Somatic APC and K-ras codon 12 mutations in aberrant crypt foci from human colons.

Aberrant crypt foci (ACF) are microscopic lesions which have been postulated to precede the development of adenomatous polyps, the precursors to colorectal cancer. APC and ras gene mutations have been shown to be important early molecular events in the development of colorectal neoplasms. The objective of this study was to establish the nature and frequency of these two genetic alterations in ACF harvested from human colorectal resection specimens. One hundred and fifty-four ACF comprised of between 1 and 56 crypts were harvested from the grossly normal mucosa of colorectal resection specimens of 28 patients with varying pathological diagnoses. One hundred and twenty-five ACF from 20 colons were screened for the presence of K-ras codon 12 mutations with a polymerase chain reaction/restriction enzyme-based method. The APC gene mutation cluster region was screened in 65 ACF from 20 colons using a polymerase chain reaction/single strand conformation polymorphism technique. Putative mutations were confirmed by direct sequencing. K-ras codon 12 mutations were identified in 13% (16 of 125) of ACF. We also identified APC mutations in 4.6% (3 of 65) of ACF. The results of this study demonstrate that both APC and K-ras mutations occur in ACF. These observations support the role of the ACF as a colorectal cancer precursor and provide further insight into the early genetic changes which occur during colorectal tumorigenesis.

MSH2 deficiency contributes to accelerated APC-mediated intestinal tumorigenesis.

Accelerated intestinal tumorigenesis is probable in hereditary nonpolyposis colorectal cancer, a condition associated with germ line DNA mismatch repair (MMR) gene defects, and is believed to be caused by rapid accumulation of replication errors in critical genes, such as the APC (adenomatous polyposis coli) tumor suppressor gene. To study the potential contribution of MMR genes to accelerated intestinal tumorigenesis, we crossed the Min mouse, heterozygous for a germ line mutation of Apc, with an MMR gene (Msh2)-deficient mouse. MSH2 deficiency resulted in the development of many colonic aberrant crypt foci, as well as reduced survival of the mice, secondary to both a greater number and more rapidly developing adenomas. The mechanism of inactivation of the wild-type Apc allele depended on MSH2 status. In the presence of functional MSH2, all tumors demonstrated loss of heterozygosity. In contrast, whereas all adenomas were APC negative by immunostaining, only 5 of 34 adenomas from Apc+/-/Msh2-/- mice demonstrated loss of heterozygosity of the wild-type Apc allele, suggesting that somatic Apc mutations are responsible for the additional tumors. These findings provide evidence for the important role of MMR genes in accelerated intestinal tumorigenesis, thus supporting more aggressive surveillance strategies to prevent colorectal cancer in hereditary nonpolyposis colorectal cancer.

Somatic APC and K-ras codon 12 mutations in periampullary adenomas and carcinomas from familial adenomatous polyposis patients.

Periampullary adenomas in the duodenum of Familial Adenomatous Polyposis (FAP) patients are among the most frequent and clinically important extracolonic neoplasms in FAP. The purpose of this study was to characterize the frequency and nature of somatic adenomatous polyposis coli (APC) gene and K-ras codon 12 mutations in periampullary adenomas and carcinomas in FAP. These molecular changes have been shown to be important during the early stages of colorectal carcinogenesis. DNA was prepared from endoscopic periampullary biopsies and paraffin blocks from 49 FAP patients. Of 143 samples, 77 were histologically normal, 29 were biopsies from small periampullary adenomas, 29 biopsies were from 19 large adenomas and eight samples were from periampullary cancers. APC mutations in the mutation cluster region and K-ras codon 12 mutations were detected by polymerase chain reaction based techniques. Somatic APC mutations consisting of deletions at codons 1464 and 1465 were detected in one small and two large periampullary adenomas. Loss of heterozygosity was seen in one periampullary carcinoma. K-ras codon 12 mutations were detected in seven of 19 large periampullary adenomas and in one of eight periampullary carcinomas. These data suggest that K-ras codon 12 mutations may be important during periampullary tumorigenesis in FAP but somatic APC mutations in the mutation cluster region are infrequent. Local environmental factors in the duodenum may contribute to differences in the molecular changes which occur during the adenoma-to-carcinoma sequence in periampullary compared to colonic tumorigenesis.

