Genetics of hereditary colorectal cancer

Mutational Analysis of a Familial Adenomatous Polyposis Pedigree with Bile Duct Polyp Phenotype

A large number of colorectal cancers have a genetic background in China. However, due to insufficient awareness, the diagnostic rate remains low and merely 5-6% of colorectal cancer patients are diagnosed with hereditary colorectal cancer. Familial adenomatous polyposis (FAP) is an autosomal dominant genetic disease caused by mutations in the adenomatous polyposis coli (APC) gene. Different mutation sites in APC are associated with the severity of FAP, risks of carcinogenesis, and extraintestinal manifestations. We used next-generation sequencing (NGS) and capture techniques to screen suspected mutation points in the proband in this pedigree. Using modified Sanger sequencing, we identified members of the family who were carriers of this variant and whether this segregated well with disease occurrence. FAP family members had multiple adenomatous polyps in their gastrointestinal tracts, some of which developed into cancer with age. Two subjects presented a rare common bile duct polyp phenotype. No extraintestinal manifestations were observed. A heterozygous frameshift mutation in APC exon 16 (NM_000038.6) was observed in the proband and in other patients: c.3260_3261del (p.Leu1087GlnQfs ^∗ 31) (rs587782305); the variant call format was CCT/C. Due to the deletion of two bases, a stop codon appeared after 31 amino acids, and the protein was truncated prematurely, which affected the conformation of the protein. Pedigree genetic linkage analysis showed that the clinical phenotype cosegregated with the APC mutation p.L1087fs. This mutation may be the pathogenic in this FAP family and responsible for this rare common bile duct polyp.

Bioengineered gold nanoparticles from marine seaweed Acanthophora spicifera for pharmaceutical uses: antioxidant, antibacterial, and anticancer activities

In this study, we report a green synthesis of pharmaceutically active gold nanoparticles from marine red alga Acanthophora spicifera by the reduction of chloroauric acid. The formation of A. spicifera-mediated gold nanoparticles (As-AuNPs) was characterized by several analytical techniques. The crystalline and face-centered cubic (fcc) structure were confirmed by X-ray diffraction (XRD) analysis. Electron microscopy results confirmed that As-AuNPs were spherical and the average size of particles was < 20 nm. As-AuNPs hold a significant level of antioxidant activities than A. spicifera extract. As-AuNPs exhibited the highest antibacterial activity against Vibrio harveyi than Staphylococcus aureus at 100 µg/ml. Furthermore, As-AuNPs exhibited the utmost cytotoxicity against human colon adenocarcinoma (HT-29) cells and registered the half-maximal inhibitory concentration (IC₅₀) at 21.86 µg/ml. These findings authenticated that the synthesized As-AuNPs possess a broad spectrum of biological activities, and it can be effectively applied in the field of aquaculture and biomedical application.

Prognostic Relevance of MLH1 and MSH2 Mutations in Hereditary Non-Polyposis Colorectal Cancer Patients

Aims and Background

Colorectal carcinoma patients from hereditary non-polyposis colorectal cancer families are suggested to have a better prognosis than sporadic colorectal carcinoma cases. Since the majority of hereditary non-polyposis colorectal cancer-related colorectal carcinomas are characterized by microsatellite instability due to germline mutations in DNA mismatch repair genes, this is consistent with the prolonged survival observed in sporadic microsatellite instability-positive colorectal carcinoma compared to microsatellite stable cases. However, a fraction of colorectal carcinoma cases belongs to families that, despite fulfilling the clinical criteria for hereditary non-polyposis colorectal cancer, do not carry mismatch repair gene mutations. Our aim was to verify to what extent the genotypic heterogeneity influences the prognosis of hereditary non-polyposis colorectal cancer patients.

Methods

A survival analysis was performed on 526 colorectal carcinoma cases from 204 Amsterdam Criteria-positive hereditary non-polyposis colorectal cancer families. Enrolled cases were classified as MLH1-positive, MSH2-positive and mutation-negative, according to the results of genetic testing in each family.

