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Biomedical subjects

F J Couch

Publications and source records attributed to F J Couch.

At least 19 recordsLinked to original sources
PubMed2001

Efficacy of bilateral prophylactic mastectomy in BRCA1 and BRCA2 gene mutation carriers.

BACKGROUND: In women with a family history of breast cancer, bilateral prophylactic mastectomy is associated with a decreased risk of subsequent breast cancer of approximately 90%. We examined the association between bilateral prophylactic mastectomy and breast cancer risk in women at high risk for breast cancer who also had mutations in BRCA1 and BRCA2 genes. METHODS: We obtained blood samples from 176 of the 214 high-risk women who participated in our previous retrospective cohort study of bilateral prophylactic mastectomy. We used conformation-sensitive gel electrophoresis and direct sequence analysis of the blood specimens to identify women with mutations in BRCA1 and BRCA2. The carriers' probabilities of developing breast cancer were estimated from two different penetrance models. RESULTS: We identified 26 women with an alteration in BRCA1 or BRCA2. Eighteen of the mutations were considered to be deleterious and eight to be of uncertain clinical significance. None of the 26 women has developed breast cancer after a median of 13.4 years of follow-up (range, 5.8-28.5 years). Three of the 214 women are known to have developed a breast cancer after prophylactic mastectomy. For two of these women, BRCA1 and BRCA2 screening was negative, and no blood specimen was available for the third. Estimations of the effectiveness of prophylactic mastectomy were performed, considering this woman as both a mutation carrier and a noncarrier. These calculations predicted that six to nine breast cancers should have developed among the mutation carriers, which translates into a risk reduction, after bilateral prophylactic mastectomy, of 89.5%-100% (95% confidence interval = 41.4% to 100%). CONCLUSIONS: Prophylactic mastectomy is associated with a substantial reduction in the incidence of subsequent breast cancer not only in women identified as being at high risk on the basis of a family history of breast cancer but also in known BRCA1 or BRCA2 mutation carriers.

Breast Neoplasms↗
PubMed2001

Genetic analysis of early- versus late-stage ovarian tumors.

In the United States, ovarian cancer is the fourth most common cause of cancer-related deaths among women. The most important prognostic factor for this cancer is tumor stage, or extent of disease at diagnosis. Although women with low-stage tumors have a relatively good prognosis, most women diagnosed with late-stage disease eventually succumb to their cancer. In an attempt to understand early events in ovarian carcinogenesis, and to explore steps in its progression, we have applied multiple molecular genetic techniques to the analysis of 21 early-stage (stage I/II) and 17 advanced-stage (stage III/IV) ovarian tumors. These techniques included expression profiling with cDNA microarrays containing approximately 18,000 expressed sequences, and comparative genomic hybridization to address the chromosomal locations of copy number gains as well as losses. Results from the analysis indicate that early-stage ovarian cancers exhibit profound alterations in gene expression, many of which are similar to those identified in late-stage tumors. However, differences observed at the genomic level suggest differences between the early- and late-stage tumors and provide support for a progression model for ovarian cancer development.

Disease Progression↗
PubMed2001

Structural analysis of the 17q22-23 amplicon identifies several independent targets of amplification in breast cancer cell lines and tumors.

A novel region of amplification in breast tumors has recently been identified on chromosome 17q22-23. In an effort to identify the oncogenes in the region that are targeted by the amplification process, we determined the structure of the amplicon in breast cancer cell lines and tumors. Physical and transcription maps of the approximately 3.5-Mb region were established and used as the basis for copy number analysis within the region by Southern blot and fluorescence in situ hybridization. Seven specific and independent amplification maxima were identified in breast cancer cell lines and breast tumors. We present correlative amplification and overexpression studies for the FLJ21316 and Hs.6649 genes suggesting a role for these candidates as amplification-dependent oncogenes.

Amino Acid Sequence↗
PubMed2001

PS6K amplification characterizes a small subset of anaplastic meningiomas.

