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

The HER2 I655V Polymorphism and Breast Cancer Risk in Ashkenazim

SUMMARY

BACKGROUND Over-expression of the human epidermal growth factor receptor 2 (Her2) protooncogene is associated with poor prognosis among female patients with breast cancer. A polymorphism in the HER2 gene (I655V) has been associated with an elevated risk of breast cancer in some ethnic groups. METHODS Subjects from a community-based study of 5318 Ashkenazim from the Washington, DC area were selected for analysis of the I655V HER2 germline polymorphism. We estimated age-specific breast cancer risk from HER2 I655V based on the family history data, using the female first-degree relatives of the study participants and a novel extension of the kin cohort method. RESULTS The estimated cumulative risk of breast cancer to age 70 was approximately 30% higher among HER2 I655V carriers than noncarriers (RR = 1.33; 95% confidence interval [CI] = 1.03-1.83). The effect of the allele seems stronger at younger ages (among women younger than 50 years, RR = 2.11; CI = 1.39-3.28) and especially among younger women with a family history of breast cancer (RR = 8.9; CI = 1.9-19.7). Increased risk of breast cancer associated with the I655V allele was also observed among BRCA1/2 mutation carriers, although these results are based on small numbers. CONCLUSION These analyses suggest that the HER2 valine allele might be associated with increased risk of breast cancer, especially in young women and in women with a family history of the disease.

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.

A putative molecular-activation switch in the transmembrane domain of erbB2

Overexpression of the receptor tyrosine kinase (RTK) erbB2 (also designated neu or HER2) was implicated in causing a variety of human cancers, including mammary and ovarian carcinomas. Ligand-induced receptor dimerization is critical for stimulation of the intrinsic protein tyrosine kinase (PTK) of RTKs. It was therefore proposed that PTK activity is stimulated as a result of the reorientation of the cytoplasmic domains within receptor dimers, leading to transautophosphorylation and stimulation of enzymatic activity. Here, we propose a molecular mechanism for rotation-coupled activation of the erbB2 receptor. Using a computational exploration of conformation space of the transmembrane (TM) segments of an erbB2 homodimer, we found two stable conformations of the TM domain. We suggest that these conformations correspond to the active and inactive states of erbB2, and that the receptor molecules may switch from one conformation to the other without crossing exceedingly unfavorable states. This model provides an explanation for the biochemical and oncogenic properties of erbB2, such as the effects of erbB2 overexpression on kinase activity and cell transformation. Furthermore, the opposing effects of the neu* activating oncogenic point mutation and the Val-655-->Ile single-nucleotide polymorphism shown to be linked to reduced risk of breast cancer are explained in terms of shifts in the equilibrium between the active and inactive states of erbB2 in vivo.

Biomedical informatics: the future for drug development

The problems that exist in drug development are well documented: the limited number of new chemical entities, increased cost of drug development, problems in clinical trials (Phase III), product launches that result in withdrawal, and pressure to reduce the cost of pharmaceuticals from the government. It appears that the promise of genomics has not yet reached its full potential to impact the process. This review identifies the need to develop and implement the area of biomedical informatics for increased success in drug development and healthcare in general.

c-erbB-2 in breast cancer: development of a clinically useful marker

c-erbB-2 amplification and/or overexpression occurs in 20% to 30% of breast cancers and appear to be associated with a more aggressive phenotype. Detecting abnormalities in c-erbB-2 might provide important clinical information for breast cancer patients. However, several of the potential clinical uses of c-erbB-2 remain unproven. Many variables influence c-erbB-2 results, including selection and characteristics of test populations and methods of analysis. Current literature suggests two roles for c-erbB-2, either as a pure prognostic factor with no association with therapy or as a factor predictive of benefit from specific types of systemic treatments. c-erbB-2 appears to be only a weak prognostic factor, although some individual studies suggest greater prognostic importance. c-erbB-2 abnormalities appear to predict for relative, but not absolute, resistance to endocrine therapy in estrogen receptor (ER)-positive women. When adjuvant chemotherapy is indicated, some studies have indicated that patients with c-erbB-2-positive cancers (by immunohistochemistry [IHC] or fluoresence in situ hybridization [FISH]) receive more benefit from anthracycline-containing regimens as compared to alkylating agents. c-erbB-2 testing appears critical for selecting patients with metastatic disease who should receive the anti-c-erbB-2 antibody, trastuzumab. Prospective randomized clinical trials of trastuzumab as adjuvant therapy are underway. Well-designed, prospective, randomized clinical trials (designed to test the value of c-erbB-2) or formal meta-analyses will help to better establish the predictive role of c-erbB-2 in breast cancer.

