncogene hypothesis and etiologically links amplification of the HER2 gene locus with human cancer pathogenesis. The molecular mechanisms underlying HER2 tumorigenesis appear to be complex and a unified mechanistic model of HER2-induced transformation has not emerged. Numerous hypotheses implicating diverse transforming pathways have been proposed and are individually supported by experimental models and HER2 may indeed induce cell transformation through multiple mechanisms. Here I review the evidence supporting the oncogenic function of HER2, the mechanisms that are felt to mediate its oncogenic functions, and the evidence that links the experimental evidence with human cancer pathogenesis.

Evaluation of the HER2/neu-derived peptide GP2 for use in a peptide-based breast cancer vaccine trial

BACKGROUND

E75 and GP2 are human leukocyte antigen (HLA)-A2-restricted immunogenic peptides derived from the HER2/neu protein. In a E75 peptide-based vaccine trial, preexisting immunity and epitope spreading to GP2 was detected. The purpose of this study was to further investigate GP2 for potential use in vaccination strategies. Importantly, a naturally occurring polymorphism (I-->V at position 2, 2VGP2) associated with increased breast cancer risk was addressed.

METHODS

Prevaccination peripheral blood samples (PBMC) from HLA-A2 breast cancer patients and CD8+ T cells from HLA-A2 healthy donors were stimulated with autologous dendritic cells (DC) pulsed with GP2 and tested in standard cytotoxicity assays with HER2/neu+ tumor cells or GP2- or 2VGP2-loaded T2 targets. Additional cytotoxicity experiments used effectors stimulated with DC pulsed with E75, GP2, or the combination of E75+GP2.

RESULTS

GP2-stimulated prevaccination PBMC from 28 patients demonstrated killing of MCF-7, SKOV3-A2, and the HLA-A2- control target SKOV3 of 28.8+/-3.7% (P<.01), 29.5+/-4.0% (P<.01), and 16.9+/-2.7%, respectively. When compared with E75, GP2-stimulated CD8+ T cells lysed HER2/neu+ targets at 43.8+/-5.2% versus 44.2+/-5.7% for E75 (P=.87). When combined, an additive effect was noted with 58.6+/-5.4% lysis (P=.05). GP2-stimulated CD8+ T cells specifically recognized both GP2-loaded (19.6+/-5.7%) and 2VGP2-loaded T2 targets (17.7+/-5.2%).

CONCLUSIONS

GP2 is a clinically relevant HER2/neu-derived peptide with immunogenicity comparable to that of E75. Importantly, GP2-specific effectors recognize 2VGP2-expressing targets; therefore, a GP2 vaccine should be effective in patients carrying this polymorphism. GP2 may be most beneficial used in a multiepitope vaccine.

Investigation of HER-2 codon 655 single nucleotide polymorphism frequency and c-ErbB-2 protein expression alterations in gastric cancer patients

AIM: To investigate both whether the risk of gastric cancer is associated with the Ile/Val single nucleotide polymorphism (SNP) of human epidermal growth factor receptor-2 (HER-2) transmembrane domain-coding region at codon 655 and the suggested existence of HER-2 expression in gastric cancer cases in a Turkish patient group.

METHODS: Polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) strategy was used to analyze the presence of HER-2 SNP at codon 655. c-erbB-2 expression pattern was analyzed by immunohistochemistry. The results were compared between gastric carcinoma group and chronic gastritis group, as well as between clinicopathological parameters and carcinoma.

RESULTS: Results showed that Ile/Val genotype accounted for 20% within the Turkish gastric carcinoma group, and none in chronic gastritis group, and this genotyping was associated with stage IV gastric cancers (P = 0.04). Positive membranous HER-2 immunoreactivity, on the other hand, accounted for 24% within the Turkish gastric carcinoma group and none from chronic gastritis cases; further, it was correlated with intestinal type carcinomas (P = 0.007), and stage III-IV carcinomas (P = 0.004).