PS6K, a putative oncogene mapped to chromosome 17q23, encodes a serine/threonine kinase, which phosphorylates ribosomal subunit 6 and is part of the insulin receptor signal transduction pathway involved in the regulation of messenger RNA translation, protein synthesis, cell cycle progression, and cell size. Comparative genomic hybridization studies have detected 17q23 amplifications in a subset of meningiomas, particularly those with aggressive histologic features. PS6K amplifications have been reported in breast cancer, another hormonally driven neoplasm. We assessed PS6K dosage in 94 archival paraffin-embedded meningiomas using dual-color fluorescence in situ hybridization. We found high-level PS6K amplifications in 3 of 22 anaplastic grade III meningiomas. Amplification was confirmed by differential polymerase chain reaction in 1 of these cases. In contrast, no amplifications were identified in 37 benign (grade I) and 35 atypical (grade II) meningiomas. To our knowledge, this represents the first report of gene amplification in primary human meningiomas. Given its exclusive association with anaplastic meningiomas, PS6K amplification likely occurs during the malignant progression of a small subset of anaplastic tumors. Further studies are needed to map the 17q23 amplicon to determine whether additional genes in this region are amplified in high-grade meningiomas.

DNA Primers↗
PubMed2001

Cigarette smoking increases risk for breast cancer in high-risk breast cancer families.

Most epidemiological studies of cigarette smoking and breast cancer have failed to demonstrate a strong association. Only one study has been performed on women at high genetic risk, and smoking was reported to be a protective factor. To further explore this observation, we examined the association of cigarette smoking with the risk of breast cancer in a historical cohort study of high-risk breast cancer families. A total of 426 families ascertained through a consecutive series of breast cancer patients (probands) between 1944 and 1952 were followed through 1996. Occurrence of breast cancer and detailed smoking histories for sisters, daughters, granddaughters, nieces, and marry-ins were obtained through telephone interviews between 1991 and 1996. Cox proportional hazards regression, accounting for age, birth cohort, and other risk factors, was used to calculate relative risks and 95% confidence intervals (CIs) of breast cancer. All of the models were constructed within strata defined by relationship to the index case (proband), with nonsmokers designated as the referent group. Of the 426 families in the cohort, 132 had at least three incident breast and/or ovarian cancers in the biological relatives at the end of the follow-up period. Among sisters and daughters in these 132 high-risk families, those who ever smoked were at 2.4-fold increased risk of breast cancer (95% CI, 1.2-5.1) relative to never-smokers. No association between breast cancer and smoking was observed among nieces and granddaughters of probands or among marry-ins. When the analysis was restricted to 35 families at highest genetic risk (each containing five breast and/or ovarian cancers), smoking became an even stronger risk factor. Among sisters and daughters, ever-smokers were at 5.8-fold greater risk than nonsmokers (95% CI, 1.4-23.9). Among nieces and granddaughters, the risk of breast cancer associated with smoking was increased 60% (95% CI, 0.8-3.2). These results suggest that smoking may increase risk for breast cancer in families with multiple cases of breast or ovarian cancer, especially those with the strongest apparent familial predisposition.

Adolescent↗
PubMed2000

Induction of the BRCA2 promoter by nuclear factor-kappa B.

BRCA2 is a tumor suppressor gene that has been implicated in response to DNA damage, cell cycle control, and transcription. BRCA2 has been found to be overexpressed in many breast tumors, suggesting that altered expression of the BRCA2 gene may contribute to breast tumorigenesis. To determine how BRCA2 is overexpressed in tumors, we investigated the transcriptional regulation of the BRCA2 promoter. Deletion mapping of the BRCA2 promoter identified three regions associated with 3-fold activation or repression and one upstream stimulatory factor binding site associated with 20-fold activation. Gel shift and cotransfection studies verified the role of USF in regulation of BRCA2 transcription. Analysis of the -144 to -59 region associated with 3-fold activation identified a putative NFkappaB binding site. Cotransfection of the p65 and p50 subunits of NFkappaB up-regulated the BRCA2 promoter 16-fold in a luciferase reporter assay, whereas mutations in the binding site ablated the effect. Gel shift and supershift assays with anti-p65 and -p50 antibodies demonstrated that NFkappaB binds specifically to the NFkappaB site. In addition, ectopic expression of NFkappaB resulted in increased levels of endogeneous BRCA2 expression. Thus, NFkappaB and USF regulate BRCA2 expression through the BRCA2 promoter.

BRCA2 Protein↗
PubMed2000

BRCA1 facilitates stress-induced apoptosis in breast and ovarian cancer cell lines.

