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The search for genetic damage in neoplastic cells now occupies a central place in cancer research. Diverse examples of such damage are in hand, and they in turn hint at biochemical explanations for neoplastic growth. The way may be open to solve the riddles of how normal cells govern their replication and why cancer cells do not.
The genetic basis of human cancer is well established, although much work remains to be done to unravel the mechanisms of carcinogenesis. Multiple genetic alterations appear to the hallmark in the adult cancers. Molecular cloning and characterization of the amplified proto-oncogenes and mutated recessive oncogenes would shed light on the mechanisms involved in the initiation and progression of human cancer. New tests are likely to be available in the near future (for specific oncogenes) for the diagnosis and management of various forms of human cancer.
The aim of this study was to assess the effects of cancer genetic consultations on women's perception of their family risk of breast/ovarian cancer, and to determine which factors were associated with an inaccurate perception after the consultation. A multicenter prospective survey was carried out on women (n = 397) attending cancer genetic clinics in France for the first time, in which the perceived family risk was measured both before and after the consultation, using self-administered questionnaires. The effects of the consultation on risk perception were significant among low (P <.001) and moderate risk women (P <.05). However, after the consultation, 76.3% of the "low"-risk women did not perceive their family as "low"-risk families, and 21.9% of the moderate-risk women were still definitely sure there was a genetic risk running in their family. The consultation did not affect the family risk perception of the high risk women (n = 171): the risk was thought to be very high both before (87.7%) and after (89.5%) the consultation (NS); however 10.5% of this group still perceived their family as being unlikely to be at risk after the consultation. In the low- and moderate-risk groups after multivariate adjustment, the inaccurate perceptions varied, depending on the clinics and on the psychosocial context of the consultation: they increased when the consultee was personally affected by cancer, and decreased when the consultee had a health occupation. Cancer genetic consultations had only marginal effects on the perception of family risk on the whole, although they were significant in the case of low- and moderate-risk women. The question arises as to whether a more comprehensive approach should be implemented and how to go about providing efficient cancer risk information in the context of health care systems.
Genetic and environmental factors are responsible for the genomic lesions that cause cancer, a complex genetic disease associated with genomic instability. Studies aimed at deciphering the lesions in cancer have focused mainly on one or a few genes, despite the genomic scope of the disease. The recently decoded human DNA sequence is anticipated to foster understanding of human evolution and disease and the role of environment and heredity in the human condition. This review addresses the opportunities and challenges that the availability of the human genome sequence holds for cancer research.
Genetic testing for cancer susceptibility is already part of the clinical management of families with some of the well-defined (but uncommon) inherited cancer syndromes. In cases where the risks associated with a predisposing mutation are less certain, or where there is no clearly effective intervention to offer those with a positive result, its use is more controversial. Careful evaluation of costs and benefits, and of the efficacy of interventions in those found to be at risk, is essential and is only just beginning. An immediate challenge is to ensure that both health professionals and the public understand clearly the issues involved.
Genetic alteration is the driving force for thyroid tumorigenesis and progression, based upon which novel approaches to the management of thyroid cancer can be developed. A recent important genetic finding in thyroid cancer is the oncogenic T1799A transversion mutation of BRAF (the gene for the B-type Raf kinase, BRAF). Since the initial report of this mutation in thyroid cancer 2 years ago, rapid advancements have been made. BRAF mutation is the most common genetic alteration in thyroid cancer, occurring in about 45% of sporadic papillary thyroid cancers (PTCs), particularly in the relatively aggressive subtypes, such as the tall-cell PTC. This mutation is mutually exclusive with other common genetic alterations, supporting its independent oncogenic role, as demonstrated by transgenic mouse studies that showed BRAF mutation-initiated development of PTC and its transition to anaplastic thyroid cancer. BRAF mutation is mutually exclusive with RET/PTC rearrangement, and also displays a reciprocal age association with this common genetic alteration in thyroid cancer. The T1799A BRAF mutation occurs exclusively in PTC and PTC-derived anaplastic thyroid cancer and is a specific diagnostic marker for this cancer when identified in cytological and histological specimens. This mutation is associated with a poorer clinicopathological outcome and is a novel independent molecular prognostic marker in the risk evaluation of thyroid cancer. Moreover, preclinical and clinical evaluations of the therapeutic value of novel specific mitogen-activated protein kinase pathway inhibitors in thyroid cancer are anticipated. This newly discovered BRAF mutation may prove to have an important impact on thyroid cancer in the clinic.