Immunohistochemistry for hMLH1 and hMSH2: a practical test for DNA mismatch repair-deficient tumors.

Inactivation of deoxyribonucleic acid (DNA) mismatch repair genes, most commonly human mutL homologue 1 (hMLH1) or human mutS homologue 2 (hMSH2), is a recently described alternate pathway in cancer development and progression. The resulting genetic instability is characterized by widespread somatic mutations in tumor DNA, and is termed high-frequency microsatellite instability (MSI-H). Although described in a variety of tumors, mismatch repair deficiency has been studied predominantly in colorectal carcinoma. Most MSI-H colorectal carcinomas are sporadic, but some occur in patients with hereditary nonpolyposis colorectal cancer (HNPCC), and are associated with germline mutations in mismatch repair genes. Until now, the identification of MSI-H cancers has required molecular testing. To evaluate the role of immunohistochemistry as a new screening tool for mismatch repair-deficient neoplasms, the authors studied the expression of hMLH1 and hMSH2, using commercially available monoclonal antibodies, in 72 formalin-fixed, paraffin-embedded tumors that had been tested previously for microsatellite instability. They compared immunohistochemical patterns of 38 MSI-H neoplasms, including 16 cases from HNPCC patients with known germline mutations in hMLH1 or hMSH2, with 34 neoplasms that did not show microsatellite instability. Thirty-seven of 38 MSI-H neoplasms were predicted to have a mismatch repair gene defect, as demonstrated by the absence of hMLH1 and/or hMSH2 expression. This included correspondence with all 16 cases with germline mutations. All 34 microsatellite-stable cancers had intact staining with both antibodies. These findings clearly demonstrate that immunohistochemistry can discriminate accurately between MSI-H and microsatellite-stable tumors, providing a practical new technique with important clinical and research applications.

Clonality of thyroid nodules in sporadic goiter.

Clonality studies have suggested that neoplasms are monoclonal and hyperplasias are polyclonal. To investigate this question in thyroid, we analyzed the clonality of 26 morphologically characterized hyperplastic nodules from 19 patients with sporadic goiters. For comparison we studied six thyroid carcinomas. We used the highly informative M27 beta probe that maps to the X-chromosome DXS255 locus (X cen-p11.22). Material was obtained from 52 nodules; tissue from nine nodules was rejected because of contamination with normal elements, five patients (eight nodules) were homozygous at Pst I sites in nonnodular thyroid tissue, and three nodules were excluded for technical reasons. Methylation patterns after Hpa II digestion confirmed polyclonality in all nontumorous thyroids of informative patients. Seven hyperplastic nodules were polyclonal, and 18 were monoclonal; one showed loss of heterozygosity. One nodule exhibited aberrant methylation. Multiple nodules were obtained from four patients; in three, all were monoclonal with activation of the same allele. Three papillary carcinomas were monoclonal; two exhibited aberrant methylation. One follicular carcinoma showed loss of heterozygosity. Our data indicate that morphologically indistinguishable hyperplastic thyroid nodules may be monoclonal or polyclonal. These findings suggest that variable molecular mechanisms are involved in the pathogenesis of nodules in sporadic goiter. Future studies will need to explore the biological significance of nodules of variable clonal origin.

Familial segregation in the occurrence and severity of periampullary neoplasms in familial adenomatous polyposis.

