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PubMed2002

Race and cancer genetics: lessons from BRCA1.

The effect of a patient's race or ethnicity on cancer incidence and mortality rates remains a neglected area of cancer research. However, with cancer statistics differing among various populations, research on racial and ethnic groups could provide clues to cancer trends. Definitions of ethnicity and/or race need to be established and standardizedfor use in study protocols. Accordingly, all research on ethnic groups must address two questions: (1) When is genetic research on a population appropriate? (2) How should researchers define a given population being studied?

BRCA1 Protein↗
PubMed2004

Alcohol and cancer: genetic and nutritional aspects.

Chronic alcohol consumption is a major risk factor for cancer of upper aero-digestive tract (oro-pharynx, hypopharynx, larynx and oesophagus), the liver, the colo-rectum and the breast. Evidence has accumulated that acetaldehyde is predominantly responsible for alcohol-associated carcinogenesis. Acetaldehyde is carcinogenic and mutagenic, binds to DNA and protein, destroys the folate molecule and results in secondary cellular hyper-regeneration. Acetaldehyde is produced by mucosal and cellular alcohol dehydrogenase, cytochrome P450 2E1 and through bacterial oxidation. Its generation and/or its metabolism is modulated as a result of polymorphisms or mutations of the genes responsible for these enzymes. Acetaldehyde can also be produced by oral bacteria. Smoking, which changes the oral bacterial flora, also increases salivary acetaldehyde. Cigarette smoke and some alcoholic beverages, such as Calvados, contain acetaldehyde. In addition, chronic alcohol consumption induces cytochrome P450 2E1 enxyme activity in mucosal cells, resulting in an increased generation of reactive oxygen species and in an increased activation of various dietary and environmental carcinogens. Deficiencies of riboflavin, Zn, folate and possibly retinoic acid may further enhance alcohol-associated carcinogenesis. Finally, methyl deficiency as a result of multiple alcohol-induced changes leads to DNA hypomethylation. A depletion of lipotropes, including methionine, choline, betaine and S-adenosylmethionine, as well as folate, results in the hypomethylation of oncogenes and may lead to DNA strand breaks, all of which are associated with increased carcinogenesis.

Acetaldehyde↗
PubMed2000

Molecular epidemiology of breast cancer: genetic variation in steroid hormone metabolism.

The age-specific incidence rate of breast cancer in women rises until menopause, levels off and then rises again at a much lower rate indicating a possible hormonal influence on the disease risk. A large amount of evidence has implicated hormones and other compounds with oestrogen activity in the pathogenesis of certain endocrine cancers, particularly breast cancer. Widely dispersed hormone-like chemicals, capable of disrupting the endocrine system and interfering with proliferation, have been described. Compounds such as dioxins, some polychlorinated biphenyls and the plastic ingredient bisphenol-A have been shown to interfere with human reproduction and hormonal regulation. The levels of these foreign compounds as well as the levels of endogenous oestradiol may influence the risk of breast cancer. Endogenous oestradiol is synthesised in the ovarian theca cells of premenopausal women or in the stromal adipose cells of the breast of postmenopausal women and minor quantities in peripheral tissue. These cells, as well as breast cancer tissue, express all the necessary enzymes for this synthesis: CYP17, CYP11a, CYP19, hydroxysteroid hydrogenase, steroid sulphatase as well as enzymes further hydroxylating oestradiol such as CYP1A1, CYP3A4, CYP1B1. Polymorphisms in these enzymes may have a possible role in the link between environmental estrogens and hormone-like substances and the interindividual risk of breast cancer.

17-Hydroxysteroid Dehydrogenases↗
PubMed1998

Hereditary and sporadic ovarian cancer: genetic testing and clinical implications (review).

