Gene Summary

Gene:PARL; presenilin associated, rhomboid-like
Summary:This gene encodes a mitochondrial integral membrane protein. Following proteolytic processing of this protein, a small peptide (P-beta) is formed and translocated to the nucleus. This gene may be involved in signal transduction via regulated intramembrane proteolysis of membrane-tethered precursor proteins. Variation in this gene has been associated with increased risk for type 2 diabetes. Alternative splicing results in multiple transcript variants encoding different isoforms. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:presenilins-associated rhomboid-like protein, mitochondrial
Source:NCBIAccessed: 25 June, 2015


What does this gene/protein do?
Show (8)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 25 June 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Risk Factors
  • Case-Control Studies
  • Tumor Markers
  • Signal Transduction
  • CpG Islands
  • Neoplasm Invasiveness
  • Estrogens
  • Cytochrome P-450 Enzyme System
  • Ductal Breast Carcinoma
  • Molecular Sequence Data
  • Reproducibility of Results
  • Polymorphism
  • Chromosome 3
  • TNF
  • Transcription
  • Base Sequence
  • Genetic Predisposition
  • Cancer DNA
  • Alleles
  • p53 Protein
  • Breast Cancer
  • Polymerase Chain Reaction
  • Neoplastic Cell Transformation
  • Aryl Hydrocarbon Hydroxylases
  • Follow-Up Studies
  • Receptors, Progesterone
  • Glutathione Transferase
  • Genotype
  • Estradiol
  • Exons
  • Cancer Gene Expression Regulation
  • Single Nucleotide Polymorphism
  • Cytochrome P-450 CYP1A1
  • DNA Methylation
  • Estrogen Receptors
  • European Continental Ancestry Group
  • Mutation
  • African Continental Ancestry Group
  • Breast
  • CYP1B1
Tag cloud generated 25 June, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: PARL (cancer-related)

Canzoneri R, Lacunza E, Isla Larrain M, et al.
Rhomboid family gene expression profiling in breast normal tissue and tumor samples.
Tumour Biol. 2014; 35(2):1451-8 [PubMed] Related Publications
Rhomboid is an evolutionary conserved and functionally diversified group of proteins composed of proteolytically active and inactive members that are involved in the modulation of multiple biological processes such as epidermal growth factor receptor signaling pathway, endoplasmic reticulum-associated degradation, cell death, and proliferation. Recently, several human rhomboid genes have been associated with the development of chronic myeloid leukemia and pituitary, colorectal, ovarian, and breast cancers. In this study, we evaluated the mRNA and protein expression profiles of rhomboid genes in cancer cell lines and breast tissue/tumor samples. In silico analysis of publicly available gene expression datasets showed that different rhomboid genes are specifically expressed according to the breast cancer intrinsic subtypes. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis showed a significant RHBDD2 mRNA overexpression in advanced breast cancer compared with normal tissue samples (p = 0.012). In addition, we found that RHBDL2 and PARL mRNA expression was associated with a low/intermediate histologic tumor grade (p = 0.024 and p = 0.015, respectively). Immunohistochemistry analysis showed a significant increase of RHBDD2 protein expression in association with breast cancer samples negative for progesterone receptor (p = 0.015). Moreover, protein expression analysis corroborated the quantitative RT-PCR results, indicating that breast primary tumors belonging to patients with a more disseminated disease expressed significantly increased levels of RHBDD2 protein compared with less disseminated tumors (p = 0.01).

Higginbotham KS, Breyer JP, Bradley KM, et al.
A multistage association study identifies a breast cancer genetic locus at NCOA7.
Cancer Res. 2011; 71(11):3881-8 [PubMed] Free Access to Full Article Related Publications
Estrogen metabolism and growth factor signaling pathway genes play key roles in breast cancer development. We evaluated associations between breast cancer and tagging single-nucleotide polymorphisms (SNP) of 107 candidate genes of these pathways using single allele- and haplotype-based tests. We first sought concordance of associations between two study populations: the Nashville Breast Cohort (NBC; 510 cases, 988 controls), and the Cancer Genetic Markers of Susceptibility (CGEMS) breast cancer study (1,145 cases, 1,142 controls). Findings across the two study populations were concordant at tagging SNPs of six genes, and at previously published SNPs of FGFR2. We sought further replication of results for EGFR, NCOA7, and FGFR2 in the independent Collaborative Breast Cancer Study (CBCS; 1,552 cases, 1,185 controls). Associations at NCOA7 and FGFR2 replicated across all three studies. The association at NCOA7 on 6q22.32, detected by a haplotype spanning the initial protein-coding exon (5'-rs9375411, rs11967627, rs549438, rs529858, rs490361, rs17708107-3'), has not been previously reported. The haplotype had a significant inverse association with breast cancer in each study [OR(Het): 0.69 (NBC), 0.76 (CGEMS), 0.79 (CBCS)], and a meta-analysis OR(Het) of 0.75 (95% CI, 0.65-0.87, P = 1.4 × 10(-4)) in the combined study populations. The haplotype frequency was 0.07 among cases, and 0.09 among controls; homozygotes were infrequent and each OR(Hom) was not significant. NCOA7 encodes a nuclear receptor coactivator that interacts with estrogen receptor α to modulate its activity. These observations provide consistent evidence that genetic variants at the NCOA7 locus may confer a reduced risk of breast cancer.