CONCLUSION: These observations imply that the tested HER-2 SNP may participate in the development and progression of gastric cancer. Thus, after confirming these results with large sample groups, HER-2 codon 655 SNP and/or c-erbB-2 overexpression may also be used as a poor prognostic indicator for gastric carcinomas.

Allelic imbalance of HER2 variant in sporadic breast and ovarian cancer

Both breast and ovarian cancers are associated with HER2 receptor activation, which usually results from receptor overexpression and/or gene amplification. The HER-2 gene harbors a polymorphism at codon 655 (GTC/valine to ATC/isoleucine) in the transmembrane domain region, which has been associated with an elevated risk of breast cancer. The objective of this study was to determine whether the polymorphism is under a selection pressure during breast and ovarian carcinogenesis. The Ile/Val genotype was present in 41% (9/22) of the normal DNA of breast cancer patients. An allelic imbalance in the tumor tissue was found in three breast tumors, with overrepresentation of the Val allele. HER-2 was amplified and overexpressed in these tumors. Half of the eight ovarian tumor patients carried heterozygous Ile/Val genotypes. In contrast to breast tumors, all these ovarian cancer specimens showed the presence of the Ile allele. In our selected set of tumors, the Val allele was overrepresented in the subset of HER2-positive breast cancers and the Ile allele in serous ovarian cancer. Further analyses of tumors with known gene amplifications and overexpression may reveal novel associations between germline polymorphisms and development of sporadic tumors.

Comparative analysis of cancer genes in the human and chimpanzee genomes

BACKGROUND

Cancer is a major medical problem in modern societies. However, the incidence of this disease in non-human primates is very low. To study whether genetic differences between human and chimpanzee could contribute to their distinct cancer susceptibility, we have examined in the chimpanzee genome the orthologous genes of a set of 333 human cancer genes.

RESULTS

This analysis has revealed that all examined human cancer genes are present in chimpanzee, contain intact open reading frames and show a high degree of conservation between both species. However, detailed analysis of this set of genes has shown some differences in genes of special relevance for human cancer. Thus, the chimpanzee gene encoding p53 contains a Pro residue at codon 72, while this codon is polymorphic in humans and can code for Arg or Pro, generating isoforms with different ability to induce apoptosis or interact with p73. Moreover, sequencing of the BRCA1 gene has shown an 8 Kb deletion in the chimpanzee sequence that prematurely truncates the co-regulated NBR2 gene.

CONCLUSION

These data suggest that small differences in cancer genes, as those found in tumor suppressor genes, might influence the differences in cancer susceptibility between human and chimpanzee. Nevertheless, further analysis will be required to determine the exact contribution of the genetic changes identified in this study to the different cancer incidence in non-human primates.

HER-2 codon 655 polymorphism in cervical carcinogenesis

HER-2 codon 655 polymorphism together with human papillomavirus (HPV) types were examined in a total of 279 cervical smear samples. Forty-nine patients with high-grade squamous intraepithelial lesion had higher frequency of high-risk HPV than 167 patients with low-grade squamous intraepithelial lesion and 63 controls. There was no statistical difference in the frequencies of HER-2 Ile/Ile, Ile/Val, and Val/Val genotypes between squamous intraepithelial lesions (SILs) and controls. When the Ile/Ile genotype was compared to the Ile/Val + Val/Val genotypes, there was also no statistical difference in the genotype prevalence between SILs and controls either in 91 or 188 patients with or without high-risk HPV, respectively. These results suggest that the HER-2 polymorphism at codon 655 in cervical cell samples is unlikely to be associated with HPV status and the onset of cervical cancer in a Japanese population.

