Fritz F. Parl

Multifactor-Dimensionality Reduction Reveals High-Order Interactions among Estrogen-Metabolism Genes in Sporadic Breast Cancer

One of the greatest challenges facing human geneticists is the identification and characterization of susceptibility genes for common complex multifactorial human diseases. This challenge is partly due to the limitations of parametric-statistical methods for detection of gene effects that are dependent solely or partially on interactions with other genes and with environmental exposures. We introduce multifactor-dimensionality reduction (MDR) as a method for reducing the dimensionality of multilocus information, to improve the identification of polymorphism combinations associated with disease risk. The MDR method is nonparametric (i.e., no hypothesis about the value of a statistical parameter is made), is model-free (i.e., it assumes no particular inheritance model), and is directly applicable to case-control and discordant-sib-pair studies. Using simulated case-control data, we demonstrate that MDR has reasonable power to identify interactions among two or more loci in relatively small samples. When it was applied to a sporadic breast cancer case-control data set, in the absence of any statistically significant independent main effects, MDR identified a statistically significant high-order interaction among four polymorphisms from three different estrogen-metabolism genes. To our knowledge, this is the first report of a four-locus interaction associated with a common complex multifactorial disease.

Breast cancer risk associated with proliferative breast disease and atypical hyperplasia

Background. Women with proliferative breast disease (PD) have been observed to have an increased risk of breast cancer. The authors evaluated the effect of PD on breast cancer risk in a case–control study among participants of the Breast Cancer Detection Demonstration Project (BCDDP).

Mitochondrial DNA G10398A Polymorphism and Invasive Breast Cancer in African-American Women

Mitochondria generate oxygen-derived free radicals that damage mitochondrial DNA (mtDNA) as well as nuclear DNA and in turn promote carcinogenesis. The mtDNA G10398A polymorphism alters the structure of Complex I in the mitochondrial electron transport chain, an important site of free radical production. This polymorphism is associated with several neurodegenerative disorders. We hypothesized that the 10398A allele is also associated with breast cancer susceptibility. African mitochondria harbor the 10398A allele less frequently than Caucasian mitochondria, which predominantly carry this allele. Mitochondrial genotypes at this locus were therefore determined in two separate populations of African-American women with invasive breast cancer and in controls. A preliminary study at Vanderbilt University (48 cases, 54 controls) uncovered an association between the 10398A allele and invasive breast cancer in African-American women, [odds ratio (OR), 2.90; 95% confidence interval (95% CI), 0.61-18.3; P = 0.11]. We subsequently validated this finding in a large, population-based, case-control study of breast cancer, the Carolina Breast Cancer Study at the University of North Carolina (654 cases, 605 controls). African-American women in this study with the 10398A allele had a significantly increased risk of invasive breast cancer (OR, 1.60; 95% CI, 1.10-2.31; P = 0.013). The 10398A allele remained an independent risk factor after adjustment for other well-accepted breast cancer risk factors. No association was detectable in white women (879 cases, 760 controls; OR, 1.03; 95% CI, 0.81-1.31; P = 0.81). This study provides novel epidemiologic evidence that the mtDNA 10398A allele influences breast cancer susceptibility in African-American women. mtDNA polymorphisms may be underappreciated factors in breast carcinogenesis.

Prognostic significance of estrogen receptor status in breast cancer in relation to tumor stage, axillary node metastasis, and histopathologic grading

The value of estrogen receptor (ER) measurements for predicting recurrence and survival rates in primary breast cancer was examined in 121 women who were followed from 5 to 12 years after mastectomy with a median follow‐up of 64 months. The prognostic significance of the ER status was evaluated independently and in association with tumor stage, axillary node metastasis, and histopathologic grade. The independent evaluation demonstrated no statistically significant difference in prognosis between women with ER‐negative and ER‐positive cancers, although the latter group tended to have a longer time to recurrence and longer survival. Multivariate analysis of the data by Coxs proportional hazard regression techniques revealed a synergistic effect of ER status on the risk associated with axillary node metastasis. Patients with nodal metastasis were at 2.8 times the risk of recurrence compared to patients without metastasis. For women with nodal metastasis whose primary cancer was ER‐negative, this risk increased to 4.6 times compared to women without metastasis and ER‐positive tumors (P = 0.0003). The risk of cancer‐related death was 5.6 times more likely for poorly differentiated tumors than for highly differentiated tumors. Patients with poorly differentiated ER‐negative tumors were at an even higher risk (7.0) of dying than women with highly differentiated ER‐positive carcinomas (P = 0.009). In conjunction with tumor stage, axillary node metastasis and histopathologic grade ER determination is useful for identifying subpopulations at increased risk of tumor recurrence or mortality.