The BRCA1 tumor suppressor gene has previously been implicated in induction of high levels of apoptosis in osteocarcinoma cell lines. Overexpression of BRCA1 was shown to induce an apoptotic signaling pathway involving the c-Jun N-terminal kinase (JNK), but the signaling steps upstream and downstream of JNK were not delineated. To better understand the role of BRCA1 in apoptosis, we examined the effect of wild-type and C-terminal-truncated dominant negative BRCA1 on breast and ovarian cancer cell lines subjected to a number of different pro-apoptotic stimuli, including growth factor withdrawal, substratum detachment, ionizing radiation, and treatment with anticancer agents. All of these treatments were found to induce substantial levels of apoptosis in the presence of wild-type BRCA1, whereas dominant negative BRCA1 truncation mutants diminished the apoptotic response. Subsequent mapping of the apoptotic pathway induced by growth factor withdrawal demonstrated that BRCA1 enhanced signaling through a pathway that sequentially involved H-Ras, MEKK4, JNK, Fas ligand/Fas interactions, and caspase-9 activation. In addition, the pathway functioned independently of the p53 tumor suppressor. These data suggest that BRCA1 is an important modulator of the response to cellular stress and that loss of this apoptotic potential due to BRCA1 mutations may contribute to tumor development.

Apoptosis↗
PubMed2000

Risk of breast cancer with oral contraceptive use in women with a family history of breast cancer.

CONTEXT: Oral contraceptive (OC) use is weakly associated with breast cancer risk in the general population, but the association among women with a familial predisposition to breast cancer is less clear. OBJECTIVE: To determine whether the association between OC use and risk of breast cancer is influenced by family history of the disease. DESIGN AND SETTING: Historical cohort study of 426 families of breast cancer probands diagnosed between 1944 and 1952 at the Tumor Clinic of the University of Minnesota Hospital. Follow-up data on families were collected by telephone interview between 1991 and 1996. PARTICIPANTS: A total of 394 sisters and daughters of the probands, 3002 granddaughters and nieces, and 2754 women who married into the families. MAIN OUTCOME MEASURE: Relative risk (RR) of breast cancer associated with history of OC use by relationship to proband. RESULTS: After accounting for age and birth cohort, ever having used OCs was associated with significantly increased risk of breast cancer among sisters and daughters of the probands (RR, 3.3; 95% confidence interval [CI], 1.6-6.7), but not among granddaughters and nieces of the probands (RR, 1.2; 95% CI, 0.8-2.0) or among marry-ins (RR, 1.2; 95% CI, 0.8-1.9). Results were essentially unchanged after adjustment for parity, age at first birth, age at menarche, age at menopause, oophorectomy, smoking, and education. The elevated risk among women with a first-degree family history of breast cancer was most evident for OC use during or prior to 1975, when formulations were likely to contain higher dosages of estrogen and progestins (RR, 3.3; 95% CI, 1.5-7.2). A small number of breast cancer cases (n = 2) limited the statistical power to detect risk among women with a first-degree relative with breast cancer and OC use after 1975. CONCLUSIONS: These results suggest that women who have ever used earlier formulations of OCs and who also have a first-degree relative with breast cancer may be at particularly high risk for breast cancer. Further studies of women with a strong family history who have used more recent lower-dosage formulations of OCs are needed to determine how women with a familial predisposition to breast cancer should be advised regarding OC use today. JAMA. 2000;284:1791-1798.

Adult↗
PubMed2000

17q23 amplifications in breast cancer involve the PAT1, RAD51C, PS6K, and SIGma1B genes.

Amplification of the 17q23 region occurs frequently in breast tumors. To characterize the structure of 17q23 amplicons and to identify oncogene targets associated with this alteration, we performed a copy number analysis of 87 17q23 localized expressed sequence tags in seven breast cancer cell lines. Three major regions of amplification were detected in the MCF7 and BT474 cell lines. Amplification of at least one of four known genes (PAT1, PS6K, RAD51C, and SIGMA1B) was detected in the cell lines and in 28% of 94 breast tumors. In most cases, these four genes were overexpressed when amplified, but there was a particularly good association between amplification of the SIGMA1B gene and elevated expression in tumors, which suggested a possible role for this gene in tumor progression. Our data show that this region contains at least four independent targets of amplification, which suggests that there is considerable variability in the structure of the 17q23 amplicon.

