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Biomedical subjects

G M Petersen

Publications and source records attributed to G M Petersen.

At least 55 records · Page 3Linked to original sources
PubMed1996

Hepatoblastoma and APC gene mutation in familial adenomatous polyposis.

BACKGROUND: Hepatoblastoma is a rare, rapidly progressive, usually fatal childhood malignancy, which if confined to the liver can be cured by radical surgical resection. An association between hepatoblastoma and familial adenomatous polyposis (FAP), which is due to germline mutation of the APC (adenomatous polyposis coli) gene, has been confirmed, but correlation with site of APC mutation has not been studied. AIM: To analyse the APC mutational spectrum in FAP families with hepatoblastoma as a possible basis to select kindreds for surveillance. PATIENTS: Eight patients with hepatoblastoma in seven FAP kindreds were compared with 97 families with identified APC gene mutation in a large Registry. METHODS: APC gene mutation was evaluated by RNase protection assay or in vitro synthesis protein assay. The chi 2 test and correlation were used for data analysis. RESULTS: APC gene mutation was identified in all seven FAP kindreds in which an at risk member developed hepatoblastoma. A male predominance was noted (six of eight), similar to literature cases (18 of 25, p < 0.01. Mutations were restricted to codons 141 to 1230, but no significant difference in site of mutation between pedigrees with and without hepatoblastoma was identified. CONCLUSIONS: Hepatoblastoma occurs primarily in boys in FAP kindreds and is associated with germline APC mutation in the 5' end of the gene. However, the site of APC mutation cannot be used to predict occurrence of this extracolonic cancer in FAP pedigrees.

Adenomatous Polyposis Coli↗
PubMed1996

Genetic testing and counseling in familial adenomatous polyposis.

Testing for adenomatous polyposis coli (APC), the gene responsible for familial adenomatous polyposis (FAP), can now be offered to family members in FAP kindreds. With the availability of this test, genetic counseling has become a crucial tool for helping FAP patients and their relatives understand the syndrome and its implications and for assisting at-risk individuals in making informed decisions about whether or not to undergo genetic testing. Genetic counseling can occur at several time points: when FAP is diagnosed, when an FAP patient is considering reproductive options, when a patient is deciding whether to have his or her children screened, and when an at-risk person is considering genetic testing. Based on our experiences from working with families in a large FAP registry, we explore the different issues that emerge in each of these settings, and how the genetic counselor or clinician can help FAP patients, family members, and at-risk persons deal with these issues.

Adenomatous Polyposis Coli↗
PubMed1995

Genetic instability occurs in the majority of young patients with colorectal cancer.

Replication errors (RER) associated with genetic instability have been found in cancers of several different types and particularly in the tumours of patients with hereditary non-polyposis colorectal cancer (HNPCC). We have here determined the prevalence of such instability in relation to age among patients without HNPCC. Colorectal cancers (CRCs) in the majority of patients 35 years of age or younger exhibited instability (58% of 31 patients), whereas CRCs from patients older than 35 uncommonly did (12% of 158, p < 0.0001). Twelve of the patients under 35 with instability were evaluated for alterations of mismatch repair genes, and five were found to harbour germline mutations. These data suggest that the mechanisms underlying tumour development in young CRC patients differ from those in most older patients, regardless of HNPCC status. The results have important implications for genetic testing and management of young CRC patients and their families.

Adult↗
PubMed1995

Gene tests and counseling for colorectal cancer risk: lessons from familial polyposis.

Familial adenomatous polyposis (FAP) is a well-defined, inherited colorectal cancer syndrome due to mutations in the APC gene. Genetic counseling and predictive gene tests for FAP will likely be incorporated as a first step in risk assessment for this condition. Our experience with predictive gene testing for FAP sheds important light on the impact of such tests for families at risk for FAP or colorectal cancer. We counseled and tested 47 adults and 36 minors at risk for FAP. Gene test results changed the risk of FAP for a given individual from a priori 50% to essentially zero or 100%. These individuals and their family members were interviewed before and after disclosures of APC gene test results to examine issues related to patients' knowledge about FAP, risk perception, reasons for seeking gene testing, and anticipated meaning of the results. We found that the gene test is imbued with meaning beyond determination of gene status in families who choose gene testing. The at-risk patient has preformed, well-entrenched conceptions of what having FAP or colorectal cancer entails, and family relationships and identity may be strongly linked with disease or gene status. We have found that genetic testing of minors requires additional counseling considerations and effort to ensure their understanding of FAP and the gene test. Importantly, their understanding of the clinical and social meaning of the gene test result must be elicited. For all patients, the value of counseling includes reduction of uncertainty and adjustment of misperceptions. Genetic counseling guidelines for this emerging clinical service are presented.