The influence of HER2 genotypes as molecular markers in ovarian cancer outcome

A relevant clinical problem in the treatment of ovarian cancer (OC) is the development of resistance to chemotherapy, frequently due to genetic variations in enzymes and receptors. Changes in the HER2 receptor have been associated with breast and ovarian cancers. The role of a polymorphism in the HER2 gene in the clinical outcome of OC patients was investigated in this study. We characterized DNA samples from 111 patients with OC treated with cisplatin and paclitaxel, using PCR-RFLP. Our results indicate that patients carrying the valine homozygotic genotype present a lower overall survival mean, suggesting a role for this polymorphism in the outcome of ovarian cancer patients. The G allele has been implicated in the formation of active HER2 receptors, with a more aggressive phenotype. We hypothesize that HER2 genotypes can be predictive biomarkers in ovarian cancer, contributing to a genetic individual profile of great interest in clinical oncology.

The erbB2/HER2/neu receptor polymorphism Ile655Val and breast cancer risk

The erbB2 (HER2/neu) gene is found amplified in tumours. A single nucleotide polymorphism at codon 655 (Ile655Val) has been studied in a number of case-control studies with respect to breast cancer risk, with conflicting results. The aim of the present study was to examine the association between this polymorphism and breast cancer risk in a prospective, predominantly Caucasian cohort of women, the Nurses' Health Study. We genotyped the Ile655Val single nucleotide polymorphism (rs1801200) in 1271 incident breast cancer cases, and 1667 controls who were selected from the Nurses' Health Study blood cohort. Controls were matched to cases on age, menopausal status, fasting status and postmenopausal hormone use at blood draw. An inverse association was observed between the Val/Val genotype and breast cancer risk (Val/Val versus Ile/Ile odds ratio=0.68, 95% confidence interval 0.47-0.98). We conclude that this polymorphism is not associated with an increase in breast cancer risk, and may in fact be associated with a modest decrease in risk.

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.

The association of p53 mutations and p53 codon 72, Her 2 codon 655 and MTHFR C677T polymorphisms with breast cancer in Northern Greece

The aim of this study was to explore a possible association between p53 codon 72, Her 2 codon 655 and MTHFR C677T polymorphisms and breast cancer in Northern Greece. We examined 42 women with breast cancer and 51 controls. A total of 42 women with breast cancer as well as healthy controls were investigated and results showed that p53 codon 72 polymorphism is statistically significantly associated with breast cancer (OR for Arg/Arg to non-Arg/Arg was 6.66, P = 0.0001 at 95% CI 2.63-16.9), but not Her 2 and MTHFR polymorphisms are associated with breast cancer (OR for Ile/Ile to non-Ile/Ile was 1.33, P = 0.54 at 95% CI 0.52-3.38 and OR for T/T versus non-T/T was 1.07, P = 0.89 at 95% CI 0.35-3.25). All subjects were examined for p53 exons 5-8 mutations. Three novel sequence variations in exons 7 and 8 of TP53 gene were found in three patients. One of them induces an amino acid change at Ser 241Gly, the second is a silent mutation Gly244Gly, and the third one results in a premature stop codon 294 (Glu294stop) and a truncated p53 protein.

Breast cancer in sub-Saharan Africa: how does it relate to breast cancer in African-American women?

BACKGROUND

African-American women have had a lower incidence, yet higher mortality rate from breast cancer compared with White-American women. African-American women also have had a higher risk for early-onset, high-grade, node-positive, and hormone receptor-negative disease. Similar features have characterized hereditary breast cancer, prompting speculation that risk factors could be genetically transmitted. Further evaluation of this theory required the study of breast cancer among women from sub-Saharan Africa because of their shared ancestry with African-American women.

METHODS

Publications from 1988 to 2004 of English-language literature on breast cancer in Africa were reviewed.

RESULTS

Women from sub-Saharan Africa were found to have a low incidence of breast cancer. This was partly explained by a largely protective reproductive history, including late menarche, early menopause, high parity with prolonged breastfeeding, irregular menses, and fewer ovulatory cycles. The average age at diagnosis, however, was approximately 10 years younger than breast cancer patients of western nations, and disease stage distribution was shifted toward more advanced disease, which resulted in higher mortality rates. These features were found to be similar to data on breast cancer in African-American women. Mutations in BRCA1 and BRCA2 have been reported in African-American women, but the extent of the contribution of BRCA1 and BRCA2 to breast cancer burden in Africa was uncertain. Limited financial resources lead to suboptimal cancer data collection, as well as delayed diagnosis and treatment of many African breast cancer patients.

