Peutz-Jeghers syndrome: a systematic review and recommendations for management

Peutz-Jeghers syndrome (PJS, MIM175200) is an autosomal dominant condition defined by the development of characteristic polyps throughout the gastrointestinal tract and mucocutaneous pigmentation. The majority of patients that meet the clinical diagnostic criteria have a causative mutation in the STK11 gene, which is located at 19p13.3. The cancer risks in this condition are substantial, particularly for breast and gastrointestinal cancer, although ascertainment and publication bias may have led to overestimates in some publications. Current surveillance protocols are controversial and not evidence-based, due to the relative rarity of the condition. Initially, endoscopies are more likely to be done to detect polyps that may be a risk for future intussusception or obstruction rather than cancers, but surveillance for the various cancers for which these patients are susceptible is an important part of their later management. This review assesses the current literature on the clinical features and management of the condition, genotype-phenotype studies, and suggested guidelines for surveillance and management of individuals with PJS. The proposed guidelines contained in this article have been produced as a consensus statement on behalf of a group of European experts who met in Mallorca in 2007 and who have produced guidelines on the clinical management of Lynch syndrome and familial adenomatous polyposis.

APC germ-line allele-specific expression in familial adenomatous polyposis

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Background: About 13% of Familial Adenomatous Polyposis (FAP) families and 70% of Attenuated FAP families remain with unknown molecular pathogenic cause after APC and MYH mutational analyses. Also, mutations can affect specific allele expression (ASE) at the germline level. The aim of the study was to determine the presence of germline ASE in the APC gene in FAP and AFP with and without detectable APC or MYH mutations. Methods: Germline RNA from fresh frozen and/or cultured lymphocytes of 17 APC/MYH-negative Polyposis (7 FAP, 10 AFAP) families (21 individuals) and 35 APC-mutated Polyposis (30 FAP, 5 AFAP) families (60 individuals) was analyzed. Fourteen controls were also studied. ASE was investigated by single nucleotide primer extension (SNuPE) of rs2229992 APC coding SNP. Results: In controls ASE was 1.04± 0.3. We found that 17% (3 of 17) APC/MYH(-) FAP and AFAP families showed ASE (range=1.17–1.39) and ASE co-segregated with disease. ASE was more intense in short-cultured lymphocytes except for two cases and completely reversed by puromycin treatment. Eleven of 35 (31%) APC-FAP/AFAP harbored ASE (range=1.20–7.76), and the mutant allele was underexpressed in each case. ASE was restricted to splicing (4 families), nonsense (3 families) and frameshift (3 families) mutations outside of exon 15. Puromycin reversed ASE in all cases analyzed. Conclusions: APC ASE is present in a significant proportion (17%) of APC/MYH(-) FAP or AFAP. ASE, due to nonsense-mediated decay (NMD), is present in APC-FAP and is associated with specific mutation location, similar to reports for other hereditary syndromes.

No significant financial relationships to disclose.

Wnt signaling somatic alterations in apc-associated fap adenomas

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Background: APC mutations are believed to constitutively activate the wnt pathway in colorectal tumors. Our goal was to comprehensively characterize Wnt signaling components in a set of APC-associated FAP tumors both at the DNA and RNA levels. Methods: Sixty adenomas from FAP cases harboring pathogenic APC mutations were included (10 adenomas and 1 normal mucosa per case). Somatic APC and KRAS alterations, β-catenin immunostaining and qRT-PCR of APC, MYC, AXIN2 and SFRP1 were analyzed. aCGH was also assessed in 26 FAP adenomas and 24 additional paired normal-adenoma-carcinoma samples. Results: A second APC alteration was present in 30 (50%) of adenomas (26 LOH and 4 point mutations). LOH was only occasionally associated with loss of genetic material. In 3 of 6 cases APC mRNA was overexpressed in macroscopically normal mucosa. In these cases diminished APC levels mRNA were observed in 11 of 30 adenomas analyzed.. In the remaining 3 cases APC mRNA was already underexpressed in normal mucosa with only 3 of 30 adenomas showing further underexpression. In FAP normal mucosae MYC was overexpressed (logratio range: 3.37–5.66). All adenomas showed further MYC (logratio range: 1.78–2.92) and AXIN2 overexpression (logratio range: 1.62–4.65), corregulating with APC mRNA levels (r=0.31 for MYC; r=0.59 for AXIN2). β-catenin nuclear immunostaining was detected in 80% of adenomas correlating with MYC mRNA levels. SFRP1 was underexpressed in all tumors (logratio range= -3.06–27). While copy number changes were rare in adenomas (median number :2.5; range 0–5). DNA changes were more often detected in areas containing wnt genes when FAP and sporadic tumors were jointly analyzed (p=0.02). Conclusions: Wnt pathway is altered, at the DNA and/or RNA level, in all APC mutant FAP tumors. MYC overexpression is a universal event that correlates with APC and AXIN2 expression levels as well as bcatenin nuclear accumulation.

No significant financial relationships to disclose.

