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At least 19 recordsLinked to original sources

PubMed1997

Cell cycle arrest defect in Li-Fraumeni Syndrome: a mechanism of cancer predisposition?

Cancer predisposition in approximately 60% of Li-Fraumeni Syndrome (LFS) families is associated with germline mutation of the TP53 gene. The p53 protein has been shown to mediate G1 arrest following DNA damage. We have investigated gamma-irradiation-induced transient and permanent G1 arrest in normal and LFS fibroblasts. The duration of transient G1 arrest varied between strains, but there was no difference in the range between normal (2-12 h) and LFS (1-13 h) cells. However, the extent of permanent G1 arrest was greatly reduced in LFS fibroblasts (mean 33+/-8% of the cell population) compared with normals (mean 67+/-9%) and correlated with their increased radiation survival (r=0.97, P<0.001). This phenotype was observed in LFS fibroblasts both with (seven cases) and without (two cases) TP53 mutation. Parallel studies with fibroblasts derived from cancer-prone, p53-deficient mice revealed no radiation-induced G1 cell cycle arrest in p53 null (-/-) cells. The p53 +/- cells were comparable to the wt p53 cells in transient G1 arrest capacity, but showed a diminished permanent G1 arrest. These data clearly implicate p53 function in permanent G1 arrest. The reduced capacity for DNA damage-induced, permanent G1 arrest in LFS may contribute significantly to cancer predisposition in this familial syndrome.

Animals↗

PubMed1995

Cancer predisposition, radiosensitivity and the risk of radiation-induced cancers. II. A Mendelian single-locus model of cancer predisposition and radiosensitivity for predicting cancer risks in populations.

Individuals genetically predisposed to cancer may be more sensitive to cancers induced by ionizing radiation than those who are not so predisposed. Should this be true, under conditions of radiation exposure, a population consisting of cancer-predisposed and non-predisposed individuals will be expected to respond with a higher total frequency of induced cancers than one in which all the individuals are assumed to have the same sensitivity to radiation-induced cancers. To study this problem quantitatively, we have developed a Mendelian autosomal one-locus, two-allele model; this model assumes that one of the alleles is mutant and the genotypes carrying the mutant allele(s) are cancer-predisposed and are also more sensitive to radiation-induced cancer. Formal analytical predictions as well as numerical illustrations of this model show that: (1) when such heterogeneity with respect to cancer predisposition and radiosensitivity is present in the population, irradiation results in a greater increase in the frequency of induced cancers than when it is absent; (2) this increase is detectable only when the proportion of cancers due to genetic predisposition is large and when the degree of predisposition is considerable; and (3) even when the effect is small, most of the radiation-induced cancers will occur in predisposed individuals. These conclusions are valid for models of cancer when predisposition and radiosensitivity may be either dominant or recessive. The published data on breast cancers in Japanese A-bomb survivors show that at 1 Sv, the radiation-related excess relative risk in women irradiated before age 20 is 13 compared to about 2 for those irradiated at later ages. We examined the application of our model to the above data using two assumptions, namely, that the proportion of cancers due to genetic susceptibility at the BRCA1 locus (1/200) and the frequency of the mutant allele (0.0033) estimated for Western populations are valid for Japanese women. With our model, these results can be explained only if there are very large differences in cancer susceptibility (> 1000-fold) and radiosensitivity (> 100-fold) of the heterozygotes.

BRCA1 Protein↗

PubMed2003

Lung cancer risk in germline p53 mutation carriers: association between an inherited cancer predisposition, cigarette smoking, and cancer risk.