BACKGROUND: Familial adenomatous polyposis (FAP) patients often develop periampullary adenomas that may progress to periampullary cancer, a common cause of death in this population. The risk of periampullary cancer in FAP is unclear, and variables that predict the occurrence and severity of periampullary tumors are not well understood. The specific aim of this study was to determine whether the risk of periampullary neoplasia segregates in specific FAP families. MATERIALS AND METHODS: A total of 144 FAP patients from 74 families were either screened by gastroduodenoscopy (n = 132) or information was obtained from surgical or autopsy reports (n = 12). The severity of periampullary neoplasia was recorded for each patient and graded based on maximum polyp size and histology. Linear regression was used to determine the significance of a number of variables with respect to periampullary neoplasia. A blood sample was available from at least one member of 50 unrelated families and used to detect germline mutations in codons 686 through 1693 of the adenomatous polyposis coli (APC) gene. RESULTS: Statistically significant familial segregation was found for the incidence and severity of periampullary neoplasia (P < 0.02). Age was also a statistically significant variable (P < 0.01). No correlation was observed between specific APC germline mutations and periampullary polyp frequency and severity. CONCLUSIONS: The occurrence and severity of periampullary neoplasms in patients with FAP segregates in families. This familial association may be related to as yet unidentified modifier genes or perhaps common environmental factors. These results should prove useful in developing upper gastrointestinal screening protocols for FAP patients at risk for periampullary neoplasia.

Local anti-fertility effect of inhibin-enriched preparation (IEP) in female hamsters.

An inhibin-enriched preparation (IEP) involved in the regulation of follicle stimulating hormone (FSH) is known to play an important role in the normal ovarian cycle. In utero administration of 10 micrograms of IEP on day 3 of pregnancy completely prevented implantation in hamsters. No toxic effect of IEP was observed on the blastocysts as indicated by the dye exclusion test performed with Trypan blue. Thus, the results of the present study indicate an extra-pituitary site of action for the anti-implantation effect of IEP.

Familial variation in retinal pigmentation in adenomatous polyposis.

OBJECTIVE: To examine the relationship between familial adenomatous polyposis and retinal pigment epithelial (RPE) pigmentation in affected patients and their first-degree relatives. DESIGN: Retrospective study. SETTING: Affected families across Canada registered in the Steve Atanas Stavro Familial Gastrointestinal Cancer Registry. SUBJECTS: A total of 134 subjects aged 10 to 35 years (at high risk for the disease) who had undergone examination of the gut by sigmoidoscopy, colonoscopy with biopsy or resection with biopsy and indirect ophthalmoscopy. MAIN OUTCOME MEASURES: Weighted eye score for large and small retinal lesions; family eye pigmentation index (FEPI), calculated from the weighted eye scores for individual affected family members. RESULTS: Families differed in the number and type of RPE lesions manifest, but affected family members showed similar pigmentation. An FEPI below 3 was uninformative, but with a medium or high FEPI the sensitivity and specificity of the index approached 100%. CONCLUSIONS: A positive retinal examination signifies a high risk for adenomatous polyposis, whereas a negative retinal examination is uninformative. Current molecular analysis is informative in 95% of families. However, in cases of spontaneous mutation and in patients with no first-degree relatives available or with unknown parenthood, RPE lesions are the most valuable extracolonic manifestation of adenomatous polyposis.

Antiestrogen binding sites: general and comparative properties.

Nonsteroidal antiesterogens, such as tamoxifen, bind estrogen receptors with relatively high affinity. They also bind with high affinity and distinctive specificity to another class of intracellular sites, often termed "antiestrogen binding sites" or "AEBS". These sites do not bind estrogens and their function is unknown. In this article we compare and contrast the binding specificity, intracellular localization, concentration, tissue distribution and detergent solubilization characteristics of AEBS from a number of species. In general the sites are found in highest concentration in microsomal fractions from liver. AEBS from chicken liver can be solubilized with CHAPS detergent giving rise to a detergent-associated complex with an apparent molecular mass of about 265 kDa.

Reversal of the anti-implantation effect of inhibin with progesterone in the hamster.

Inhibin, the gonadal peptide involved in regulation of follicle-stimulating hormone (FSH), exhibited anti-implantation activity in intact and ovariectomized pregnant hamsters. Administration of progesterone reversed the anti-implantation activity of inhibin. Studies were carried out to determine the effect of inhibin on the in vitro synthesis and release of progesterone by the corpora lutea of pregnant hamsters. Inhibin (10 micrograms) was observed to decrease progesterone release by 28%. The administration of exogenous progesterone (2 mg/day) was observed to overcome the anti-implantation effect of inhibin in ovariectomized, pregnant hamsters. These results indicate a possible action of inhibin to interfere with progesterone at the ovarian and/or uterine level in order to exhibit the anti-implantation activity in the hamster.