Evaluation of stool melting curve analysis of methylated CpG island promoters as an alternative for early noninvasive diagnosis of colorectal tumors

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Background: Previous studies have shown that assessment of promoter hypermethylation of a limited number of genes in tumor biopsies may identify all colorectal tumors analyzed. The aim of the present study was to assess the clinical usefulness of a panel of methylation biomarkers in stool DNA in the diagnosis of colorectal tumors using Methylation Curve (MC) analyses, a technique that simultaneously analyze all CpG residues within a promoter. Methods: Promoter methylation status of 5 tumor-related genes (RARB2, p16INK4a, MGMT, p14ARF and APC) was analyzed in DNA stool samples and corresponding tissues in an initial set of 12 newly diagnosed patients with primary colorectal carcinomas and 20 with colorectal adenomas using Methylation-specific PCR (MSP). Results were validated in a set of 88 patients (20 healthy subjects, 17 inflammatory bowel disease, 23 adenomas, 28 carcinomas) using MC analyses. Median age for every group was 63, 51, 66 and 67 y respectively. Results: In the initial set, the majority [10 of 12 (83%) carcinomas and 18 of 20 (90%) adenomas] of biopsies were positive for at least one marker. In stool DNA prevalence was 75% for carcinomas (9 of 12) and 60% for adenomas (12 of 20) with no false positive in stools. In the validation set MC was used. Analytical sensitivity of MC was 5% of methylated alleles for p16INK4a, p14ARF, RARB2 and APC and 10% for MGMT. In the validation set MC analyses of biopsies showed that at least one marker was positive in 22 of 28 (79%) carcinomas and 16 of 23 (70%) adenomas. In stool DNA, these percentages were 64% (18 of 28) for carcinomas and 42% (9 of 23) for adenomas. No aberrant methylation was observed in healthy subjects and in 2 of 15 (13%) of IBD patients aberrant RARB2 methylation was detected. Conclusions: Melting Curve analysis of a panel of methylation markers in stool DNA is a good alternative for the early non-invasive diagnosis of colorectal tumors.

[Table: see text]

APC allele-specific expression in carriers of Ashkenazi Jewish mutation I1307K

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Background: I1307K is a missense APC variant with incomplete penetrance that has been found in 6% of Jewish Ashkenazi population and confers a two-fold increased risk to develop multiple adenomas and colorectal tumours. It is believed that it creates a hypermutable region within the gene that leads to an accumulation of mutations. It remains unknown whether the presence of this mutation modifies APC expression. Our goal was to study whether allele-specific expression (ASE) of I1307K is present at the germline and tumoral level. Methods: Paired germline/carcinoma RNA and DNA was studied from eleven I1307K carriers. To analyze changes in the mutant/wt allelic ratio we used single nucleotide primer extension (SNuPE) for the I1307K and the rs2229992 APCcoding SNP. Fourteen controls were also analyzed. Results: No germline allele specific expression was found in I1307K carriers (range=0.954–1.173). Significant ASE was observed in 8 of the 10 carcinomas analyzed. In 4 cases the I1307K allele was overexpressed (range=2.51–9.51) and in 4 cases was underexpressed (range=0.09–0.28). Tumor ASE correlated with the DNA mutant/wt allelic dose. Conclusions: I1307K variant is not associated with allelic specific expression at the germline level. I1307K overexpression is not selected for during tumor progression.

No significant financial relationships to disclose.

Development and validation of a robust prognostic and predictive signature for colorectal cancer (CRC) patients

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Background: Between 25 and 35% of stage II CRC patients will experience a recurrence of their disease and may benefit from adjuvant chemotherapy. Official guidelines give suggestions but no clear recommendation for best risk stratification. Here we describe the development a robust signature that predicts disease relapse and can assist in treatment decisions. Methods: Fresh frozen tumor tissues from 180 patients with stage I, II and III colorectal cancer undergoing surgery were analyzed using high density Agilent 44K oligonucleotide arrays. Median FU was 70.2 months; 85% of patients did not receive adjuvant chemotherapy. Unsupervised hierarchical clustering based on full-genome gene expression measurement indicated the existence of 3 main colon molecular subclasses. Survival analysis of the 3 classes showed that subtype C (n= 27) had a poor outcome and subtype A (n= 48) good outcome. Only the intermediate group B (n=104) was used to develop a signature by using a cross validation procedure to score all genes for their association with 5-yr distant metastasis free survival (DMFS) and subsequently applied to all samples (n=180). The obtained gene signature was further validated on an independent cohort of 178 stage II + III colon samples. Results: A set of 38 prognosis related gene probes showed robust DMFS association in over 50% of all iterations in the Training Set of 180 samples. The gene signature was validated on an independent cohort of 178 samples from stage II + III colon cancer patients. The profile classified 61% of the validation samples as low-risk and 39% as high-risk. The low- and high-risk samples showed a significant difference in DMFS with a HR of 3.19 (P= 8.5e-4). Five-year DMFS rates were 89% (95%CI 83–95) for low-risk and 62% (95%CI 50–77) for high-risk samples. Moreover, the profile showed a significant performance within stage II (P=0.0058) and III (P=0.036) only samples. The performance of the profile was significant for both untreated (P=0.0082) and treated patients (P=0.016) suggesting that its power is independent of treatment benefits. Conclusions: ColoPrint is able to predict the prognosis of stage II and III colon cancer patients and facilitates the identification of patients who would benefit from adjuvant chemotherapy.

[Table: see text]

Guidelines for the clinical management of familial adenomatous polyposis (FAP)

Familial adenomatous polyposis (FAP) is a well-described inherited syndrome, which is responsible for <1% of all colorectal cancer (CRC) cases. The syndrome is characterised by the development of hundreds to thousands of adenomas in the colorectum. Almost all patients will develop CRC if they are not identified and treated at an early stage. The syndrome is inherited as an autosomal dominant trait and caused by mutations in the APC gene. Recently, a second gene has been identified that also gives rise to colonic adenomatous polyposis, although the phenotype is less severe than typical FAP. The gene is the MUTYH gene and the inheritance is autosomal recessive. In April 2006 and February 2007, a workshop was organised in Mallorca by European experts on hereditary gastrointestinal cancer aiming to establish guidelines for the clinical management of FAP and to initiate collaborative studies. Thirty-one experts from nine European countries participated in these workshops. Prior to the meeting, various participants examined the most important management issues according to the latest publications. A systematic literature search using Pubmed and reference lists of retrieved articles, and manual searches of relevant articles, was performed. During the workshop, all recommendations were discussed in detail. Because most of the studies that form the basis for the recommendations were descriptive and/or retrospective in nature, many of them were based on expert opinion. The guidelines described herein may be helpful in the appropriate management of FAP families. In order to improve the care of these families further, prospective controlled studies should be undertaken.