The two most common forms of hereditary ovarian cancer are: the breast ovarian cancer syndrome, and ovarian cancer associated with HNPCC (hereditary nonpolyposis colorectal cancer) syndrome. Studies have shown that these diseases may be associated with mutations in a number of tumor suppressor genes, mainly BRCA1 and BRCA2. Malfunction of the protein products of these genes have also been found to be involved in sporadic ovarian cancer, which makes up the majority of ovarian cancer cases. HNPCC-ovarian cancer associated families reveal frequent mutations in at least four genes (hMSH2, hMLH1, hPMS1, and hPMS2) involved in the repair of mismatched DNA. With ovarian cancer being such an important health issue, the push is on to design reliable screening tests to detect defective inherited or somatic alleles in individual carriers. So far, most progress has been demonstrated in those patients with family histories of the disease who are at increased risk. The ramifications of such research may impact a variety of scientific, clinical, legal, ethical, and psychosocial issues. In addition to current treatment modalities, positive results of these tests may indicate the need for increased clinical surveillance, prophylactic treatment, and genetic counseling of patients on an individual basis. It remains to be seen whether the technology can be made reliable enough to not only benefit high-risk individuals but also the general population.

BRCA2 Protein↗
PubMedDate not supplied

[The supply of breast/ovarian cancer genetic susceptibility tests in France].

One example of the recent advances of scientific research on the human genome is the identification of two susceptibility genes to breast/ovarian cancer, BRCA1 and BRCA2, making possible the introduction in medical practices of genetic testing to detect patients with an increased risk of developing such cancers. In this context of diffusion, two surveys were carried out to appraise the activity profiles in 1998 and in 2001 of all the different participants in those new medical practices in France, physicians in charge of genetic counselling, medical centres where consultations take place and laboratories. Results show that over the period 1998-2001, few changes occurred, mainly the reduction of the average waiting time to get the result of a genetic test, the increase in the annual number of BRCA2 families identified to a level similar to the one of BRCA1 and the automation of the biological analyses without noting a considerable increase in the annual output of laboratories till 2001 however. This surprising moderate evolution must be connected to the existence of some particular external factors making the framework of the development of these new medical and biological practices and their future really uncertain. The diffusion of BRCA1/2 genetic testing has been carried out facing the traditional difficulties of any innovating activities, but also the uncertainties related to intellectual property rights on genes and the reimbursement of genetic counselling and biological testing. These uncertainties have certainly restrained the pace of change as many actors in this field have opted for a wait and see strategy bearing in mind the possible future constraints imposed to their future activity, especially if European patents on the BRCA1/2 genes are finally granted by the European patent office (EPO).

Breast Neoplasms↗
PubMed2003

Advanced cancer genetics in neurosurgical research.

RAPID ADVANCES IN the technology used to study nucleic acids have revealed a great deal regarding the underlying biology of cancer. Most cancers arise as a result of chromosomal rearrangements and deoxyribonucleic acid mutations that lead to the activation of proto-oncogenes and loss of function of tumor suppressor genes. There are a number of different molecular routes that lead to these common goals, necessitating several different techniques of mutational analysis. Although many of these techniques can be difficult in practice, most are conceptually simple. We discuss several of the current techniques in cytogenetics and molecular genetics that are widely used in cancer biology laboratories. Understanding the molecular events that lead to cancer should allow the future development of targeted, nontoxic therapeutics similar to modern-day antibiotics. These technologies are being progressively applied in clinical neurosurgery, where they will be used to detect, diagnose, stratify, and treat cancers of the nervous system. High demand from an increasingly educated patient population means that neurosurgeons will need to be familiar with many of these techniques.

Cytogenetic Analysis↗
PubMed2003

Genome-wide scan for prostate cancer susceptibility genes using families from the University of Michigan prostate cancer genetics project finds evidence for linkage on chromosome 17 near BRCA1.