CONCLUSIONS

Parallels between breast cancer burdens of African-American and sub-Saharan-African women were provocative, indicating the need for further exploration of possible genetically transmitted features related to estrogen metabolism and/or breast cancer risk.

The transmembrane domains of ErbB receptors do not dimerize strongly in micelles

The epidermal growth factor receptors (erbB) constitute an important class of single pass transmembrane receptors involved in the transduction of signals important for cell proliferation and differentiation. Receptor association is a key event in the signal transduction process, but the molecular basis of this interaction is not fully understood. Previous biochemical and genetic studies have suggested that the single transmembrane helices of these receptor proteins might play a role in stabilizing the receptor complexes. To determine if the erbB transmembrane domains could provide a driving force to stabilize the receptor dimers, we carried out a thermodynamic study of these domains expressed as C-terminal fusion proteins with staphylococcal nuclease. Similar fusion constructs have been used successfully to investigate the oligomerization and association thermodynamics of a number of transmembrane sequences, including that of glycophorin A. Using SDS-PAGE analysis and sedimentation equilibrium analytical ultracentrifugation, we do not find strong, specific homo or hetero-interactions between the transmembrane domains of the erbB receptors in micellar solutions. Our results indicate that any preferential interactions between these domains in micellar solutions are extremely modest, of the order of 1 kcal mol(-1) or less. We applied a thermodynamic formalism to assess the effect of weakly interacting TM segments on the behavior of a covalently attached soluble domain. In the case of the ligand-bound EGFR ectodomain, we find that restriction of the ectodomain to the micellar phase by a hydrophobic TM, even in the absence of strong specific interactions, is largely sufficient to account for the previously reported increase in dimerization affinity.

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.

Common ERBB2 polymorphisms and risk of breast cancer in a white British population: a case-control study

Introduction

About two-thirds of the excess familial risk associated with breast cancer is still unaccounted for and may be explained by multiple weakly predisposing alleles. A gene thought to be involved in low-level predisposition to the disease is ERBB2 (HER2). This gene is involved in cell division, differentiation, and apoptosis and is frequently amplified in breast tumours. Its amplification correlates with poor prognosis. Moreover, the coding polymorphism I655V has previously been associated with an increased risk of breast cancer.

Methods

We aimed to determine if common polymorphisms (frequency ≥ 5%) in ERBB2 were associated with breast cancer risk in a white British population. Five single-nucleotide polymorphisms (SNPs) were selected for study: SNP 1 near the promoter, SNP 2 in intron 1, SNP 3 in intron 4, SNP 4 in exon 17 (I655V), and SNP 5 in exon 27 (A1170P). We tested their association with breast cancer in a large case–control study (n = 2192 cases and 2257 controls).

Results

There were no differences in genotype frequencies between cases and controls for any of the SNPs examined. To investigate the possibility that a common polymorphism not included in our study might be involved in breast cancer predisposition, we also constructed multilocus haplotypes. Our set of SNPs generated all existing (n = 6) common haplotypes and no differences were seen in haplotype frequencies between cases and controls (P = 0.44).

Conclusions

In our population, common ERBB2 polymorphisms are not involved in predisposition to breast cancer.

Association of HER-2 polymorphism with Japanese sporadic prostate cancer susceptibility

BACKGROUND

Genetic polymorphisms may affect the development of prostate cancer (Pca). HER-2 is a proto-oncogene that has an important role in many human cancers, including Pca. To determine the association of the HER-2 gene with Japanese sporadic Pca, we analyzed the frequency of codon 655 (A/G, isoleucine, or valine) in case and control group.

METHODS

We genotyped Ile 655 Val in Pca patients (n = 285) and in matched controls (n = 233). Statistical analyses were performed by Fisher's exact test and logistic regression analysis.