Guidelines for the clinical management of Lynch syndrome (hereditary non-polyposis cancer)

Lynch syndrome (hereditary non-polyposis colorectal cancer) is characterised by the development of colorectal cancer, endometrial cancer and various other cancers, and is caused by a mutation in one of the mismatch repair genes: MLH1, MSH2, MSH6 or PMS2. The discovery of these genes, 15 years ago, has led to the identification of large numbers of affected families. In April 2006, a workshop was organised by a group of European experts in hereditary gastrointestinal cancer (the Mallorca-group), aiming to establish guidelines for the clinical management of Lynch syndrome. 21 experts from nine European countries participated in this workshop. Prior to the meeting, various participants prepared the key management issues of debate according to the latest publications. A systematic literature search using Pubmed and the Cochrane Database of Systematic Reviews reference lists of retrieved articles and manual searches of relevant articles was performed. During the workshop, all recommendations were discussed in detail. Because most of the studies that form the basis for the recommendations were descriptive and/or retrospective in nature, many of them were based on expert opinion. The guidelines described in this manuscript may be helpful for the appropriate management of families with Lynch syndrome. Prospective controlled studies should be undertaken to improve further the care of these families.

Nuclear IKK activity leads to dysregulated notch-dependent gene expression in colorectal cancer

Nuclear functions for IkappaB kinase (IKK), including phosphorylation of histone H3 and nuclear corepressors, have been recently described. Here, we show that IKK is activated in colorectal tumors concomitant with the presence of phosphorylated SMRT (silencing mediator of retinoic acid and thyroid hormone receptor) corepressor that is aberrantly localized in the cytoplasm. In these tumors, IKKalpha associates to the chromatin of specific Notch targets, leading to the release of SMRT. Abrogation of IKK activity by BAY11-7082 or by expressing dominant negative IKKalpha restores the association of SMRT with Notch target genes, resulting in specific gene repression. Finally, BAY11-7082 significantly reduces tumor size in colorectal cancer xenografts (CRC-Xs) implanted in nude mice.

TP53 status is an important prognostic marker for patients with hepatic metastases from colorectal carcinoma

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Background: The aim of this study was to analyze the value of TP53 gene mutations as a prognostic marker to improve the selection of patients candidates to surgery in a consecutive series of liver metastases from colorectal cancer patients. Methods: 91 patients with liver metastases from colorectal carcinoma (CRC) were included. Mutational study of TP53 gene, exons 4 to 10, was assessed both in paraffin-embedded hepatic metastasis and normal liver parenchyma by SSCP (Single Strand Chain Polymorphism) followed by sequencing of abnormal electrophoretic mobility patterns. Immunostaining of P53 and P21 proteins were assessed in the same group of patients. Results: Forty-eight out 91 (50.05%) metastases showed mutation in TP53. Higher incidence of mutations was detected in exons 5–8, although exons 9 and 10 were mutated in 28.26% of metastases. Protein-truncating mutations (nonsense and frameshift) occur in 47.8% of metastasis harboring TP53 mutations. TP53 mutation was associated with poor prognosis in univariate (P=0.0062) and multivariate Cox proportional hazard model (P=0.012) analysis. Prognosis association was maintained in the group of patients undergoing radical resection, named R0 series (n=79; P=0.008). High prevalence of TP53 mutations happen in patients with >3 metastases (65.6%; P=0.034), primary tumors Duke’s C-D stages (57.4%; 63.0%; respectively; p=0.026) and patients with age <57 years at resection. Interestingly, patients with TP53 mutations in their metastases relapsed earlier after the resection of the primary tumor (P=0.026). Postoperative 5-FU-based chemotherapy showed a better survival outcome in patients with wild-type TP53 hepatic metastases (HR: 2.92; 95% CI: 1.32–6.46; P=0.006). Conclusions: TP53 mutational status seems to be an important prognostic factor in patients with hepatic metastases from CRC.

No significant financial relationships to disclose.

Antitumoral effect of gemcitabine metronomic schedule in a xenograft pancreatic model

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Background: Human tumor xenografts in mice can be remarkably predictive of response in humans to cytotoxic chemotherapeutic drugs. Tumor endothelial cells are sensitive to the action of conventional cytotoxic drugs when they are regularly administrated at low doses. This concept, known as metronomic chemotherapy, has been demonstrated in preclinical studies using transplanted tumor models. We aim to investigate the potential anti-tumoral activity of Gemcitabine (G) when administered in a low-dose schedule in an ortothopic implantation model of human pancreatic carcinomas. Methods: Standard gemcitabine schedule: NP18 tumor orthotopically implanted nude mices were randomly distributed to experimental (n = 13, G100 mg/kg intraperitoneally on days 0, 3, 6 and 9 post-implantation) and control group (n = 13, saline). Animal were sacrificed after 4 weeks and we compared weigths (grams) and volume (cm3) of tumors betwen the two groups by the Mann-Whitney U test. Metronomic schedule: After a toxicological study an optimal metronomic dose of 1 mg G /kg per day was chosen. Thirty xenografted mices were randomly distributed to experimental group (n = 15, intraperitoneal G1 mg/kg) and control group (n = 15, saline) and treated for 30 days. Animal were analysed as described before. Results: Standard schedule: Tumor weight mean of treatment group was 0.01 grams ± 0.01 versus 0.54 grams ± 0.48 of the control group. Tumor volume mean in G group was 0.01 cm 3 ± 0.01 versus 0.51 cm 3 ± 0.67) in the control group.Treatment significantly inhibited NP18 tumour growth (p < 0.001). No differences in mice weight were observed between both groups. Metronomic schedule: Tumor weight mean in the treatment group was 0.04 grams ± 0.08 versus 0.53 grams ± 0.46 in control group. Tumor volume mean in G group was 011 cm 3 ± 0.19 versus 0.37 cm 3. Treatment with low-dose of G significantly inhibited NP18 tumour growth (p < 0.003). There were no differences in mice weight between the two groups. Conclusions: Our data show that G administered in a metronomic schedule is effective in inhibiting the growth of NP18 tumor orthotopically implanted in the nude mice. We now aim to study the angiogenic profile of tumors receiving the standard and metronomic schedule and to set up a new experiment to compare survival benefit in the animal model.