BACKGROUND: Previous linkage studies have suggested prostate cancer susceptibility genes located on chromosomes 1, 20, and X. Several putative prostate cancer candidate genes have also been identified including RNASEL, MSR1, and ELAC2. Presently, these linkage regions and candidate genes appear to explain only a small proportion of hereditary prostate cancer cases suggesting the need for additional whole genome analyses. METHODS: A genome-wide mode-of-inheritance-free linkage scan, using 405 genetic markers, was conducted on 175 pedigrees, the majority containing three or more affected individuals diagnosed with prostate cancer. Stratified linkage analyses were performed based on previously established criteria. RESULTS: Results based on the entire set of 175 pedigrees showed strong suggestive evidence for linkage on chromosome 17q (LOD = 2.36), with strongest evidence coming from the subset of pedigrees with four or more affected individuals (LOD = 3.27). Race specific analyses revealed strong suggestive evidence for linkage in our African-American pedigrees on chromosome 22q (LOD = 2.35). CONCLUSIONS: Genome-wide analysis of a large set of prostate cancer families indicates new areas of the genome that may harbor prostate cancer susceptibility genes. Specifically, our linkage results suggest that there is a prostate cancer susceptibility gene on chromosome 17 that is independent of ELAC2. Further research including combined analyses of independent genome-wide scan data may clarify the most important regions for future investigation.

Age of Onset↗
PubMed1997

Common cancers--genetics, origin, prevention, screening: Parts I and II.

Carcinogenesis is a stepwise process that occurs through mutations of cancer-related genes. Five or more genes must be mutated before malignant transformation occurs in most adult cancers; in some childhood cancers as few as two mutated genes may be sufficient. A rare inherited mutation of a critical gene may predestine cancer to occur in one or more sites. This germline mutation is present in virtually every cell in the body, except half of the germ cells, which do not contain the mutated gene in their haploid chromosome set. These and other genes have been used to piece together a puzzle of regulatory systems that govern cell division and proliferation, as well as apoptosis or programmed cell death. Mutations of these genes result not only in increased cell proliferation but also in diminished cell death. Most genetic changes that occur during carcinogenesis are not inherited or germline. They are acquired after birth and are called somatic mutations. A somatic mutation affects only the mutated cell and its progeny. Each time a cell divides, there is a chance of somatic mutation, and therefore there always is a low, background risk for cancer and other malignant lesions. A far more prevalent cause of cancer-related death in the United States is environmental exposure. Such exposure causes somatic mutations of cancer-related genes through direct damage to DNA or through alteration of proliferation or cell death, which enhances the baseline risk for mutation. As carcinogenesis becomes understood, interventions may be designed that selectively interfere in important steps. Screening for cancer is based on the premise that one can treat a patient for a cancer that has not spread from its primary site. Nevertheless, cancer screening is controversial and often confusing. Issues of costs, risks versus benefits, physical time and effort, and patient compliance all affect the clinician's view of screening, often to the extent that the true value of this approach to cancer control is underappreciated and underutilized. A clinician should consider the following questions when assessing the priority, scope, and intensity of cancer screening. Is the cancer an important public health problem? Can preclinical stages be detected and cured? Are effective screening tests available? Are the tests feasible and acceptable? Have screening programs reduced cancer-specific mortality? Is the screening program cost effective? Is screening generally recommended? There is clear-cut evidence of benefit from screening for cancer of the cervix, breast, colon and rectum, and skin and some specific genetic syndromes. Evidence of survival benefit from screening for prostate cancer is lacking, although prostate specific antigen screening is widely used. Screening for lung and ovarian cancer is ineffective.

Adult↗
PubMed2006

Colorectal cancer: genetics of development and metastasis.

It has been well documented that there are two major pathways in colorectal carcinogenesis. One is the chromosomal instability pathway (adenoma-carcinoma sequence), which is characterized by allelic losses on chromosome 5q (APC), 17p (p53), and 18q (DCC/SMAD4), and the other is a pathway that involves microsatellite instability. Recent progress in molecular biology, however, has shown that colorectal carcinogenesis is not necessarily clearly divided into these two pathways, but is in fact more complicated. Other routes, including the transforming growth factor-beta/SMAD pathway, the serrated pathway, and the epigenetic pathway, have been reported. Cross talk among these pathways has also been reported. In the invasion and metastasis steps of colorectal cancers, many more genes have now been identified as being involved in proteolysis, adhesion, angiogenesis, and cell growth. Recently accumulated evidence indicates that colorectal cancer is a genetically heterogeneous and complicated disease.