Breast Neoplasms↗
PubMed2000

BRCA1 and BRCA2 have a limited role in familial prostate cancer.

Epidemiological studies have suggested that the breast cancer susceptibility genes, BRCA1 and BRCA2, may be involved in the development of prostate cancer. Several studies have screened prostate cancer populations for the presence of BRCA1 and BRCA2 mutations, with few mutations identified. In this study, 22 high-risk prostate cancer families (at least three cases of prostate cancer) were screened by conformation-sensitive gel electrophoresis (CSGE) for mutations in BRCA1 and BRCA2. To maximize the chance of finding mutations in these two genes, families were also selected for the presence of at least two cases of breast and/or ovarian cancer. We identified one previously reported BRCA2 missense mutation and two previously unreported BRCA2 intron polymorphisms. No BRCA1 or BRCA2 truncating mutations were detected. Thus, BRCA1 and BRCA2 appear to have a limited role in familial prostate cancer, and families with both prostate and breast cancer may result from mutations in other predisposition genes.

Aged↗
PubMed2000

Genetic heterogeneity in Peutz-Jeghers syndrome.

LKB1, the human gene encoding a serine threonine kinase, was recently identified as a susceptibility gene for Peutz-Jeghers syndrome (PJS), a disease characterized by the constellation of intestinal hamartomata, oral mucocutaneous hyperpigmentation, and an increased risk for gastrointestinal as well as extraintestinal malignancies. To date, the majority of individuals with PJS have been found to have genetic alterations in LKB1, most of which result in protein truncation. Additionally, linkage analyses have suggested a modicum of genetic heterogeneity, with the majority of PJS families showing linkage to the LKB1 locus. In this study, we evaluated five kindreds with greater than two affected family members, five PJS probands with only one other affected family member, as well as 23 individuals with sporadic PJS for mutations within the LKB1 gene. Conformation sensitive gel electrophoresis was utilized for the initial screen, followed by direct sequence analysis for characterization. Long-range PCR was used for the detection of larger genetic insertions or deletions. Mutation analysis revealed genetic alterations in LKB1 in two probands who had a family history of PJS. LKB1 mutations were detected in only four of the remaining 23 cases of sporadic PJS. These data suggest the presence of significant genetic heterogeneity for PJS and the involvement of other loci in this syndrome.

AMP-Activated Protein Kinase Kinases↗
PubMed2000

Association of Peutz-Jeghers-like mucocutaneous pigmentation with breast and gynecologic carcinomas in women.

Most reports describe an increased risk of malignancy in Peutz-Jeghers syndrome (PJS). We identified individuals with PJS-like pigmentation but no polyposis, designated as isolated mucocutaneous melanotic pigmentation (IMMP), and 1) characterized their clinical features, 2) assessed them for cancer events, and 3) screened a sample of these subjects for mutations in LKB1, a gene responsible for a portion of PJS cases. Review of Mayo Clinic records from 1945 to 1996 identified 26 patients with IMMP. All were then interviewed or their medical records reviewed to determine if cancer had developed. Conformation-sensitive gel electrophoresis (CSGE) screening for LKB1 mutations was followed by direct sequencing. Ten of these 26 individuals (38%) developed 12 malignancies that arose in the cervix (n = 3), endometrium (n = 3), breast (n = 1), kidney (n = 1), lung (n = 2), colon (n = 1), and lymphatic tissue (n = 1). In females with IMMP, the relative risk for cancer was 3.2 (95% CI, 1.2-6.9), while that for males was not increased. The relative risk for breast and gynecologic cancers was 7.8 (95% CI, 2.5-18.1) in affected females. Of 9 individuals tested, no LKB1 mutations were detected. Classical PJS is associated with an increased cancer risk. Our results indicate that IMMP is another lentiginosis with cancer predisposition. In particular, the relative risk for cancer in females with IMMP was significantly increased, as is true in females with PJS. However, LKB1 mutations did not contribute to the development of IMMP in the patients tested.

Adult↗
PubMed1999

Localization of PS6K to chromosomal region 17q23 and determination of its amplification in breast cancer.