Son DS, Wilson AJ, Parl AK, Khabele D
The effects of the histone deacetylase inhibitor romidepsin (FK228) are enhanced by aspirin (ASA) in COX-1 positive ovarian cancer cells through augmentation of p21.
Cancer Biol Ther. 2010; 9(11):928-35 [PubMed] Free Access to Full Article Related Publications
Histone deacetylase (HDAC) inhibitors have shown preclinical efficacy in solid tumors, including ovarian cancers. Our group has published that the HDAC inhibitor, romidepsin (FK228) suppresses ovarian cancer cell growth at nanomolar concentrations in vitro. HDAC inhibitors appear to be even more effective when used in combination with other antitumor agents. However, it remains unclear which antitumor agents are best suited for combination therapy. A recent report suggested that aspirin (acetylsalicylic acid, ASA ) is synergistic with HDAC inhibitors in ovarian cancer cells. ASA is a relatively selective inhibitor of cyclooxygenase-1 (COX-1) and has anti-proliferative effects in ovarian cancer cells. The goal of this study was to investigate the impact of ASA on the activity of the HDAC inhibitor, FK228 in COX-1 positive (OVCAR-3) and COX-1 negative (SKOV-3) human ovarian cancer cell lines. The growth inhibitory effects of FK228 were enhanced by ASA in COX-1 positive ovarian cancer cells. In contrast, ASA had no influence on the results of FK228 treatment in COX-1 negative ovarian cancer cells. Upregulation of the cell cycle control protein p21 was induced robustly by FK228 in both cell lines. In the COX-1 positive cells, p21 expression was augmented by the addition of ASA to FK228 treatment. Furthermore, COX-1 siRNA attenuated the effects of combined ASA and FK228 on the levels of p21 expression and the amount of growth inhibition. The additional increase in p21 by ASA in FK228-treated cells was not observed at the promoter or transcriptional levels. However, a significant delay in p21 protein degradation in the presence of ASA and FK228 in COX-1 positive cells was associated with inhibition of proteasome activity. Our study provides a potential rationale for combining ASA with HDAC inhibitors in a subset of ovarian cancers.

Son DS, Parl AK, Rice VM, Khabele D
Keratinocyte chemoattractant (KC)/human growth-regulated oncogene (GRO) chemokines and pro-inflammatory chemokine networks in mouse and human ovarian epithelial cancer cells.
Cancer Biol Ther. 2007; 6(8):1302-12 [PubMed] Related Publications
Chronic inflammation is an important underlying condition for ovarian tumor development, growth and progression. Since chemokine networks are activated by inflammation, patterns of chemokine gene expression were investigated in ovarian cancer cells. Chemokine specific microarrays were performed after mouse (ID8) and human (SKOV-3) ovarian surface epithelial cancer cells were exposed to the inflammatory agent bacterial endotoxin lipopolysaccharide (LPS, 10 microg/ml) and pro-inflammatory cytokines interleukin-1beta (IL-1, 10 ng/ml) and tumor necrosis factor-alpha (TNF, 10 ng/ml). In the mouse ID8 cells, LPS, IL-1 and TNF led to robust upregulation of keratinocyte chemoattractant (KC) chemokines CXCL1/2, mouse homologues of human growth-regulated oncogenes (GRO). Other chemokines, interferong inducible protein (IP)-10 (CXCL10), CCL7 and CCL20 were moderately upregulated. ID8 cells constitutively expressed CXCL16 and CCL2, but only CCL2 expression was enhanced by LPS, IL-1 and TNF. In the human SKOV-3 cells, LPS had no effect on chemokines expression due to the absence of the LPS receptor, toll-like receptor 4 (TLR4). However, IL-1 and TNF induced GROalpha/beta (CXCL1/2) in human SKOV-3 cells in a similar manner as observed with mouse ID8 cells. In SKOV-3 cells, IL-8 (CXCL8) was highly expressed and other chemokines GROgamma (CXCL3) and CCL20 were moderately expressed in response to IL-1 and TNF. The nuclear factor-kappaB (NF-kappaB) is a known mediator of cytokine and chemokines signaling. The NFkappaB inhibitor BAY 11-7082 attenuated expression of inflammatory-induced chemokines in the mouse and human ovarian cancer cells. Taken together, the results indicate that KC/GRO chemokines are the principal chemokines induced by LPS and pro-inflammatory cytokines IL-1 and TNF via NFkappaB signaling in ovarian surface epithelial cancer cells.

Khabele D, Son DS, Parl AK, et al.
Drug-induced inactivation or gene silencing of class I histone deacetylases suppresses ovarian cancer cell growth: implications for therapy.
Cancer Biol Ther. 2007; 6(5):795-801 [PubMed] Related Publications
There is an urgent need to develop new strategies to treat ovarian cancer, the most deadly gynecologic malignancy. Histone deacetylase (HDAC) inhibitors are emerging as novel therapeutic drugs in the treatment of a variety of cancers, including those resistant to standard chemotherapy. Since there are multiple HDAC isoforms, determining the precise role of individual HDAC isoenzymes in the growth and progression of ovarian cancer has the potential to influence the use of selective HDAC inhibitors as strategic therapeutic agents that elicit fewer undesirable side effects. Unfortunately, there is limited information about the expression of HDAC isoforms in human ovarian tissues. This report provides evidence for the first time that Class I HDACs are expressed at significantly higher levels in ovarian cancers in comparison to normal ovarian tissues, with no significant difference in Class II HDAC expression between the two groups. Furthermore, ovarian cancer cells are far more sensitive than normal ovarian cells to the potent HDAC inhibitor romidepsin (FK228), a drug that displays greater inhibitory selectivity for Class I HDACs over Class II isoforms. Using small interfering RNA (siRNA) methodology, we demonstrate that knocking down the gene expression of HDAC3 and other members of the Class I HDAC family suppresses ovarian cancer cell growth. Taken together, the present studies offer several novel findings that have direct relevance for the strategic use of inhibitors that target Class I HDACs, particularly HDAC3, in the treatment of ovarian cancer.

