Biology of the adenomatous polyposis coli tumor suppressor

Oncogenic KRAS is not necessary for Wnt signalling activation in APC-associated FAP adenomas

Recent studies have suggested that APC loss alone may be insufficient to promote aberrant Wnt/beta-catenin signalling. Our aim was to comprehensively characterize Wnt signalling components in a set of APC-associated familial adenomatous polyposis (FAP) tumours. Sixty adenomas from six FAP patients with known pathogenic APC mutations were included. Somatic APC and KRAS mutations, beta-catenin immunostaining, and qRT-PCR of APC, MYC, AXIN2 and SFRP1 were analysed. Array-comparative genomic hybridization (aCGH) was also assessed in 26 FAP adenomas and 24 paired adenoma-carcinoma samples. A somatic APC alteration was present in 15 adenomas (LOH in 11 and four point mutations). KRAS mutations were detected in 10% of the cases. APC mRNA was overexpressed in adenomas. MYC and AXIN2 were also overexpressed, with significant intra-case heterogeneity. Increased cytoplasmic and/or nuclear beta-catenin staining was seen in 94% and 80% of the adenomas. beta-Catenin nuclear staining was strongly associated with MYC levels (p value 0.03) but not with KRAS mutations. Copy number aberrations were rare. However, the recurrent chromosome changes observed more frequently contained Wnt pathway genes (p value 0.012). Based on beta-catenin staining and Wnt pathway target genes alterations the Wnt pathway appears to be constitutively activated in all APC-FAP tumours, with alterations occurring both upstream and downstream of APC. Wnt aberrations are present at both the DNA and the RNA level. Somatic profiling of APC-FAP tumours provides new insights into the role of APC in tumourigenesis.

The mitochondrial protein hTID-1 partners with the caspase-cleaved adenomatous polyposis cell tumor suppressor to facilitate apoptosis

BACKGROUND & AIMS

The adenomatous polyposis cell (APC) tumor suppressor is a multifunctional protein involved in cell migration, proliferation, differentiation, and apoptosis. Cleavage of APC and the subsequent release of an amino-terminal segment are necessary for a transcription-independent mechanism of APC-mediated apoptosis. The aim of the current study is to elucidate the mechanism by which the amino-terminus of APC contributes to the enhancement of apoptosis.

METHODS

Previous yeast 2-hybrid screens, using the armadillo repeat domain of APC as bait, identified hTID-1 as a potential binding partner. Coimmunoprecipitations, coimmunofluorescence, and binding assays confirm a direct interaction between caspase-cleaved APC and hTID-1 in vivo at the mitochondria. Overexpression and small interfering RNA (siRNA) knockdown studies were designed to determine the significance of this interaction.

RESULTS

These experiments have identified hTID-1 as a directly interacting protein partner of caspase-cleaved APC. hTID-1 is an apoptosis modulator: 2 of its known mitochondrial protein isoforms, 43-kilodaltons and 40-kilodaltons, have opposing effects in apoptosis. We demonstrate that the amino-terminal segment of APC interacts with both hTID-1 isoforms directly, although there is a stronger association with the apoptotic suppressor 40-kilodalton isoform in vitro. This interaction localizes to amino acids 202-512 of APC, a region including 2 of the 7 armadillo repeats. Overexpression of the 40-kilodalton hTID-1 isoform partially rescues cells from apoptosis mediated by APC 1-777, whereas siRNA knockdown of this hTID-1 isoform enhances apoptosis.

CONCLUSIONS

These data suggest that the amino-terminal segment of APC promotes cell sensitivity to apoptosis modulated through its binding to 40- and 43-kilodalton hTID-1 isoforms.

Germinated brown rice (GBR) reduces the incidence of aberrant crypt foci with the involvement of beta-catenin and COX-2 in azoxymethane-induced colon cancer in rats

Chemoprevention has become an important area in cancer research due to the failure of current therapeutic modalities. Epidemiological and preclinical studies have demonstrated that nutrition plays a vital role in the etiology of cancer. This study was conducted to determine the chemopreventive effects of germinated brown rice (GBR) in rats induced with colon cancer. GBR is brown rice that has been claimed to be richer in nutrients compared to the common white rice. The male Sprague Dawley rats (6 weeks of age) were randomly divided into 5 groups: (G1) positive control (with colon cancer, unfed with GBR), (G2) fed with 2.5 g/kg of GBR (GBR (g)/weight of rat (kg)), (G3) fed with 5 g/kg of GBR, (G4) fed with 10 g/kg of GBR and (G5) negative control (without colon cancer, unfed with GBR). GBR was administered orally once daily via gavage after injection of 15 mg/kg of body weight of azoxymethane (AOM) once a week for two weeks, intraperitonially. After 8 weeks of treatment, animals were sacrificed and colons were removed. Colonic aberrant crypt foci (ACF) were evaluated histopathologically. Total number of ACF and AC, and multicrypt of ACF, and the expression of beta-catenin and COX-2 reduced significantly (p < 0.05) in all the groups treated with GBR (G2, G3 and G4) compared to the control group (G1). Spearman rank correlation test showed significant positive linear relationship between total beta-catenin and COX-2 score (Spearman's rho = 0.616, p = 0.0001). It is demonstrated that GBR inhibits the development of total number of ACF and AC, and multicrypt of ACF, reduces the expression of beta-catenin and COX-2, and thus can be a promising dietary supplement in prevention of colon cancer.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is characterized by the development of many tens to thousands of adenomas in the rectum and colon during the second decade of life. FAP has an incidence at birth of about 1/8,300, it manifests equally in both sexes, and accounts for less than 1% of colorectal cancer (CRC) cases. In the European Union, prevalence has been estimated at 1/11,300-37,600. Most patients are asymptomatic for years until the adenomas are large and numerous, and cause rectal bleeding or even anemia, or cancer develops. Generally, cancers start to develop a decade after the appearance of the polyps. Nonspecific symptoms may include constipation or diarrhea, abdominal pain, palpable abdominal masses and weight loss. FAP may present with some extraintestinal manifestations such as osteomas, dental abnormalities (unerupted teeth, congenital absence of one or more teeth, supernumerary teeth, dentigerous cysts and odontomas), congenital hypertrophy of the retinal pigment epithelium (CHRPE), desmoid tumors, and extracolonic cancers (thyroid, liver, bile ducts and central nervous system). A less aggressive variant of FAP, attenuated FAP (AFAP), is characterized by fewer colorectal adenomatous polyps (usually 10 to 100), later age of adenoma appearance and a lower cancer risk. Some lesions (skull and mandible osteomas, dental abnormalities, and fibromas on the scalp, shoulders, arms and back) are indicative of the Gardner variant of FAP. Classic FAP is inherited in an autosomal dominant manner and results from a germline mutation in the adenomatous polyposis (APC) gene. Most patients (~70%) have a family history of colorectal polyps and cancer. In a subset of individuals, a MUTYH mutation causes a recessively inherited polyposis condition, MUTYH-associated polyposis (MAP), which is characterized by a slightly increased risk of developing CRC and polyps/adenomas in both the upper and lower gastrointestinal tract. Diagnosis is based on a suggestive family history, clinical findings, and large bowel endoscopy or full colonoscopy. Whenever possible, the clinical diagnosis should be confirmed by genetic testing. When the APC mutation in the family has been identified, genetic testing of all first-degree relatives should be performed. Presymptomatic and prenatal (amniocentesis and chorionic villous sampling), and even preimplantation genetic testing is possible. Referral to a geneticist or genetic counselor is mandatory. Differential diagnoses include other disorders causing multiple polyps (such as Peutz-Jeghers syndrome, familial juvenile polyps or hyperplastic polyposis, hereditary mixed polyposis syndromes, and Lynch syndrome). Cancer prevention and maintaining a good quality of life are the main goals of management and regular and systematic follow-up and supportive care should be offered to all patients. By the late teens or early twenties, colorectal cancer prophylactic surgery is advocated. The recommended alternatives are total proctocolectomy and ileoanal pouch or ileorectal anastomosis for AFAP. Duodenal cancer and desmoids are the two main causes of mortality after total colectomy, they need to be identified early and treated. Upper endoscopy is necessary for surveillance to reduce the risk of ampullary and duodenal cancer. Patients with progressive tumors and unresectable disease may respond or stabilize with a combination of cytotoxic chemotherapy and surgery (when possible to perform). Adjunctive therapy with celecoxib has been approved by the US Food and Drug Administration and the European Medicines Agency in patients with FAP. Individuals with FAP carry a 100% risk of CRC; however, this risk is reduced significantly when patients enter a screening-treatment program.