Women who test positive for a genetic breast cancer marker may have more than a 50% chance of developing the disease. Although past screening technologies have sought to identify actual breast cancers, as opposed to predisposition, the history of screening may help predict the societal response to genetic testing. For decades, educational messages have encouraged women to find breast cancers as early as possible. Such messages have fostered the popular assumption that immediately discovered and treated breast cancers are necessarily more curable. Research, however, has shown that screening improves the prognosis of some--but not all--breast cancers, and also that it may lead to unnecessary interventions. The dichotomy between the advertised value of early detection and its actual utility has caused particular controversy in the United States, where the cultural climate emphasizes the importance of obtaining all possible medical information and acting on it. Early detection has probably helped to lower overall breast cancer mortality. But it has proven hard to praise aggressive screening without exaggerating its merits. Women considering genetic breast cancer testing should weight the benefits and limitations of early knowledge.
Genetic inactivation of key components of the Wnt signal transduction system is a frequent event in colorectal cancer. These genetic mutations lead to stabilization of beta-catenin, a cytoplasmic-nuclear shuttling protein with a potent transcription activation domain. Stabilization and subsequent nuclear localization of beta-catenin produces aberrant, Wnt-independent signals to target genes, an activity tightly linked to the genesis of colon cancers. In the nucleus, the transcription factor family of LEF/TCF proteins transmits Wnt signals by binding to beta-catenin and recruiting it to target genes for activation. Such activities are carried out by full-length LEF/TCFs that are thought to be mostly interchangeable and redundant. However, truncated forms of LEF-1 and TCF-1 that do not bind to beta-catenin function as dominant negatives and an alternatively spliced TCF isoform with a unique activation function has recently been discovered. The dominant negative forms block Wnt signals because they occupy Wnt target genes and limit beta-catenin access; the alternatively spliced TCF isoform activates certain Wnt target promoters whereas other TCF isoforms and LEF-1 do not. A study of LEF/TCF expression and activity in normal intestine and colon carcinomas suggests that the relative amounts of LEF/TCF isoforms may change as tumors progress and this may influence the strength and specificity of Wnt signals in the nucleus. While the underlying mechanism for a change in the LEF/TCF isoform expression is not yet known, recent evidence implicates the Wnt signaling pathway itself as a potential modulator.
Most breast cancer has a complex, multifactorial etiology. One consequence of this multifactorial phenomenon is that etiological heterogeneity may exist. This heterogeneity implies simply that two or more groups of breast cancer cases in the general population may have been caused by different sets of events. The ability to define etiologically heterogeneous subgroups in the population may facilitate a number of research and clinical issues. Studying etiologically homogeneous subgroups in the general population may improve the ability to identify etiologic agents. Identification of a homogeneous group of breast cancer cases may also aid breast cancer diagnosis or treatment, and may allow a more effectively application of cancer prevention and control strategies. Defining etiologic heterogeneity in the general population is one initial step in the process of understanding cancer etiology. Using knowledge such as that provided in the two examples presented here, formal case-control or cohort studies can be undertaken to examine whether the factors that define etiologic heterogeneity are involved in etiology. Furthermore, the results of studies of etiologic heterogeneity can point toward potential gene-gene or gene-environment interactions. The type of studies presented here can therefore serve a useful role in leading to more formal molecular epidemiological analyses.