Darvishi K, Sharma S, Bhat AK, et al.
Mitochondrial DNA G10398A polymorphism imparts maternal Haplogroup N a risk for breast and esophageal cancer.
Cancer Lett. 2007; 249(2):249-55 [PubMed] Related Publications
Mitochondria are the major source of Reactive Oxygen Species (ROS) and mtDNA G10398A (Ala-->Thr) polymorphism, proposed to be involved in increased ROS production, has been shown in association with invasive breast cancer in African-American (AA) women [J.A. Canter, A.R. Kallianpur, F.F. Parl, R.C. Millikan, Mitochondrial DNA G10398A polymorphism and invasive breast cancer in African-American women, Cancer Res. 65 (2005) 8028-8033] and prostate cancer in AA men [M.P. Mims, T.G. Hayes, S. Zheng, S.M. Leal, A. Frolov, M.M. Ittmann, et al., Mitochondrial DNA G10398A polymorphism and invasive breast cancer in African-American women, Cancer Res. 66 (2006) 1880; author reply 1880-1881]. The role of mitochondria, however, in cancer development has been in question recently [A. Salas, Y.G. Yao, V. Macaulay, A. Vega, A. Carracedo, H.J. Bandelt, A critical reassessment of the role of mitochondria in tumorigenesis, PLoS Med. 2 (2005) e296], which has made it pertinent to analyze the data and test the hypotheses by conducting fresh case-control studies. This study, therefore, makes an attempt to validate the exclusive presence of mtG10398A (Ala-->Thr) polymorphism in a haplotype constituting mtDNA haplogroup N and its sublineages, imparting this group a higher risk for breast cancer, based on the re-analyses of approximately 1000 complete human mtDNA sequences worldwide and collated information on 2334 individuals belonging to 18 regions in India. The conclusion drawn of mt10398A allele providing a risk towards cancer is confirmed in a case-control comparison study of 124 sporadic breast cancer patients and 273 controls; and 55 squamous cell carcinoma of esophagus, ESCC, and 163 controls, matched for age, ethnicity and sex from north India. It is further apparent from the study that such a mtDNA polymorphism background provides a higher risk for the cancers of the tissues which could be affected by environmental insults directly as in the ESCC, observed with a high acquired (somatic) rate of mutation in p53 when compared to the breast cancer, suggesting that the mtDNA variants that arose as energetic adaptations, influence our health differentially under different environment conditions and a given genetic background of the mt genome.

Paracchini V, Raimondi S, Gram IT, et al.
Meta- and pooled analyses of the cytochrome P-450 1B1 Val432Leu polymorphism and breast cancer: a HuGE-GSEC review.
Am J Epidemiol. 2007; 165(2):115-25 [PubMed] Related Publications
The association between the cytochrome P-450 1B1 (CYP1B1) Val432Leu polymorphism and breast cancer was assessed through a meta-analysis of all published case-control studies and a pooled analysis of both published and unpublished case-control studies from the Genetic Susceptibility to Environmental Carcinogens (GSEC) database ( ). GSEC is a collaborative project that gathers information on studies of metabolic gene polymorphisms and cancer. Thirteen articles were included in the meta-analysis (14,331 subjects; 7,514 cases, 6,817 controls); nine data sets were included in the pooled analysis (6,842 subjects; 3,391 cases, 3,451 controls). A summary meta- or pooled estimate of the association between the CYP1B1 Val432Leu polymorphism and breast cancer could not be calculated because of statistically significant heterogeneity in the point estimates among studies. No association between the CYP1B1 Val432Leu polymorphism and breast cancer was observed in Asians (for Val/Val and Val/Leu combined, odds ratio (OR) = 1.0, 95% confidence interval (CI): 0.8, 1.2). An inverse association was observed in populations of mixed/African origin (OR = 0.8, 95% CI: 0.7, 0.9). The pooled analysis suggested a possible association in Caucasians (for Val/Val and Val/Leu combined, OR = 1.5, 95% CI: 1.1, 2.1), with effect modification across age categories. The observed effect of age on the association in Caucasians indicates that further studies are needed on the role of CYP1B1 Val432Leu in estrogen metabolism according to age, ethnicity, and menopausal status.

Wen W, Cai Q, Shu XO, et al.
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.
Cancer Epidemiol Biomarkers Prev. 2005; 14(2):329-35 [PubMed] Related Publications
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.

Gold B, Kalush F, Bergeron J, et al.
Estrogen receptor genotypes and haplotypes associated with breast cancer risk.
Cancer Res. 2004; 64(24):8891-900 [PubMed] Related Publications
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), approximately 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 approximately 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.