Genes other than BRCA1 and BRCA2 involved in breast cancer susceptibility

This review focuses on genes other than the high penetrance genes BRCA1 and BRCA2 that are involved in breast cancer susceptibility. The goal of this review is the discovery of polymorphisms that are either associated with breast cancer or that are in strong linkage disequilibrium with breast cancer causing variants. An association with breast cancer at a 5% significance level was found for 13 polymorphisms in 10 genes described in more than one breast cancer study. Our data will help focus on the further analysis of genetic polymorphisms in populations of appropriate size, and especially on the combinations of such polymorphisms. This will facilitate determination of population attributable risks, understanding of gene-gene interactions, and improving estimates of genetic cancer risks.

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.

c-erbB-2 is not a major factor in the development of colorectal cancer

We have investigated c-erbB-2 protein expression in a large cohort of well-characterized colorectal tumours, and in a subset of lymph node metastases. We have also evaluated a Val(655)Ile single nucleotide polymorphism, which is associated with an increased risk of breast cancer, in a subset of the colorectal cancer patients and in healthy control subjects. Immunohistochemical studies revealed that while 81.8% of tumours expressed c-erbB-2, in the majority of cases equivalent levels of c-erb-B2 were seen in adjacent normal mucosa. Colon tumours were significantly more likely to express c-erbB-2 than rectal tumours (P=0.015). Only 52.4% of the metastases displayed staining patterns concordant with their primary tumour, indicating that determination of c-erbB-2 protein in colorectal tumours cannot predict the status of lymph node metastases. PCR--RFLP analysis of the Val(655)Ile single nucleotide polymorphism demonstrated that allele frequencies were identical between colorectal cancer patients and a control group of Caucasian subjects (Ile=0.80 and Val=0.20 in each case), indicating that it is not related to the risk of developing colorectal cancer in this population. Furthermore, there was no relationship between c-erbB-2 protein expression and gene polymorphism (P=0.58). In terms of prognosis, no association was seen between either c-erbB-2 protein expression or the presence of the Val allele and patient survival (P>0.05 in each case), suggesting that c-erbB-2 is not a prognostic marker in colorectal cancer.

Female patients with breast carcinoma age 30 years and younger have a poor prognosis: the M.D. Anderson Cancer Center experience

BACKGROUND

The objective of this study was to analyze the outcome of treatment in young women with breast carcinoma who were treated at a single institution and to develop a clearer understanding of the natural history of the disease in these women.

METHODS

One hundred eighty-five women age < or = 30 years in whom a diagnosis of invasive breast carcinoma was made between October 1985 and September 1995 were identified in the Tumor Registry data base. Patient data were obtained by chart review. All female patients with breast carcinoma who were age > 30 years and who were identified in the same data base and received treatment during the same period served as the control population. The stage-stratified overall survival (OS) rate for the study patients was compared with the OS rate for both the control population and patients in the National Cancer Data Base (NCDB).

RESULTS

Of 185 patients, 11% presented with Stage I disease, 45% presented with Stage II disease, 38% presented with Stage III disease, and 6% presented with Stage IV disease. Twenty-nine percent of patients with Stage I disease received adjuvant therapy, and 84% of patients with Stage II disease and 96% of patients with Stage III disease received either adjuvant or neoadjuvant chemotherapy. Among patients with Stage I disease, 8 patients underwent mastectomy and 13 patients underwent breast-conserving surgery (BCS). Among patients with Stage II disease, 66 patients underwent mastectomy and 17 patients underwent BCS. Among patients with Stage III disease, 65 patients underwent mastectomy and 5 patients underwent BCS. The 5-year OS rate was 87% for patients with Stage I disease, 60% for patients with Stage II disease, 42% for patients with Stage III disease, and 16% for patients with Stage IV disease. Compared with the control patients and those in the NCDB, there was a trend toward worse OS rates in women age < or = 30 years.

CONCLUSIONS

Women who are diagnosed with breast carcinoma at an age < or = 30 years appear to have a poorer prognosis compared with that for their older counterparts.

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.