Influence of exogenous estrogens, proliferative breast disease, and other variables on breast cancer risk

The authors reevaluated 10,366 consecutive breast biopsy specimens of benign lesions performed between 1950 and 1968. Follow‐up information was obtained on 3303 women with a median duration of follow‐up of 17 years. This sample contained 84% of the patients originally selected for follow‐up. The relative risk (RR) of developing breast cancer was 0.98 for women who took exogenous estrogens as compared to 1.8 for women who did not. Exogenous estrogens lowered the observed breast cancer risk in women with atypical hyperplasia (RR = 3.0 versus 4.5), proliferative disease without atypia (RR = 0.92 versus 1.9), and in women without proliferative disease (RR = 0.69 versus 0.91). Women who took estrogens before 1956 were at 2.3 times the risk of other estrogen users, presumably due to a dose effect. There was no significant association between breast cancer risk and birth control pills, cigarette smoking, or alcohol consumption. Exogenous estrogens are not associated with increased breast cancer risk in women with benign breast disease. A previous history of benign breast disease does not contraindicate replacement estrogen therapy.

Estrogen Receptor Genotypes and Haplotypes Associated with Breast Cancer Risk

Nearly one in eight US women will develop breast cancer in their lifetime. Most breast cancer is not associated with a hereditary syndrome, occurs in postmenopausal women, and is estrogen and progesterone receptor-positive. Estrogen exposure is an epidemiologic risk factor for breast cancer and estrogen is a potent mammary mitogen. We studied single nucleotide polymorphisms (SNPs) in estrogen receptors in 615 healthy subjects and 1011 individuals with histologically confirmed breast cancer, all from New York City. We analyzed 13 SNPs in the progesterone receptor gene (PGR), 17 SNPs in estrogen receptor 1 gene (ESR1), and 8 SNPs in the estrogen receptor 2 gene (ESR2). We observed three common haplotypes in ESR1 that were associated with a decreased risk for breast cancer [odds ratio (OR), ∼ O.4; 95% confidence interval (CI), 0.2–0.8; P < 0.01]. Another haplotype was associated with an increased risk of breast cancer (OR, 2.1; 95% CI, 1.2–3.8; P < 0.05). A unique risk haplotype was present in ∼7% of older Ashkenazi Jewish study subjects (OR, 1.7; 95% CI, 1.2–2.4; P < 0.003). We narrowed the ESR1 risk haplotypes to the promoter region and first exon. We define several other haplotypes in Ashkenazi Jews in both ESR1 and ESR2 that may elevate susceptibility to breast cancer. In contrast, we found no association between any PGR variant or haplotype and breast cancer. Genetic epidemiology study replication and functional assays of the haplotypes should permit a better understanding of the role of steroid receptor genetic variants and breast cancer risk.

p53 gene mutations and steroid receptor status in breast cancer. Clinicopathologic correlations and prognostic assessment.

Background. There is increasing evidence linking development and progression of cancer to an accumulation of mutations at the genomic level. The most frequently mutated gene known to date in sporadic breast cancer appears to be the tumor suppressor gene p53. This study was designed to determine the frequency of p53 gene mutations in primary breast cancer, to correlate the presence of p53 mutations with established clinicopathologic parameters, including the estrogen receptor (ER) and progesterone receptor (PR) status, and to assess the prognostic significance of p53 mutations regarding patient survival.

Cytochrome P450 1B1 and catechol-O-methyltransferase genetic polymorphisms and breast cancer risk in Chinese women: results from the shanghai breast cancer study and a meta-analysis.