miRNA expression profiles in head and neck squamous cell carcinoma and adjacent normal tissue

BACKGROUND

The expression of miRNA in head and neck squamous cell carcinomas (HNSCCs) that had been classified as high risk by surgical pathologic features and validated by trial outcome for disease recurrence was determined and compared with matched adjacent normal tissues.

METHODS

miRNA and corresponding gene expression were determined using miRNA bioarrays and gene expression arrays.

RESULTS

Twenty miRNAs were determined to be differentially regulated in the HNSCC samples when compared with their normal tissue counterparts. Quantitative reverse transcriptase-polymerase chain reaction confirmed differential regulation of miRNA expression, and gene expression analysis on these same-paired samples confirmed the loss of putative mRNA targets including genes such as adenomatous polyposis coli, programmed cell death protein 4, and TGF beta receptor 3 in the tumor samples.

CONCLUSIONS

These data suggest a role for the upregulation of specific miRNAs in high-risk HNSCC. Furthermore, upregulation of these miRNAs may be responsible for the elimination of mRNAs that lead to the growth and progression of HNSCC.

Biallelic APC inactivation was responsible for functional adrenocortical adenoma in familial adenomatous polyposis with novel germline mutation of the APC gene: report of a case

Familial adenomatous polyposis (FAP) patients develop various extracolonic lesions, among which functional adrenocortical neoplasms are infrequent. A 44-year-old woman was hospitalized because of pseudo-Meigs' syndrome, caused by bilateral ovarian metastases from an advanced ascending colon cancer due to FAP of intermediate type. Furthermore, bilateral adrenocortical adenomas were detected, and functional analyses showed a hormonal secretion pattern consistent with Cushing's syndrome. She underwent a right hemicolectomy with extirpation of bilateral ovaries. At 10 months post-operative with no detectable metastatic lesions, the residual colorectum and the larger, left adrenal gland were resected, and the hormonal hypersecretion was normalized. Direct sequencing of the adenomatous polyposis coli (APC) gene revealed a nonsense germline mutation at codon 1577 and an additional nonsense somatic mutation at codon 554 in cancer tissues. Biallelic APC inactivation due to loss of the normal allele was evident in the adrenocortical adenoma. There were no hypermethylated CpG islands detected in APC promoter regions. Immunostaining for beta-catenin revealed diffuse cytoplasmic expression in resected tissues including adrenocortical adenoma. Biallelic APC inactivation may play a role in developing cortisol-secreting adrenocortical adenoma in FAP patients. It is noteworthy that biallelic APC inactivation was caused in different ways in different tumors from the same individual.

May the APC gene somatic mutations in tumor tissues influence the clinical features of Chinese sporadic colorectal cancers?

The APC gene plays an important role in colorectal carcinogenesis. The impact of APC mutations on the clinical features in sporadic CRC remains to be uncovered. The APC gene was screened for mutations with systematic analysis techniques including DHPLC, PTT, MLPA and DNA sequencing in 43 Chinese sporadic CRC patients. Twenty nine somatic mutations (in 17 different types) in APC gene were found in 18 of 43 sporadic CRC patients. Of those, nine were novel mutations. Higher frequency of somatic APC mutations was found in younger CRC patients than that in elder ones. The biallelic somatic mutations of APC gene were identified in four CRC patients whose tumors had more invasive clinical features. The nonsense mutation Arg1114X in APC gene was found in five of 43 CRC tumor tissues. A higher cancer metastasis rate was uncovered in CRC patients with this mutation. The somatic mutations of APC gene may influence the clinical features of sporadic CRC. Arg1114X in APC gene, as a hot spot mutation in Chinese CRC, may predispose to the cancer metastasis of sporadic CRC.

Endoscopic management of large colorectal polyps

OBJECTIVES

The optimal treatment for large colorectal polyps (LCPs) is still a controversial issue. The aim of this study was to evaluate the safety and effectiveness of endoscopic polypectomy (EP) of colorectal polyps >or=2 cm in size.

PATIENTS AND METHODS

One hundred fifty-one EP LCPs were performed over a period of 7 years. Diathermal snare was used for pedunculated and pseudopedunculated polyps and endoscopic mucosal resection (EMR) or biopsy forceps polypectomy for sessile and flat polyps. The resected polyps were recovered and collected for histology. At scheduled follow-up visits 1, 3, 6, and 12 months after polypectomy, complications and recurrences were recorded in all patients.

RESULTS

Fifteen polyps were located in the rectum, 84 in the sigmoid colon, 11 in the descending colon, four in the splenic flexure, 11 in the transverse colon, 11 in the hepatic flexure, seven in the ascending colon and eight in the cecum. Fifty-six polyps were sessile, 54 pedunculated, 25 pseudopedunculated, and 16 flat. At histology, most of polyps (131) were adenomas (nine with adenocarcinoma in situ). Five were invasive polypoid carcinomas and required colonic resection. Immediate bleeding occurred in ten patients (7.6%) and it was stopped by endoscopic hemoclips (7), epinephrine injection (1), or surgery (2). There were three perforations (2.3%; all polypoid carcinomas), managed endoscopically (1) or surgically (2). Delayed bleeding occurred in two patients (1.5%) and was treated by endoscopic diathermy and hemoclips (1) or surgery (1). During follow-up, six (4.6%) incompletely excised polyps and three (2.3%) relapses in the site of previous EP were detected and endoscopically removed.

CONCLUSION

EP is relatively safe and effective for benign-appearing LCPs.

Multiple neoplasia in a 15-year-old girl with familial adenomatous polyposis

A 15-year-old girl with adenomatous polyposis coli gene (APC) mutation and brain tumor-polyposis syndrome developed an unusual succession of cervicocephalic tumors (medulloblastoma, meningeal low-grade myxoid tumor, and papillary thyroid carcinoma), at the age of 5, 9, and 15 years, respectively. We discuss the genetic profile of the thyroid tumor in which a large somatic deletion of APC gene was found and the physiopathology of thyroid carcinoma in patients with germline APC mutation. We also point out the uncommon phenotype in this young girl with early multiple neoplasias and the difficulties of management of such familial adenomatous polyposis patients with occurrence of extracolonic cancers that require the use of potential trigger agents as radiotherapy or chemotherapy.