Adenomatous Polyposis Coli↗
PubMed1994

hMSH2 mutations in hereditary nonpolyposis colorectal cancer kindreds.

It has recently been shown that hereditary nonpolyposis colorectal cancer (HNPCC) is caused by hereditable defects in DNA mismatch repair genes. However, the fraction of HNPCC due to defects in any one repair gene and the nature of these mutations are not known. We analyzed 29 HNPCC kindreds for mutations in the prototype DNA mismatch repair gene hMSH2 by a combination of linkage analysis, polymerase chain reaction-based screening, and sequencing of the coding region. The complete intron/exon structure of the gene was ascertained to facilitate this analysis. The results suggest that at least 40% of classic HNPCC kindreds are associated with germline mutations in hMSH2 and that most of these mutations produce drastic alterations in the predicted protein product.

Amino Acid Sequence↗
PubMed1994

Phenotypic variability of familial adenomatous polyposis in 11 unrelated families with identical APC gene mutation.

BACKGROUND/AIMS: Familial adenomatous polyposis is caused by germline mutation of the adenomatous polyposis coli (APC) gene. Affected individuals develop hundreds of colorectal adenomas at young age and can have extracolonic lesions. METHODS: This study evaluated the phenotype of 74 patients with familial adenomatous polyposis from 11 unrelated families with an identical 5-base pair deletion at codon 1309 of the APC gene. RESULTS: Polyp density in the sigmoid colon of 16 patients from 9 families varied from 3.8 to 13.1/cm2, and mean polyp diameter ranged from 1.4 +/- 0.1 to 2.7 +/- 0.1 mm. The distribution of colonic adenomas also varied, with diffuse polyposis in 6 patients but relative polyp sparing in the more proximal colon in 6 others. Age at diagnosis of colorectal cancer ranged from 19 to 62 years, but the mean age did not differ among the 4 families with multiple cases. Colorectal cancers occurred predominantly in the rectosigmoid (80%) but also in the more proximal colon. The percentage of patients affected by various extracolonic lesions differed widely among and within the 11 families (range, 0%-100%). CONCLUSIONS: APC gene mutation at codon 1309 results in intrafamily and interfamily phenotypic variation in familial adenomatous polyposis. Environmental and/or other genetic factors must play roles in the expression of germline APC gene mutations.

Adenomatous Polyposis Coli↗
PubMed1994

Epidemiology, screening, and prevention of lung cancer.

With an estimated 170,000 new cases and 149,000 deaths in the United States during 1993, lung cancer is now the leading cause of cancer deaths in both men and women. Tobacco smoking is an important risk factor, and a large fraction of the risk can be attributed to it. Other risk factors have been implicated, including environmental tobacco smoke, occupational exposures to carcinogens, and genetic susceptibility. Prevention of lung cancer through early detection and identification of individuals at risk is the goal of many recent studies. This review summarizes the current status of epidemiologic and biomarker research in understanding both the etiology and prognostic utility of environmental and host factors.

Biomarkers, Tumor↗
PubMed1994

Desmoid tumours in familial adenomatous polyposis.

Desmoids are rare, benign fibromatous lesions, which can arise in patients with familial adenomatous polyposis (FAP), a disorder caused by germline adenomatous polyposis coli (APC) gene mutation. This study investigated the risk of desmoids in FAP, the relation between specific APC gene mutations and desmoid formation, and the clinical characteristics of FAP patients with desmoids. Eighty three of 825 FAP patients (10%) from 49 of 161 kindreds (30%) had desmoids. The absolute risk of desmoids in FAP patients was 2.56/1000 person years; comparative risk was 852 times the general population. APC gene mutations were similar in families with and without desmoids. The female/male ratio was 1.4 (p = NS). Previous abdominal surgery was noted in 68% of patients with abdominal desmoids (55% developed within five years postoperatively). Desmoid risk in FAP family members of a desmoid patient was 25% in first degree relatives v 8% in third degree relatives. Desmoids are a comparatively common complication of FAP associated with surgical trauma and familial aggregation. Desmoid development was not linked to specific APC gene mutations and was not found predominantly in women. Studies of chemopreventive therapy, given within five years after abdominal surgery, should be considered in FAP patients with a family history of desmoid disease.

Abdominal Neoplasms↗
PubMed1994

Knowledge of the adenomatous polyposis coli gene and its clinical application.