We recently observed a significantly increased risk for lung cancer in carriers of p53 germline mutations. Because cigarette smoking is known to play an important role in increasing the risk for lung cancer in the general population, we wanted to determine the role of cigarette smoking in lung cancer risk in people with a genetic susceptibility based on a p53 germline mutation. We studied 1263 people from 97 families enrolled in a cohort study of families systematically ascertained through childhood soft-tissue sarcoma patients treated at the M.D. Anderson Cancer Center, University of Texas, between 1944 and 1975. We assessed the incidence of lung and smoking-related cancers in 33 carriers of germline p53 mutations and in 1,230 noncarriers to determine whether there was an association between an inherited cancer predisposition, cigarette smoking, and cancer risk. We analyzed the association between cigarette smoking, mutation status, and lung and other smoking-related cancers by the Kaplan-Meier method and the Cox proportional hazards model with adjustments for birth year, race, and sex. In the hazards model, we incorporated a robust variance estimation to adjust for familial correlation. We observed an increased risk of a variety of histological types of lung cancer in the carriers of the p53 germline mutation. Mutation carriers who smoked had a 3.16-fold (95% confidence interval =1.48-6.78) higher risk for lung cancer than the mutation carriers who did not smoke. Our results demonstrate that cigarette smoking significantly increases lung cancer risk in carriers of a germline p53 mutation. This finding could be useful in designing strategies for early detection and treatment of lung and smoking-related cancers in individuals with this inherited cancer predisposition.

Adult↗

PubMed2025

Established Cancer Predisposition Genes in Single and Multiple Cancer Diagnoses.

IMPORTANCE: Much of the understanding of cancer risk associated with rare pathogenic variants (RPVs) is derived from family-based studies or clinically ascertained samples, which may be limited by ascertainment and selection bias. OBJECTIVE: To quantify associations between RPVs in previously implicated cancer predisposition genes and single and multiple cancer diagnoses in a large population-based study. DESIGN, SETTING, AND PARTICIPANTS: In this genetic association study, whole-exome sequencing data were used from the UK Biobank, a UK population-based cohort that enrolled participants aged 40 to 69 years between 2006 and 2010. Participants who were involved in the whole-exome sequencing release of 200 000 genomes in 2020 were included in this study. This analysis included White participants only, as findings in other racial and ethnic groups had small sample sizes. Participants were diagnosed before or after biobank enrollment until March 2024. EXPOSURES: The sequencing data of a set of 96 previously implicated cancer predisposition genes were analyzed and compared using 2 methods. To determine the statistical significance of an association, a robust optimal sequence kernel association test was used, while odds ratios (ORs) and 95% CIs were obtained through Firth logistic regression. MAIN OUTCOMES AND MEASURES: The primary study outcome was the diagnosis of 1 of 11 cancers (bladder, breast, central nervous system, colorectal, lung, melanoma, ovary, pancreatic, prostate, renal, thyroid) defined by relevant diagnosis codes in inpatient hospital diagnosis, cancer registry, and/or death registry data. RESULTS: Data from 183 627 participants (101 414 [55.2%] female) were analyzed, including 25 824 participants with at least 1 cancer diagnosis, of whom 23 704 (91.8%) had a single cancer diagnosis and 2130 (8.2%) had 2 or more cancer diagnoses. A total of 157 793 controls had no cancer diagnosis. The median (IQR) age was 62 (56-65) years in participants with at least 1 cancer diagnosis, compared to 57 (50-63) years in those without a cancer diagnosis. Genetic variation in 16 genes was significantly associated with at least 1 cancer of interest (ATM, BARD1, BRCA1, BRCA2, BRIP1, CDKN2A, CHEK2, HOXB13, MITF, MLH1, MSH2, MSH6, NF1, PALB2, RAD51C, and RAD51D). The presence of an RPV in 1 of these 16 genes was associated with increased odds of at least 1 cancer (OR, 1.87; 95% CI, 1.76-1.98) and multiple primary cancers (OR, 2.56; 95% CI, 2.18-2.99). Carrier frequency was 6.28% and 8.36%, respectively. CONCLUSIONS AND RELEVANCE: This genetic association study demonstrates several established associations between cancer predisposition genes and cancer diagnoses in an unselected population-based study. These results also demonstrate that RPVs in cancer predisposition genes are associated with multiple primary cancer diagnoses, suggesting that multigene panel testing may be warranted in these individuals.

Humans↗

PubMed1979

Genetic mechanisms in cancer predisposition: report of a cancer family.