Molecular analysis of the APC and MUTYH genes in Galician and Catalonian FAP families: a different spectrum of mutations?

BACKGROUND

Familial adenomatous polyposis (FAP) is an autosomal dominant-inherited colorectal cancer syndrome, caused by germline mutations in the APC gene. Recently, biallelic mutations in MUTYH have also been identified in patients with multiple colorectal adenomas and in APC-negative patients with FAP. The aim of this work is therefore to determine the frequency of APC and MUTYH mutations among FAP families from two Spanish populations.

METHODS

Eighty-two unrelated patients with classical or attenuated FAP were screened for APC germline mutations. MUTYH analysis was then conducted in those APC-negative families and in 9 additional patients from a previous study. Direct sequencing, SSCP analysis and TaqMan genotyping were used to identify point and frameshift mutations, meanwhile large rearrangements in the APC gene were screened by multiplex ligation-dependent probe amplification (MLPA).

RESULTS

APC germline mutations were found in 39% of the patients and, despite the great number of genetic variants described so far in this gene, seven new mutations were identified. The two hotspots at codons 1061 and 1309 of the APC gene accounted for 9,4% of the APC-positive families, although they were underrepresented in Galician samples. The deletion at codon 1061 was not found in 19 APC-positive Galician patients but represented 23% of the Catalonian positive families (p = 0,058). The same trend was observed at codon 1309, even though statistical analysis showed no significance between populations. Twenty-four percent of the APC-negative patients carried biallelic MUTYH germline mutations, and showed an attenuated polyposis phenotype generally without extracolonic manifestations. New genetic variants were found, as well as the two hotspots already reported (p.Tyr165Cys and p.Gly382Asp).

CONCLUSION

The results we present indicate that in Galician patients the frequency of the hotspot at codon 1061 in APC differs significantly from the Catalonian and also other Caucasian populations. Similar results had already been obtained in a previous study and could be due to the genetic isolation of the Galician population. MUTYH analysis is also recommended for all APC-negative families, even if a recessive inheritance is not confirmed.

Effects of dietary flaxseed on intestinal tumorigenesis in Apc(Min) mouse

Dietary flaxseed has been shown to prevent azoxymethane (AOM)-induced colorectal cancers in male Fisher rats. The present study was designed to investigate the chemopreventive effects of dietary flaxseed on the development of intestinal tumors in Apc(Min) mice. Apc(Min) mice were divided into five different groups, fed with control (AIN-93M meal), corn meal, flaxseed meal, corn oil, and flaxseed oil supplemented diets. Results showed that dietary flaxseed significantly decreased (P < 0.05) tumor multiplicity and size in the small intestine and colon as compared to control, corn-treated groups. Intestine, colon, and serum samples of corn-treated groups showed higher levels of omega -6 fatty acids, whereas the flaxseed treated groups exhibited higher levels of omega -3 fatty acids. Lignans were detected in the serum, intestine, and colon samples for flaxseed meal group. COX-1 and COX-2 expression in the colon samples from the flaxseed meal group were significantly lower (P < 0.05) as compared to the corn meal group. Dietary flaxseed may be chemopreventive for intestinal tumor development in Apc(Min) mice possibly by increasing omega -3 fatty acid levels, lignans, and decreasing COX-1 and COX-2 levels.

Relative role of APC and MUTYH mutations in the pathogenesis of familial adenomatous polyposis

OBJECTIVE

Familial adenomatous polyposis (FAP) is an interesting model for the study of colorectal tumour. Two genes contribute to the FAP phenotype - APC and MUTYH - but their relative role is still undefined. The objective of this study was to evaluate the contribution of the two genes to the pathogenesis of FAP by means of a series of FAP families.

MATERIAL AND METHODS

Sixty-one unrelated families with a diagnosis of FAP and a total of 187 affected individuals were evaluated. After extracting DNA, APC and MUTYH genes were sequenced.

RESULTS

In the whole series of patients, colectomy with ileorectal anastomosis was the most frequent surgery, although the number of patients treated by total proctocolectomy and ileoanal anastomosis was increasing. Duodenal and jejunal-ileal adenomas were present in more than half of the patients. Constitutional mutations were detected in 37 of the 45 families (82.2%); there were 33 families with APC and 4 with MUTYH alterations. Age at onset of polyposis and age at surgery were 10-15 years delayed for carriers of MUTYH mutations; cancer at diagnosis was frequent, and extracolonic manifestations were diagnosed in the majority of MUTYH-positive families. MUTYH-associated polyposis showed the horizontal transmission expected for recessive inheritance (at variance with the dominant pattern seen with APC mutations).

CONCLUSIONS

At least two genes are associated with the FAP phenotype. APC mutations account for the majority of cases, while MUTYH mutations can be observed in 10% of patients. There are few but definite differences between APC- and MUTYH-associated FAP, such as age at diagnosis and pattern of transmission.

Natural products as inhibitors of carcinogenesis

BACKGROUND

Although carcinogenesis and cancer have been studied intensively for > 50 years, the rates of cancer incidence and mortality remain high. The most successful approach for reducing these rates has been primary prevention. For individuals at a high risk of developing cancer owing to certain genetic, environmental and occupational factors, cancer chemoprevention is a logical approach.

OBJECTIVE

This review discusses natural products as inhibitors of carcinogenesis.

CONCLUSION

Natural product chemopreventive agents are inherently biologically active and have been demonstrated to prevent and reverse the carcinogenic process in a pleiotropic manner. Derivatives of compounds discovered by screening natural products for chemopreventive agents have shown efficacy in clinical trials. Despite the obstacles that must be overcome before chemopreventive drugs become an integral component of standard medical practice for cancer prophylaxis, there is vast potential for significant improvement in cancer morbidity and mortality through the use of natural product chemopreventive drugs.

Broad phenotypic spectrum in familial adenomatous polyposis; from early onset and severe phenotypes to late onset of attenuated polyposis with the first manifestation at age 72

Background

Familial adenomatous polyposis (FAP) is typically characterized by multiple colonic polyps and frequent extracolonic features. Whereas the number of colonic polyps has been linked to the APC gene mutation, possible genotype-phenotype correlations largely remain to be defined for the extracolonic manifestations.

Methods

Full genomic sequencing combined with multiplex ligation-dependent probe amplification was used to identify APC gene mutations, which were correlated to the clinical presentations.

Results

10 novel APC gene mutations were identified in 11 families. A broad spectrum of extracolonic manifestations was identified in most of these individuals. Two sisters with an insertion in codon 528 (c.1582_1583insGC) both showed severe phenotypes with classical polyposis, upper gastrointestinal polyps and thyroid cancer. A woman with a 3'APC mutation (c.5030_5031insAA) developed colon cancer at age 72 as the first manifestation of attenuated FAP.

Conclusion

With an increasing number of FAP families diagnosed, a broad and variable tumor spectrum and a high frequency of extracolonic manifestations are gradually recognized. We report novel APC mutations and present two FAP cases that suggest familial aggregation of thyroid cancer and demonstrate the need to consider attenuated FAP also among elderly patients with colon cancer.