No significant financial relationships to disclose.

DNA methylation patterns in hereditary human cancers mimic sporadic tumorigenesis

Cancer cells have aberrant patterns of DNA methylation including hypermethylation of gene promoter CpG islands and global demethylation of the genome. Genes that cause familial cancer, as well as other genes, can be silenced by promoter hypermethylation in sporadic tumors, but the methylation of these genes in tumors from kindreds with inherited cancer syndromes has not been well characterized. Here, we examine CpG island methylation of 10 genes (hMLH1, BRCA1, APC, LKB1, CDH1, p16(INK4a), p14(ARF), MGMT, GSTP1 and RARbeta2) and 5-methylcytosine DNA content, in inherited (n = 342) and non-inherited (n = 215) breast and colorectal cancers. Our results show that singly retained alleles of germline mutated genes are never hypermethylated in inherited tumors. However, this epigenetic change is a frequent second "hit", associated with the wild-type copy of these genes in inherited tumors where both alleles are retained. Global hypomethylation was similar between sporadic and hereditary cases, but distinct differences existed in patterns of methylation at non-familial genes. This study demonstrates that hereditary cancers "mimic" the DNA methylation patterns present in the sporadic tumors.

Promoter hypermethylation of the DNA repair gene O(6)-methylguanine-DNA methyltransferase is associated with the presence of G:C to A:T transition mutations in p53 in human colorectal tumorigenesis

Defects in DNA repair may be responsible for the genesis of mutations in key genes in cancer cells. The tumor suppressor gene p53 is commonly mutated in human cancer by missense point mutations, most of them G:C to A:T transitions. A recognized cause for this type of change is spontaneous deamination of the methylcytosine. However, the persistence of a premutagenic O(6)-methylguanine can also be invoked. This last lesion is removed in the normal cell by the DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (MGMT). In many tumor types, epigenetic silencing of MGMT by promoter hypermethylation has been demonstrated and linked to the appearance of G to A mutations in the K-ras oncogene in colorectal tumors. To study the relevance of defective MGMT function by aberrant methylation in relation to the presence of p53 mutations, we studied 314 colorectal tumors for MGMT promoter hypermethylation and p53 mutational spectrum. Inactivation of MGMT by aberrant methylation was associated with the appearance of G:C to A:T transition mutations at p53 (Fischer's exact test, two-tailed; P = 0.01). Overall, MGMT methylated tumors displayed p53 transition mutations in 43 of 126 (34%) cases, whereas MGMT unmethylated tumors only showed G:C to A:T changes in 37 of 188 (19%) tumors. A more striking association was found in G:C to A:T transitions in non-CpG dinucleotides; 71% (12 of 17) of the total non-CpG transition mutations in p53 were observed in MGMT aberrantly methylated tumors (Fischer's exact test, two-tailed; P = 0.008). Our data suggest that epigenetic silencing of MGMT by promoter hypermethylation may lead to G:C to A:T transition mutations in p53.

p14ARF silencing by promoter hypermethylation mediates abnormal intracellular localization of MDM2

The INK4a/ARF locus encodes two distinct tumor suppressors, p16INK4a and p14ARF. Although the contribution of p16INK4a to human tumorigenesis through point mutation, deletion, and hypermethylation has been widely documented, little is known about specific p14ARF lesions and their consequences. Recent data indicate that p14ARF suffers inactivation by promoter hypermethylation in colorectal cancer cells. Because it is known that p14ARF prevents MDM2 nucleocytoplasmic shuttling and thus stabilizes p53 by attenuating MDM2-mediated degradation, we studied the relationship of p14ARF epigenetic silencing to the expression and localization of MDM2 and p53. Cancer cell lines with an unmethylated p14ARF promoter showed strong nuclear expression of MDM2, whereas in a colorectal cell line with p14ARF hypermethylation-associated inactivation, MDM2 protein was also seen in the cytosol. Treatment with the demethylating agent 5-aza-2'-deoxycytidine was able to reinternalize MDM2 to the nucleus, and p53 expression was restored. No apparent changes in retinoblastoma localization were observed. We also studied the profile of p14ARF promoter hypermethylation in an extensive collection of 559 human primary tumors of different cell types, observing that in colorectal, gastric, renal, esophageal, and endometrial neoplasms and gliomas, aberrant methylation of p14ARF was a relatively common epigenetic event. MDM2 expression patterns revealed that lack of p14ARF promoter hypermethylation was associated with tumors showing exclusive nuclear MDM2 staining, whereas MDM2 cytosolic staining was frequently observed in neoplasms with aberrant p14ARF methylation. Taken together, these data support that epigenetic silencing of p14ARF by promoter hypermethylation is a key mechanism in the disturbance of the MDM2 nuclear localization in human cancer.