Vogl FD, Taioli E, Maugard C, et al.
Glutathione S-transferases M1, T1, and P1 and breast cancer: a pooled analysis.
Cancer Epidemiol Biomarkers Prev. 2004; 13(9):1473-9 [PubMed] Related Publications
The glutathione S-transferase (GST) genes are involved in the metabolism of various carcinogens. Deletion polymorphisms in the genes GSTM1 and GSTT1 and a base transition polymorphism at codon 105 (Ile-->Val) in GSTP1 were investigated in relation to breast cancer risk. Tobacco smoking and reproductive factors were examined as potential effect modifiers. Individual data from seven case-control studies were pooled within the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens. To measure the effect of GSTs on breast cancer risk, odds ratios and 95% confidence intervals were computed adjusting for study center and age. The modifying effect was investigated by stratification on variables of smoking habits and reproductive history. A total of 2,048 cases with breast cancer and 1,969 controls were analyzed. The relative odds ratio (95% confidence interval) of breast cancer was 0.98 (0.86-1.12) with the GSTM1 null, 1.11 (0.87-1.41) with the GSTT1 null, 1.01 (0.79-1.28) with GSTP1 heterozygous mutants, and 0.93 (0.62-1.38) with GSTP1 homozygous mutants. Stratification by smoking or reproductive factors did not reveal a modifying effect of these variables, nor was there any association between GSTM1 and age at diagnosis of breast cancer. This is the largest study investigating susceptibility to breast cancer due to polymorphisms in the GST genes. The results conclusively show that single gene GST polymorphisms do not confer a substantial risk of breast cancer to its carriers. Furthermore, GSTs did not interact with smoking or reproductive history to modify cancer risk.

Kallianpur AR, Hall LD, Yadav M, et al.
Increased prevalence of the HFE C282Y hemochromatosis allele in women with breast cancer.
Cancer Epidemiol Biomarkers Prev. 2004; 13(2):205-12 [PubMed] Related Publications
Individuals with the major hemochromatosis (HFE) allele C282Y and iron overload develop hepatocellular and some extrahepatic malignancies at increased rates. No association has been previously reported between the C282Y allele and breast cancer. We hypothesized that due to the pro-oxidant properties of iron, altered iron metabolism in C282Y carriers may promote breast carcinogenesis. Because 1 in 10 Caucasians of Northern European ancestry carries this allele, any impact it may have on breast cancer burden is potentially great. We determined C282Y genotypes in 168 patients who underwent high-dose chemotherapy and blood cell transplantation for cancer: 41 with breast cancer and 127 with predominantly hematological cancers (transplant cohort). Demographic, clinical, and tumor characteristics were reviewed in breast cancer patients. The frequency of C282Y genotypes in breast cancers was compared with the frequency in nonbreast cancers, an outpatient sample from Tennessee (n = 169), and a published United States national sample. The frequency of at least one C282Y allele in breast cancers was higher (36.6%, 5 homozygotes/10 heterozygotes) than frequencies in Tennessee (12.7%, P < 0.001), the general population (12.4%, P < 0.001), and similarly selected nonbreast cancers (17.0%, P = 0.008). The likelihood of breast cancer in the transplant cohort increased with C282Y allele dose (P(trend) = 0.010). These results were supported by the finding in a nontransplant cohort of a higher frequency of C282Y mutations in Caucasian (18.4%, P = 0.039) and African-American (8.5%, P = 0.005) women with breast cancer than race-specific national frequency estimates. A high prevalence of C282Y alleles in women with breast cancer with and without poor risk features suggests that altered iron metabolism in C282Y carriers may promote the development of breast cancer and/or more aggressive forms of the disease.

Garte S, Gaspari L, Alexandrie AK, et al.
Metabolic gene polymorphism frequencies in control populations.
Cancer Epidemiol Biomarkers Prev. 2001; 10(12):1239-48 [PubMed] Related Publications
Using the International Project on Genetic Susceptibility to Environmental Carcinogens (GSEC) database containing information on over 15,000 control (noncancer) subjects, the allele and genotype frequencies for many of the more commonly studied metabolic genes (CYP1A1, CYP2E1, CYP2D6, GSTM1, GSTT1, NAT2, GSTP, and EPHX) in the human population were determined. Major and significant differences in these frequencies were observed between Caucasians (n = 12,525), Asians (n = 2,136), and Africans and African Americans (n = 996), and some, but much less, heterogeneity was observed within Caucasian populations from different countries. No differences in allele frequencies were seen by age, sex, or type of controls (hospital patients versus population controls). No examples of linkage disequilibrium between the different loci were detected based on comparison of observed and expected frequencies for combinations of specific alleles.