Age-specific incidence of cancer: Phases, transitions, and biological implications

The observation that the age-specific incidence curve of many carcinomas is approximately linear on a double logarithmic plot has led to much speculation regarding the number and nature of the critical events involved in carcinogenesis. By a consideration of colorectal and pancreatic cancers in the Surveillance Epidemiology and End Results (SEER) registry we show that the log-log model provides a poor description of the data, and that a much better description is provided by a multistage model that predicts two basic phases in the age-specific incidence curves, a first exponential phase until the age of approximately 60 followed by a linear phase after that age. These two phases in the incidence curve reflect two phases in the process of carcinogenesis. Paradoxically, the early-exponential phase reflects events between the formation (initiation) of premalignant clones in a tissue and the clinical detection of a malignant tumor, whereas the linear phase reflects events leading to initiated cells that give rise to premalignant lesions because of abrogated growth/differentiation control. This model is consistent with Knudson's idea that renewal tissue, such as the colon, is converted into growing tissue before malignant transformation. The linear phase of the age-specific incidence curve represents this conversion, which is the result of recessive inactivation of a gatekeeper gene, such as the APC gene in the colon and the CDKN2A gene in the pancreas.

A proteomics approach to identify changes in protein profiles in serum of Familial Adenomatous Polyposis patients

Familial adenomatous polyposis (FAP) is one of the most important clinical hereditary forms of inherited susceptibility to colorectal cancer and is characterized by a high degree of phenotypic heterogeneity. We used a mass spectrometry driven-proteomic strategy to identify serum molecules differently expressed in FAP patients. The data obtained were subsequently processed by bioinformatic analysis and confirmed by Western blotting. Significant differences were highlighted in the expression of serum proteins of FAP patients. In particular, two proteins (alpha-2-HS-glycoprotein and apoliprotein D) were down-regulated (about 0.5- and 0.7-fold, respectively) in carpeting versus diffuse FAP patients and healthy donors, while alpha-2-antiplasmin was up-regulated (about 1.4-fold). Moreover, mass spectrometry approach enabled us to identify serum biomarkers specific for two distinct clinical form of FAP, i.e. carpeting and diffuse FAP. In particular, vitronectin was up-regulated (more than 1.4-fold) in diffuse FAP patients versus carpeting FAP and versus healthy donors, and two additional proteins (Haptoglobin and alpha-1-acid glycoprotein 1) were up-regulated in 2 out of 3 carpeting FAP patients. Our study suggests that mass spectrometry combined to a strong bioinformatics analysis is a valuable tool for the identification of quali/quantitative differences in the serum proteome of otherwise indistinguishable FAP phenotypes. Moreover, the definition of a proteomic profile, supported by the supervised classification, is a powerful and highly sensitive approach for the identification molecular signatures that are able to outperform the traditional disease markers and can therefore be efficiently applied for the diagnosis and clinical management of FAP patients.

A novel function of adenomatous polyposis coli (APC) in regulating DNA repair

Prevailing literature suggests diversified cellular functions for the adenomatous polyposis coli (APC) gene. Among them a recently discovered unique role of APC is in DNA repair. The APC gene can modulate the base excision repair (BER) pathway through an interaction with DNA polymerase beta (Pol-beta) and flap endonuclease 1 (Fen-1). Taken together with the transcriptional activation of APC gene by alkylating agents and modulation of BER activity, APC may play an important role in carcinogenesis and chemotherapy by determining whether cells with DNA damage survive or undergo apoptosis. In this review, we summarize the evidence supporting this novel concept and suggest that these results will have implications for the development of more effective strategies for chemoprevention, prognosis and chemotherapy of certain types of tumors.

Extra-intestinal manifestations of familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominantly inherited disorder, which results from a germ line mutation in the APC (adenomatous polyposis coli) gene. FAP is characterized by the formation of hundreds to thousands of colorectal adenomatous polyps. Although the development of colorectal cancer stands out as the most prevalent complication, FAP is a multisystem disorder of growth. This means, it is comparable to other diseases such as the MEN syndromes, Von Hippel-Lindau disease and neurofibromatosis. However, the incidence of many of its clinical features is much lower. Therefore, a specialized multidisciplinary approach to optimize health care-common for other disorders-is not usually taken for FAP patients. Thus, clinicians that care for and counsel members of high-risk families should have familiarity with all the extra-intestinal manifestations of this syndrome. FAP-related complications, for which medical attention is essential, are not rare and their estimated lifetime risk presumably exceeds 30%. Affected individuals can develop thyroid and pancreatic cancer, hepatoblastomas, CNS tumors (especially medulloblastomas), and various benign tumors such as adrenal adenomas, osteomas, desmoid tumors and dental abnormalities. Due to improved longevity, as a result of better prevention of colorectal cancer, the risk of these clinical problems will further increase. We present a clinical overview of extra-intestinal manifestations, including management and treatment options for the FAP syndrome. Furthermore, we provide recommendations for surveillance of FAP complications based on available literature.

The APC tumor suppressor inhibits DNA replication by directly binding to DNA via its carboxyl terminus

BACKGROUND & AIMS

The APC tumor suppressor is well known for its ability to regulate Wnt signaling through mediation of beta-catenin levels in the cell. Transient over expression of the tumor suppressor gene APC in colon cancer cells prevents entry into S phase of the cell cycle, a phenotype only partially restored by cotransfection of a transcriptionally active form of beta-catenin. In an attempt to define its transcription-independent tumor suppressor functions, we tested whether APC directly affects DNA replication.

METHODS

A transcriptionally quiescent in vitro DNA replication system, the polymerase chain reaction, DNA binding assays, and transient transfections in colon cancer cell lines were used to determine the effects of APC on DNA replication and the mechanism by which it works.

RESULTS

We report that exogenous full-length APC inhibits replication of template DNA through a function that maps to amino acids 2140-2421, a region of the protein commonly lost by somatic or germline mutation. This segment of APC directly interacts with DNA, while mutation of the DNA-binding S(T)PXX motifs within it abolishes DNA binding and reduces inhibition of DNA replication. Phosphorylation of this segment by cyclin-dependent kinases also reduces inhibition of DNA replication. Furthermore, transient transfection of an APC segment encoding amino acids 2140-2421 into a colon cancer cell line with mutant APC prevents cell cycle progression into or through S phase.

CONCLUSIONS

Our results suggest that APC can negatively regulate cell cycle progression through inhibition of DNA replication by direct interaction with DNA.