A family is described in which four children developed cancer affecting different organs:lymphoma, meningeal sarcoma, osteogenic sarcoma, and adenocarcinoma of the cecum. Since there was only one other case of cancer in previous generations of this family, an hypothesis is put forth to explain this unusual aggregation on the basis of recombination of common genes. It is postulated that each parent carried a different combination of genes which, though not associated with increased cancer predisposition in the combinations in which they were present in the parents, due to independent assortment resulted in a combination producing cancer susceptibility in half of the offspring. Such genetic loci could include factors similar to an oncogene which is normally held in control by genes at another locus; thus the dominant oncogene without the dominant controlling genes would make for cancer susceptibility, while the controlling genes without the oncogene would be associated with cancer resistance since two mutations would then be required for malignant development. To explain the occurrence of lymphoma in one of the children in this family, a third set of genes is included in this model--genes affecting immunocompetence, in which the normal allele is dominant. This three locus model has the advantage of being able to explain not only the occasional cancer family, but also the distribution of cancer susceptibility and resistance in the general population.

Adenocarcinoma↗

PubMed2000

Defective nucleotide excision repair in xpc mutant mice and its association with cancer predisposition.

Mice that are genetically engineered are becoming increasingly more powerful tools for understanding the molecular pathology of many human hereditary diseases, especially those that confer an increased predisposition to cancer. We have generated mouse strains defective in the Xpc gene, which is required for nucleotide excision repair (NER) of DNA. Homozygous mutant mice are highly prone to skin cancer following exposure to UVB radiation, and to liver and lung cancer following exposure to the chemical carcinogen acetylaminofluorene (AAF). Skin cancer predisposition is significantly augmented when mice are additionally defective in Trp53 (p53) gene function. We also present the results of studies with mice that are heterozygous mutant in the Apex (Hap1, Ref-1) gene required for base excision repair and with mice that are defective in the mismatch repair gene Msh2. Double and triple mutant mice mutated in multiple DNA repair genes have revealed several interesting overlapping roles of DNA repair pathways in the prevention of mutation and cancer.

Animals↗

PubMed2001

Genetic testing for cancer predisposition.

Clinical cancer genetics is becoming an integral part of the care of cancer patients. This review describes the clinical aspects, genetics, and clinical genetic management of most of the major hereditary cancer susceptibility syndromes. Multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and familial adenomatous polyposis are examples of syndromes for which genetic testing to identify at-risk family members is considered the standard of care. Genetic testing for these syndromes is sensitive and affordable, and it will change medical management. Cancer genetic counseling and testing is probably beneficial in other syndromes, such as the hereditary breast cancer syndromes, hereditary nonpolyposis colorectal cancer syndrome, Peutz-Jeghers syndrome, and juvenile polyposis. There are also hereditary cancer syndromes for which testing is not yet available and/or is unlikely to change medical management, including Li-Fraumeni syndrome and hereditary malignant melanoma. Thorough medical care requires the identification of families likely to have a hereditary cancer susceptibility syndrome for referral to cancer genetics professionals.

Breast Neoplasms↗

PubMed2005

Hereditary cancer predisposition syndromes.

Cancer genetics is increasingly becoming integrated into the practice of modern medical oncology. The ability to distinguish a growing proportion of the 5% to 10% of all cancers that develop in individuals who have inherited a genetic mutation conferring heightened susceptibility to specific cancers may permit targeted efforts in cancer surveillance and prevention. While these individuals comprise a small proportion of the overall burden of cancer, strategies successful in reducing their remarkable cancer risks may be generalizable to the broader population. In this review, we highlight the most common hereditary cancer syndromes, most attributable to genes inherited in an autosomal dominant manner with incomplete penetrance, and a number of rare syndromes in which particular progress has been made. The prevalence, penetrance, tumor spectrum, and underlying genetic defects are discussed and summarized in a large table in which a more comprehensive enumeration of syndromes is provided.

Breast Neoplasms↗

PubMed1998

Cancer predisposition, radiosensitivity and the risk of radiation-induced cancers. IV. Prediction of risks in relatives of cancer-predisposed individuals.