RESULTS

We observed a significantly lower frequency of the Val655 allele in the Pca patients (14.7%) compared to the control group (26.2%) (P = 0.0025, odds ratio (OR) = 0.476, 95% CI = 0.306-0.740). This SNP was not found to be correlated with clinical stage, PSA level, Gleason score of biopsies or age at diagnosis.

CONCLUSIONS

Our results indicate that the frequency of Val655 in HER-2 was significantly lower in Japanese Pca patients, however, it was recently reported that Val655 was significant higher in breast cancer patients. This contradictory observation in prostate and breast cancer patients is interesting considering the opposite hormonal sensitivity of these two cancers.

Oligogenic combinations associated with breast cancer risk in women under 53 years of age

Common, but weakly penetrant, functional polymorphisms probably account for most of the genetic risk for breast cancer in the general population. Current polygenic risk models assume that component genes act independently. To test for potential gene-gene interactions, single nucleotide polymorphisms in ten genes with known or predicted roles in breast carcinogenesis were examined in a case-control study of 631 Caucasian women diagnosed with breast cancer under the age of 53 years and 1,504 controls under the age of 53 years. Association of breast cancer risk with individual genes and with two- and three-gene combinations was analyzed. Sixty-nine oligogenotypes from 37 distinct two- and three-gene combinations met stringent criteria for significance. Significant odds ratios (ORs) covered a 12-fold range: 0.5-5.9. Of the observed ORs, 17% differed significantly from the ORs predicted by a model of independent gene action, suggesting epistasis, i.e., that these genes interact to affect breast cancer risk in a manner not predictable from single gene effects. Exploration of the biological basis for these oligogenic interactions might reveal etiologic or therapeutic insights into breast cancer and other cancers.

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 polymorphism and breast cancer risk in Portugal

Breast cancer is a major public health problem around the world, and its carcinogenesis is not yet well understood. The human epidermal growth factor Receptor 2 (HER2) seems to play an important role in the development of this neoplasia, and genetic alterations in this gene, such as point mutations and polymorphisms have been detected in breast cancer patients. We analysed the frequency of a single nucleotide polymorphism in the HER2 gene in blood samples from 152 breast cancer patients and 146 healthy controls using the polymerase chain reaction methodology, followed by restriction fragment length polymorphism (PCR-RFLP). We found a twofold increase in risk of breast cancer in women who are carriers of a Val allele genotype-Ile/Val and Val/Val genotypes [odds ratio (OR)=2.00; 95% confidence interval (CI) 1.23-3.25; P=0.005]. Our results indicate an association between the presence of the Val allele in the HER2 polymorphism and the risk of breast cancer. Further studies are needed to evaluate the role of this polymorphism in the behaviour of breast cancer.

Genetic polymorphisms in uridine diphospho-glucuronosyltransferase 1A1 (UGT1A1) and risk of breast cancer

Uridine diphospho-glucuronosyltransferase 1A1 (UGT1A1) is involved in catalyzing estrogen, the hormone that plays a central role in the etiology of breast cancer. A common polymorphism [A(TA)6TAA (allele *1) to A(TA)7TAA change (allele *28)] in the TATA-box of the promoter region of the UGT1A1 gene has been reported to be associated with a reduced transcription of this gene. We investigated the association of this polymorphism with the risk of breast cancer among 1047 breast cancer cases and 1083 community controls in the Shanghai Breast Cancer Study, a population-based case-control study. Approximately same proportion of cases (12.5%) and controls (13.0%) carried the variant allele *28 in the Chinese population (p = 0.32). When stratified by age, carrying the *28 allele was associated with an increased risk of breast cancer among women aged less than 40 years (odds ratio [OR] = 1.7; 95% CI = 1.0-2.7) but not among women 40 years old and over (OR = 0.8; 0.7-1.1). Only a few women were homozygous for the *28 allele, precluding a detailed gene-dose association analysis. Additional analyses showed that, the elevated risk associated with the UGT1A1 *28 allele among young women was primarily seen in women who had a later menarche, short menstrual years, absence of family history of breast cancer, low waist-to-hip ratio, or low body-mass index. These results suggested that the *28 allele in the UGT1A1 gene may be associated with an increased risk for breast cancer among Chinese women under age 40. No significant associations were observed with *28 allele and breast cancer risk by estrogen receptor/progesterone receptor status.