Complementary antitumor immunity induced by plasmid DNA encoding secreted and cytoplasmic human ErbB-2

A plasmid DNA was constructed to encode the N-terminal 505 aa of human ErbB-2 (E2, HER-2/neu) and designated as secreted ErbB-2 (secE2). Recombinant secE2 protein was detected in the transfected cells and was secreted as an 80-kDa glycoprotein. Vaccination of BALB/c mice with secE2 DNA induced both IgG1 and IgG2a ErbB-2-specific Abs and protected approximately 90% of mice against mouse mammary tumor D2F2, which expressed human ErbB-2 (D2F2/E2). The efficacy of secE2 vaccine was comparable with that of wild-type ErbB-2 DNA, which encodes the entire 1258 aa of ErbB-2 protein, induced only IgG2a E2-specific Abs, and stimulated greater CTL activity. Immune lymphocytes were stimulated in vitro with irradiated 3T3 cells, which expressed ErbB-2, K(d), and B7.1. CTL activity was measured by the lysis of E2-positive target cells and by intracellular IFN-gamma production. To enhance CTL activation, mice were immunized with a combination of secE2 and cytoplasmic E2 (cytE2); the latter encodes the 1258-aa ErbB-2 protein that was released into the cytoplasm upon synthesis. Significant increase in CTL activity was demonstrated after mice were immunized with the combined vaccines and all mice were protected from D2F2/E2 tumor growth. Therefore, secE2, which induced Th2 Ab and weak CTL, conferred similar protection as E2, which induced Th1 Ab and strong CTL. Combined vaccination with secE2 and cytE2 resulted in Th2 Ab, strong CTL, and the most effective protection against tumor growth. The strategy of coimmunization with DNA that direct Ags to different subcellular compartments may be adapted as appropriate to optimize immune outcome.

Sulfation pharmacogenetics: SULT1A1 and SULT1A2 allele frequencies in Caucasian, Chinese and African-American subjects

Sulfotransferase (SULT) enzymes catalyze the sulfate conjugation of drugs, other xenobiotics, neurotransmitters and hormones. The genes for SULT1A1 and SULT1A2 contain common genetic polymorphisms that are associated with individual variations in levels of enzyme activity as well as variations in biochemical and physical properties. We set out to compare the frequencies of common SULT1A1 and SULT1A2 alleles in Caucasian, Chinese and African-American subjects. Allele frequencies for SULT1A1*1, *2 and *3 in 242 Caucasian subjects were 0.656, 0.332 and 0.012, respectively. Frequencies of those same alleles were significantly different in 290 Chinese subjects: 0.914, 0.080 and 0.006, respectively, as were frequencies in 70 African-American subjects: 0.477, 0.294 and 0.229, respectively. Ethnic variation in allele frequencies was also observed for SULT1A2, with frequencies in Caucasian subjects for SULT1A2*1, *2 and *3 of 0.507, 0.389 and 0.104; frequencies in Chinese of 0.924 and 0.076 with no *3 alleles observed; and, finally, in African-Americans frequencies of 0.637, 0.249 and 0.114, respectively. We also found that SULT1A1*2 and SULT1A2*2, the most common variant alleles for these two genes, were in positive linkage disequilibrium in all three populations studied, with D' values of 0.776 in Caucasian (P < 0.001), 0.915 in Chinese (P < 0.001) and 0.864 in African-American subjects (P < 0.001). These observations represent a step towards determining the possible functional implications for individual variations in sulfate conjugation of common genetic polymorphisms for SULT1A1 and SULT1A2.

DNA vaccination against rat her-2/Neu p185 more effectively inhibits carcinogenesis than transplantable carcinomas in transgenic BALB/c mice

The ability of vaccination with plasmids coding for the extracellular and the transmembrane domain of the product of transforming rat Her-2/neu oncogene (r-p185) to protect against r-p185(+) transplantable carcinoma (TUBO) cells and mammary carcinogenesis was evaluated. In normal BALB/c mice, DNA vaccination elicits anti-r-p185 Ab, but only a marginal CTL reactivity, and protects against a TUBO cell challenge. Massive reactive infiltration is associated with TUBO cell rejection. In BALB/c mice transgenic for the rat Her-2/neu gene (BALB-neuT), DNA vaccination elicits a lower anti-r-p185 Ab response, no CTL activity and only incompletely protects against TUBO cells, but markedly hampers the progression of carcinogenesis. At 33 wk of age, when control BALB-neuT mice display palpable tumors in all mammary glands, about 60% of immunized mice are tumor free, and tumor multiplicity is markedly reduced. Tumor-free mammary glands still display the atypical hyperplasia of the early stages of carcinogenesis, and a marked down-modulation of r-p185, along with a massive reactive infiltrate. However, BALB-neuT mice protected against mammary carcinogenesis fail to efficiently reject a TUBO cell challenge. This suggests that the mechanisms required for the rejection of transplantable tumors may not coincide with those that inhibit the slow progression of carcinogenesis.