Individuals carrying cancer-predisposing germline mutations are known to be at a higher risk for cancers than those who do not carry them. This is also true of their biological relatives because they have a higher probability of being carriers of such mutant genes than unrelated individuals in the population. Further, there are now sufficient grounds for assuming that cancer-predisposed individuals may also be at a higher risk for cancers induced by ionizing radiation. In our earlier work, we examined the impact of this heterogeneity (with respect to cancer predisposition and radiosensitivity differentials) on risks of radiation-induced cancer at the population level. This paper is focused on the question of risks of radiation-induced cancer in relatives of cancer-predisposed individuals. Using an autosomal dominant model of cancer predisposition and radiosensitivity developed earlier and applying it to breast cancer risks associated with mutations in the BRCA1 gene, we show that: (1) The risk ratio (i.e. the ratio of risk of radiation-induced cancer in relatives to that in unrelated individuals) in the population increases with the degree of biological relatedness of the relative, being higher for close than for distant relatives; incomplete penetrance of the mutant gene "dilutes" this risk ratio. (2) The proportion of excess radiation-induced cancers in relatives (i.e. the attributable fraction) is higher than in unrelated individuals. (3) In relatives, the proportion of excess cancers due to radiosensitivity differentials alone depends on the strength of predisposition, the radiosensitivity differentials assumed, the radiation dose, the proportion of cancers due to predisposition, the mutant gene frequency and the penetrance of the mutant gene. This is in contrast to the situation for unrelated individuals, for whom the above-mentioned proportion is dependent on the first three but not on the last three of these factors. Further, even when the proportion of excess cancers is small, most of it is due to radiosensitivity differential alone both in unrelated individuals and in relatives. (4) For values of predisposition strength and radiosensitivity differential <10, even when the estimated frequency of a mutant BRCA1 gene is 0.0047 and the proportion of breast cancers due to these mutations is 38% (as is the case for Ashkenazi Jewish women under age 30), the increase in breast cancer risks is only marginal even for first-degree relatives. (5) These findings support the conclusion that increases in radiation risks to relatives (compared to those in unrelated individuals), to be detectable epidemiologically, will occur only when the mutant alleles are common and the strength of predisposition and radiosensitivity differentials are conjointly dramatic.

Breast Neoplasms↗

PubMed1998

Possible role of telomerase activation in the cancer predisposition of patients with hereditary nonpolyposis colorectal cancers.

BACKGROUND: Hereditary nonpolyposis colorectal cancer syndrome (HNPCC syndrome; also called Lynch syndrome) is one of the most common cancer predisposition syndromes. Most cases of cancer associated with this syndrome are due to the inheritance of germline mutations in genes that encode proteins required for DNA mismatch repair; defects in these proteins allow mutations to accumulate more rapidly in the DNA and influence the rate of cancer development. Recent studies indicate that the reactivation of the activity of telomerase, an enzyme involved in the synthesis of chromosomal ends, in somatic cells may play a role in carcinogenesis. In this study, we evaluated the expression of telomerase in normal and cancerous colorectal tissue specimens from HNPCC and non-HNPCC patients. METHODS: The polymerase chain reaction-based telomeric repeat amplification protocol was used to assay telomerase activity in colorectal tissue specimens from 33 non-HNPCC patients (23 normal, 26 polyps, and 37 cancer specimens) and from 24 HNPCC patients (24 normal, 0 polyps, and 28 cancer specimens). RESULTS: Thirty-one of 37 carcinoma samples from 18 non-HNPCC patients and 27 of 28 carcinoma samples from 24 HNPCC patients were found to be positive for telomerase activity. Whereas only one of 23 normal mucosa samples from 23 non-HNPCC patients was found to have (weak) telomerase activity, eight of 24 normal mucosa samples from 24 HNPCC patients were positive for telomerase; the difference between the two groups was statistically significant (two-sided P = .0226). IMPLICATION: This study generates the hypothesis that genetic defects in individuals with HNPCC syndrome facilitate the reactivation of telomerase activity, a process which may be associated with their predisposition to develop cancer.

Adult↗

PubMed2001

Impact of cancer predisposition and radiosensitivity on the population risk of radiation-induced cancers.