Difference in characteristics of APC mutations between colonic and extracolonic tumors of FAP patients: variations with phenotype

To clarify the differences in characteristics of adenomatous polyposis coli (APC) mutations between colorectal tumors from various phenotypes of familial adenomatous polyposis (FAP) and between colorectal and extracolonic tumors, we analyzed APC mutations in 86 colorectal tumors from FAP patients including profuse, sparse and attenuated types, 23 sporadic colorectal tumors and 40 FAP extracolonic tumors including duodenal, gastric and desmoid tumors. In all tumors, 1 allele of the truncated APC gene retained armadillo repeats, 15-amino-acid (aa) repeats and various numbers of 20-aa repeats, but lacked SAMP repeats, as a result of germline and somatic mutations. Regarding 20-aa repeats, the truncated APC gene retained 1 repeat due to allele loss in 96% (27/28) of colorectal tumors from profuse-type FAP, 69% (36/52) of sparse-type retained 2 repeats due to somatic mutation, and 100% (6/6) of attenuated-type retained 2 or 3 repeats due to the third or second hit. In sporadic colorectal tumors 74% (17/23) retained 1 or 2 repeats. The truncated APC gene retained 3 repeats in 88% (7/8) of FAP duodenal tumors, 100% (26/26) of gastric tumors retained 2 or 3 repeats and 83% (5/6) of desmoid tumors retained 2 repeats. These data suggest that the number of beta-catenin downregulating 20-aa repeats in truncated APC gene associated with colorectal tumorigenesis is different in profuse, sparse and attenuated types of FAP, and that the association with tumorigenesis is also different between colorectal and extracolonic tumors.

Rare coincidence of familial adenomatous polyposis and a retroperitoneal fibromyxoid sarcoma: report of a case

PURPOSE

Familial adenomatous polyposis is an autosomal-dominant inherited disease with development of as many as thousands of adenomas within colon and rectum. All untreated patients will develop colorectal adenocarcinoma. A variety of extracolonic manifestations can occur, although malignant tumors are rare. An association of familial adenomatous polyposis and sarcomas was reported in a few cases only.

METHODS

We present the exceptional case of a 24-year-old male with genetically verified familial adenomatous polyposis (deletion of 10 base pairs at position 228-237 of exon 15A). The patient underwent prophylactic subtotal proctocolectomy and ileal-pouch rectal anastomosis in 2003. Two years later, an obstruction of the left ureter caused by a retroperitoneal mass was diagnosed.

RESULTS

Histopathologic findings after complete tumor resection showed a low-grade fibromyxoid sarcoma. CT scan and clinical follow-up through 15 months postoperatively revealed no recurrent tumor growth.

CONCLUSIONS

To our knowledge, this is the first reported case of familial adenomatous polyposis with metachronous retroperitoneal fibromyxoid sarcoma. Proctocolectomy or total colectomy and complete tumor resection is the treatment of choice in this case. In addition to more common semimalignant retroperitoneal desmoid tumors in familial adenomatous polyposis patients, a malignant soft-tissue tumor also has to be considered for differential diagnosis.

Mild depletion of dietary folate combined with other B vitamins alters multiple components of the Wnt pathway in mouse colon

Preclinical and clinical studies suggest that diminished folate status increases the risk of colorectal carcinogenesis. However, many biochemical functions of folate are dependent on the adequate availability of other 1-carbon nutrients, including riboflavin, vitamin B-6, and vitamin B-12. Aberrations in the Wnt pathway are thought to play an important role in human colorectal cancers. This study therefore investigated if mild depletion of folate combined with depletion of riboflavin, vitamin B-6, and vitamin B-12 could induce alterations in the Wnt pathway in the colonic mucosa. Ninety-six mice were pair-fed diets with different combinations of B vitamin depletion for 10 wk. Genomic DNA methylation and uracil misincorporation were measured by LC/MS and GC/MS. Gene-specific methylation, strand breaks, and expressions were measured by real-time PCR and immunoblotting. Proliferation and apoptosis were determined by immunohistochemistry. DNA strand breaks within the Apc mutation cluster region were induced by folate depletion combined with inadequacies of riboflavin, vitamin B-6, and vitamin B-12 (P < 0.05), but such effects were not induced by folate depletion alone. Similarly, minor changes in the expression of Apc, beta-catenin, and cyclin D1 produced by mild folate depletion were significantly magnified by multiple vitamin depletion. Apoptosis, which can be suppressed by increased Wnt-signaling, was attenuated by the combined deficiency state (P < 0.05) but not by singlet or doublet deficiencies. These findings indicate that a mild depletion of folate that is of insufficient magnitude by itself to induce alterations in components of the Wnt pathway may produce such effects when present in conjunction with mild inadequacies of other 1-carbon nutrients.

Smad3 deficiency promotes tumorigenesis in the distal colon of ApcMin/+ mice

Colorectal cancer, one of the most common human malignancies in the Western world, is often subdivided based on tumor location in either the distal or proximal colon. Several mouse models have been developed to study human colorectal cancer, but few display this clear distinction between the two colonic locations. By crossing Apc(Min/+) and Smad3 mutant mice, we showed that combined activation of the Wnt pathway and attenuation of the transforming growth factor-beta (TGF-beta) pathway causes high multiplicity and rapid onset of invasive tumorigenesis almost exclusively in the distal colon, closely mimicking the familial adenomatous polyposis (FAP) disease and consisting with distinct colorectal cancer etiologies based on tumor location. Transcriptional profiling revealed higher expression of several TGF-beta activators in the normal distal mucosa than in proximal mucosa, suggesting a stronger reliance on TGF-beta-mediated growth control in the distal than in the proximal colon. Apc(Min/+)Smad3(-/-) mice provide an alternative model to Apc(Min/+) mice to study FAP and distal sporadic colorectal cancer. This model will be useful in dissecting mechanistic and etiologic differences between proximal and distal colonic cancer, whereas the confinement of tumorigenesis to the distal colon offers unique advantages in monitoring tumor progression by in vivo imaging.

Impact of adenomatous polyposis coli (APC) tumor supressor gene in human colon cancer cell lines on cell cycle arrest by apigenin

This research assessed the importance of the adenomatous polyposis coli (APC) tumor suppressor mutation in the ability of apigenin to induce cell cycle arrest using HT29-APC cells, which contain inducible wild-type APC under the metallothionein promoter. HT29-GAL cells, containing beta-galactosidase (GAL), were included as control. Treatment with apigenin (0, 20, 40, 60, and 80 microM) for 48 h resulted in reduction in the cell number (P < 0.05) concurrent with flow cytometry results showing a dose-dependent accumulation of cells in the G2/M phase in both HT29-APC and HT29-GAL cells without ZnCl(2) treatment. Flow cytometric analysis showed an increase (P < 0.05) in the percentage of cells in G2/M when HT29-APC cells were treated with 80 microM apigenin for 120 h. This increase was not present in HT29-APC cells when treated with both 80 microM apigenin and 100 microM ZnCl(2) for 120 h. Western blot analysis verified the induction of APC protein expression in ZnCl(2)-treated HT29-APC cells but not in ZnCl(2)-treated HT29-GAL cells. Apigenin plus ZnCl(2) treatment increased the expression of APC protein in HT29-APC cells by 50 fold above expression observed with ZnCl(2) alone. Upon induction of the APC gene with ZnCl(2) in HT29-APC cells, the percentage of apoptotic cells increased significantly (P < 0.05) after 120-h treatment. Additionally, apigenin treatment (80 microM) further increased the percentage of apopototic HT29-APC following ZnCl(2) treatment to induce wild-type APC expression. These results suggest that APC dysfunction may be critical for apigenin to induce cell cycle arrest in human colon cancer cell lines and furthermore, apigenin enhances APC expression and apoptosis in cells with wild-type APC.

Cyclooxygenase-2 and platelet-derived growth factor receptors as potential targets in treating aggressive fibromatosis

PURPOSE

To explore the molecular bases of potential new pharmacologic targets in aggressive fibromatosis (desmoid tumor).