BACKGROUND: While a definitive genetic test for Hereditary Prostate Cancer (HPC) is not yet available, future HPC risk testing may become available. Past survey data have shown high interest in HPC testing, but without an in-depth analysis of its underlying rationale to those considering it. METHODS: Telephone computer-assisted interviews of 400 men were conducted in a large metropolitan East-coast city, with subsequent development of psychometric scales and their correlation with intention to receive testing. RESULTS: Approximately 82% of men interviewed expressed that they "probably" or "definitely" would get genetic testing for prostate cancer risk if offered now. Factor analysis revealed four distinct, meaningful factors for intention to receive genetic testing for prostate cancer risk. These factors reflected attitudes toward testing and were labeled "motivation to get testing," "consequences and actions after knowing the test result," "psychological distress," and "beliefs of favorable outcomes if tested" (alpha = 0.89, 0.73, 0.73, and 0.60, respectively). These factors accounted for 70% of the total variability. The domains of motivation (directly), consequences (inversely), distress (inversely), and positive expectations (directly) all correlated with intention to receive genetic testing (p < 0.001). CONCLUSIONS: Men have strong attitudes favoring genetic testing for prostate cancer risk. The factors most associated with testing intention include those noted in past cancer genetics studies, and also highlights the relevance in considering one's motivation and perception of positive outcomes in genetic decision-making.
The cancer genetics consultation and comprehensive breast centers logically go hand in hand. Breast surgeons may be interacting for the first time with a relatively new class of colleagues-genetics professionals, such as medical geneticists and genetic counselors. This article introduces surgical oncologists to the current applications of genetic counseling in oncology practice through the involvement of genetics professionals on interdisciplinary teams, in case conference, at grand rounds and oncology meetings, and through genetic risk assessment, counseling, and possible susceptibility testing. Surgeons interacting with the cancer genetics specialists have critical roles to play in the organization of cancer genetics programs, recognition of patients and families at increased genetic risk, appropriate referrals for genetic counseling and testing, and management of high-risk families.
This study examined the demand for breast cancer genetic testing and counseling among Canadian women diagnosed with breast cancer under the age of 50, together with some of the factors predicting both their intentions to be tested and the degree to which they act on their intentions. Participants were 110 women under the age of 50 and comprised of two groups: 1) women diagnosed with breast cancer (BC, n = 60): and 2) an index group of unaffected women from the general population (GP, n = 50). All participants completed a survey that addressed family history of breast and other cancers, demographic variables, knowledge and attitudes about breast cancer, and genetic testing. Members of the BC group were offered genetic counseling and testing for BRCA1 and BRCA2 free of charge. Overall, 60% of participants indicated they would like the test, and 40% either did not want it or were uncertain. Seventy-two percent of women in the BC group wanted to be tested. Of these, only 49% had actually contacted the genetic counselor about testing at follow-up 3-15 months later. Intention to be tested was associated with presence of breast cancer, greater perceived benefits of testing, fewer perceived 'costs' of testing, and higher levels of concern about the risk of relatives developing breast cancer. Actual arranging to meet with the genetic counselor among women in the BC group was associated with fewer perceived costs of having the test. Results suggest a moderate level of interest in gene testing, though intention to be tested may not translate into actual uptake. Women who do choose to have the test may believe the potential 'costs' of using this new genetic technology to be relatively few. This has implications for genetic counselors in terms of providing balanced and complete information to women considering genetic testing for breast cancer susceptibility.
A family history of colorectal cancer has been consistently associated with an increased risk of developing colon cancer. However, there is limited information on the association between family history of colorectal cancer and genetic alterations that occur in colon tumors. In this study, we evaluate the association among genetic alterations of Ki-ras and p53, microsatellite instability and having a family history of colorectal cancer in a study of incident colon cancer cases (n = 1993) and population-based controls (n = 2,410). Although there was a slight nonsignificant increase in risk of having an unstable tumor among those with a family history of colorectal cancer, this increase in risk disappeared after excluding those people with a known mutation in either of the mismatch repair genes hMLH1 or hMSH2. A family history of colorectal cancer was not associated with Ki-ras mutations overall, although those with a G to T mutation of the second base of codon 12 were more likely to have a family history of colorectal cancer than were those without this specific type of Ki-ras mutation. Cases with p53 mutations were less likely to have a family history of colorectal cancer than were cases without a p53 mutation. We believe that, given the general lack of association between having a family history of colorectal cancer and genetic alterations in tumors, these alterations are acquired through disease pathways that involve exposure from diet, lifestyle or other environmental factors.