This paper provides a brief overview of the current evidence for cancer predisposition and for an increased sensitivity of individuals carrying such predisposing mutations to cancers induced by ionizing radiations. We also discuss the use of a Mendelian one-locus, two-allele autosomal dominant model for predicting the impact of cancer predisposition and increased radiosensitivity on the risk of radiation-induced cancers in the population and in relatives of affected individuals using breast cancer due to BRCA1 mutations as an example. The main conclusions are the following: (1) The relative risk ratio of the risks of radiation-induced cancer in a heterogeneous population which has subgroups of normal and cancer-predisposed individuals to the risks in a homogeneous population (i.e., one which does not have these subgroups) increases with increasing dose; however, the dose dependence of the RR decreases at higher doses because of the fact that at high doses, the radiation risk to a homogeneous population will already be high. (2) The attributable risk (the proportion of cancers attributable to increased cancer susceptibility and increased radiosensitivity) follows a similar pattern. (3) When the proportion of cancers due to the susceptible genotypes is small (< 10%), as is likely to be the case for breast cancers in non-Ashkenazi Jewish women, the increases in risk ratios and attributable risks are small, and become marked only when there are very large increases in cancer susceptibility (> 1000-fold) and radiosensitivity (> 100-fold) in the susceptible group. (4) When the proportion of cancers due to the susceptible genotypes is appreciable (> or = 10%), as may be the case for breast cancers in Ashkenazi Jewish women, there may be significant increases in the risk ratios and attributable risk for comparatively moderate increases in cancer susceptibility (> 10-fold) and radiosensitivity (> 100-fold) in the susceptible subpopulation. (5) The ratio of the risk of radiation-induced cancer in relatives to that in unrelated individuals in the population increases with the biological relatedness of the relative, being higher for close than for distant relatives; however, even when the mutant BRCA1 gene frequency and the proportion of breast cancers due to these mutations are high, as in Ashkenazi Jewish women, for values of predisposition strength and radiosensitivity differential < 10, the increase in breast cancer risks is only marginal, even for first-degree relatives.

Alleles↗

PubMed2006

Hereditary cancer predisposition in children: genetic basis and clinical implications.

Although cancer predisposition syndromes are rare and malignancies arising in this context account for only 1-10% of childhood tumors, studies performed in affected patients and their families have been of unique value for the understanding of cancer development. Three classes of genes (tumor suppressor genes, oncogenes and stability genes) have been identified and shown to be involved in the pathogenesis of familial, as well as sporadic tumors. Cancer has long been recognized as a genetic disease of somatic cells. Despite improved understanding of the molecular basis of predisposition to cancer and better diagnostic tools, the care of these patients and their families remains a major challenge for the clinician. Medical, psychological, ethical and legal issues have to be considered. This review focuses on examples of each class of inherited cancer predisposition syndromes with special implications for patients in the pediatric age group, including retinoblastoma predisposition, Li-Fraumeni syndrome, multiple endocrine neoplasia disorders and Fanconi anemia. The genetic basis of cancer predisposition is discussed as well as the major concepts and controversies in the clinical management of these patients and their families.

Child↗

PubMed1999

HNPCC-like cancer predisposition in mice through simultaneous loss of Msh3 and Msh6 mismatch-repair protein functions.

Cancer predisposition in hereditary non-polyposis colon cancer (HNPCC) is caused by defects in DNA mismatch repair (MMR). Mismatch recognition is attributed to two heterodimeric protein complexes: MutSalpha (refs 2, 3, 4, 5), a dimer of MutS homologues MSH2 and MSH6; and MutSbeta (refs 2,7), a dimer of MSH2 and MSH3. These complexes have specific and redundant mismatch recognition capacity. Whereas MSH2 deficiency ablates the activity of both dimers, causing strong cancer predisposition in mice and men, loss of MSH3 or MSH6 (also known as GTBP) function causes a partial MMR defect. This may explain the rarity of MSH6 and absence of MSH3 germline mutations in HNPCC families. To test this, we have inactivated the mouse genes Msh3 (formerly Rep3 ) and Msh6 (formerly Gtmbp). Msh6-deficient mice were prone to cancer; most animals developed lymphomas or epithelial tumours originating from the skin and uterus but only rarely from the intestine. Msh3 deficiency did not cause cancer predisposition, but in an Msh6 -deficient background, loss of Msh3 accelerated intestinal tumorigenesis. Lymphomagenesis was not affected. Furthermore, mismatch-directed anti-recombination and sensitivity to methylating agents required Msh2 and Msh6, but not Msh3. Thus, loss of MMR functions specific to Msh2/Msh6 is sufficient for lymphoma development in mice, whereas predisposition to intestinal cancer requires loss of function of both Msh2/Msh6 and Msh2/Msh3.