Changing causes of mortality in patients with familial adenomatous polyposis.

Widespread use of prophylactic colectomy has resulted in a reduction in the incidence of colorectal cancer in familial adenomatous polyposis (FAP) patients. A retrospective chart review of families registered at the Steve Atanas Stavro Familial Gastrointestinal Cancer Registry in Toronto was performed to determine whether the decrease in the number of patients developing colorectal cancer implies that causes of mortality in FAP patients are shifting to that of extracolonic manifestations of FAP. Information was available on 140 deaths within 158 families and among 461 individuals with FAP. When stratified by decade, from the 1930s to the 1990s, the ratio of deaths caused by extracolonic manifestations of FAP compared with deaths caused by colorectal cancer was noted to have risen. Even though most deaths in FAP patients are still from colorectal cancer, it appears that screening policies and prophylactic colectomy have resulted in a reduction in the number of FAP patients who develop colorectal cancer. Thus, in recent decades, a greater percentage of deaths in FAP patients appears to be attributable to extracolonic manifestations of the disease.

Sulindac for periampullary polyps in FAP patients.

BACKGROUND: Gastro-duodenal polyps develop in up to 90% of familial adenomatous polyposis (FAP) patients and periampullary carcinoma is one of the most common extra-colonic malignancies in this syndrome. Periampullary adenomas have been shown to be precursor lesions to periampullary carcinoma. Sulindac, a non-steroidal anti-inflammatory drug, has been reported to cause regression of rectal polyps in FAP patients, however its role in periampullary polyp regression is unclear. METHODS: In May 1993, a prospective study was begun to evaluate the role of sulindac in prevention of polyp recurrence after resection of large (> 1 cm) duodenal polyps in FAP patients. Eight patients, mean age 50 years (range 35 to 65), with documented large periampullary polyps were placed on sulindac 150 mg twice daily. Prior to enrollment, all patients had their large polyps removed from the periampullary region by interventional endoscopy or by surgery. All patients had multiple small residual duodenal polyps. Follow-up was performed by one experienced endoscopist with a side-viewing video endoscope. Endoscopy was performed 6 monthly. Median follow-up time was 17.5 months (range 10 to 24 months). RESULTS: In 3 patients, sulindac was discontinued due to side effects: abdominal cramps (n = 2) and upper G-I bleeding (n = 1). None of the patients had regression of small periampullary polyps. In addition, one patient developed an invasive periampullary carcinoma while on sulindac and 3 patients developed large recurrent periampullary polyps requiring further treatment. SUMMARY: In our experience, sulindac is of no significant benefit for the control of periampullary polyps in FAP. Effective medical treatment of these polyps is still lacking.

A preventive registry for hereditary nonpolyposis colorectal cancer.

Hereditary nonpolyposis colorectal cancer (HNPCC) is a genetic disorder characterized by a strong family history of colorectal and extracolonic cancers, usually at a young age. This article presents a new provincial service for families with HNPCC. The Steve Atanas Stavro Familial Gastrointestinal Cancer Registry at Mount Sinai Hospital is accruing patients that meet a set of criteria establishing a putative diagnosis of HNPCC. The objectives of the Registry are to develop and assess patient pedigrees, to coordinate screening procedures for at-risk persons, to maintain a prospective database of patient information, to provide education and support for families and to contribute to research. To date, surgeons and patients are the most common referral sources, while oncologists and geneticists are the least common. The ultimate goal of the HNPCC service is the secondary prevention of cancer and a corresponding decrease in mortality for HNPCC family members.

Combined use of molecular and biomarkers for presymptomatic carrier risk assessment in familial adenomatous polyposis: implications for screening guidelines.