EXPERIMENTAL DESIGN

Tumor specimens from 14 patients surgically treated for aggressive fibromatosis (6 familial adenomatous polyposis and 8 sporadic cases), analyzed for adenomatous polyposis coli (APC) and CTNNB1 (beta-catenin) mutations, were further investigated for beta-catenin, cyclooxygenase-2 (COX-2), platelet-derived growth factor (PDGF) receptor alpha (PDGFRA)/PDGF receptor beta (PDGFRB), their cognate ligands (PDGFA and PDGFB), and KIT using a comprehensive immunohistochemical, biochemical, molecular, and cytogenetic approach.

RESULTS

No CTNNB1 (beta-catenin) mutations were found in the familial adenomatous polyposis patients, but previously reported activating mutations were found in six of the eight sporadic patients. All of the cases carrying an altered WNT pathway showed nuclear and cytoplasmic immunoreactivity for beta-catenin, whereas beta-catenin expression was restricted to the cytoplasm in the sporadic patients lacking CTNNB1 mutations. COX-2 protein and mRNA overexpression was detected in all 14 cases, together with the expression and phosphorylation of PDGFRA and PDGFRB, which in turn paralleled the presence of their cognate ligands. No PDGFRB mutations were found. The results are consistent with PDGFRA and PDGFRB activation sustained by an autocrine/paracrine loop.

CONCLUSIONS

Aggressive fibromatosis is characterized by WNT/oncogene pathway alterations triggering COX-2-mediated constitutive coactivation of PDGFRA and PDGFRB, and may therefore benefit from combined nonsteroidal anti-inflammatory drug + tyrosine kinase inhibitor treatment.

Deregulated Wnt/beta-catenin program in high-risk neuroblastomas without MYCN amplification

Neuroblastoma (NB) is a frequently lethal tumor of childhood. MYCN amplification accounts for the aggressive phenotype in a subset while the majority have no consistently identified molecular aberration but frequently express MYC at high levels. We hypothesized that activated Wnt/beta-catenin (CTNNB1) signaling might account for this as MYC is a beta-catenin transcriptional target and multiple embryonal and neural crest malignancies have oncogenic alterations in this pathway. NB cell lines without MYCN amplification express higher levels of MYC and beta-catenin (with aberrant nuclear localization) than MYCN-amplified cell lines. Evidence for aberrant beta-catenin-TCF transcriptional activity was demonstrated using expression profiles from 73 primary NBs. Findings included increased WNT ligands (WNT1, WNT6, WNT7A, WNT10B), DVL1 and TCF7 expression in high-risk NBs without MYCN amplification, consistent with canonical beta-catenin signaling. More directly, Patterns of Gene Expression and Gene Set Enrichment Analyses demonstrated beta-catenin target genes (for example, MYC, PPARD, NRCAM, CD44, TCF7) as coordinately upregulated in high-risk NBs without MYCN amplification in comparison to high-risk MYCN-amplified or intermediate-risk NBs, supporting pathway activation in this subset. Thus, high-risk NBs without MYCN amplification may deregulate MYC and other oncogenic genes via altered beta-catenin signaling providing a potential candidate pathway for therapeutic inhibition.

The surgeon's role in cancer prevention. The model in colorectal carcinoma

Cancer Prevention is an emerging field, capturing the old traditional concept of anticipating the development of a major disease and preventing its full impact by early detection, treatment, or aborting the tumorigenic process by a "molecular vaccine" and alleviating the full impact of the disease. Surgeons are important clinician scientists who can carry this discipline forward and develop its full potential in the clinics and in the community. Advances in molecular biology, genetics, and other technologies have permitted seminal understanding of the carcinogenic pathways and identification of targets and intermediate end points in neoplasia. In this review, we will see that we have the means of preventing significant numbers of colorectal carcinomas (CRC).

Oral and maxillofacial manifestations of familial adenomatous polyposis

Patients with familial adenomatous polyposis (FAP) develop multiple premalignant colorectal adenomas. Untreated, one or more of these polyps will progress to colorectal carcinoma in middle-aged adults. Extra-intestinal manifestations of FAP are frequently observed and this combination has been called Gardner's syndrome. Oral and maxillofacial symptoms of FAP include an increased risk of jaw osteomas, odontomas and supernumerary or unerupted teeth. Early diagnosis of FAP is crucial and may be life saving. As oral signs usually precede gastrointestinal symptoms, the dentist may play an important role in the diagnosis of FAP.

The alphaVbeta6 integrin as a novel molecular target for colorectal cancer

Recent advances in the treatment of colorectal cancer have resulted from a shift towards the use of molecular targeting strategies, with the identification of specific antigens critical for the development and progression of these tumors allowing the rational design of new therapeutic agents. The integrin receptor family provides very attractive targets for this 'magic bullet' approach, as they play key roles at all points during the malignant evolution of tumors, influencing growth, progression, angiogenesis and metastasis. One integrin in particular, alphaVbeta6, was recently shown to be upregulated in a model of colorectal tumor progression. Importantly, the consequences of this elevated receptor expression not only impact tumor cell function, but also indicate that alphaVbeta6 is a prognostic variable for colorectal cancer and one that is predictive of patient outcome in early-stage disease. Taken together with its normal expression pattern and known biologic functions, alphaVbeta6 thus emerges as a novel therapeutic candidate.

Eukaryotic initiation factor 6 selectively regulates Wnt signaling and beta-catenin protein synthesis

Eukaryotic initiation factor 6 (eIF6), an essential protein important in ribosome biosynthesis and assembly, was identified as an interacting partner of the beta-catenin C terminus in the yeast two-hybrid assay. Independent studies identified Drosophila eIF6 (DeIF6) in a genetic screen designed to detect new genes involved in the regulation of the Wnt/Wg (wingless) pathway. Ectopic expression of DeIF6 in wing discs results in a Wg phenotype. Expression of eIF6 in adenomatous polyposis coli (APC)-mutant colon cancer cells, which express high levels of active beta-catenin, showed that eIF6 selectively inhibits the Wnt pathway at the level of beta-catenin protein independently of proteasomal degradation. Incorporation of radiolabeled amino acids into beta-catenin was selectively decreased in cells that overexpressed eIF6. A similar inverse relationship of the two proteins was observed in the APC(min/+) mouse intestine, in which beta-catenin levels are very high. Taken together these data reveal a link between eIF6 and Wnt signaling, perhaps at the level of ribosome recycling on beta-catenin mRNA.

Epithelial-Mesenchymal Transition and Colorectal Cancer: Gaining Insights into Tumor Progression Using LIM 1863 Cells

In addition to allowing epithelial cells to escape the structural constraints imposed by tissue architecture and adopt a phenotype more amenable to cell movement, it is now recognized that the epithelial-mesenchymal transition (EMT) may also represent a critical component permitting the progression of carcinomas towards invasive and metastatic disease. However, data supporting the actual occurrence of EMT in specific solid tumors and its relevance to the process of progression of these cancers has been scant. Despite an extensive knowledge of the genetic basis for colorectal cancer, the translation of this information into effective treatments has been limited. Clearly, there is a desperate need for new and improved therapies and since the switch to a metastatic phenotype is critical for outcome, it is of paramount importance to elucidate the biology that underlies the progression of this disease. Thus, the unique LIM 1863 model for studying the EMT of colorectal carcinoma has been used to both substantiate the importance of the transition for this cancer type and to identify molecular events that contribute to disease progression. Importantly, it has emerged that not only does EMT enhance migratory capacity, but also elicits additional selective advantages to colonic tumor cells. Specifically, the acquisition of autocrine growth factor signaling loops, mechanisms to evade apoptosis, and expression of specific integrins allowing invasive cells to interact with interstitial matrices and sustain activation of TGF-beta combine to provide a compelling new biochemical framework for understanding how EMT contributes to tumor evolution.