Redefining the significance of aneuploidy in the prognostic assessment of colorectal cancer

The aberrant content of DNA, or aneuploidy, is a hallmark of tumor cells and may be associated with malignant potential. Based on the hypothesis that aneuploidy, as a form of genetic instability, results in an increased capability to generate cell heterogeneity, we investigated whether a comprehensive assessment of aneuploidy extent and degree might be a reliable indicator of tumor aggressiveness. DNA content was determined by flow cytometry in the infiltrating front of 131 paraffin-embedded primary colorectal carcinomas collected in a prospective design. Enrichment of tumor cells by sample microdissection resulted in neoplastic cell contents above 75%. An estimate of aneuploidy, the aneuploidy index (AI), was calculated as the tumor DNA content adjusted by the percentage of diploid and aneuploid cells in G0/G1. Thirty-nine tumors were diploid, 90 hyperdiploid, and 2 hypodiploid. The mean AI in aneuploid tumors was 1.20+/-0.17 and correlated with Dukes' stage and metastasis (p < 0.05). A high AI (receiver operating characteristic curve cutoff value greater than 1.14) predicted a poorer outcome in univariate (p = 0.004) and multivariate (p = 0.01) analyses. Based on these results, we postulate that aneuploidy is the molecular engine of progression in a subset of colorectal cancers, in which the AI seems to be a sensible and independent gauge of malignant potential. The AI determination may have prognostic application in colorectal cancer, especially in low-grade tumors, which might benefit from coadjuvant therapies.

Analysis of adenomatous polyposis coli promoter hypermethylation in human cancer

Germ-line mutations in the tumor suppressor gene APC are associated with hereditary familial adenomatous polyposis (FAP), and somatic mutations are common in sporadic colorectal tumors. We now report that methylation in the promoter region of this gene constitutes an alternative mechanism for gene inactivation in colon and other tumors of the gastrointestinal tract. The APC promoter is hypermethylated in 18% of primary sporadic colorectal carcinomas (n = 108) and adenoma (n = 48), and neoplasia with APC methylation fails to express the APC transcript. Methylation affects only wild-type APC in 95% of cases and is not observed in tumors from FAP patients who have germ-line APC mutations. As with APC mutation, aberrant APC methylation occurs early in colorectal carcinogenesis. When other tumor types are analyzed (n = 208), methylation of the APC promoter is not restricted to the colon but is present in tumors originating elsewhere in the gastrointestinal tract but rarely in other tumors. Our data suggest that hypermethylation of APC provides an important mechanism for impairing APC function and further underscores the importance of the APC pathway in gastrointestinal tumorigenesis.

Inactivation of the DNA repair gene O6-methylguanine-DNA methyltransferase by promoter hypermethylation is associated with G to A mutations in K-ras in colorectal tumorigenesis

O6-methylguanine DNA methyltransferase (MGMT) is a DNA repair protein that removes mutagenic and cytotoxic adducts from the O6 position of guanine. O6-methylguanine mispairs with thymine during replication, and if the adduct is not removed, this results in conversion from a guanine-cytosine pair to an adenine-thymine pair. In vitro assays show that MGMT expression avoids G to A mutations and MGMT transgenic mice are protected against G to A transitions at ras genes. We have recently demonstrated that the MGMT gene is silenced by promoter methylation in many human tumors, including colorectal carcinomas. To study the relevance of defective MGMT function by aberrant methylation in relation to the presence of K-ras mutations, we studied 244 colorectal tumor samples for MGMT promoter hypermethylation and K-ras mutational status. Our results show a clear association between the inactivation of MGMT by promoter hypermethylation and the appearance of G to A mutations at K-ras: 71% (36 of 51) of the tumors displaying this particular type of mutation had abnormal MGMT methylation, whereas only 32% (12 of 37) of those with other K-ras mutations not involving G to A transitions and 35% (55 of 156) of the tumors without K-ras mutations demonstrated MGMT methylation (P = 0.002). In addition, MGMT loss associated with hypermethylation was observed in the small adenomas, including those that do not yet contain K-ras mutations. Hypermethylation of other genes such as p16INK4a and p14ARF was not associated with either MGMT hypermethylation or K-ras mutation. Our data suggest that epigenetic silencing of MGMT by promoter hypermethylation may lead to a particular genetic change in human cancer, specifically G to A transitions in the K-ras oncogene.

Intron splice acceptor site polymorphism in the hMSH2 gene in sporadic and familial colorectal cancer

A polymorphism in hMSH2 gene has been associated with an increased susceptibility to develop colorectal cancer (CRC). Here we show that it is a genetic risk factor for CRC in the Spanish population. However, its presence does not apparently affect hMSH2 function.

Hypermethylation-associated inactivation of p14(ARF) is independent of p16(INK4a) methylation and p53 mutational status

The INK4a/ARF locus encodes two cell cycle-regulatory proteins, p16INK4a andp14ARF, which share an exon using different reading frames. p14ARF antagonizes MDM2-dependent p53 degradation. However, no point mutations in p14ARF not altering p16INK4a have been described in primary tumors. We report that p14ARF is epigenetically inactivated in several colorectal cell lines, and its expression is restored by treatment with demethylating agents. In primary colorectal carcinomas, p14ARF promoter hypermethylation was found in 31 of 110 (28%) of the tumors and observed in 13 of 41 (32%) colorectal adenomas but was not present in any normal tissues. p14ARF methylation appears in the context of an adjacent unmethylated p16INK4a promoter in 16 of 31 (52%) of the carcinomas methylated at p14ARF. Although p14ARF hypermethylation was slightly overrepresented in tumors with wild-type p53 compared to tumors harboring p53 mutations [19 of 55 (34%) versus 12 of 55 (22%)], this difference did not reach statistical significance. p14ARF aberrant methylation was not related to the presence of K-ras mutations. Our results demonstrate that p14ARF promoter hypermethylation is frequent in colorectal cancer and occurs independently of the p16INK4a methylation status and only marginally in relation to the p53 mutational status.

p53 and K-ras gene mutations correlate with tumor aggressiveness but are not of routine prognostic value in colorectal cancer

PURPOSE

p53 gene and K-ras mutations are among the most common genetic alterations present in colorectal cancer. The prognostic utility of such mutations remains controversial. The purpose of this study was to prospectively evaluate the prognostic significance of p53 and K-ras gene mutations in colorectal cancer.