Dawling S, Roodi N, Mernaugh RL, et al.
Catechol-O-methyltransferase (COMT)-mediated metabolism of catechol estrogens: comparison of wild-type and variant COMT isoforms.
Cancer Res. 2001; 61(18):6716-22 [PubMed] Related Publications
The oxidative metabolism of 17beta-estradiol (E2) and estrone (E1) to catechol estrogens (2-OHE2, 4-OHE2, 2-OHE1, and 4-OHE1) and estrogen quinones has been postulated to be a factor in mammary carcinogenesis. Catechol-O-methyltransferase (COMT) catalyzes the methylation of catechol estrogens to methoxy estrogens, which simultaneously lowers the potential for DNA damage and increases the concentration of 2-methoxyestradiol (2-MeOE2), an antiproliferative metabolite. We expressed two recombinant forms of COMT, the wild-type (108Val) and a common variant (108Met), to determine whether their catalytic efficiencies differ with respect to catechol estrogen inactivation. The His-tagged proteins were purified by nickel-nitrilo-triacetic acid chromatography and analyzed by electrophoresis and Western immunoblot. COMT activity was assessed by determining the methylation of 2-OHE2, 4-OHE2, 2-OHE1, and 4-OHE1, using gas chromatography/mass spectrometry for quantitation of the respective methoxy products. In the case of 2-OHE2 and 2-OHE1, methylation occurred at 2-OH and 3-OH groups, resulting in the formation of 2-MeOE2 and 2-OH-3-MeOE2, and 2-MeOE1 and 2-OH-3-MeOE1, respectively. In contrast, in the case of 4-OHE2 and 4-OHE1, methylation occurred only at the 4-OH group, yielding 4-MeOE2 and 4-MeOE1, respectively. Individual and competition experiments revealed the following order of product formation: 4-MeOE2 > 4-MeOE1 > 2-MeOE2 > 2-MeOE1 > 2-OH-3-MeOE1 > 2-OH-3-MeOE2. The variant isoform differed from wild-type COMT by being thermolabile, leading to 2-3-fold lower levels of product formation. MCF-7 breast cancer cells with the variant COMT 108Met/Met genotype also displayed 2-3-fold lower catalytic activity than ZR-75 breast cancer cells with the wild-type COMT 108Val/Val genotype. Thus, inherited alterations in COMT catalytic activity are associated with significant differences in catechol estrogen and methoxy estrogen levels and, thereby, may contribute to interindividual differences in breast cancer risk associated with estrogen-mediated carcinogenicity.

Ritchie MD, Hahn LW, Roodi N, et al.
Multifactor-dimensionality reduction reveals high-order interactions among estrogen-metabolism genes in sporadic breast cancer.
Am J Hum Genet. 2001; 69(1):138-47 [PubMed] Free Access to Full Article Related Publications
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.

Nass SJ, Herman JG, Gabrielson E, et al.
Aberrant methylation of the estrogen receptor and E-cadherin 5' CpG islands increases with malignant progression in human breast cancer.
Cancer Res. 2000; 60(16):4346-8 [PubMed] Related Publications
Loss of expression for both the estrogen receptor-alpha and E-cadherin genes has been linked to disease progression in human ductal breast carcinomas and has been associated with aberrant 5' CpG island methylation. To assess when, during malignant progression, such methylation begins and whether such methylation increases with advancing disease, we have surveyed 111 ductal carcinomas of the breast for aberrant methylation of the estrogen receptor-alpha and E-cadherin 5' CpG islands. Hypermethylation of either CpG island was evident prior to invasion in approximately 30% of ductal carcinoma in situ lesions and increased significantly to nearly 60% in metastatic lesions. Coincident methylation of both CpG islands also increased significantly from approximately 20% in ductal carcinoma in situ to nearly 50% in metastatic lesions. Furthermore, in all cases, the pattern of methylation displayed substantial heterogeneity, reflecting the well-established, heterogeneous loss of expression for these genes in ductal carcinomas of the breast.

Sharan C, Hamilton NM, Parl AK, et al.
Identification and characterization of a transcriptional silencer upstream of the human BRCA2 gene.
Biochem Biophys Res Commun. 1999; 265(2):285-90 [PubMed] Free Access to Full Article Related Publications
Expression of the breast cancer susceptibility tumor-suppressor protein BRCA2, a protein potentially involved in DNA recombination repair, is tightly regulated throughout development. We have identified a transcriptional silencer at the distal end of the human BRCA2 gene promoter. This silencer is involved in the negative regulation of the expression of this gene in breast cell lines tested but not in HeLa or HepG2 cells. The 221-base-pair silencer region is characterized by a full-length Alu-repeat. Presence of specific BRCA2 silencer-binding proteins in the breast cell extracts indicates the potential regulation of BRCA2 gene expression by these proteins.

Wang LG, Liu XM, Kreis W, Budman DR
Androgen antagonistic effect of estramustine phosphate (EMP) metabolites on wild-type and mutated androgen receptor.
Biochem Pharmacol. 1998; 55(9):1427-33 [PubMed] Related Publications
Estramustine phosphate is used frequently, alone or in combination with other antitumor agents, for the treatment of hormone-refractory prostate cancer. Estramustine phosphate is metabolically activated in vivo, and its metabolites, estramustine, estromustine, estrone, and beta-estradiol inhibit the assembly of microtubules [for review see: Kreis W, In: Concepts, Mechanisms, and New Targets for Chemotherapy (Ed. Muggia FM), pp. 163-184. Kluwer Academic Publishers, Boston, 1995]. We investigated, by displacement of [3H]methyltrienolone in the presence of 2.5 mM of triamcinolone acetonide, the binding of estramustine phosphate and its metabolites, estramustine, estromustine, estrone, and beta-estradiol, as well as other antiandrogen agents including alpha-estradiol, bicalutamide, and hydroxyflutamide, to the mutated androgen receptor (m-AR) in LNCaP cells and to the wild-type androgen receptor in wild-type AR cDNA expression plasmid (w-pAR0) cDNA-transfected HeLa cells. Analogous to the antiandrogens, bicalutamide and hydroxyflutamide, binding of estramustine phosphate metabolites to the androgen receptor was observed. The EC50 values (in microM) were: estramustine phosphate, > 10; estramustine, 3.129 +/- 0.312; estromustine; 2.612 +/- 0.584; estrone, 0.800 +/- 0.090; alpha-estradiol, 1.051 +/- 0.096; beta-estradiol, 0.523 +/- 0.028; bicalutamide, 4.920 +/- 0.361; and hydroxyflutamide, 0.254 +/- 0.012. The transactivation assay demonstrated that, analogous to bicalutamide, estramustine could not induce luciferase activity in either w-pAR0 or m-pARL transfected HeLa cells. In contrast, a strong induction of the reporter activity by dihydrotestosterone was observed. Down-regulation of prostate-specific antigen (PSA) expression, an AR-target gene, by estramustine and bicalutamide was accompanied by the blockade of the mutated androgen receptor. Exposure of LNCaP cells to estramustine for 24 hr caused transcriptional inhibition of PSA in a concentration-dependent manner. The levels of PSA mRNA decreased 56 and 90% when LNCaP cells were treated with 5 and 10 microM of estramustine, respectively (IC50 = 10.97 +/- 1.68 microM). Binding of hydroxyflutamide to m-AR in LNCaP cells resulted in a concentration-dependent stimulation of PSA expression, suggesting that hydroxyflutamide acted as an agonist of the m-AR. Our data indicate that estramustine phosphate metabolites perform as androgen antagonists of AR, an additional mechanism involved in the therapeutic effect of estramustine phosphate in patients with prostate cancer.