The application of comparative genomic hybridization to the analysis of genetic abnormalities in breast carcinoma has consistently revealed that chromosome region 17q22-24 is a frequent site of gene amplification in this type of cancer. As part of an examination of expressed sequence tags for novel amplified genes in this region, we identified PS6K amplifications in both breast tumor tissues and cell lines. PS6K was localized to 17q23 and encodes a serine-threonine kinase whose activation is thought to regulate a wide array of cellular processes involved in the mitogenic response including protein synthesis, translation of specific mRNA species, and cell cycle progression from G1 to S phase. Northern and Western analyses revealed that amplification of this gene was accompanied by corresponding increases in mRNA and protein expression, respectively. These data represent the first determination of a gene amplification within 17q22-24 in breast cancer and suggest an oncogenic activity for PS6K.

Breast Neoplasms↗
PubMed1999

p73 mutations are not detected in sporadic and hereditary breast cancer.

Recently, a novel tumor suppressor gene, p73, was isolated and mapped to chromosome 1p36, a region commonly associated with loss of heterozygosity in neuroblastoma and other human malignancies, including breast cancer. The p73 gene shares considerable homology with the common tumor suppressor gene p53, both in composition and function. This study examines the potential participation of p73 in the pathogenesis of sporadic and hereditary breast cancers. Mutation analysis of 29 hereditary breast cancer cases revealed five independent silent mutations in the hereditary cases that are unlikely to play a role in tumor development. Mutation analysis of 48 sporadic breast tumors did not identify any unique variants. Eleven common polymorphisms scattered throughout the gene were also detected. Thus, mutations in the p73 gene appear to play little if any role in hereditary or sporadic breast cancer.

Breast Neoplasms↗
PubMed1999

Polymorphisms in PTEN in breast cancer families.

Germline mutations in PTEN are the underlying genetic defect in Cowden disease, which is associated with a lifetime risk of 25-50% of developing breast cancer. To investigate the role of PTEN in inherited breast cancer in the absence of manifestations of Cowden disease, we screened 177 unrelated subjects with breast cancer who also had a family history of breast cancer in at least one relative. We found no disease associated PTEN mutations in this cohort, supporting previous studies suggesting that PTEN mutations do not contribute to inherited susceptibility to breast cancer without associated manifestations of Cowden disease. We did identify an association between a common polymorphism in intron 4 and lower mean age of diagnosis of breast cancer. While preliminary, these findings suggest that further study is warranted to determine whether this allelic variant of PTEN could function as a low penetrance breast cancer susceptibility allele.

Age Factors↗
PubMed1999

Fifty-year follow-up of cancer incidence in a historical cohort of Minnesota breast cancer families.

A family history of breast cancer is well established as a risk factor for the disease. Because family history is a dynamic rather than a static characteristic, longitudinal studies of entire families can be very instructive in quantifying the significance of risk classification. The Minnesota Breast Cancer Family Study is a historical cohort study of relatives of a consecutive series of 426 breast cancer cases (probands) identified between 1944 and 1952. The incidence of cancer and the measurement of risk factors in sisters, daughters, granddaughters, nieces, and marry-ins was determined through telephone interviews and mailed questionnaires. Ninety-eight percent of eligible families were recruited, and 93% of members participated. A total of 9073 at-risk women were studied: 56% were biological relatives of the case probands, whereas the others were related through marriage. Through 1996, 564 breast cancers were identified in nonprobands. Compared to the rate of breast cancer among marry-ins (188 cases), sisters and daughters of the probands were at a 1.9-fold greater age-adjusted risk (128 cases; 95% confidence interval, 1.4-2.4); granddaughters and nieces were at a 1.5-fold greater risk (248 cases, 95% confidence interval, 1.2-1.8). The breast cancer risk since 1952 was not distributed equally across families: although all biological relatives had a family history of breast cancer, 166 families (39%) experienced no additional cases. Most of the cases occurred among a subset of families: 21 families had 5 breast or ovarian cancers, 8 had 6, 2 had 7, and 4 had > or =8. There was no evidence of significantly increased risk for cancer at other sites, including the ovaries, cervix, uterus, colon, pancreas, stomach, or lymphatic tissue, although there was some evidence that stomach cancer in previous generations may help define the susceptible subset. These families contain four to five generations of validated occurrences of cancer, thus minimizing the uncertainty of genetic risk inherent in a disease with a late and variable age at onset. The patterns of breast cancer in these multigeneration families is consistent with the influence of autosomal dominant susceptibility in a subset, low penetrance genes in another, and purely environmental influences in the remainder.

Adolescent↗