Lung cancer is the number one cause of cancer death for all citizens of the United States regardless of gender, race, or ethnic background. Surgery, the only curative treatment available, is feasible in only 35% of all patients with lung cancer. But even in this group of patients, most will die of recurrent disease. Treatment advances have been modest at best, and the 5-year survival rate of approximately 15% has not changed appreciably in the past two decades. Population projections indicate a continuation of the lung cancer epidemic among men and a rise among women, in whom rates of smoking have remained relatively high. It is estimated that 90% of all lung cancers are smoking related, and gender, race, and family history are important risk modifiers. Several promising markers of lung cancer susceptibility have recently been identified. However, the relative contribution of individual intrinsic factors (genetic markers, family history, race, gender) on lung cancer susceptibility in the context of complex extrinsic factors (behavior, environmental exposure, socioeconomic status) is unknown and requires further study for more informed screening and primary prevention.
Cancers are the most frequent and at the same time the most complicated of somatic genetic diseases. Technical progress in the last fifteen years has enabled to analyse the acquired genetic abnormalities found in the vast majority of cancers. This molecular dissection of cancer has led to an understanding of this disease that can basically be viewed as a rupture of the balance between two class of genes, the oncogenes and the antioncogenes. This article defines the properties of these cancer genes and gives through a few examples an insight into the various mechanisms of cancerogenesis.
Genetic alterations in early superficial colorectal cancers have rarely been reported. In the present study, we searched for alterations in the APC and p53 genes in 27 superficial (20 depressed and 7 elevated) and 21 protruding colorectal cancers with submucosal invasion by means of PCR-single strand conformation polymorphism. Allelic imbalance (AI) on five loci, i.e., 1p34-36, 8p21-22, 14q32, 18q21 and 22q12-13, was also analyzed. Since a high incidence of 18q21 AI was detected in the superficial depressed cases, we further screened for alterations in Smad2, Smad4 and DCC. APC alterations were observed in three superficial depressed, one superficial elevated, and 11 protruding colorectal cancers, indicating that the frequency of APC alterations in superficial depressed cases was significantly lower than that in the protruding ones. There was no significant association between p53 alterations and macroscopic types. AI on 18q21 (13/20, 65%) was much higher than those on the other four loci in the superficial depressed cases. Moreover, the frequency of 18q21 AI in the superficial depressed cases was significantly higher than that in the protruding ones. Smad4 alterations were only detected in 1 of the 13 superficial depressed and 3 of the 17 protruding cases, while Smad2 and DCC alterations were not detected in any case examined. These data suggest that the carcinogenetic pathways of protruding and superficial depressed colorectal cancers are different, and that alterations of tumor suppressor gene(s) located on 18q21 other than Smad2, Smad4 and DCC might be associated with most superficial depressed colorectal cancers.
Genetically determined polymorphisms of N-acetylation and oxidative capacity have been studied using dapsone and metoprolol in 51 Japanese patients with spontaneous bladder cancer and 203 healthy control subjects. The results for N-acetylation pharmacogenetics were against the initial expectation that there would be a preponderance of slow acetylators in the cancer group, as 3 such patients (5.9%) were found as compared to 13 (6.4%) in the healthy group. There was no poor metabolizer (PM) of metoprolol in the cancer group, whereas in the healthy group one (0.5%) was a PM. There were no significant differences between the groups in the frequency of slow acetylator and poor oxidiser phenotypes, or in the frequency distribution profiles of acetylation (monoacetyldapsone/dapsone) and oxidative metabolic ratio (log metoprolol/alpha-hydroxymetoprolol). The results indicate that neither N-acetylation nor the debrisoquine/sparteine-type oxidative phenotype and/or capacity represent a genetic predisposition to spontaneous bladder carcinogenesis in Japanese patients. In the normal Japanese population there is a great predominance of rapid acetylators and extensive oxidisers.
Genetic alterations are responsible for the development of cancer in ductal cells of the pancreas. These genetic changes result in abnormal molecular expression of proteins that are involved in cell proliferation, cell cycle control and adhesion. Some of the genetic mutations result in aberrant proteins that can be recognized as novel or foreign by cells of innate and adaptive immune systems. These are appropriate targets for therapeutic intervention which may involve immunobiologic approaches. These approaches may be less effective because of immune escape mechanisms developed by tumor cells within the microenvironment of the tumor mass. Immunobiotherapy intervention of pancreas cancer must circumvent these obstacles and integrate effective immunotherapy with molecularly targeted approaches to pancreas cancer intervention.