Estrogen receptor codon 594 and HER2 codon 655 polymorphisms and breast cancer risk

The estrogen receptor (ER) and the human epithelial growth factor receptor 2 (HER2) genes have been implicated in the development and prognosis of breast cancer. Several genetic polymorphic sites in these genes have been identified and associated with the risk of breast cancer. We have investigated the association between the estrogen receptor codon 594 (ACA to ACG) and HER2 codon 655 (ATC to GTC) polymorphisms and breast cancer risk. Genomic DNA from breast cancer patients and control subjects was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). When allelic frequencies of the ER codon 594 and HER2 codon 655 gene were compared, no significant differences were observed between the patient and control groups. (P = 0.063, OR = 1.55, 95% CI = 0.25-9.41 and P = 0.949, OR = 1.01, 95% CI = 0.55-1.88, respectively). In conclusion, our results support the view that both the ER codon 594 and HER2 codon 655 polymorphisms are not associated with increased risk of breast cancer.

Molecular and functional characteristics of erbB2 in normal and cancer breast cells

The expression pattern of erbB2 and its transmembrane polymorphisms (Ile654Val and Ile655Val) were investigated in a panel of human normal and neoplastic breast cell lines to evaluate whether the expression pattern was affected by changes in the gene structure. At least two peptides of lower molecular mass forms (95 and 68 kDa) than the holoreceptor (185 kDa), comprehensive of the tyrosine kinase domain, were detected in all cells. Both peptides were also phosphorylated, suggesting a functional role in signal transduction. The presence of the polymorphisms found in two cell lines was unrelated to the expression of the lower molecular mass proteins.

Genetic polymorphisms in GSTM1, GSTP1, and GSTT1 and the risk for breast cancer: results from the Shanghai Breast Cancer Study and meta-analysis

PURPOSE

We studied the relation of breast cancer to common deletion mutations in GSTM1 and GSTT1 and the functional Ile(105)Val polymorphism in GSTP1 in a large, population-based case-control study conducted in China and performed a meta-analysis to summarize the literature.

EXPERIMENTAL DESIGN

In the case-control study, a total of 1144 breast cancer cases and 1221 community controls were genotyped for GSTM1, GSTP1, and GSTT1 using PCR-based methods. Associations of genotypes and breast cancer were evaluated in logistic regression models. Meta-analysis odds ratios (ORs) were estimated using a fixed effects model.

RESULTS

In the case-control study, associations were null for GSTM1 [age-adjusted OR 0.97, 95% confidence interval (CI): 0.82-1.14] and GSTT1 (OR 0.97, 95% CI: 0.83-1.15). A significant increase in risk was observed among homozygotes for the variant Ile(105)Val polymorphism (OR 1.92, 95% CI: 1.21-3.04). No combined effects of GSTM1, GSTP1, and GSTT1 genotypes or interactions with potential effect modifiers were detected. All results were similar in pre- and postmenopausal women and for early versus advanced stage breast cancer. The meta-analysis, based predominantly on Caucasian women, supported null results for the homozygous deletion variant in GSTM1 (summary OR 1.05; combining 19 studies) and GSTT1 (summary OR 1.11; 15 studies). Meta-analysis results for the homozygous GSTP1 variant indicated no overall association (summary OR 1.04; 10 studies), although results varied significantly across studies (P = 0.009).

CONCLUSIONS

This large case-control study provides strong support for earlier studies showing no overall association of the GSTM1 and GSTT1 deletion polymorphisms with breast cancer risk. The GSTP1 variant may be relevant to breast cancer risk in Asian populations.