Results

Five-year survival rates were 0.73 (95% CI, 0.66-0.80), 0.75 (95% CI, 0.66-0.84) and 0.62 (95% CI, 0.55-0.68) for MLH1-positive, MSH2-positive and mutation-negative groups, respectively (logrank test, P = 0.01). Hazard ratio, computed using Cox regression analysis and adjusted for age, sex, tumor site and stage, was 0.71 (95% CI, 0.51-0.98) for the mutation-positive compared to the mutation-negative group. Moreover, in the latter group, patients with microsatellite instability-positive colorectal carcinomas showed a better outcome than microsatellite stable cases (5-year survival rates, 0.81 and 0.60, respectively; logrank test, P = 0.006).

Conclusions

Our results suggest that the prognosis of hereditary non-polyposis colorectal cancer-related colorectal carcinoma patients depends on the associated constitutional mismatch repair genotype.

2017 update on the relationship between diabetes and colorectal cancer: epidemiology, potential molecular mechanisms and therapeutic implications

Worldwide deaths from diabetes mellitus (DM) and colorectal cancer increased by 90% and 57%, respectively, over the past 20 years. The risk of colorectal cancer was estimated to be 27% higher in patients with type 2 DM than in non-diabetic controls. However, there are potential confounders, information from lower income countries is scarce, across the globe there is no correlation between DM prevalence and colorectal cancer incidence and the association has evolved over time, suggesting the impact of additional environmental factors. The clinical relevance of these associations depends on understanding the mechanism involved. Although evidence is limited, insulin use has been associated with increased and metformin with decreased incidence of colorectal cancer. In addition, colorectal cancer shares some cellular and molecular pathways with diabetes target organ damage, exemplified by diabetic kidney disease. These include epithelial cell injury, activation of inflammation and Wnt/β-catenin pathways and iron homeostasis defects, among others. Indeed, some drugs have undergone clinical trials for both cancer and diabetic kidney disease. Genome-wide association studies have identified diabetes-associated genes (e.g. TCF7L2) that may also contribute to colorectal cancer. We review the epidemiological evidence, potential pathophysiological mechanisms and therapeutic implications of the association between DM and colorectal cancer. Further studies should clarify the worldwide association between DM and colorectal cancer, strengthen the biological plausibility of a cause-and-effect relationship through characterization of the molecular pathways involved, search for specific molecular signatures of colorectal cancer under diabetic conditions, and eventually explore DM-specific strategies to prevent or treat colorectal cancer.

Abnormality in Wnt signaling is causatively associated with oxidative stress-induced intestinal tumorigenesis in MUTYH-null mice

MUTYH is a DNA glycosylase that excises adenine paired with 8-oxoguanine to prevent mutagenesis in mammals. Biallelic germline mutations of MUTYH have been found in patients predisposed to a recessive form of familial adenomatous polyposis (MAP: MUTYH-associated polyposis). We previously reported that Mutyh-deficient mice showed a high susceptibility to spontaneous and oxidative stress-induced intestinal adenoma/carcinoma. Here, we performed mutation analysis of the tumor-associated genes including Apc, Ctnnb1, Kras and Trp53 in the intestinal tumors of Mutyh-deficient mice. In the 62 tumors, we identified 25 mutations in Apc of 18 tumors and 36 mutations in Ctnnb1 of 36 tumors. Altogether, 54 out of the 62 tumors (87.1%) had a mutation in either Apc or Ctnnb1; no tumor displayed mutations simultaneously in the both genes. Similar to MAP, 60 out of 61 mutations (98.3%) were identified as G:C to T:A transversions of which 85% occurred at either AGAA or TGAA sequences. Immunohistochemical analyses revealed the accumulation of β-catenin in the nuclei of tumors. No mutation was found in either Kras or Trp53 in the tumors. These results indicate that the uncontrolled activation of Wnt signaling pathway is causatively associated with oxidative stress-induced intestinal tumorigenesis in the Mutyh-deficient mice.