Familial adenomatous polyposis (FAP) is one of the most clearly defined and well understood of the inherited colorectal cancer syndromes. It is an autosomal dominant condition with high (> 90%) penetrance. Clinically, it is characterized by multiple (> 100) adenomatous polyps in the colon and rectum; variant features in addition to the colonic polyps may include polyps in the upper gastrointestinal tract and other extracolonic manifestations. Since the risk of colorectal cancer in untreated FAP is virtually 100%, screening and intervention for at-risk persons has consisted of annual colon examinations by endoscopy beginning around puberty. The objective of this regimen is early detection of colonic polyps in those who have FAP, followed by preventive colectomy. Because of recent findings that most cases of FAP are due to mutations of the adenomatous polyposis coli gene at chromosome 5q21, genetic testing will probably be incorporated as the first step in the management of individuals at risk for this condition, and screening regimens can be modified. Genetic counselling about the consequences of presymptomatic gene testing is an important component of this process.

Adenomatous Polyposis Coli↗
PubMed1993

Molecular diagnosis of familial adenomatous polyposis.

BACKGROUND: Familial adenomatous polyposis is an inherited disease characterized by multiple colorectal tumors. The diagnosis has classically been based on the detection of multiple colorectal adenomas. The recent identification of germline mutations of the APC gene in patients with familial adenomatous polyposis makes presymptomatic molecular diagnosis possible, but the widespread distribution of the many mutations within this very large gene have heretofore made the search for such mutations impractical. We describe a novel approach that allows molecular genetic diagnosis in the majority of patients with the disease. METHODS: We screened 62 unrelated patients from the Johns Hopkins Familial Adenomatous Polyposis Registry for germline APC mutations. Primary screening was accomplished by analysis of protein synthesized in vitro from surrogate APC genes. In addition, the relative amount of transcript from each APC allele was determined with an allele-specific--expression assay. RESULTS: The protein assay revealed truncated protein in 51 of the 62 patients (82 percent). In 3 of the 11 remaining patients, the allele-specific--expression assay revealed significantly reduced expression of one allele of the APC gene. The use of these two assays in combination successfully identified germline APC mutations in 87 percent of the 62 patients. CONCLUSIONS: The protein and allele-specific--expression assays provide a practical and sensitive method for molecular diagnosis of familial adenomatous polyposis. This approach will facilitate care, allowing routine testing of subjects at risk and genetic confirmation of spontaneous mutations.

Adenomatous Polyposis Coli↗
PubMed1993

The APC gene product in normal and tumor cells.

The APC gene has been found to be mutated during the development of sporadic colorectal tumors as well as in the germ line of familial adenomatous polyposis patients. To facilitate the characterization of both normal and mutant APC protein, a series of monoclonal and polyclonal antibodies specific for the APC protein was produced. When lymphoblastoid cell lines derived from seven familial adenomatous polyposis patients with known mutations were analyzed by Western blot, an approximately 300-kDa protein corresponding to the predicted size of full-length APC was detected in all 7 cell lines. In addition, truncated APC proteins corresponding to the product of the known mutated alleles could be detected in 4 of the 7 lines. Similar analysis of 23 colon carcinoma and 9 adenoma cell lines revealed truncated proteins in 24 (75%) of the cell lines. Moreover, 26 (81%) of the colon tumor lines were totally devoid of the normal, full-length protein. In contrast, Western blot analysis of 40 cell lines derived from sporadic tumors of other organs detected only full-length APC. Immunohistochemical analysis of APC in normal colonic mucosa revealed cytoplasmic staining with more intense staining in the basolateral margins of the epithelial cell. This staining was markedly increased in the upper portions of the crypts, suggesting an increased level of expression with maturation. These studies provide some initial clues to the function of the cytoplasmic protein APC and demonstrate the feasibility of identifying APC mutations by direct analysis of the APC protein.

Adenoma↗
PubMed1993

Presymptomatic direct detection of adenomatous polyposis coli (APC) gene mutations in familial adenomatous polyposis.

The recent identification of the familial adenomatous polyposis (FAP) gene (designated as APC) enables conclusive genetic testing of at-risk family members for the specific mutation in families in which the germline gene mutation has been characterized. Presymptomatic molecular diagnosis of FAP was performed by direct direction of mutations in lymphocyte DNA in four families. Each of the families has a different mutation of the APC gene. Twenty-seven offspring of affected individuals (a priori risk of 50%) were tested. Ten of the 27 had already developed clinical features of FAP. Of the remaining seventeen, two had had a negative colon exams at an early age, and nine had never had colon exams (mean age, 12.1 +/- 3.1 SD years). Six children from this group (54%) were found to carry their affected parent's mutation. No change in the conventional FAP colon screening regimen is recommended for these children. In contrast, when direct tests indicate that an individual does not have the FAP mutation, we recommend that screening be decreased. Reduction of uncertainty for at-risk FAP family members is an important benefit of genetic testing.