Bailey LR, Roodi N, Dupont WD, Parl FF
Association of cytochrome P450 1B1 (CYP1B1) polymorphism with steroid receptor status in breast cancer.
Cancer Res. 1998; 58(22):5038-41 [PubMed] Related Publications
A key enzyme involved in the production of potentially carcinogenic estrogen metabolites and the activation of environmental carcinogens is cytochrome P450 1B1 (CYP1B1), the predominant member of the CYP1 family expressed in normal breast tissue and breast cancer. Because of the preeminent role of CYP1B1 in mammary estrogen/carcinogen metabolism, we examined the CYP1B1 gene to determine whether genetic differences could account for interindividual differences in breast cancer risk. We focused on exon 3, because it encodes the catalytically important heme binding domain of the enzyme, and discovered three polymorphisms of which two are associated with amino acid substitutions in codons 432 (Val-->Leu) and 453 (Asn-->Ser), designated as m1 and m2, respectively. Approximately 40% of Caucasian women have the m1 Val allele compared with nearly 70% of African-American women (P < 0.0001). The allele frequency also differs significantly in m2, with the rare Ser allele being present in 17.4% of Caucasians but only in 3.4% of African Americans (P < 0.0003). To determine whether the polymorphic CYP1B1 alleles hold implications as potential breast cancer risk factors, we compared the CYP1B1 genotypes in 164 Caucasian and 59 African-American breast cancer cases with those in age-, race-, and frequency-matched controls. Odds ratio calculations failed to show a significant association between any of the genotypes and breast cancer. Because CYP1B1 is known to be involved in mammary estrogen metabolism, we investigated whether the estrogen receptor status is influenced by the CYP1B1 genotypes. Caucasian patients with the m1 Val/Val genotype have a significantly higher percentage of estrogen receptor-positive (P = 0.02) and progesterone receptor-positive breast cancers (P = 0.003). There was no correlation with the m2 genotypes. These data suggest that the CYP1B1 polymorphisms in exon 3 are not associated with increased breast cancer risk but that the m1 polymorphism may be functionally important for steroid receptor expression in breast cancer of Caucasian patients.

Lapidus RG, Nass SJ, Butash KA, et al.
Mapping of ER gene CpG island methylation-specific polymerase chain reaction.
Cancer Res. 1998; 58(12):2515-9 [PubMed] Related Publications
Southern analysis has shown that DNA from 25% of primary estrogen receptor (ER) alpha-negative breast tumors displays aberrant methylation at one site within the ER gene CpG island. To examine more sites and increase sensitivity, we developed a methylation-specific PCR assay to map methylation of the entire ER CpG island. The island was unmethylated in normal breast tissue and ER-positive breast cancer cell lines, but extensively methylated in all ER-negative cell lines and breast tumors examined. In addition, some of the ER-positive/progesterone receptor-negative and ER-positive/progesterone receptor-positive tumors (about 70% and 35%, respectively) displayed methylation of the ER CpG island, suggesting that this heterogeneity within tumor cell populations could potentially shed light on the etiology of ER-negative recurrent tumors arising from ER-positive tumors.

Bailey LR, Roodi N, Verrier CS, et al.
Breast cancer and CYPIA1, GSTM1, and GSTT1 polymorphisms: evidence of a lack of association in Caucasians and African Americans.
Cancer Res. 1998; 58(1):65-70 [PubMed] Related Publications
Genetically based differences in carcinogen metabolism have been related to polymorphisms of the cytochrome P450IA1 gene (CYPIA1) and the null genotypes of glutathione S-transferase classes mu and theta (GSTM1 and GSTT1). By PCR we examined the genotypes of CYPIA1, GSTM1, and GSTT1 in relation to breast cancer risk in Caucasian and African-American women. The study included 164 Caucasian and 59 African-American women with primary invasive breast cancer and age-matched female controls. Enzyme polymorphisms included in this study were the null deletions of GSTM1 and GSTT1 and the m1 (MspI), m2 (codon 462: isoleucine-->valine), m3 (MspI-AA), and m4 (codon 461: threonine-->asparagine) polymorphisms of CYPIA1. Contrary to previous reports by other investigators, none of the enzyme genotypes, individually or combined, appear to associate with an increased risk for breast cancer in Caucasian or African-American women. We also report that the recently described m4 allele occurs at a lower frequency in African-Americans than Caucasians and is not linked with breast cancer in either race. Thus, it is unlikely that polymorphisms of GSTM1, GSTT1, or CYPIA1 represent susceptibility factors for breast cancer in Caucasians or African-Americans.