Alleles↗

PubMed2004

Confirmation of the HPCX prostate cancer predisposition locus in large Utah prostate cancer pedigrees.

Several genetic predisposition loci for prostate cancer have been identified through linkage analysis, and it is now generally recognized that no single gene is responsible for more than a small proportion of prostate cancers. However, published confirmations of these loci have been few, and failures to confirm have been frequent. The genetic etiology of prostate cancer is clearly complex and includes significant genetic heterogeneity, phenocopies, and reduced penetrance. Powerful analyses that involve robust statistics and methods to reduce genetic heterogeneity are therefore necessary. We have performed linkage analysis on 143 Utah pedigrees for the previously published Xq27-28 (HPCX) prostate cancer susceptibility locus. We employed a robust multipoint statistic (TLOD) and a novel splitting algorithm to reduce intra-familial heterogeneity by iteratively removing the top generation from the large Utah pedigrees. In a dataset containing pedigrees having no more than five generations, we observed a multipoint TLOD of 2.74 (P=0.0002), which is statistically significant after correction for multiple testing. For both the full-structure pedigrees (up to seven generations) and the smaller sub-pedigrees, the linkage evidence was much reduced. This study thus represents the first significant confirmation of HPCX (Xq27-28) and argues for the continued utility of large pedigrees in linkage analyses for complex diseases.

Chromosome Mapping↗

PubMed1995

Cancer predisposition, radiosensitivity and the risk of radiation-induced cancers. I. Background.

This paper presents an overview of current knowledge on genetic predisposition to cancer and on enhanced sensitivity of cancer-predisposed genotypes to cancers induced by ionizing radiation. It is intended to provide a background and set the stage for the next papers in this series in which we will assess how such heterogeneity (with respect to predisposition to cancer and presence of radiosensitivity genotypes) in a population may affect estimates of the risk of radiation-induced cancers. The main findings and/or conclusions of the present paper are the following: (1) "Cancer-predisposing genes" (i.e. those at which germinal mutations predispose to cancer) are present in the human genome; these genes are responsible not only for the rare familial cancer syndromes but also for a proportion of the common cancers. At least 21 such genes have now been cloned (including 9 tumor suppressor genes, 11 DNA repair genes and 1 proto-oncogene); further, at least 8 putative tumor suppressor genes and a gene involved in ataxia telangiectasia have been localized to specific chromosomes. (2) These genes play crucial roles in the control of cellular proliferation, programmed cell death (apoptosis) and/or one or another DNA repair pathway. Consequently, mutations in these genes are likely to "liberate" the cells from the normal constraints imposed by them, resulting in unconstrained growth characteristic of cancer. (3) At present, the evidence for increased sensitivity of cancer-predisposed genotypes to radiation-induced cancers is limited. However, current knowledge of the known functions of the cancer-predisposing genes and of the consequences of mutations in these provide (a) sufficient grounds for assuming that the genotypes of those predisposed to cancer may be at an increased risk for radiation-induced cancers and (b) the rationale for attempts to estimate quantitatively the impact of genotype-dependent differences in cancer predisposition and radiosensitivity on cancer risks in an irradiated population.

Animals↗

PubMed1997

Cancer predisposition, radiosensitivity and the risk of radiation-induced cancers. III. Effects of incomplete penetrance and dose-dependent radiosensitivity on cancer risks in populations.