Adenomatous polyposis coli (APC) plays multiple roles in the intestinal and colorectal epithelia

The adenomatous polyposis coli (APC) gene is mutated in familial adenomatous polyposis and in most sporadic colorectal tumors. During both embryonic and postnatal periods, APC is widely expressed in a variety of tissues, including the brain and gastrointestinal tract. The APC gene product (APC) is a large multidomain protein consisting of 2843 amino acids. APC downregulates the Wnt signaling pathway through its binding to beta-catenin and Axin. Most mutated APC proteins in colorectal tumors lack the beta-catenin-binding regions and fail to inhibit Wnt signaling, leading to the overproliferation of tumor cells. Several mouse models (APC580D, APCDelta716, APC1309, APCMin, APC1638T) have been established to investigate carcinogenesis caused by APC mutations. APC also binds to APC-stimulated guanine nucleotide exchange factor, the kinesin superfamily-associated protein 3, IQGAP1, microtubules, EB1, and discs large (DLG). APC has both nuclear localization signals and nuclear export signals in its molecule, suggesting its occasional nuclear localization and export of beta-catenin from the nucleus. APC is highly expressed in the intestinal and colorectal epithelia and may be involved in homeostasis of the enterocyte renewal phenomena, in which proliferation, migration, differentiation, and apoptosis are highly regulated both temporally and spatially. Through the many binding proteins mentioned, APC can exert multiple functions involved in epithelial homeostasis.

Htid-1, the human homolog of the Drosophila melanogaster l(2)tid tumor suppressor, defines a novel physiological role of APC

Htid-1, the human counterpart of the Drosophila tumor suppressor gene lethal(2)tumorous imaginal discs (l(2)tid) encodes three splice forms translated into three cytosolic - Tid50, Tid48 and Tid46 - and three mitochondrial - Tid43, Tid40 and Tid38 - proteins. Here we provide evidence for the association of the endogenous Tid50/Tid48 proteins with the adenomatous polyposis coli (APC) tumor suppressor in normal colon epithelium, colorectal cancer cells and mouse NIH3T3 fibroblasts. Using the Glutathione S-transferase binding assay we show that the N-terminal region including the Armadillo domain (ARM) of APC is sufficient to bind the Tid molecules. Using immunoprecipitation and confocal microscopy we show that the two molecular partners complex at defined areas of the cells with further proteins such as Hsp70, Hsc70, Actin, Dvl and Axin. Our data implicate that the formation of the complex is not associated with APC's involvement in beta-Catenin degradation. Furthermore, though it is linked to Actin it is neither associated with regulation of Actin cytoskeleton due to APC's binding to Asef nor to Tid's binding to Ras-GAP. We suggest that the novel complex acts in maintaining APC's availability for its distinct roles in the Wnt signaling important for the cell to take the right decision, either to switch the cascade OFF or ON, thus, to regulate the onset of proliferation of the cells.

Caspase cleavage of the APC tumor suppressor and release of an amino-terminal domain is required for the transcription-independent function of APC in apoptosis

The adenomatous polyposis coli (APC) tumor suppressor is inactivated by mutation in most colorectal tumors. APC is a component of the Wnt signaling pathway and is best known for its ability to downregulate beta-catenin and consequent effects on transcriptional regulation. Previous work demonstrated that APC accelerates apoptosis-associated caspase activity independently of transcription, and suggested novel tumor suppressor functions of APC. In this work, we have mapped the APC apoptosis-accelerating region to amino acids (aa) 1-760 by testing a series of non-overlapping APC segments. Interestingly, this segment corresponds to a stable group II caspase cleavage product of APC released during apoptosis that includes the amino-terminal aa1-777. Mutation of the APC aspartic acid residue at position 777 to an alanine completely abolished in vitro cleavage of APC by a recombinant group II caspase and rendered the full-length protein unable to accelerate apoptosis in vitro. A truncated APC protein associated with familial and sporadic colorectal cancer, also unable to accelerate apoptosis in vitro and in vivo, is resistant to group II caspase cleavage. These results demonstrate that cleavage of APC and the subsequent release of an amino-terminal segment are necessary for the transcription-independent mechanism of APC-mediated apoptosis.

PPARgamma inhibitors reduce tubulin protein levels by a PPARgamma, PPARdelta and proteasome-independent mechanism, resulting in cell cycle arrest, apoptosis and reduced metastasis of colorectal carcinoma cells

The nuclear transcription factor peroxisome proliferator-activated receptor-gamma (PPARgamma) has been identified as an important therapeutic target in murine models of colorectal cancer (CRC). To examine whether PPARgamma inhibition has therapeutic effects in late-stage CRC, the effects of PPARgamma inhibitors on CRC cell survival were examined in CRC cell lines and a murine CRC model. Low doses (0.1-1 microM) of PPARgamma inhibitors (T0070907, GW9662 and BADGE) did not affect cell survival, while higher doses (10-100 microM) of all 3 PPARgamma inhibitors caused caspase-dependent apoptosis in HT-29, Caco-2 and LoVo CRC cell lines. Apoptosis was preceded by altered cell morphology, and this alteration was not prevented by caspase inhibition. PPARgamma inhibitors also caused dual G and M cell cycle arrest, which was not required for apoptosis or for morphologic alterations. Furthermore, PPARgamma inhibitors triggered loss of the microtubule network. Notably, unlike other standard antimicrotubule agents, PPARgamma inhibitors caused microtubule loss by regulating tubulin post-transcriptionally rather than by altering microtubule polymerization or dynamics. Proteasome inhibition by epoxomicin was unable to prevent tubulin loss. siRNA-mediated reduction of PPARgamma and PPARdelta proteins did not replicate the effects of PPARgamma inhibitors or interfere with the inhibitors' effects on apoptosis, cell cycle or tubulin. PPARgamma inhibitors also reduced CRC cell migration and invasion in assays in vitro and reduced both the number and size of metastases in a HT-29/SCID xenograft metastatic model of CRC. These results suggest that PPARgamma inhibitors are a novel potential antimicrotubule therapy for CRC that acts by directly reducing microtubule precursors.

Correlations between mutation site in APC and phenotype of familial adenomatous polyposis (FAP): A review of the literature

Mutations in the adenomatous polyposis coli (APC) gene cause familial adenomatous polyposis (FAP). Disease severity and the presence of extracolonic manifestations seem to be correlated with the location of the mutation on the APC gene. In this review, large studies describing genotype-phenotype correlations in FAP were evaluated and categorized. Attenuated FAP (AFAP, <100 colorectal adenomas) is correlated with mutations before codon 157, after codon 1595 and in the alternatively spliced region of exon 9. Severe polyposis (>1000 adenomas) is found in patients with mutations between codons 1250 and 1464. Mutations in the remainder of the APC gene cause an intermediate phenotype (hundred to thousands of adenomas). Congenital hypertrophy of the retinal pigment epithelium (CHRPE) and desmoid tumours are associated with mutations between codons 311 and 1444 and after codon 1444, respectively. No consistent correlations were found for upper gastrointestinal tumours. Genotype-phenotype correlations in FAP will be useful in decisions concerning screening and surgical management of FAP.