Lapidus RG, Ferguson AT, Ottaviano YL, et al.
Methylation of estrogen and progesterone receptor gene 5' CpG islands correlates with lack of estrogen and progesterone receptor gene expression in breast tumors.
Clin Cancer Res. 1996; 2(5):805-10 [PubMed] Related Publications
Hormonal factors have a profound influence on the development, treatment, and outcome of breast cancer. The absence of steroid hormone receptors is highly correlated with resistance to antihormonal treatments. Work in cultured human breast cancer cell lines has shown that the absence of estrogen receptor (ER) gene expression in ER- cells is associated with extensive methylation of the ER gene 5' CpG island, and treatment with agents that demethylate the ER gene CpG island results in the production of functional ER protein. The current study shows that CpG islands in the 5' region of the ER and progesterone receptor (PR) genes are methylated in a significant fraction of primary human breast cancer tissues. The ER CpG island is methylated at the methylation-sensitive NotI restriction site in 9 of 39 (25%) of primary ER- breast cancers but remains unmethylated in 53 ER+ breast cancers and 9 normal breast specimens. Three methylation-sensitive restriction sites in the PR gene CpG island are not methylated in normal breast specimens and PR+ human breast cancers but are hypermethylated in 40% of PR- human breast tumors. These data demonstrate that methylation of the ER and PR gene CpG islands is associated with the lack of ER and PR gene expression in a significant fraction of human breast cancers.

Roodi N, Bailey LR, Kao WY, et al.
Estrogen receptor gene analysis in estrogen receptor-positive and receptor-negative primary breast cancer.
J Natl Cancer Inst. 1995; 87(6):446-51 [PubMed] Related Publications
BACKGROUND: In breast cancer patients, about two thirds of the tumors are estrogen receptor (ER)-positive and one third are ER-negative. The molecular mechanisms leading to the ER-negative phenotype are poorly understood. Nearly all ER-negative and about 40% of ER-positive cancers are resistant to endocrine therapy.
PURPOSE: In this study, we examined the entire coding region of the ER gene in ER-positive and ER-negative primary breast tumors to determine whether deletions/insertions or point mutations might account for the ER-negative phenotype.
METHODS: We amplified exons 1 through 8 of the ER gene in 118 ER-positive and 70 ER-negative primary breast tumors and searched for mutations by single-strand conformation polymorphism analysis, denaturing gradient gel electrophoresis, and DNA sequencing.
RESULTS: Both ER-negative and ER-positive tumors contained neutral polymorphisms in codons 10 [TCT-->TCC (Ser)], 87 [GCG-->GCC (Ala)], 243 [CGC-->CGT (Arg)], 325 [CCC-->CCG (Pro)], and 594 [ACA-->ACG (Thr)]. There was no correlation of any of the polymorphic alleles with the ER phenotype or other clinicopathologic parameters including tumor type, size, grade, or stage. However, the polymorphism in codon 325 showed a strong association with a family history of breast cancer (P = .0005). This association was observed both in premenopausal and postmenopausal patients. Despite extensive searching in exons 1 through 8, we found no deletions/insertions and only two missense mutations in codons 69 [AAC (Asn)-->AAG (Lys)] and 396 [ATG (Met)-->GTG (Val)] of the same ER-negative tumor. Thus, only 1% of the primary breast cancers had point mutations in the ER gene.
CONCLUSIONS: In the majority of primary breast cancers, the ER-negative phenotype is not the result of mutations in the coding region of the ER gene, but is due to deficient ER expression at the transcriptional or post-transcriptional level.
IMPLICATIONS: The correlation reported previously, as well as our current findings, suggest that further investigations are warranted to understand the possible linkage of the ER gene locus to hereditary breast cancer.

O'Malley FP, Vnencak-Jones CL, Dupont WD, et al.
p53 mutations are confined to the comedo type ductal carcinoma in situ of the breast. Immunohistochemical and sequencing data.
Lab Invest. 1994; 71(1):67-72 [PubMed] Related Publications
BACKGROUND: Mutations in the p53 tumor suppressor gene have been identified in breast and many other carcinomas. It is not clear, however, when these mutations occur during breast carcinogenesis. Overexpression of 53 protein has been reported in some ductal carcinoma in situ (DCIS) lesions. To further study the overexpression of p53 in DCIS of the breast and correlate these findings with changes at the molecular level, we performed p53 immunostaining and direct sequencing in noncomedo and comedo DCIS.
EXPERIMENTAL DESIGN: Archival blocks were obtained on cases of noncomedo DCIS, (including encysted, noninvasive papillary carcinoma) and comedo DCIS. Immunohistochemical staining with the p53 antibody DO7 was performed on all cases. Polymerase chain reaction (PCR) amplification of exons 5, 6, and 7 of the p53 gene was performed and the PCR products were directly sequenced. Four comedo DCIS cases that were p53 immunopositive were further screened for p53 mutations by PCR/single strand conformation polymorphism in exons 8 and 9 of the p53 gene. One of these cases showing a mobility shift was directly sequenced.
RESULTS: We examined 39 lesions including comedo DCIS (N = 12) and noncomedo DCIS (N = 27), the latter including 17 encysted noninvasive papillary carcinomas. Immunostaining with DO7 was positive in 4 of 12 comedo DCIS lesions (33%) while all noncomedo lesions including encysted noninvasive papillary carcinomas were negative. Direct sequencing of PCR products confirmed wild-type DNA in exons 5 and 6 in all noninvasive papillary carcinomas, 3 randomly selected noncomedo DCIS lesions, and 4 p53 antibody-positive comedo DCIS lesions. In these latter 4 cases, wild-type DNA sequences were preserved in exon 7 for all cases. A single case had a conformational shift in exon 8 within the four cases screened in exons 8 and 9. Direct DNA sequencing of this exon revealed a G to A point mutation resulting in an arginine-to-histidine substitution at codon 273 of the protein.
CONCLUSIONS: Our results suggest that mutant p53 protein accumulation in preinvasive lesions is limited to comedo (high grade) DCIS and that p53 positivity by immunohistochemistry does not correlate in all cases with specific p53 mutations in exons 5 to 9, the most highly conserved regions of this gene.