PATIENTS AND METHODS

One hundred forty patients were analyzed. Tumors belonging to the microsatellite mutator phenotype were excluded (n = 8). Mutations at the K-ras and p53 genes were detected and characterized by restriction fragment length polymorphism, single-strand conformation polymorphism, and sequencing, as appropriate.

RESULTS

p53 mutations were detected in 66 (50%) and K-ras mutations were detected in 54 (41%) of the 132 patients. In 26 cases (20%), ras and p53 mutations coexisted; in 38 cases (29%), neither mutation was found. Multivariate analysis of the whole population analyzed (n = 132) showed that survival was strongly correlated with the presence of p53 mutations alone or in combination with K-ras mutations (P = .002; log-rank test). When only patients undergoing a radical resection were considered (R0; n = 101), p53 mutations were no longer of prognostic significance.

CONCLUSION

p53 mutations alone or in combination with K-ras mutations are correlated with a worse outcome. However, the routine use of these mutations as prognostic markers in the clinical setting is not recommended.

Cancers of the papilla of vater: mutator phenotype is associated with good prognosis

Cancer of the papilla (ampulla) of Vater is an uncommon disease that kills 60% of affected patients. There is general agreement that local spread of the tumor (T stage) is the only significant and independent prognostic factor for this cancer, whereas the predictive value of tumor grade and lymph node metastases is controversial. The genetic anomalies involved in this process have the potential to serve as additional prognostic markers. We explored 25 ampullary cancers for the occurrence of instability at simple repeat DNA sequences (microsatellites) of the type seen in replication error phenotype (RER-positive) cancers. Ten microsatellites from five different chromosomes were amplified by PCR from both normal and cancer tissue DNA of the same patients. A tumor was defined as RER-positive when microsatellite instability was found in the majority (>/=6) of the loci analyzed. Five cancers (20%) showed a RER phenotype and were associated with long survival of patients (32-96 months), whereas RER-negative cancers had a significantly poorer prognosis (Mantel-Cox test; P = 0.0084), with a median actuarial survival of 17 months. We also report that three (12%) patients belonged to cancer-prone families and four (16%) were cancer-prone individuals.

p53 in a thyroid follicular carcinoma with foci of poorly differentiated and anaplastic carcinoma

The clinical and pathologic features of a rare case of follicular carcinoma with small foci of poorly differentiated and anaplastic carcinoma are presented. Eight years after the removal of the primary neoplasm, the patient developed pulmonary and brain metastases that were predominantly composed of the poorly differentiated and anaplastic components. A comparative immunohistochemical and molecular analysis of p53 status in the follicular, poorly differentiated and anaplastic components of the tumor was performed. p53 immunostaining was restricted to the poorly differentiated and anaplastic areas. Single strand conformation polymorphism analysis (SSCP-PCR) from DNA obtained by microdissection demonstrated the presence of a mutation (TAT-->TGT; Tyr-->Cys) in codon 220, exon six of the p53 gene in the anaplastic component, that was absent in the well-differentiated follicular areas. The results of that study in this rare tumor support that p53 has a tumor progression role in thyroid tumorigenesis.

Loss of sst2 somatostatin receptor gene expression in human pancreatic and colorectal cancer

Five somatostatin receptor subtypes (sst1 to sst5) have been cloned. We demonstrated previously that sst2 and sst5 mediate the antiproliferative effect of the somatostatin analogues octreotide and vapreotide. Using reverse transcription-PCR, we investigated gene expression of the five receptors in 47 human normal and cancerous tissues or cell lines from pancreatic and colorectal origin. mRNAs of somatostatin receptor subtypes were detected in 98% of samples, with more than two mRNA subtypes being expressed in 55% of cases. sst1, sst4, and sst5 were heterogeneously expressed in both normal and cancerous tissues; sst3 was rarely or not expressed. sst2 was present in normal pancreatic tissues but was absent in exocrine pancreatic carcinomas and their metastases. sst2 mRNAs were detected in normal colon, sporadic polyadenomas, and 50% of Dukes' stage B and 20% of Dukes' stage C carcinomas but were undetectable in Dukes' stage D carcinomas, hepatic metastases, and adenomas from familial adenomatous polyposis. The loss of sst2 expression could represent a growth advantage in these tumors and provide an explanation for the lack of therapeutic effect of somatostatin analogues in such adenocarcinomas. A subtyping of somatostatin receptors should be carried out before considering a somatostatin analogue treatment in patients with colorectal or pancreatic cancer.