Alteration of DNA methylation status in K562 and MCF-7 cancer cell lines by nucleoside analogues

The effects of 2-chloro-2'-deoxyadenosine, beta-D-arabinofuranosyl-2-fluoroadenine, and 5-aza-2'-deoxycytidine on promoter methylation of the selected tumor suppressor genes (i.e., ERalpha, BRCA1, E-cadherin, PTEN, and APC) were estimated using methylation-sensitive restriction analysis (MSRA) in K562 cells (human erythroleukemic cell line) and MCF-7 cells (human breast cancer cell line). In both cell lines all tested drugs completely reduced methylation of PTEN and APC promoters. The results indicate that the tested nucleoside analogues, which are known inhibitors of DNA synthesis, also are implicated in indirect (or direct in the case of 5-aza-dCyd) regulation of post-replicative DNA modifications (i.e., DNA methylation).

Genetic testing for colon cancer

Colon cancer remains the third leading cause of death due to cancer in the US, where it affected more than 145,000 individuals in 2005. Up to 30% of these cases exhibit familial clustering, which means that tens of thousands of individuals have a disease with a potentially definable genetic component. Approximately 3-5% of colon cancers are associated with high-risk, inherited colon cancer syndromes. Identification of the genes that cause these colon cancer syndromes, coupled with additional insights into their clinical course, has led to the development of specific management guidelines--and genetic tests--that can diagnose these familial disorders. These guidelines can be life-saving, not only for the affected patient, but also for their family members.

Bacteria, inflammation, and colon cancer

Our relationship with the colonic bacterial flora has long been viewed as benign, but recent studies suggest that this symbiosis has risks as well as benefits. This relationship requires that the host not only provide a supportive environment for the symbiotic bacteria, but also actively maintain intact mechanisms for properly managing the physiologic stresses that are closely associated with the symbiont’s essential survival functions. Failure to do so breaches the host-symbiont contract, and can result in serious effects on the health of the host. Recent investigations that employ several knockout mouse models reveal the consequences of genetic deficiency in the host regarding these mechanisms, and the latent, pro-inflammatory, tumorigenic nature of normal bacterial flora. Further study of the interactions between normal bacterial flora and hosts could shed light on the etiologies and pathogenesis of inflammatory diseases and related cancers, with implications for human health.

Molecular biology of the nasal airways: how do we assess cellular and molecular responses in the nose?

We summarize studies herein that relate to use of molecular techniques to assess mechanism of toxicant and carcinogen action on the nasal mucosa. Specifically, we present the results of an in vivo mutagenesis assay with the herbicide alachlor, which causes olfactory mucosal tumors in rats following dietary administration. A positive response was found in olfactory mucosa after 3 mo of treatment. There was no increase in mutant frequency in the adjacent nasal respiratory mucosa or in liver, which are both non-target tissues for alachlor carcinogenesis. We also summarize previous findings of gene expression studies. One on these was a GeneChip experiment aimed at elucidating the mechanism of alachlor olfactory carcinogenesis, wherein we found that oxidative stress and gelatinase genes were upregulated early in the carcinogenic process, while genes consistent with activation of Wnt signaling were activated later in the carcinogenic process. The final example presented summarizes the results of a microarray experiment designed to identify novel olfactory genes involved in the plasticity of the olfactory mucosa. Those studies identified novel olfactory mucosal genes including Sgpl1 and Pon1. In each instance, precise sampling is emphasized and proper controls are discussed, and examples of independent means of validation of genomics experiments are presented.

Repair and regeneration: opportunities for carcinogenesis from tissue stem cells

This review will discuss the mechanisms of repair and regeneration in various tissue types and how dysregulation of these mechaisms may lead to cancer. Normal homeostasis involves a careful balance between cell loss and cell renewal. Stem and progenitor cells perform these biologic processes as the functional units of regeneration during both tissue homeostasis and repair. The concept of tissue stem cells capable of giving rise to all differentiated cells within a given tissue led to the concept of a cellulr hierarchy in tissues and in tumors. Thus, only a few cells may be necessary and sufficient for tissue repair or tumor regeneration. This is known as the hierarchical model of tumorigenesis. This report will compare this model with the stochastic model of tumorigenesis. Under normal circumstances, the processes of tissue regeneration or homeostasis are tightly regulated by several morphogen pathways to prevent excessive or inappropriate cell growth. This review presents the recent evidence that dysregulation of these processes may provide opportunities for carcinogenesis for the long-lived, highly proliferative tissue stem cell population. New findings of cancer initiating tissue stem cells identified in several solid and circulating cancers including breast, brain hematopoietic tumors will also be reviewed. Finally, this report reviews the cellular biology of cancer and its relevance to the development of more effective cancer treatment protocols.

High Pin1 expression is associated with tumor progression in colorectal cancer

BACKGROUND AND OBJECTIVES

Peptidyl prolyl cis-trans isomerase (Pin1) isomerizes only phosphorylated serine or threonine residues preceding proline in certain proteins and affects the protein function. Pin1 interacts with many signaling pathways, including Wnt signaling pathway that is crucial for colorectal tumorigenesis. Pin1 promotes cyclin D1 over-expression directly or through the stabilization of beta-catenin. Pin1 is over-expressed in some cancers such as prostate and breast cancers. This study aimed to determine whether Pin1 plays a role in colorectal tumorigenesis through the upregulation of beta-catenin and cyclin D1.

METHODS

Immunohistochemical analyses were performed on 105 colorectal cancer tissue samples using anti-Pin1, anti-beta-catenin, and anti-cyclin D1 antibodies. We examined the relationships between Pin1 expression and clinicopathological factors, prognosis, and beta-catenin/cyclin D1 expression.

RESULTS

High Pin1 expression was observed in 40 cases (38%) and positively correlated with histological type (P=0.0240), depth of invasion (P=0.0051), and staging (P=0.0027) of colorectal tumors. High Pin1 expression was also correlated with the over-expressions of both beta-catenin (P=0.0225) and cyclin D1 (P=0.0137).

CONCLUSIONS

These results suggest that Pin1 plays an important role in colorectal tumorigenesis, presumably by increasing beta-catenin and cyclin D1 expressions.

Primary cerebellopontine angle craniopharyngioma in a patient with Gardner syndrome

✓The authors report on the case of a craniopharyngioma arising in the cerebellopontine angle (CPA) in a patient with Gardner syndrome. Although familial adenomatous polyposis (FAP) is associated with intracranial neoplasms, the current case is only the third reported craniopharyngioma in a patient with Gardner syndrome. Two of these tumors, including that of the current case, originated in the CPA, an unusual location for craniopharyngiomas. The literature concerning FAP and its associations with intracranial neoplasia, as well as the pathogenesis of craniopharyngiomas in the posterior fossa, is discussed.