Adenocarcinoma↗
PubMed2003

High prevalence of BRAF mutations in thyroid cancer: genetic evidence for constitutive activation of the RET/PTC-RAS-BRAF signaling pathway in papillary thyroid carcinoma.

Thyroid papillary cancers (PTCs) are associated with activating mutations of genes coding for RET or TRK tyrosine kinase receptors, as well as of RAS genes. Activating mutations of BRAF were reported recently in most melanomas and a small proportion of colorectal tumors. Here we show that a somatic mutation of BRAF, V599E, is the most common genetic change in PTCs (28 of 78; 35.8%). BRAF(V599E) mutations were unique to PTCs, and not found in any of the other types of differentiated follicular neoplasms arising from the same cell type (0 of 46). Moreover, there was no overlap between PTC with RET/PTC, BRAF, or RAS mutations, which altogether were present in 66% of cases. The lack of concordance for these mutations was highly unlikely to be a chance occurrence. Because these signaling proteins function along the same pathway in thyroid cells, this represents a unique paradigm of human tumorigenesis through mutation of three signaling effectors lying in tandem.

Carcinoma, Papillary↗
PubMedDate not supplied

[Hereditary gastric cancer. Genetics and clinical management].

Recently, germline mutations in the E-cadherin/CDH1 gene have been identified in families with an autosomal-dominant inherited predisposition to gastric cancer of the diffuse type. Criteria to define familial gastric cancer syndromes have been proposed and include review of the histopathology and pedigree analysis of any family with an aggregation of gastric cancer cases. Of families with two or more cases of diffuse gastric cancer in first- or second-degree relatives < 50 years of age or three or more cases at any age, up to half may be attributable to inherited germline mutations in the E-cadherin/CDH1 gene. Cumulative lifetime risk of developing gastric cancer in CDH1 mutation carriers is 70%, women from these families also have increased risk for developing lobular breast cancer. Prophylactic gastrectomies have been performed in several unaffected CDH1 mutation carriers; despite normal endoscopic examinations and negative gastric biopsy specimens, pathologic foci of early gastric cancer were found in all surgical specimens. Based on these results, guidelines for genetic testing, counseling and management of individuals with hereditary diffuse gastric cancer have been proposed. Raised awareness among the physician community regarding this syndrome may allow for increased detection and prevention of gastric and breast cancers in these high-risk individuals.

Humans↗
PubMed1998

The use of videotaped information in cancer genetic counselling: a randomized evaluation study.

A video of introductory information about inherited susceptibility to breast cancer was made in consultation with clinicians in four Scottish cancer family clinics. One hundred and twenty-eight women, newly referred for breast cancer risk counselling were randomized to receive the video before (n = 66) or after (n = 62) counselling. Data were collected before randomization at clinic and by postal follow-up at 1 month. The Video Before group had shorter consultations with the breast surgeon (mean = 11.8 min+/-5.4 vs 14.6+/-7.2 for the Video After group). There was no difference between the groups in the accuracy of their risk estimate after counselling, although the Video Before group scored higher for self-reported (Z= 3.65, d.f. = 1, P < 0.01) and objectively assessed understanding (Z= 2.91, d.f. = 1, P < 0.01). At 1 month follow-up, the Video Before group were less likely to underestimate their risk estimate (38% vs 18%; chi2 = 4.62, d.f. = 1, P< 0.05), but there was then no difference between the groups in subjective or objective understanding. Use of the video was not associated with increased distress (GHQ, Spielberger State Anxiety) and was associated with greater satisfaction with the information given at the clinic. This study supports the value of videotape as a method of giving information to prepare women for breast cancer risk counselling. Observations of misunderstandings and distress emphasize the video should be seen as an aid to, not a substitute, for communications at the clinic.