Recent studies have identified a number of genes in the human genome at which germinal mutations predispose the individuals to one or another type of cancer. These studies also show that not all individuals carrying the mutant genes develop cancers (i.e., the mutant genes are not fully penetrant). At least some of these predisposed genotypes also have a higher sensitivity to cancers induced by ionizing radiation than those who are not so predisposed, which may be dependent on dose. This paper presents an analysis of the impact of such heterogeneity on estimates of cancer risks for an irradiated population. This is done by extending the Mendelian one-locus, two-allele model of cancer predisposition and radiosensitivity developed earlier to allow for incomplete penetrance and dose dependence of radiosensitivity differentials among genotypes. The model is applied to recently published data for breast cancer and hereditary non-polyposis colon cancer using a range of possible values for the strength of predisposition and radiosensitivity differentials. It is shown that, after radiation exposures, the ratio of cancer risks in a heterogeneous population relative to that in a homogeneous population increases with increasing dose, but that the dose dependence of the relative risk diminishes at higher doses. Likewise, the attributable risk (i.e. the proportion of the increase in risk that is due to both increased susceptibility and increased radiosensitivity) and the proportion of attributable risk due to increased radiosensitivity also increase with dose, and the dose dependence of each measurement also diminishes at higher doses. However, when the proportion of cancers due to the susceptible genotypes is small (<10%) (as is likely to be the case for breast cancer in non-Ashkenazi women), the increases in the relative risk and attributable risk are marked only when there are very large increases in cancer susceptibility (>1000-fold) and radiosensitivity (>100-fold) in the susceptible group. When the proportion of cancers due to the susceptible genotypes is appreciable (> or = 10%) (as may be the case for breast cancer in Ashkenazi Jewish women), there may be large increases in the relative risk and attributable risk for comparatively modest increases in cancer susceptibility (>10-fold) and radiosensitivity (>100-fold) in the susceptible subpopulation. For any given combination of strength of predisposition and radiosensitivity differential, incomplete penetrance dilutes the effect.

Breast Neoplasms↗

PubMed2001

Prevalence of breast cancer predisposition gene mutations in Chinese women and guidelines for genetic testing.

BACKGROUND: Breast cancer is the most common cancer among Caucasian females. On average, 1 in 12 women will have breast cancer during their lifetime. There is a marked difference in breast cancer incidence in Chinese. In Hong Kong women, the lifetime risk is 1 in 29. BRCA1 and BRCA2 are high-penetrant cancer predisposition genes, but the prevalence and nature of mutations in these genes appear to be ethnic-specific. It is not clear if the differences in cancer incidence between Caucasians and Chinese are due to genetic or environmental factors. METHODS: In our investigation of BRCA1 mutations among Chinese female patients in Hong Kong, BRCA1 mutations were found in 3.8% (CI: 1.3-8.8%) of 130 breast cancer patients. The prevalence was higher in a separate group of 56 early onset patients, aged<45 years, (8%, CI: 2.2-19.2). Most of the mutations were different from those reported in Caucasians. A deletion 589delCT was found in three unrelated patients, which may represent a common mutation. Similar prevalence of mutations was reported in Taiwan and Singapore Chinese. Other low-penetrant cancer predisposition genes may be important in the pathogenesis of the majority of breast cancers. CONCLUSIONS: Although the epidemiology of breast cancer is different between Caucasians and Chinese, the prevalence of mutations in the high-penetrant cancer-predisposition gene of BRCA1 is comparable. It may indicate that the role of genetic contribution to breast cancer may be similar in the two ethnic groups and the difference in epidemiology may be contributed more heavily by environmental factors.

BRCA2 Protein↗

PubMed1998

DNA testing for cancer predisposition.

PURPOSE/OBJECTIVES: To describe and review scientific and regulatory aspects of molecular genetic technology in the context of DNA testing for cancer predisposition. DATA SOURCES: Published professional articles, texts, and proceedings; commercial testing companies; computerized data bases; and the World Wide Web. DATA SYNTHESIS: This article reviews the basic molecular biology (e.g., DNA, genes, chromosomes, DNA mutations) that is the foundation for indirect and direct methods of DNA testing for cancer predisposition. Key issues in DNA testing include who should be tested, provision of testing, and regulatory concerns. Benefits and problems of testing contribute to its current controversial status. CONCLUSIONS: Understanding the mechanisms of DNA testing for cancer requires knowledge of basic molecular biology. Family history of the cancer in question is a key indicator for predisposition testing. Accessing information regarding research-based testing is challenging. DNA testing for cancer predisposition is not a perfect test, as exemplified by issues related to test regulation and sensitivity. IMPLICATIONS FOR NURSING PRACTICE: Basic knowledge of DNA testing for cancer predisposition will help nurses to (a) have a better understanding of the indications for and ramifications of testing, (b) provide information about testing to patients and the lay public, (c) counsel patients and families at high risk for inherited cancers more effectively, and (d) interpret DNA test results.

DNA↗