Ras oncogene mutations in thyroid tumors: polymerase chain reaction-restriction-fragment-length polymorphism analysis from paraffin-embedded tissues

Ras mutations have been found in thyroid lesions. Different studies have shown different frequencies of mutations among benign and malignant lesions. The presence of point mutations in codons 12 and 13 of the c-K-ras, c-H-ras, and N-ras genes was studied in 58 thyroid lesions (10 nodular goiters, 10 follicular adenomas, and 15 papillary, 10 follicular, and 13 anaplastic carcinomas). DNA was extracted from formalin-fixed paraffin-embedded tissue, and target sequences were amplified in vitro by the polymerase chain reaction. Mutations were detected by the presence of restriction-fragment-length polymorphisms either occurring naturally or introduced artificially by the use of mutant primers. No characterization of the mutations was performed. Results were correlated with clinicopathologic features and patient follow-up. One goiter showed a mutation at codon 13, c-K-ras. All follicular adenomas, including three hyalinizing trabecular adenomas, were negative. Four papillary carcinomas presented mutations (one at codon 13, c-K-ras; three at codon 12, N-ras). Two follicular carcinomas showed mutations at codon 12, N-ras. Five anaplastic carcinomas showed mutations (two at codon 12 and two at codon 13, c-K-ras; one at codon 12, N-ras). In summary, the results confirm that ras oncogenes play a role in thyroid tumorigenesis, probably at an early step. Ras mutations appear not to be related to prognosis.

[Low incidence of mutations in codon 12 of the c-K-ras gene in bladder cancer]

During vesical carcinogenesis a variety of genetic alterations such as oncogene mutation or loss of suppressor genes have been detected. Codon 12 mutation of the c-K-ras gene has been seen with a high frequency in several human neoplasias but its participation in the development of vesical cancers has not been fully dilucidated. Using the DNA restriction fragments polymorphism (RFLP) technique enhanced by a polymerase chain reaction (PCR) a study has been made of codon 12 mutation at the c-K-ras gene in 55 patient with vesical cancer undergoing surgery between 1991 and 1992. The tumoral stage was superficial (Ta-Tl) in 24 cases, infiltrant (T2-T4) in 28 cases and unknown in 3 cases. Two patients (3.6%) showed codon 12 mutation at the c-K-ras gene. One case was a fast evolving infiltrant tumour (T2-T3) which caused death of the patient after 4 months while the other case was a surface tumour (G2Ta) which relapsed early, the pathological anatomy revealing a stage T2-T3 squamous carcinoma. Our results suggest that codon 12 mutation at the c-K-ras gene is not a meaningful genetic change in the genesis of vesical cancer. Its emergence, however, appears to be related to a more aggressive tumoural behaviour.

Genetic heterogeneity of the c-K-ras locus in colorectal adenomas but not in adenocarcinomas

BACKGROUND

Previous molecular genetics studies of colorectal cancer have identified multiple mutations in the c-K-ras gene (also known as KRAS2) in all phases of its development. Because of technical difficulty, prior studies rarely focused attention on the detailed distribution of c-K-ras mutations in multiple regions of the same primary tumor specimen. However, with recent development of the selective UV radiation fractionation method, characterization of c-K-ras mutations in multiple regions of the same primary tumor specimen can be performed.

PURPOSE

Our purpose was to describe how c-K-ras mutations were distributed among cells obtained from multiple regions of the same primary tumor in an attempt to describe differences between early and late colorectal carcinogenesis.

METHODS

Formalin-fixed, paraffin-embedded tissue blocks were obtained. Seven adenocarcinomas and seven adenomas were selected for the presence of mutant c-K-ras genes and histologic transitions between normal and neoplastic tissue. Tissue sections were prepared for analysis by the selective UV radiation fractionation method by placing thin, fixed tissue sections on a plastic slide with no coverslip. Under the microscope, small ink dots from a felt-tip pen were manually placed directly on relatively pure cell subpopulations. The slides were placed with the tissue side exposed to a UV transilluminator for 2-4 hours to inactivate the DNA present in the unprotected ("undotted") cells. Individual dots were cut out of the plastic slide into 2 x 2-mm squares and placed into microfuge tubes. The DNA was extracted and supernatant used for polymerase chain reaction (PCR) analysis. Mutations at c-K-ras codons 12 and 13 were detected.

RESULTS

The selective UV radiation fractionation method and PCR analysis revealed that c-K-ras mutations never extended into normal mucosa and were present in all neoplastic cells regardless of phenotypes in all seven adenocarcinomas and three of the seven adenomas. Further examination of two carcinomas for p53 (also known as TP53) mutations or loss of heterozygosity demonstrated that these additional mutations were also present in all tumor cells, suggesting that a single transformed clone was responsible for the majority of growth. However, in four other adenomas, tumor heterogeneity was demonstrated, since c-K-ras mutations were detected only in discrete portions.

CONCLUSIONS

Adenoma formation may include a stage in which multiple and genetically distinct neoplastic clones are present, while most carcinomas appear to have a homogeneous composition that may result from the successful progression of one of these clones.

Mutations in the p53 suppressor gene do not correlate with C-k-ras oncogene mutations in colorectal-cancer

Mutations in the p53 tumor suppressor gene have been analyzed in 196 colorectal tumors previously analyzed for mutations at codons 12 and 13 of the c-K-ras and N-ras oncogenes by a combination of Single Strand Conformation Polymorphism (SSCP) and Cycle Sequencing (CS) using total cellular RNA. Mutations were detected in 3 of 21 adenomas, 84 of 149 primary carcinomas, and 11 of 18 hepatic metastases. Over half of the tumors were homozygous for the mutant p53 allele at the mRNA level. Although deletions were detected in 5 tumors, missense mutations were the most frequent. The spectrum of 63 point mutations was heterogeneous, with all possible nucleotide substitutions ocurring at least once. No correlation was found between the spectrum of p53 gene mutations and the age, sex, race of the cancer patients or the anatomical localization of the tumors, although mutations were significantly more frequent in tumors of the distal colon. Mutations in the p53 gene did not correlate with mutations in the c-K-ras gene, indicating that colorectal cancer can develop through pathways independent not only of the presence of mutations in any of these genes but also of their cooperation.