Cytochrome P450 1B1 (CYP1B1) and catechol-O-methyltransferase (COMT) are important estrogen-metabolizing enzymes and, thus, genetic polymorphisms of these enzymes may affect breast cancer risk. A population-based case-control study was conducted to assess the association of breast cancer risk with CYP1B1 and COMT polymorphisms. A meta-analysis was done to summarize the findings from this and previous studies. Included in this study were 1,135 incident breast cancer cases diagnosed from August 1996 through March 1998 among female residents of Shanghai and 1,235 randomly selected, age frequency-matched controls from the same general population. The common alleles of the CYP1B1 gene were Arg (79.97%) in codon 48, Ala (80.53%) in codon 119, and Leu (86.57%) in codon 432. The Val allele accounted for 72.46% of the total alleles identified in codon 108/158 of the COMT gene. No overall associations of breast cancer risk were found with any of the single nucleotide polymorphisms described above. This finding was supported by a meta-analysis of all previous published studies. No gene-gene interactions were observed between CYP1B1 and COMT genotypes. The associations of breast cancer risk with factors related to endogenous estrogen exposure, such as years of menstruation and body mass index, were not significantly modified by the CYP1B1 and COMT genotypes. We observed, however, that women who carried one copy of the variant allele in CYP1B1 codons 48 or 119 were less likely to have estrogen receptor–positive breast cancer than those who carried two copies of the corresponding wild-type alleles. The results from this study were consistent with those from most previous studies, indicating no major associations of breast cancer risk with CYP1B1 and COMT polymorphisms.

Genomic DNA analysis of the estrogen receptor gene in breast cancer

SummaryA human estrogen receptor (ER) cDNA probe was used to examine genomic DNA extracted from 59 primary invasive breast cancers. The tumors were also studied histopathologically, and their ER status was assessed by hormone-binding assay and immunohistochemical analysis. Southern blots of genomic DNA samples digested with restriction endonucleases (BamHI, EcoRI, HindIII, PvuII, XbaI) revealed identical restriction fragments for each tumor, indicating preservation of gross ER gene integrity regardless of ER status, clinical stage, or histopathologic appearance. Digestion with PvuII identified a single, two-allele polymorphism with band(s) at 1.6 and/or 0.7 kb. The homozygous 1.6 kb pattern was present in 14 (24%) patients, the heterozygous 1.6/0.7 kb pattern in 29 (49%) patients and the homozygous 0.7 kb pattern in 16 (27%) patients. The PvuII restriction fragment length polymorphism (RFLP) within the ER gene showed no correlation with the results of the ER binding assay, the immunohistochemical analysis, clinical stage, or histopathologic appearance. A significant correlation was found between the genotypes and patient age at the time of tumor diagnosis. Tumors with the homozygous 1.6 kb and the heterozygous 1.6/0.7 kb patterns were observed in older women with mean ages of 64.6 and 64.4 years, respectively. In contrast, patients with tumors containing the homozygous 0.7 kb pattern were significantly younger, with a mean age of 50.4 years (p-value = 0.0024). The mechanism by which the homozygous 0.7 kb genotype is associated with breast cancer in the premenopausal age group is unknown.

Discrepancies of the biochemical and immunohistochemical estrogen receptor assays in breast cancer

We examined the estrogen receptor (ER) content of 124 primary breast cancers by hormone binding and immunohistochemical (ER-ICA) assays. Both assays were in agreement in 110 tumors (89%; P less than .0001); 68 tumors were positive and 42 were negative. In 14 cases (11%), the assays yielded discordant results. Three tumors showed hormone binding in the absence of immunohistochemically detectable ER; the false positive hormone binding resulted from the presence of normal epithelium adjacent to ER-ICA negative malignant cells. Eleven tumors failed to show hormone binding but were ER-ICA positive. Four of these were from premenopausal patients whose circulating endogenous estrogen may occupy the receptor, giving rise to false negative hormone binding assays. In four cases, the discrepancy of negative hormone binding assay and positive ER-ICA assay was attributed to scant tumor cells in the tissue sample. The remaining three discrepancies could not be resolved with certainty, but possibly resulted from alteration of the hormone binding site with preservation of the immunoreactive epitope on the ER molecule. These results indicate that the ER-ICA assay is more accurate than the hormone binding assay in identifying the presence of ER in cancer cells. The heterogeneous immunostaining of ER in tumor sections, which may reflect mosaicism of tumor cells, rate of cell proliferation, or phase of cell cycle, remains unexplained.