MUTYH c.933+3A>C, associated with a severely impaired gene expression, is the first Italian founder mutation in MUTYH-Associated Polyposis

MUTYH variants are differently distributed in geographical areas of the world. In MUTYH-associated polyposis (MAP) patients from North-Eastern Italy, c.933+3A>C (IVS10+3A>C), a transversion causing an aberrant splicing process, accounts for nearly 1/5 of all mutations. The aim of this study was to verify whether its high frequency in North-Eastern Italy is due to a founder effect and to clarify its impact on MUTYH transcripts and protein. Haplotype analysis and age estimate performed on members of eleven Italian MAP families and cancer-free controls provided evidence that c.933+3A>C is a founder mutation originated about 83 generations ago. In addition, the Italian haplotype associated with the c.933+3A>C was also found in German families segregating the same mutation, indicating it had a common origin in Western Europe. Altogether c.933+3A>C and the two common Caucasian mutations p.Tyr179Cys and p.Gly396Asp represent about 60% of MUTYH alterations in MAP patients from North-Eastern Italy, suggesting the opportunity to perform targeted molecular screening for these variants in the diagnostic setting. Expression analyses performed on lymphoblastoid cell lines supported the notion that MUTYH c.933+3A>C alters splicing causing the synthesis of a non functional protein. However, some primary transcripts escape aberrant splicing, producing traces of full-length transcript and wild-type protein in a homozygote; this is in agreement with clinical findings that suggest a relatively mild phenotypic effect for this mutation. Overall, these data, that demonstrate a founder effect and further elucidate the splicing alterations caused by the MUTYH c.933+3A>C mutation, have important implications for genetic counseling and molecular diagnosis of MAP.

Specific hypomethylated CpGs at the IGF2 locus act as an epigenetic biomarker for familial adenomatous polyposis colorectal cancer

AIMS

The identification of specific biomarkers for colorectal cancer is of primary importance for early diagnosis. The aim of this study was to evaluate if methylation changes at the IGF2/H19 locus could be predictive for individuals at high risk for developing sporadic or hereditary colorectal cancer.

MATERIALS & METHODS

Quantitative methylation analysis using pyrosequencing was performed on three differentially methylated regions (DMRs): IGF2 DMR0 and DMR2 and the H19 DMR in DNA samples from sporadic colorectal cancer (n = 26), familial adenomatous polyposis (n = 35) and hereditary nonpolyposis colorectal cancer (n = 19) patients.

RESULTS

We report in this article for the first time, that in sporadic colorectal cancer tumor DNA both the IGF2 DMR0 and DMR2 are hypomethylated, while the H19 DMR retains its monoallelic methylation pattern. In lymphocyte DNA, a striking hypomethylation of nine contiguous correlated CpGs was found in the IGF2 DMR2 but only in familial adenomatous polyposis patients.

CONCLUSION

Methylation alterations at the IGF2 locus are more extensive than previously reported and DMR2 hypomethylation in lymphocyte DNA might be a specific epigenetic biomarker for familial adenomatous polyposis patients.

Effects of lycopene, synbiotic and their association on early biomarkers of rat colon carcinogenesis

This study evaluated whether a synergy exists for the combined treatment with lycopene and synbiotic on early biomarkers of colon carcinogenesis. Male Wistar rats received a diet containing 300 mg/kg of lycopene and/or synbiotic (Bifidobacterium lactisplus oligofructose/inulin) or their combination 2 weeks before and during carcinogen treatment with 1,2-dimethylhydrazine (DMH). Twenty-four hours after the last DMH application, the colons were processed for immunohistochemical analysis of proliferating cell nuclear antigen (PCNA), p53 protein, hematoxylin-eosin staining for apoptosis analysis and genotoxicity of fecal water by comet assay. Eight weeks after the last DMH application, the colons were analyzed for development of classical aberrant crypt foci (ACF) and mucin-negative ACF. Treatment with lycopene, synbiotic or their combination significantly increased apoptosis, reduced the PCNA and p53 labeling indexes and the development of classical ACF and mucin-negative ACF. Furthermore, a lower genotoxicity of fecal water was also detected in the groups treated with the chemopreventive agents. An additive/synergistic effect of the combined treatment with lycopene/synbiotic was observed only for the fecal water genotoxicity and mucin-negative ACF parameters. These results indicate that an additive/synergistic of the combination of chemopreventive agents on the initiation phase of colon carcinogenesis can be detected using selective early biomarkers.