Adenomatous Polyposis Coli↗
PubMed1993

Nasopharyngeal angiofibroma in patients with familial adenomatous polyposis.

Four patients with nasopharyngeal angiofibroma and familial adenomatous polyposis are reported here. Nasopharyngeal angiofibroma was 25 times more frequent in our patient population with familial adenomatous polyposis than in an age-matched hospital population. The association of these two rare conditions suggests that nasopharyngeal angiofibroma is an extracolonic manifestation of adenomatous polyposis. In addition, somatic mutation of the adenomatous polyposis coli gene, which causes adenomatous polyposis when mutated in the germline, could play a role in the pathogenesis of sporadic nasopharyngeal angiofibroma.

Adenomatous Polyposis Coli↗
PubMed1992

Screening for germ-line mutations in familial adenomatous polyposis patients: 61 new patients and a summary of 150 unrelated patients.

We report here the result of a screening for germ-line mutations in the adenomatous polyposis coli (APC) gene in 61 new familial adenomatous polyposis (FAP) patients as well as a summary of the results of 150 patients. Examination of the entire coding region of the APC gene, based on a ribonuclease protection assay coupled with the polymerase chain reaction (PCR), disclosed mutations that were considered to cause significant defects in the APC product in 97 of 150 unrelated FAP patients. Our findings revealed the following characteristics of the germ-line mutations of APC: 1) the great majority of the mutations were found to truncate the APC product; 2) almost all of the mutations were located within the first half of the coding region; 3) no correlation was observed between the locations of germ-line mutations and extracolonic manifestations in FAP patients; 4) more than 80% of base substitutions in the APC gene were from cytosine to other nucleotides, nearly one-third of which occurred at the GpG site. Our results provide information helpful to an understanding of the APC gene and will also contribute to presymptomatic diagnosis of members in FAP families.

Adenomatous Polyposis Coli↗
PubMed1992

Risk factors for gallstone formation during rapid loss of weight.

Risk factors for the development of gallstones during rapid weight loss were assessed in 457 subjects who entered a weight control program (520 kcal/day). Absence of gallstones in these subjects was documented by ultrasonography prior to entry into the study. Ultrasonography was performed again at 16 weeks on the subjects who remained in the study (N = 248). The incidence of gallstones by 16 weeks of rapid weight loss was 10.9% (27/248). Most factors associated with gallstones in the general population, eg, older age, female gender, parity, positive family history, etc, were not associated with gallstones in this population. The risk factors for developing gallstones included increased initial body mass index [weight (kg)/height (m)2], amount of body mass index loss, and serum triglyceride levels. The positive predictive value of these risk factors was 75%, but the sensitivity was only 12%. These observations indicate that risk factors for the development of gallstones during rapid weight loss are probably different from those in the general population. The factors identified by this study are useful in predicting patients at high risk for gallstones. However, since only a minority of gallstones that form can be predicted, further study is needed to identify additional factors that will improve our ability to predict gallstone formation.

Adult↗
PubMed1991

Effects of age, breast feeding, and household structure on Haemophilus influenzae type b disease risk and antibody acquisition in Alaskan Eskimos.

Invasive Haemophilus influenzae type b (Hib) disease occurs with unusually high incidence in Alaskan Eskimos. In 1983, the authors evaluated the unique susceptibility of the Yupik-speaking Eskimo population in southwest Alaska. A matched case-control design was used to assess the influence of age, breast feeding, and household composition on disease risk, with a historical cohort design to evaluate their effects on acquisition of Hib anticapsular antibody. The authors studied 103 cases with known invasive Hib disease that occurred at a mean age of 8.7 +/- 8.6 months; healthy controls were matched for age and village of residence. Living in extended families at the time of disease onset was significantly associated with Hib disease (p less than 0.04; odds ratio = 1.8; 95% confidence interval 0.87-3.25). The authors found that breast feeding was significantly less common among cases than controls (p less than 0.03; odds ratio = 0.53; 95% confidence interval 0.27-0.98). Although there was a positive correlation between age and acquired level of total anticapsular antibody (r = 0.59; p less than 0.0001), previous exposure to invasive Hib disease did not influence these levels. Household crowding and breast feeding also did not appear to affect Hib antibody acquisition.

Age Factors↗