Predictive carrier testing for the inherited disorder of familial adenomatous polyposis (FAP) can be conducted using DNA markers linked to the FAP locus. The presence of characteristic hypertrophic retinal lesions has been advocated as useful biomarkers for FAP. We have compared molecular linkage and retinal screening techniques by evaluating the presymptomatic carrier risk of 40 at-risk individuals from 15 FAP families. Linkage analysis was informative in all and retinal lesion analysis in 25 cases. For informative at-risk population, predictive diagnosis by both techniques was completely concordant and identified 15 members at "high" and 10 at "low" risk of inheriting FAP. Because of the unique advantages offered by each technique, a strategy integrating both techniques will increase the number of FAP families that can be screened presymptomatically. Identification of individuals at high risk of polyposis will improve their clinical surveillance and further reduce the incidence of colorectal cancer in FAP families.

Familial adenomatous polyposis-associated thyroid cancer: a clinical, pathological, and molecular genetics study.

We report two familial adenomatous polyposis (FAP) kindreds with thyroid cancer, harboring two apparently novel germlineAPC mutations. The clinical phenotype in the first kindred was typical of classical adenomatous polyposis, whereas the second kindred exhibited an attenuated adenomatous polyposis phenotype. There was a female predominance with a mean age of 34 years (range, 23-49) at cancer diagnosis. Multiple sections of four thyroid tumors from three FAP patients were analyzed in detail. Histological examination of thyroid tumors showed a range of morphological features. Some tumors exhibited typical papillary architecture and were associated with multifocal carcinoma; in others, there were unusual areas of cribriform morphology, and spindle-cell components with whorled architecture. Immunoreactivity for thyroglobulin and high molecular weight keratins was strong. Somatic APC mutation analysis revealed an insertion of a novel long interspersed nuclear element-1-like sequence in one tumor sample, suggesting disruption of APC. In three FAP patients, ret/PTC-1 and ret/PTC-3 were expressed in thyroid cancers. No positivity was observed for ret/ PTC-2. p53 immunohistochemistry was positive in only one section of a recurrent thyroid tumor sample. Our data suggest that genetic alterations in FAP-associated thyroid cancer involve loss of function of APC along with the gain of function of ret/PTC, while alterations of p53 do not appear to be an early event in thyroid tumorigenesis.

Family history characteristics, tumor microsatellite instability and germline MSH2 and MLH1 mutations in hereditary colorectal cancer.

Recent characterization of the molecular genetic basis of hereditary nonpolyposis colorectal cancer provides an important opportunity for identification of individuals and their families with germline mutations in mismatch repair genes. Cancer family history criteria that accurately define hereditary colorectal cancer are necessary for cost-effective testing for germline mutations in mismatch repair genes. The present report describes the results of analysis of 33 colorectal cancer cases/families that satisfy our modified family history criteria (Mount Sinai criteria) for colorectal cancer. Fourteen of these families met the more stringent Amsterdam criteria. Germline MSH2 and MLH1 mutations were identified by the reverse transcription-polymerase chain reaction and the protein truncation test, and confirmed by sequencing. Microsatellite instability analysis was performed on available tumors from affected patients. MSH2 or MLH1 mutations were detected in 8 of 14 Amsterdam criteria families and in 5 of the remaining 19 cases/families that only satisfied the Mount Sinai criteria. Three of the latter families had features of the Muir-Torre syndrome. A high level of microsatellite instability (MSI-H) was detected in almost all (16/18) colorectal cancers from individuals with MSH2 and MLH1 mutations, and infrequently (1/21) in colorectal cancer specimens from cases without detectable mutations. Families with germline MSH2 and MLH1 mutations tended to have individuals affected at younger ages and with multiple tumors. The Amsterdam criteria are useful, but not sufficient, for detecting hereditary colorectal cancer families with germline MSH2 and MLH1 mutations, since a proportion of cases and families with mutations in mismatch repair genes will be missed. Further development of cancer family history criteria are needed, using unbiased prospectively collected cases, to define more accurately those who will benefit from MSH2 and MLH1 mutation analysis.