Epidemiology and management options for colorectal cancer in children

Colorectal carcinoma (CRC), although primarily a disease of adulthood, accounts for 2% of malignancies in adolescents and has been reported in children as young as 9 months of age. Our knowledge of CRC in pediatrics is based on a handful of case series and case reports. Apart from one small clinical trial, there has been a lack of prospective clinical studies in this age group. Based on these published reports, most CRC in children is sporadic, but it can also arise in the setting of predisposing conditions, such as gastrointestinal polyposis syndromes, nonpolyposis familial cancer syndromes, and inflammatory bowel disease. Despite some similarities to adult disease, CRC in childhood may be intrinsically different biologically, because it differs from adult-onset CRC in several respects. Childhood CRC tends to be diagnosed at an advanced stage, is largely of mucinous histology, and (probably because of these features) tends to have a poorer outcome. As a result of its rarity in children and the lack of prospective pediatric studies, recommendations for therapy are primarily extrapolated from adult clinical trials. A review of pediatric case series in the English literature emphasizes the prognostic significance of stage of disease, as well as extent of surgical resection. As in adults, early detection is critical in an effort to capture the disease at less advanced stages. Complete surgical resection with aggressive lymph node dissection is essential for cure, and neoadjuvant chemotherapy may be used in an effort to render unresectable lesions resectable. Active agents in adults with CRC include fluorouracil, folinic acid (leucovorin), oxaliplatin, and irinotecan. Furthermore, newer targeted therapeutic agents, such as bevacizumab and cetuximab, have added additional efficacy to the standard chemotherapy backbone. Collaborative multi-institutional pediatric clinical trials are needed to evaluate the prognosis, optimal treatment response, and the basic biology of childhood onset CRC.

Understanding genomics: no longer optional for gastroenterology nurses

National news was made in 2003 with an amazing accomplishment: the completion of the Human Genome Project. This landmark endeavor produced a human DNA blueprint that helps scientists identify disease-causing genes and DNA variations affecting health promotion, disease prevention, and treatment responses. In October 2007, the Society of Gastroenterology Nurses and Associates joined the American Nurses Association and 48 other nursing organizations endorsing the document Essential Nursing Competencies and Curricula Guidelines for Genetics and Genomics. This document describes the minimum essential genetic/genomic competencies for all registered nurses regardless of education, practice role, or specialty area. How do these two pivotal events--mapping the human genome and establishing genetic/genomic nursing competencies--interface with each other and with gastroenterology nursing practice? This article defines genetics and genomics; discusses associated terminology and technology; and relates information to hereditary, familial, and sporadic colon cancer. Two case studies highlight essential nursing competencies, the genetic concepts of hereditary colon cancer, and the genomic aspects of sporadic colon cancer. A genomics glossary and a Web site resource chart for nurses and clients are included. The author shows how genetics and genomics are relevant for today's gastroenterology nurse.

Polyamines and the intestinal tract

Owing to their high turnover, the intestinal mucosal cells have a particularly high requirement for polyamines. Therefore, they are an excellent charcol for the study of polyamine function in rapid physiological growth and differentiation. After a cursory introduction to the major aspects of polyamine metabolism, regulation, and mode of action, we discuss the contribution of the polyamines to the maintenance of normal gut function, the maturation of the intestinal mucosa, and its repair after injuries. Repletion of cellular polyamine pools with (D,L)-2-(difluoromethyl)ornithine has considerably improved our understanding of how the polyamines are involved in the regulation of normal and neoplastic growth. Unfortunately, the attempts to exploit polyamine metabolism as a cancer therapeutic target have not yet been successful. However, the selective inactivation of ornithine decarboxylase appears to be a promising chemopreventive method in familial adenomatous polyposis. Presumably, it relies on the fact that ornithine decarboxylase is a critical regulator of the proliferative response of the protooncogene c-myc, but not of its apoptotic response.

Preimplantation genetic diagnosis for cancer predisposition syndromes

OBJECTIVES

Mutations in the APC, NF2 and BRCA1 genes cause adult-onset cancer predisposition syndromes. Prenatal diagnosis (PND) and selective pregnancy termination for adult-onset disorders is emotionally difficult and, in some cases, socially not well accepted. Preimplantation genetic diagnosis (PGD) appears as an attractive alternative to PND, as it ensures the establishment of a pregnancy free of the mutation from the onset, circumventing the potentially difficult decision of termination of pregnancy.

METHODS

Development of single-cell PCRs using Epstein-Barr virus transformed lymphoblasts as single-cell model, followed by clinical application in PGD.