Experimental study of the efficacy of the endoluminal prosthesis in colonic anastomoses

Colorectal surgery is still associated with a significant morbidity and mortality rate, mostly related to suture failure. We have carried out a randomized experimental study in dogs on colonic anastomoses exposed to a number of anastomotic risk situations. A total of 42 dogs was used. They were divided into three study groups (control, occlusion and diverticulitis), with and without an endoluminal tube. The aim was to assess the efficacy of the endoluminal prosthesis using clinical and radiological assessment of anastomotic healing. Pre- and post-anastomotic intraluminal pressures were also measured to determine whether these might be a factor in suture failure. There were significant differences in suture failure in animals in which the endoluminal tube was used. Mean duration of placement was 10.5 days. In the colon healing study, no significant differences were found between the groups in the pathological examination or in the assay of hydroxyproline content. The presence of the endoluminal tube may increase the maximum pressure applied on the colon wall. No significant differences were found in the intracolonic pressure differentials between the different groups or after the inclusion of the endoluminal prosthesis. The results obtained establish the efficacy of the endoluminal prosthesis in protecting the colonic anastomosis, and could be a valuable technique in colonic anastomoses with a high risk of suture dehiscence.

[Gastric villous adenoma. 2 new cases]

Villous adenomas are extremely rare in the stomach. This type of lesion is characterized by its high capacity of malignant degeneration, as well as by its association with other tumors of the gastrointestinal tract. In this regard, we present two cases of villous adenoma of the stomach observed in our hospital, as well as a review of the characteristics of these tumors and of the treatment required.

Frequency and spectrum of mutations at codons 12 and 13 of the c-K-ras gene in human tumors

The frequency of point mutations at codons 12 and 13 of the c-K-ras gene has been determined in a panel of more than 400 human tumors. Mutant c-K-ras genes were detected in about 75% of adenocarcinomas of the pancreas (n = 84); 40% of adenomas (n = 72) and carcinomas (n = 244) of the colon end rectum; 30% of carcinomas of the bile duct (n = 19); 25% of carcinomas of the lung (n = 92), and in lower frequency in other carcinomas, including liver, stomach, and kidney. No mutations were found in carcinomas of the breast, prostate, esophagus, and gall bladder, among others. Comparative analysis of the spectrum of mutations show that while G to A transitions were the most frequent mutations in pancreatic and colo-rectal tumors, G to T transversions were more prevalent in lung carcinomas. The aspartic acid mutation at codon 13 (GGC----GAC) was relatively frequent in colo-rectal tumors but rare in pancreatic and lung carcinomas. The differences in the mutation spectrum of the c-K-ras gene in cancers of the gastrointestinal and respiratory tracts are suggestive of differential exposure to genotoxic agents.

Mutational activation of the c-K-ras gene in human pancreatic carcinoma

We have reported the presence of c-K-ras oncogenes activated by single point mutations at codon 12 in a vast majority of human pancreatic carcinomas. Formalin-fixed, paraffin-embedded specimens from surgical resections, autopsies and biopsies were used as well as snap frozen surgical specimens. The high oncogene incidence has been confirmed in other studies and indicate that somatic mutational activation of the c-K-ras gene is an important event in the development, maintenance or progression of cancer of the exocrine pancreas. While the role that these point mutations play in any or all of these processes remains to be determined, their presence is useful clinically for the diagnosis of pancreatic carcinoma at the molecular genetic level. The detection of mutated c-K-ras oncogenes in fine needle aspirates of pancreatic masses, that by cytomorphology may be suspicious but not diagnostic of malignant disease, increases the sensitivity of the diagnosis for this cancer. The identification of codon 12 mutations in the c-K-ras gene in pancreatic adenocarcinomas has been possible by advances in recombinant DNA techniques, especially by the development of in vitro gene amplification by the polymerase chain reaction (PCR). The possibility of analysing formalin-fixed, paraffin-embedded tissue for the presence of genetic alterations as small as single point mutations by PCR in concert with other mutation detection techniques, should facilitate the molecular genetic analysis of pancreatic carcinoma. Retrospective studies using stored specimens are now feasible with the technology described and should yield important information on the molecular epidemiology and aetiology of this and other diseases.

[Laryngeal paraganglioma]

A case is reported of laryngeal paraganglioma observed among 49,959 patients. A comparison is made of the characteristics of paragangliomas in general to those of laryngeal paraganglioma, which are more common in males; the case presented is that of a woman. Microscopic dissection failed to reveal the paraganglia in the trajectories of the superior and inferior laryngeal nerves, but they were found in histological sections of these nerves and their images were equal to those of the tumor studied. The trajectory of these nerves was investigated in preparations of the Embrioteca de Bellaterra (Prof. Doménech Mateu) and the clumps of paraganglioma cells from which these tumors proceed have been found; we emphasize the concept of neural crest pathology to which they pertain.

[Right cardiac echinococcosis with coronary compression. Description of a clinical case]

An outstanding case of cardiac echinococcosis is described. Clinical symptomatology was characterized by typical nitroglycerin-responsive crisis of angina pectoris associated to an electrocardiographic pattern of negative T wave on anterolateral and inferior leads. The diagnosis was suspected on the basis of thoracic computerized tomography and coronary arteriography. The anatomical localization was mainly pericardial but the right ventricle was involved too. Left anterior descending artery was dislocated and squeezed.

Chronic myocarditis leading to a right ventricular cardiomyopathy. Case report

A case of dilated cardiomyopathy arose after a spontaneous abortion at the second month of pregnancy is reported. Whereas clinical, hemodynamic and gross features pointed to a diagnosis of right ventricular cardiomyopathy, histologic findings of inflammatory infiltration, myocyte degeneration and interstitial fibrosis of the atrial and ventricular walls allowed to a correct diagnosis of chronic myocarditis.