Ottaviano YL, Issa JP, Parl FF, et al.
Methylation of the estrogen receptor gene CpG island marks loss of estrogen receptor expression in human breast cancer cells.
Cancer Res. 1994; 54(10):2552-5 [PubMed] Related Publications
Breast cancer is the most common malignancy in women and hormone resistance is a challenging problem in its treatment. Loss of estrogen receptor expression is an important means of hormone resistance, but the mechanisms involved are poorly understood. We now demonstrate a potential role for abnormal DNA methylation in transcriptional inactivation of the estrogen receptor gene. Estrogen receptor-negative human breast cancer cells growing in culture lack estrogen receptor mRNA, have a higher capacity to methylate DNA, and display extensive methylation of the CpG island in the 5' promoter region of the estrogen receptor gene, which would correlate with silencing of expression. These results suggest that abnormal methylation could account for transcriptional inactivation of the estrogen receptor gene and subsequent hormone resistance in some human breast cancers.

Caleffi M, Teague MW, Jensen RA, et al.
p53 gene mutations and steroid receptor status in breast cancer. Clinicopathologic correlations and prognostic assessment.
Cancer. 1994; 73(8):2147-56 [PubMed] Related Publications
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.
METHODS: We examined the p53 gene in genomic DNA samples from 192 primary breast cancers. Using denaturant gradient gel electrophoresis, the authors analyzed exons 5-9 in all tumors for mutations and performed DNA sequencing in 20 tumors to identify the exact nature of the p53 mutations.
RESULTS: p53 gene alterations were identified in 43 of the 192 tumors (22%), the majority localized in exons 5 and 6. DNA sequencing showed mostly missense mutations resulting from G or C substitutions. p53 mutations were found more often in tumors of younger women (P = 0.002), Afro-American women (P = 0.05), and in tumors lacking ER (P = 0.03), PR (P = 0.04), or both (P = 0.06). There were no significant correlations with family history, tumor size, histologic grade or type, nodal status, or disease stage. The overall survival rates showed no significant difference between patients with mutant and wild-type p53 tumors. The same was true when the comparison was limited to node-negative patients or patients with ER-positive or ER-negative tumors. Finally, there was no significant difference in survival between patients with tumors harboring mutations in exons 5 and 6 versus exons 7-9.
CONCLUSIONS: The results of this and other studies demonstrate a consistent relationship between ER-positive tumors and wild-type p53 on one hand and ER-negative cancers and p53 mutations on the other. Our data do not support a significant prognostic role for p53 mutations in predicting survival.

Yaich L, Dupont WD, Cavener DR, Parl FF
Analysis of the PvuII restriction fragment-length polymorphism and exon structure of the estrogen receptor gene in breast cancer and peripheral blood.
Cancer Res. 1992; 52(1):77-83 [PubMed] Related Publications
The presence of estrogen receptor (ER) is a well-known predictor of clinical outcome in human breast cancer. We examined the ER gene in 26 primary breast cancers (14 ER-positive, 12 ER-negative) to determine if alterations of the gene are associated with the ER-negative status. In tumor biopsies and peripheral blood DNA obtained from the same patients we analyzed the ER exon structure using polymerase chain reaction amplification, restriction endonuclease digestion, and agarose gel electrophoresis. All blood and tumor samples, regardless of ER status, showed a complete set of eight exons of normal sizes, ruling out deletions or rearrangements of the ER gene in excess of +/- 20 nucleotides. Previous reports indicate that the two-allele ER PvuII polymorphism could be associated with ER expression in breast cancer (Hill et al., Cancer Res., 49: 145-148, 1989) as well as with patient age at time of tumor diagnosis (Parl et al., Breast Cancer Res. Treat., 14: 57-64, 1989). We localized the PvuII polymorphism in intron 1, 0.4 kilobase upstream of exon 2. Sequence analysis showed the polymorphism to result from a point mutation (T----C) at the fifth position of the restriction site (CATCTG). We determined the PvuII restriction fragment-length polymorphism genotype in 257 primary breast cancers and 140 peripheral blood DNA samples obtained from women without breast cancer. The results indicate that the PvuII polymorphism is not associated with ER content or patient age at tumor diagnosis.

Parl FF, Cavener DR, Dupont WD
Genomic DNA analysis of the estrogen receptor gene in breast cancer.
Breast Cancer Res Treat. 1989; 14(1):57-64 [PubMed] Related Publications
A 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.

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