RESULTS

A total of five duplex-PCRs were developed, three for adenomatous polyposis of the colon (APC), one for neurofibromatosis type 2 (NF2) and one for inherited breast and ovarian cancer caused by BRCA1 mutations. Eleven clinical cycles were performed, resulting in the birth of an unaffected girl. For one of the couples undergoing PGD for NF2, a spontaneous pregnancy ensued after five unsuccessful PGD cycles. The couple underwent chorionic villus sampling (CVS) and the application of the same protocol as used during PGD showed an unaffected fetus.

CONCLUSION

In this work, we present the development and clinical application of PGD for three cancer predisposition syndromes.

Base-excision repair of oxidative DNA damage

Maintaining the chemical integrity of DNA in the face of assault by oxidizing agents is a constant challenge for living organisms. Base-excision repair has an important role in preventing mutations associated with a common product of oxidative damage to DNA, 8-oxoguanine. Recent structural studies have shown that 8-oxoguanine DNA glycosylases use an intricate series of steps to locate and excise 8-oxoguanine lesions efficiently against a high background of undamaged bases. The importance of preventing mutations associated with 8-oxoguanine is shown by a direct association between defects in the DNA glycosylase MUTYH and colorectal cancer. The properties of other guanine oxidation products and the associated DNA glycosylases that remove them are now also being revealed.

Hereditary colorectal cancer syndromes: an overview

Approximately 5% of the 140,000 cases of colorectal cancer diagnosed annually are attributable to an underlying hereditary colorectal cancer syndrome. However, this is likely to be an underestimation. Our understanding of the genetic basis, as well as the guidelines for clinical management of these syndromes, continue to evolve rapidly. Because of the high risk of not only colorectal cancer but also multiple extracolonic tumors, it is crucial for clinicians to recognize the unique features in the diagnosis and management of these high-penetrance syndromes, including familial adenomatous polyposis, MYH-associated polyposis, and hereditary nonpolyposis colon cancer.

The hepatocyte nuclear factor 6 (HNF6) and FOXA2 are key regulators in colorectal liver metastases

The molecular causes leading to secondary liver malignancies are unknown. Here we report regulation of major hepatic nuclear factors in human colorectal liver metastases and primary colonic cancer. Notably, the genes coding for HNF6, HNF1beta, and C/EBPgamma were selectively regulated in liver metastases. We therefore studied protein expression of regulated transcription factors and found unacetylated HNF6 to be a hallmark of colorectal liver metastases. For its known interaction with HNF6, we investigated expression of FOXA2, which we found to be specifically induced in colorectal liver metastases. By electromobility shift assay, we examined DNA binding of disease regulated transcription factors. Essentially, no HNF6 DNA binding was observed. We also searched for sequence variations in the DNA binding domains of HNF6, but did not identify any mutation. Furthermore, we probed for expression of 28 genes targeted by HNF6. Mostly transcript expression was repressed except for tumor growth. In conclusion, we show HNF6 protein expression to be driven by the hepatic environment. Its expression is not observed in healthy colon or primary colonic cancer. HNF6 DNA binding is selectively abrogated through lack of post-translational modification and interaction with FOXA2. Targeting of FOXA2 and HNF6 may therefore enable mechanism-based therapy for colorectal liver metastases.

Self-Surveillance for Genetic Predisposition to Cancer: Behaviors and Emotions

PURPOSE/OBJECTIVES

To describe the kinds of self-monitoring activities and the emotional responses associated with those activities in patients with a genetic predisposition to multiple endocrine neoplasia type 2a (MEN2a) or familial adenomatous polyposis (FAP).

RESEARCH APPROACH

Thematic analysis of the transcripts of patient interviews conducted for two previous grounded theory investigations of participation in lifelong surveillance for patients with cancer predisposition syndromes and their family members.

SETTING

In the original studies, participants were recruited through a high-risk gastrointestinal cancer clinic (for FAP) and pediatric and adult endocrinology clinics (for MEN2a) at two eastern U.S. medical centers and by patient referral.

PARTICIPANTS

58 transcripts of interviews with 29 patients; 17 diagnosed with FAP or the variants of Gardner syndrome and attenuated FAP and 12 patients diagnosed with MEN2a.