Adult↗
PubMedDate not supplied

Guidelines for breast and ovarian cancer genetic counseling referral: adoption and implementation in HMOs.

PURPOSE: To describe referral guidelines for hereditary breast and ovarian cancer (HBOC) counseling among a group of Health Maintenance Organizations (HMOs) and awareness of such among primary care clinicians. METHODS: An organizational assessment of plan policies and a primary care clinician survey. RESULTS: Five of the 7 HMOs reported having HBOC referral guidelines. Differences between plan's criteria included age of breast cancer onset, inclusion of male breast cancer, and second-degree relatives. Of the 91% clinicians responding, only half were aware of the HBOC guidelines. Awareness was higher in the plan with the most intense implementation effort (OR=3.0, 1.5-5.9) and among gynecologists (OR=2.8, 1.5-5.4). CONCLUSIONS: Although HBOC counseling guidelines within participating HMOs identify persons for referral that can be easily incorporated into routine practice, continued work is needed to better understand how to help primary care providers identify high-risk persons, and new models of providing genetic services may need to be considered.

Breast Neoplasms↗
PubMed1975

Elevated ribonuclease activity in the thymus and white blood cells of genetically cancer prone mice.

Ribonuclease activity in cell-free thymus homogenates was elevated for five strains of mice genetically predisposed toward leukemia or reticulum cell neoplasms (AKR, C58, PL, RF, and SJL). Such increased activity was directed against polyuridylic acid and was observed in 8-wk old mice, well before the onset of neoplastic transformation. Similarly, white blood cell ribonuclease activity was elevated in mice of the strains AKR, C2H/He, PL and RF. Statistical analysis indicated that such elevated activity in these strains related to their high incidence of spontaneous neoplastic disease. Elevated ribonuclease activity thus represents a new biochemical marker relating to the genetic propensity of some strains of mice to die prematurely of spontaneous neoplasia.

Animals↗
PubMed1996

The role of DNA methylation in cancer genetic and epigenetics.

The past few years have seen a wider acceptance of a role for DNA methylation in cancer. This can be attributed to three developments. First, the documentation of the over-representation of mutations at CpG dinucleotides has convincingly implicated DNA methylation in the generation of oncogenic point mutations. The second important advance has been the demonstration of epigenetic silencing of tumor suppressor genes by DNA methylation. The third development has been the utilization of experimental methods to manipulate DNA methylation levels. These studies demonstrate that DNA methylation changes in cancer cells are not mere by-products of malignant transformation, but can play an instrumental role in the cancer process. It seems clear that DNA methylation plays a variety of roles in different cancer types and probably at different stages of oncogenesis. DNA methylation is intricately involved in a wide diversity of cellular processes. Likewise, it appears to exert its influence on the cancer process through a diverse array of mechanisms. It is our task not only to identify these mechanisms, but to determine their relative importance for each stage and type of cancer. Our hope then will be to translate that knowledge into clinical applications.

Animals↗
PubMed2003

New tools for functional mammalian cancer genetics.

Knowledge of the function of individual genes that encode components of cell-signalling pathways is crucial to our understanding of normal growth control and its deregulation in cancer, but we have functional information for only 15% of human genes at present. Several new technologies have recently become available to identify gene function in mammalian cells using high-throughput genetic screens. These new tools will make it possible to identify new and innovative classes of anticancer drugs, including those that show synthetic lethal interactions with cancer-specific mutations.

Animals↗
PubMed1996

Hepatitis and cancer: genetic aspects.

Hepatocellular carcinoma (HCC) is one of the most common tumours in the world. It is the seventh most common cancer in men and the ninth in women with an estimated 500,000 to 1,000,000 new HHC cases per year. However, there are considerable variations in the incidence of HCC throughout the world, related to geographical areas, socioeconomic factors, sex and age-specific incidence rates, suggesting genetic differences in susceptibility to HCC.

Age Factors↗