METHODOLOGIC APPROACH

Informants participated in two hour-long, in-depth interviews and completed a self-administered sociodemographic questionnaire.

MAIN RESEARCH VARIABLES

Types of self-surveillance activities.

FINDINGS

Patients engage in an elaborate set of self-surveillance activities that are grouped into five categories of behavior: Medication Appraisal, Phenotype Tracking, Intake and Output Monitoring, Laboratory and Treatment Recording, and Tracking of Visits. Self-surveillance behaviors are grouped independent of type of syndrome, penetrance, age, or gender of the patient. Each category comprises a variety of behaviors that correspond with treatment recommendations and understanding of the disorder.

CONCLUSIONS

Self-surveillance may be driven by a combination of anticipation and the need for control and understanding.

INTERPRETATION

Findings from the study could be used to create an assessment tool to evaluate the extent to which patients are involved in day-to-day self-monitoring. Clinicians may use the categories to better understand patients' knowledge deficits and the emotional impact of enhanced vigilance. Self-surveillance activities performed by patients with MEN2a and FAP also may be performed by patients with other cancer predisposition syndromes.

MUTYH-associated polyposis: 70 of 71 patients with biallelic mutations present with an attenuated or atypical phenotype

To determine the frequency, mutation spectrum and phenotype of the recently described autosomal recessive MUTYH-associated polyposis (MAP), we performed a systematic search for MUTYH (MYH) mutations by sequencing the complete coding region of the gene in 329 unselected APC mutation-negative index patients with the clinical diagnosis of familial adenomatous polyposis (FAP) or attenuated FAP (AFAP). Biallelic germline mutations in MUTYH were identified in 55 of the 329 unselected patients (17%) and in another 9 selected index cases. About one-fifth (20%) of the 64 unrelated MAP patients harboured none of the 2 hot-spot missense mutations Y165C and/or G382D. Including 7 affected relatives, almost all MAP patients presented with either an attenuated (80%) or with an atypical phenotype (18%). Fifty percentage of the MAP patients had colorectal cancer at diagnosis. Duodenal polyposis was found in 18%, thyroid and stomach cancer in 1 case, other extraintestinal manifestations associated with FAP were not observed. In 8 families, vertical segregation was suspected; in 2 of these families, biallelic mutations were identified in 2 generations. Monoallelic changes with predicted functional relevance were found in 0.9% of the 329 patients, which is in accordance with the carrier frequency in the general population. In conclusion, biallelic MUTYH mutations are the underlying genetic basis in a substantial fraction of patients with adenomatous polyposis. The phenotype of MAP is best characterised as attenuated or atypical, respectively. Colorectal surveillance starting at about 18 years of age is recommended for biallelic mutation carriers and siblings of MAP patients, who refuse predictive testing.

The roles of specific glycosylases in determining the mutagenic consequences of clustered DNA base damage

The potential for genetic change arising from specific single types of DNA lesion has been thoroughly explored, but much less is known about the mutagenic effects of DNA lesions present in clustered damage sites. Localized clustering of damage is a hallmark of certain DNA-damaging agents, particularly ionizing radiation. We have investigated the potential of a non-mutagenic DNA base lesion, 5,6-dihydrothymine (DHT), to influence the mutagenicity of 8-oxo-7,8-dihydroguanine (8-oxoG) when the two lesions are closely opposed. Using a bacterial plasmid-based assay we present the first report of a significantly higher mutation frequency for the clustered DHT and 8-oxoG lesions than for single 8-oxoG in wild-type and in glycosylase-deficient strains. We propose that endonuclease III has an important role in the initial stages of processing DHT/8-oxoG clusters, removing DHT to give an intermediate with an abasic site or single-strand break opposing 8-oxoG. We suggest that this mutagenic intermediate is common to several different combinations of base lesions forming clustered DNA damage sites. The MutY glycosylase, acting post-replication, is most important for reducing mutation formation. Recovered plasmids commonly gave rise to both wild-type and mutant progeny, suggesting that there is differential replication of the two DNA strands carrying specific forms of base damage.

Lack of chemopreventive effects of ginger on colon carcinogenesis induced by 1,2-dimethylhydrazine in rats

Ginger (Zingiber officinale Roscoe) has been proposed as a promising candidate for cancer prevention. Its modifying potential on the process of colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) was investigated in male Wistar rats using the aberrant crypt foci (ACF) assay. Five groups were studied: Groups 1-3 were given four s.c. injections of DMH (40 mg/kg b.w.) twice a week, during two weeks, whereas Groups 4 and 5 received similar injections of EDTA solution (DMH vehicle). After DMH-initiation, the animals were fed a ginger extract mixed in the basal diet at 0.5% (Group 2) and 1.0% (Groups 3 and 4) for 10 weeks. All rats were killed after 12 weeks and the colons were analyzed for ACF formation and crypt multiplicity. The rates of cell proliferation and apoptosis were also evaluated in epithelial colonic crypt cells. Dietary consumption of ginger at both dose levels did not induce any toxicity in the rats, but ginger meal at 1% decreased significantly serum cholesterol levels (p<0.038). Treatment with ginger did not suppress ACF formation or the number of crypts per ACF in the DMH-treated group. Dietary ginger did not significantly change the proliferative or apoptosis indexes of the colonic crypt cells induced by DMH. Thus, the present results did not confirm a chemopreventive activity of ginger on colon carcinogenesis as analyzed by the ACF bioassay and by the growth kinetics of the colonic mucosa.

Intestinal polyposis syndromes: progress in understanding and treatment

PURPOSE OF REVIEW

Dramatic advances in the understanding of the genetic basis for inherited diseases and in diagnosis and treatment are particularly applicable to intestinal polyposis. Recent contributions have impacted our understanding of the molecular basis for the disease and improved our ability to treat them.

RECENT FINDINGS

Insights into the genetic basis of the spectrum of disease and refinement of genetic screening, diagnostic tests, and surgical management of intestinal polyposis and extraintestinal manifestations are reviewed.

SUMMARY

Our understanding of the genetic basis for the intestinal polyposis syndromes remains incomplete, but recent studies have contributed to filling in significant gaps in our knowledge. Specific genetic alterations have been identified in the majority of the 30% of patients with familial adenomatous polyposis that do not test positive for mutations in the APC gene with routine testing. A novel gene ENG has been identified in a subgroup of patients with Peutz-Jegher's syndrome and a hypothesis has been proposed to explain the pathogenesis of the mucosal defects. Technological advancements in diagnosis and treatment include the use of capsule endoscopy for screening and the minimally invasive approach to total colectomy with ileoanal pullthrough. Treatment of desmoid tumors remains a challenge, but new chemotherapy regimens show some promise in treating this rare, but devastating, extraintestinal manifestation.

Colorectal cancer screening: today and tomorrow

Colorectal cancer remains a disease with significant morbidity and mortality. However, the prognosis can be greatly improved with early detection. Here, we review the current screening modalities and guidelines for patients at average, moderate, and high risk for colorectal cancer. New experimental modalities are also introduced.

Surveillance against tumors—is it mainly immunological?

The concept of tumor surveillance was first formulated by immunologists Mcfarlane Burnet and Lewis Thomas, respectively. They assumed that the immune system would recognize precancerous and cancer cells as non-self and reject them. This concept is only valid for virally transformed cells, however. In humans, EBV, HHV-8, and the papilloma viruses are relevant viral agents in this context. Tumors arising without a contribution by these viruses are regarded by the immune system as "self", with possible rare exceptions like melanoma. Immunological attempts to influence them therefore implies the breaking of tolerance, a much more difficult proposition. Multicellular organisms have powerful surveillance mechanisms of a non-immunological nature against potential neoplastic cells that threaten to disrupt the organism. Four distinct categories can be recognized: (1) DNA repair. Deficiency of repair enzymes may lead to multiple tumors and/or to multicancer syndromes. (2) Epigenetic mechanisms are currently emerging as being capable of modulating the incidence of certain tumors. e.g., by determining the stringency of imprinting and by influencing chromatin structure. (3) Intracellular surveillance. DNA damage, illegitimate activation of oncogenes, and other pathological changes may activate one or several apoptotic pathways. (4) Intercellular surveillance. The tissue microenvironment influences the probability of disseminated tumor cell growth. Moreover, appropriate differentiation inducing signals may revert the tumor cell phenotype.